Why do musk deer have the smallest red blood cells and amphibians have the largest?

Why do musk deer have the smallest red blood cells and amphibians have the largest?

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What is the reason that musk deer have the smallest red blood cells and amphibians have the largest? Should they not be proportionate to the size of the organism?

In the abstract of (Duke, 1963) we see that mouse deer (Tragulus) have the smallest erythrocytes, not musk deer (Moschus). The paper also explains the origin of the confusion. Mouse deer have 1.5 µm erythrocytes but those of musk deer are 3.6 µm (p. 240). In fact musk deer erythrocytes are the same size as goat erythrocytes at (2.5-3.9) µm (Weiss, D. (2010). Schalm's Veterinary Hematology. 6th ed. pp. 836-842). Whether smaller erythrocytes have since been found, I can't say.

I don't have a definite answer why mouse deer erythrocytes are the size they are but I'd posit a few factors. The size of the erythrocyte needs to approximately match the size of the capillaries so they can press tightly to the epithelium and increase the efficiency of gas exchange. Another factor affecting erythrocyte size is cell number. If you have smaller cells, you need a larger number of them to keep the same sum total volume (as in the figure below). So then factors affecting blood vessel size and the rate of erythrocyte production could possibly affect erythrocyte size.

Size also changes surface area to volume ratio (sa/vol) by the square-cube law and this changes characteristics of diffusion over the cell membrane. A larger erythrocyte may have more plasma membrane, which would allow more diffusion and transporter activity but this may also increase the erythrocyte's volume, which would limit the rate of gas exchange due to solutes needing to work their way out of the middle of the cell. Having a high sa/vol is dependent on morphology (hence, our erythrocytes are biconcave) but Duke claims that mouse deer erythrocytes are actually spherical. So, in theory, the cells' small size could be a compensation to keep their sa/vol high, despite not being biconcave.

Interestingly the size of the cells might not affect the sum total intracellular volume of the cells. In fact, sphere packing density is independent of the size of the spheres. If the cells were made larger, this would increase the size of the gaps between them by the same amount. This could indicate that the the total amount of solutes in the blood is independent of the size of the cells, which could explain the great variation in the size of erythrocytes.

All cells need oxygen, the crucial ingredient for extracting energy from organic compounds. Animals obtain oxygen from their environment with their respiratory systems. The lungs of land-dwelling vertebrates gather oxygen from the air, the gills of ocean-dwelling vertebrates filter oxygen from the water, and the exoskeletons of invertebrates facilitate the free diffusion of oxygen (from water or air) into their bodies. The respiratory systems of animals also excrete carbon dioxide, a waste product of metabolic processes that would be fatal if left to accumulate in the body.


A rare and unusual category of mammal birth where the animal lays eggs. There are only five known monotremes mammals on the planet, with the platypus and echidna’s being the most well known.


Marsupial mammals give birth to their young before they are fully developed. The babies then complete their growth outside of the mother but in a ‘pouch’. Well known marsupial examples include kangaroos, opossums, and wombats.

Placental Mammals

Members of this birth group have a birth procedure containing a placenta. The presence of a placenta transfers important nutrients between the mother and offspring, helping protect the young and ensure a well developed birth. Placental births are the most common among all mammals with examples including dogs, horses, cats, and humans.

Animals that Survived the Ice Age

The Ice Age lasted around one hundred thousand years from about 110,000 to 10,000 years ago. The ice grew and retreated over this time but the largest extent of ice glaciers was around 18,000 years ago. The ice covered most of the northern hemisphere and some ice even got into the southern hemisphere. There were huge ice sheets covering North America, Eurasia, and Antarctica, most of Canada, New Zealand and Tasmania, as well as huge ice caps on all the world&rsquos mountains.

Many animals could not adapt to the freezing conditions and died out, but amazingly, many others did adapt and survive. Some of them still live on Earth today. Some evolved into modern animals. Other animals took evasive action avoiding the worst excesses of the Ice Age, and these animals are the same today as they were then.

One animal that survived the Ice Age is, the one we never count, the human animal Neanderthal man survived the Ice Age. Heidelbergensis evolved physical adaptations to cold and became Neanderthal man. The tall physique of Heidelbergensis became the Neanderthal&rsquos shorter, stockier body, which was ideal for conserving heat. Neanderthals also became very muscular to cope with the rigours of living in the Ice Age. Neanderthal children grew faster than modern children do an eight-year-old Neanderthal child was as developed as a twelve-year-old homosapien is. Experiments at Loughborough University show that the Neanderthal shape was better adapted at dealing with cold than the shape of modern humans. Neanderthals were skilled hunters, and omnivores and those animals that survived the Ice Age tended to be those who could eat a wide range of foods.

Some animals changed other attributes to survive the Ice Age. Some animals, such as mammoths and mastodons developed changes in their teeth in order to eat different kinds of vegetation. These were also very large animals, and their sheer size helped them to retain heat and animals such as mammoths grew long thick oily coats. Mammoths&rsquo ears and tails shrunk. Scientists recently discovered [1] that mammoths&rsquo blood also changed during the Ice Age. Their haemoglobin, the protein in red blood cells that delivers oxygen to the tissues, evolved to release oxygen more easily in the cold. It is possible that other animals made similar adaptations to help them live in the cold. The mammoth&rsquos closest living relative is the Asian elephant and they do not have this adaptation. It is likely that other large mammals may have adapted similarly. Other creatures may also have adapted their bodies to cope with the Ice Age. There is an Antarctic fish called chionodraco hamatus, which has a kind of natural antifreeze in its blood.

Some animals coped by moving south, for example, the Jaguar moved down from the southern United States into Mexico and Central America. Crocodiles are remnants of the dinosaur age and lived through the Ice Age because they lived in the warmer climates near to the equator. Polar, grizzly and brown bears all survived the Ice Age, as did musk ox, red deer, reindeer, bison. The Arctic hare and Arctic fox are also, unsurprisingly, remnants from the Ice Age. Small mammals such as muskrats, raccoons, stoats, opossum, and flying and fox squirrels also lived through the Ice Age.

Some of the tiniest creatures also survived – insects, dragonflies and spiders. Spiders are very interesting because they can alter their whole metabolism to ensure their survival in all kinds of extreme conditions. In Greenland today, there are 320 species of native insects, including several butterflies, which shows that even the tiniest creatures can adapt to extreme cold.

In the oceans, many creatures survived the Ice Age – sponges, corals, starfish, clams, sharks, turtles and the coelacanth. Many familiar birds, such as bald and golden eagles, black vultures and some woodpeckers also flew in Ice Age skies.

A surprising number of familiar species survived the Ice Age. Others like the wooly mammoth and the Neanderthal adapted well to the Ice Age, but they could not adapt to the earth&rsquos warming afterwards. Animals survived the Ice Age by various means some ran from the cold and some adapted to survive.

Why do musk deer have the smallest red blood cells and amphibians have the largest? - Biology

How do I import or export my commercial wildlife shipment?
Generally, you must import or export your shipment through one of our designated ports , declare your shipment to us on a special form , and receive clearance from us for your shipment.

In most cases, you must be licensed with us and pay user fees for each shipment.

What is wildlife?
Wildlife is any living or dead wild animal, its parts, and products made from it. Wildlife not only includes mammals, birds, reptiles, amphibians, and fish, but also invertebrates such as insects, crustaceans, arthropods, molluscs and coelenterates.

What about animals that are captive-born or bred, or hatched in captivity?
These animals and their parts, products, eggs, and offspring are also wildlife.

How do you define import?
Any wildlife introduced or brought into, or landed on, any place under U.S. jurisdiction is an import.

How do you define export?
Any wildlife that departs, is sent, or shipped from, is carried out of, or is consigned to a carrier from a place under U.S. jurisdiction with a destination outside of the United States is an export.

Does U.S. Customs and Border Protection use the same definitions?
No. Our rules apply to some shipments that Customs does not consider imports or exports.

What if my shipment is in transit through the United States?
Shipments that are in transit through the United States and remain under Customs bond do not have to be declared to us. Your in-transit shipment, however, must comply with foreign wildlife laws, and live wildlife must be transported humanely.

Be aware that shipments of certain species (such as those listed as endangered and threatened species, migratory birds, marine mammals, or injurious species) may not transit the United States.

Is my shipment an import or export if it is placed in a customs bonded warehouse or free trade zone?
Yes. Such shipments would be imports or exports, even though U.S. Customs and Border Protection does not regulate them as such. You and your shipment must meet wildlife requirements.

Are any wildlife species exempt from these requirements?
Certain shellfish and dead fish products that are to be eaten by humans or animals may be exempt if they do not require a permit under 50 CFR 17 (endangered and threatened species) or 50 CFR 23 (species listed under CITES – the Convention on International Trade in Endangered Species).

Certain domesticated animals are exempt provided they did not originally come from the wild.

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When may I use a border port?
You may import or export your shipment at an authorized border port only if the wildlife itself originally comes from the United States, Canada, or Mexico and your shipment is being sent from and going to one of these countries.

You may not use a border port for wildlife that originates outside of North America or for species that require a permit under 50 CFR 16, 17, 18, 21, or 23. (These regulations deal with injurious species, endangered and threatened species, bald and golden eagles, migratory birds, marine mammals and CITES species.)

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Special ports are located in Alaska, Puerto Rico, and Guam. You may use special ports to import wildlife into these places as a final destination.

You may export wildlife that originates in Alaska, Puerto Rico, or Guam from a special port in that specific state or territory. Exports of wildlife that originates in the U.S. Virgin Islands may only use the special port of Guam. You may not use special ports for wildlife that requires a permit under 50 CFR 16, 17, 18, 21, or 23 (These regulations deal with injurious species, endangered and threatened species, bald and golden eagles, migratory birds, marine mammals and CITES species .)

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Under very limited circumstances, you may be authorized under permit to use a port that does not normally handle wildlife trade. You must show that using one of our authorized ports would result in substantial deterioration or loss of the wildlife, or would cause an undue economic hardship. Final approval to use a non-authorized port depends on the availability of inspection services.

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You must file a Declaration for Importation or Exportation of Fish or Wildlife (Form 3-177) with us at an authorized port of entry and receive clearance from us before U.S. Customs releases your shipment.

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You must file Form 3-177 with us at an authorized port and receive clearance from us before your shipment is containerized or physically loaded on a vehicle, aircraft, or vessel, unless authorized otherwise by us.

Are there any exceptions to the declaration requirement?
Yes. There are two exceptions.

Live oysters, clams, mussels, and scallops, and their eggs, larvae, or juvenile forms that are exported for propagation or research related to propagation are exempt from declaration requirements, provided they do not require a permit under 50 CFR 17 (endangered and threatened species) or 23 (CITES-protected species).

You do not have to declare exports of live farm-raised fish eggs or live farm-raised fish unless they require a permit under 50 CFR 17 or 23.

Do I need a license to import or export wildlife?
Yes. Generally anyone engaging in business as an importer or exporter of wildlife must obtain a license from us.

Do I have to pay fees to import or export wildlife?
Yes. You must pay user fees for each shipment imported or exported once you are licensed by us. These fees differ based on the type of port you use.

Are there other wildlife laws I need to know about?
Yes. Many federal laws that protect wildlife have import/export requirements. These laws include the Lacey Act, Endangered Species Act, Migratory Bird Treaty Act, Eagle Protection Act, Marine Mammal Protection Act, African Elephant Conservation Act, Rhinoceros and Tiger Conservation Act, and Wild Bird Conservation Act.

You must also ensure that your wildlife shipment complies with state and foreign wildlife laws.

Are there any other agencies I need to contact?
Yes. Other federal agencies involved with the import and export of wildlife may have additional requirements. These agencies include U.S. Customs and Border Protection the Department of Agriculture’s Animal and Plant Health Inspection Service the U.S. Public Health Service the U.S. Food and Drug Administration and the National Marine Fisheries Service .

You should also contact your state fish and wildlife agency about any state requirements or restrictions


A mammal is an animal that feeds its babies with milk when it is young. There are over 4,500 types of mammals. Many of the most popular animals we know are mammals, for example, dogs, cats, horses, cows, but exotic animals like kangaroos, giraffes, elephants and anteaters belong to this group, too. Humans are also mammals.

Mammals live in all regions and climates. They live on the ground, in trees or underground. Polar bears, reindeer and seals are mammals that live in the Arctic regions. Others, like camels or kangaroos prefer the world&rsquos dry areas. Seals and whales are mammals that swim in the oceans bats are the only mammals that can fly.

Mammals have five features that make them different from other animals:

  • Female mammals produce milk and feed their babies with it.
  • Only mammals have hair or hair-like skin. All mammals have hair at least some time in their lives.
  • Mammals are warm-blooded. Their body temperature always stays the same and does not change with the outside temperature.
  • Most mammals have a larger and well-developed brain. They are more intelligent than other animals.
  • Mammals protect their babies more than other animals. They prepare them for future life.

People have hunted mammals for ages. They ate their food and made clothes out of their skins. Thousands of years ago wild mammals were domesticated and gave human beings milk, wool and other products. Some mammals, like elephants and camels are still used to transport goods. In poorer countries farmers use cows or oxen, to plough fields.

Today some mammals are hunted illegally. Whales are killed because people want their meat and oil, elephants are killed for the ivory of their tusks.

Mammals are often kept as pets. Among them are cats, dogs, rabbits or guinea pigs.

Mammals are useful to people in many other ways. Some help plants grow and eat harmful insects. Others eat weeds and prevent them from spreading too far. The waste of mammals is used as fertilizers that improve the quality of soil.

Types of mammals

Mammals are divided into three groups:

  1. Monotremes are mammals that lay eggs, like a bird. They live in Australia and New Zealand. The platypus belongs to this group
  2. Marsupials are mammals that raise their young ones in a pouch in their bodies.
  3. Placentals are the largest group of mammals. The babies grow inside their mothers until they are ready to be born. Humans are placentals.

Mammals and their bodies

Skin and hair cover a mammal&rsquos body. Some mammals have horns, claws and hoofs. The hair or fur of a mammal has many functions. The colour often blends in with the world around them and allows them to hide from their enemies. Some mammals produce needles or sharp hair that protects them from attack. But the main function is to keep the body warm.

Mammals have glands that produce substances that the body needs like hormones, sweat and milk.

A mammal&rsquos skeleton is made up of three parts:

  1. The skull contains the brain, teeth and other organs.
  2. The spine or backbone enables mammals to stand or walk.
  3. Limbs are legs and arms of a mammal, often with strong bones.

Mammals have a four-chambered heart system that pumps blood into all parts of their body. The blood brings oxygen to muscles and tissue. The red blood cells of mammals can carry more oxygen than in many other animals. Because mammals have a high body temperature they must burn a lot of food.

Mammals digest food through their digestive system. After food is eaten through the mouth it goes down the throat into the stomach and passes through the intestines. Mammals that eat plants have a complicated system with long intestines that help break down food. Flesh is easier to digest so meat-eating mammals have a simpler stomach.

Mammals breathe air through their lungs. Most of them have noses or snouts with which they take in air. Dolphins and whales breathe through a hole in the top of their back.

A whale blowing air out of its body - Aqqa Rosing-Asvid

Mammals and their senses

Mammals have five senses that tell them what is happening in their surroundings. Not all senses are developed equally among mammals.

Mammals rely on smell to find food and warn them of their enemies. Many species use smell to communicate with each other. Humans, apes and monkeys have a relatively bad sense of smell.

Taste helps mammals identify the food that they eat. Most mammals have a good sense of hearing. Some mammals use their hearing to detect objects in the dark. Bats, for example, use sounds to navigate and detect tiny insects. Dolphins also use such a system to find their way around.

While higher primates, like humans, apes and monkeys have a highly developed sense of sight other mammals are nearly blind. Most of these mammals, like bats, are active at night.

Mammals have a good sense of touch. They have nerves on all parts of their body that let them feel things. Cats and mice have whiskers with which that they can feel themselves around in the dark.

What mammals eat

Herbivores are mammals that eat plants. They have special teeth that allow them to chew food better. Examples of herbivores are deer, cows and elephants. The giant panda is a plant eater that only eats bamboo.

Carnivores are mammals that eat other animals. Cats, dogs, tigers, lions, wolves belong to this group. They are hunters that tear their prey apart with sharp teeth. They do not chew their food very much.

Omnivores are mammals that eat plants and meat. Bears, , apes, pigs and humans are examples of omnivores.

How mammals move

Most mammals live and move on the ground. They have four legs and walk by lifting one foot at a time or by trotting. Kangaroos hop and use their tail for balancing.

Mammals that live in forests spend a lot of their time in trees. Monkeys can grasp tree branches with claws and can hang on to them with their curved tail. Often mammals spend time hanging upside down in trees.

Dolphins and whales are mammals that live and move around in water. Instead of limbs they have flippers which they use to move forward. Other animals, like the hippopotamus, only spend some time in the water.

Bats are the only flying mammals. Their wings are made of skin stretched over their bones. They can fly by beating their wings up and down.

Gophers and moles are mammals that spend most of their life underground.

How mammals have babies

Mammals reproduce when a male&rsquos sperm gets into contact with a female egg and fertilizes it. A young mammal grows inside the female&rsquos body. Before this can happen mammals mate. Males and females stay together for a certain time.

Unborn mammals live their mother&rsquos body for different periods of time. While hamsters are born after only 16 days, it takes elephants 650 days to give birth. Human pregnancies last about 9 months.
Many new-born mammals, like horses and camels, can walk and run shortly after they are born.

Marsupials give birth to babies that attach themselves to their mothers. They stay in pouches because they are too weak to live alone. Almost all marsupials, including kangaroos, koala bears or wombats live in Australia .

After birth the glands of a female mammals produce milk. Some mammals nurse their babies for only a few weeks. Others, for example elephants, give milk to their babies for a few years.

The duck-billed platypus and echidnas are the only mammals that lay eggs. After the young hatch they drink milk from their mother, just like other mammals do.

Life habits

Many mammals live in families or groups. Wolves and lions help each other in their search for food and protect each other from attackers.
Leopards, cats, tigers and other mammals prefer living alone . They do not share their living space and food that they have, however males and females get together to mate.
Mammals can mark the areas that they live in. They defend these areas by fighting off attackers. Some mammals claim territories only during the breeding season.

Many mammals migrate during special times of the year in order to get food and survive. North American bats travel to the south because insects become scarce during the cold winter months. Zebras and other wild animals follow the rainy seasons in Africa to find green grass. Whales migrate to warmer southern waters off the coast of Mexico to give birth to babies because they could not survive in the cold waters of the Arctic Ocean.

Some mammals hibernate because they cannot find enough food to survive. Their body temperature falls, heartbeat and breathing become slower. During this period hibernating mammals do not eat. They live from the fat of their bodies. Bats, squirrels and other rodents hibernate.

Mammals defend themselves from attackers in many ways. Hoofed mammals can run quickly in order to get food or escape. Squirrels rush into trees to hide. Some animals have special features that protect them from enemies. Skunks spray a bad smelling liquid to keep off attackers. The fur of mammals sometimes changes with its surroundings. Arctic foxes, for example, are brown in summer and in the winter their coats turn white.

Squirrel eating a peanut by DAVID ILIFF

History of mammals

The first mammals probably evolved from reptiles about 200 million years ago during the Mesozoic period. They were rather small in a time when dinosaurs ruled the lands. When the dinosaurs died out about 65 million years ago mammals became the dominant land animals. Many mammals became extinct during the Ice Age , which ended thousands of years ago.

Today, some species are in constant danger of becoming extinct because they are hunted by humans. Hunters and poachers earn money by selling fur, tusks and other parts of mammals. Larger wild animals are often brought to zoos where they are protected.

Now we can screen hundreds of compounds in a month. Fifteen years ago that wouldn’t have been possible – Christine Beeton

“Now we can screen hundreds of compounds in a month. Fifteen years ago that wouldn’t have been possible. You would have had to look at them one by one, and it would have taken 10 years,” Beeton says.

Instead of having to laboriously milk snakes and scorpions for their venoms in order to analyse them, researchers can simply mine databases of codes to find peptides with specific properties.

Numerous drugs are already available on pharmaceutical shelves: Enexatide, derived from the saliva of the Gila monster, prescribed for type two diabetes Ziconitide, extracted from cone snail venom, for chronic pain Eptifibatide, a synthetic modelled on the venom of the southern pygmy rattlesnake, administered to prevent heart attacks Batroxobin, extracted from South American pit vipers and used in several different blood treatments, including the appropriately named “Reptilase” and Captopril, the first pharmaceutical derived from an animal, an anti-hypertensive approved by the US’s Food and Drug Administration (FDA) in 1981.

The venom from a species of pygmy rattlesnake inspired Eptifibatide, a synthetic which prevents heart attacks (Credit: Getty Images)

Almost all of these animal-derived pharmaceuticals are sourced from venoms – some of the most complex chemical mixtures found on earth. Though we may think of venoms as rarefied poisons that only a few species possess, 220,000 known animal species produce these chemical cocktails – fully 15% of all animal species.

These intricate poisons, many of which have evolved over hundreds of millions of years, have exquisite potency, stability, speed, and above all, precision to specific molecular targets.

Brain healing

One of the most promising areas of venom-derived medicines is in preventing permanent brain damage from stroke. Though it is the second leading cause of death worldwide, killing six million a year and leaving a further five million with permanent disabilities, we have no treatments that can heal or prevent brain damage following this loss of blood flow to the brain.

The only drug approved by the FDA for this need is tissue plasminogen activator (tPA), which may be given to break up blood clots in the cerebral artery. But we still have no treatments that can prevent the neuronal damage due to oxygen starvation.

“This is the biggest issue we have: millions of people are left to the whims of what that stroke can do to their brain in the hours or days following it,” says Glenn King, a biochemist at Australia’s University of Queensland. King specialises in nervous system disorders in which the underlying cause is a defect in nerve cells’ ion channels – tiny tunnels through membranes that let charged ions, like sodium, flow in and out of cells, triggering nerve firings. These defects can be caused either through structural anomalies, or an abnormal number of channels.

The bite of a funnel-web spider can kill a human, but one component of its venom could prevent brain damage in stroke survivors (Credit: Getty Images)

As it happens, venoms largely target ion channels. King works with the world’s largest physical collection of venom samples milked from living invertebrates, with peptides extracted from more than 700 species including scorpions, spiders, assassin bugs and centipedes. Toxins from insects would have evolved over far longer time spans compared to vertebrates – in some cases 400 million years or more – so they are “exquisitely targeted”, says King.

When King searched his invertebrate venom library, he found just one molecule that seemed a promising candidate for the treatment of stroke. This was Hi1a, a component of venom from the Australian funnel-web spider Hadronyche infensa – a mixture of 3,000 molecules which Professor King describes as “the most complex chemical arsenal in the world”.

#2021MMM Round 2

TONIGHT'S #2021MMM ROUND 2 WINNERS: Anchovy, Devil Frog, Ifrit, Sea Star, Ammonite, Vampire Squid, Harpy Eagle, and Sphinx Monkey. We will see you on Wednesday 3/24 at 8 PM Eastern for the Sweet 16 battles!

&mdash March Mammal Madness (@2021MMMletsgo) March 23, 2021

Round 2, Of Myths & Monsters & Sea Beasties Results: Saber-Toothed Anchovy, Devil Frog, Blue-Capped Ifrit, Midgardia Seastar, Ammonite, Vampire Squid, Harpy Eagle, and Sphinx Monkey ADVANCE.

Sports Summaries by Prof Kate Lesciotto, Sam Houston State University

Saber-Toothed Anchovy (1) v. Pink Vent Fish (8) &ndash Round 1 saw Saber-Toothed Anchovy sending Planktonic Copepod adrift and Pink Vent Fish eating Lathe Acteon snail. Tonight&rsquos first marine battle takes place 47 million years ago (Eocene Epoch of Cenozoic Era) in an ancient sea over modern-day Pakistan. Even though oxygen levels at shallower depths are relatively low, Pink Vent Fish is breathing just fine with its amped up hemoglobin that has a super-high affinity for oxygen. But Pink Vent Fish is used to deep-sea hydrothermal vents and now finds itself out in the open ocean (pelagic) without any rocks or tube works to hide behind! Lacking a lateral line (sensory system found in most fish), Pink Vent Fish is unable to sense a subtle change in water movement and is blind-sided as Saber-Toothed Anchovy launches an ambush! SABER-TOOTHED ANCHOVY (def)eats Pink Vent Fish. Narrated by Prof Patrice Connors.

Picado&rsquos Jumping Pitviper (4) v. Devil Frog (5) &ndash The namesake of the genus for Picado&rsquos Jumping Pitviper (Atropoides) is Atropos, featured in the poem Shield of Heracles, with fitting descriptions for a pitviper, such as &ldquoteeth are bright-white like those of Fear.&rdquo This sit-and-wait predator does have a horrific method of killing its typically mammalian prey &ndash injecting venom made of enzymes that break down proteins. However, Devil Frog is not a mammal. In the cloud forest of Parque Nacional Los Quetzales, a national park in Costa Rica, Devil Frog finds itself along a stream edge and sits in a depression next to an animal track. And waits &ndash Devil Frog is a sit-and-wait predator. While waiting, Devil Frog takes in the many scents of unfamiliar prey, because in Devil Frog&rsquos time, mammals did not yet exist! Used to preying on tasty small mammals in modern times and the current habitat, Picado&rsquos Jumping Pitviper slowly slithers along the streambank and uses its tongue to &lsquosmell&rsquo the environment and search for prey. Settling within striking distance of Devil Frog, Picado&rsquos Jumping Pitviper also follows a sit-and-wait strategy. As Devil Frog sizes up the snake and decides that it might be too much to handle, Picado&rsquos Jumping Pitviper picks up the scent of a mammal and follows the scent off the field of battle. DEVIL FROG out-sits Picado&rsquos Jumping Pitviper. Narrated by Dr. Tara Chestnut.

Blue-Capped Ifrit (7) v. Crypt-Keeper Wasp (15) &ndash Blue-Capped Ifrit may have some beetles to thank for its win over Brussels Griffon in Round 1 due to the batrachotoxins on its feathers. Blue-Capped Ifrit does not produce its own toxins, but rather acquires toxins through its diet, possibly from beetles in the genus Choresine. The battle with underdog Crypt-Keeper Wasp begins in the Madang Province of Papua New Guinea near the village of Simbai, where Blue-Capped Ifrit has camouflaged its nest with moss and liverworts, although the nest itself is made of plant fibers and feathers. Crypt-Keeper Wasp is looking for a gall to oviposit in and saunters along a liverwort until it starts to brush up against the outside of the Blue-Capped Ifrit nest. As it touches the batrachotoxin-laced feathers on the nest, Crypt-Keeper Wasp starts to not feel so great. Batrachotoxins can affect nearly every animal that contains voltage-dependent sodium channels, including distantly related arthropods. As the feeling of discomfort grows, Crypt-Keeper Wasp flees the field of battle. BLUE-CAPPED IFRIT repels Crypt-Keeper Wasp. Narrated by Prof Chris Anderson.

Midgardia Seastar (2) v. Yeti Crab (15) &ndash This battle&rsquos top-seed &ndash Midgardia Seastar &ndash is an elusive species of the deep sea, with only 20 specimens in natural history collections. Yeti Crab is another deep-sea resident, preferring the dark but warm waters that surround hydrothermal vents. Midgardia Seastar is sitting along the seafloor, about 512 m deep off the coast of Texas in the Gulf Coast, where an actual specimen has been collected. With a small mouth and a lack of food in the digestive track of collected specimens, scientists have hypothesized that Midgardia Seastar does not feed directly, but instead absorbs nutrients through its general body tissues. Yeti Crab is approximately 7300 km away in the Annie&rsquos Anthill vent site in the Pacific Ocean, waving her claws through the water near a vent to circulate more of the methane and hydrogen sulfide gasses to help the bacteria growing on her setae. A magic MMM portal opens up next to Yeti Crab &hellip through the portal in the Gulf of Mexico, Midgardia Seastar waves its arms in the current, each thin arm ending in a plate armed with small spines that looks like a tiny cat&rsquos paw with extended claws. Deciding that its own bacteria farming activities are just too important, Yeti Crab steps away from the portal and elects not to enter the field of battle. MIDGARDIA SEASTAR outlasts Yeti Crab. Narrated by Prof Jessica Light.

Platyzilla (3) v. Ammonite (6) &ndash Platyzilla&rsquos scientific name (O. tharalkooschild) pays homage to the Indigenous Australian dreamtime origin story about a duck named Tharalkoo. Ignoring the advice of elders, Tharalkoo explored upriver and #YadaYadaYada which lead to the origin of the first platypus being the offspring of a male water rate and a female duck. Ammonite is another extinct combatant in #2021MMM, belonging to a group of shelled cephalods. However, Ammonite is only found in its last chamber &ndash the other chambers are filled with liquid and gas to control buoyancy and maintain orientation in the water. These extinct Sea Beasties find themselves 10 million years ago in what is now Riversleigh, Australia, as Platyzilla uses electric receptors on its bill to sense prey in the water. Ammonite notices a large animal swimming right towards it and spins vertically! The adult orientation of its shell spirals is not suited to horizontal movement. CRUNCH!! Platyzilla bites Ammonite! But Platyzilla bites the wrong end and ends up with a mouth full of the hard calcium carbonite shell and a broken tooth. Platyzilla&rsquos teeth are adapted for crushing, but mostly for softer foods like insect larvae and small vertebrates like frogs. Knowing the value of its teeth and not wanting to risk them further, Platyzilla swims off to find more easily masticated prey. AMMONITE survives Platyzilla. Narrated by Dr. Brian Tanis.

Black Dragonfish (4) v. Vampire Squid (5) &ndash Both adapted to the cold, deep waters of the ocean, home habitat advantage might not actually give Vampire Squid much of an advantage tonight. Each combatant enters the field of battle with hungry bellies. While Vampire Squid eats mostly detritus, Black Dragonfish craves living flesh. As Vampire Squid floats horizontally using eyes and tentacles to find its next meal, Black Dragonfish fires up its photophores to bathe Vampire Squid in near infra-red light. Researchers aren&rsquot sure whether Vampire Squid can actually see this light, but most of Black Dragonfish&rsquos usual prey can&rsquot see this wavelength, which is rare at this depth, rending them unaware of the dangers it brings. As Vampire Squid&rsquos tentacles brush up against something, Black Dragonfish strikes, and Vampire Squid flips out! Literally &ndash Vampire Squid is able to turn inside out, exposing a black inner mantle lined with sharp cirri in a &lsquospiky pineapple&rsquo form. Although this has become a super-sized meal, Black Dragonfish is not deterred and has its own morphological malarky. Like other members of its phylogenetic family, Black Dragonfish has a bit of free-floating spinal column that allows it to crank its head back and open its mouth even wider. The gaping maw of Black Dragonfish aims toward Vampire Squid, but Vampire Squid has one last trick &ndash it fires a series of photophores on the tips of its arms! The sudden flaring of light distracts Black Dragonfish, who is only able to get a mouthful of tentacles but leaves the vital bits of Vampire Squid intact. Black Dragonfish swims back to the depths with a belly full of calamari, leaving Vampire Squid victorious &hellip but damaged. VAMPIRE SQUID defeats Black Dragonfish. Narrated by Prof Josh Drew.

Harpy Eagle (1) v. Ghost Bat (8) &ndash Harpy Eagle may be the &ldquoQUEEN of the jungle&rdquo avian predator, but they take a more hands-off approach to teaching their young about hunting. Rather than directly teaching their young, Harpy Eagles slowly stop provisioning them with food, forcing juveniles to figure it out on their own. Ghost Bat isn&rsquot typically on the menu &ndash although Ghost Bat has no known natural predators, their populations are still on the decline, likely due to roost disturbance, habitat loss, and invasive species. Still enjoying home-habitat advantage, Harpy Eagle makes its way through the forest in Tambopata National Reserve in southeastern Peru and spies a tayra (solitary omnivorous animal from the weasel family). The tayra has found a ripe hog plum tree. In an unfamiliar environment, Ghost Bat has been searching for a cave to rest in but now settles for the pointy green leaves of the very same hog plum tree. The tayra catches the new scent of Ghost Bat and deftly climbs the tree. Ghost Bat stretches its wings to take off, but the tayra closes the distance with a quick horizontal bound across the tree branch. Before Ghost Bat can extend its wings, the tayra swipes and pins Ghost Bat, snapping wing bones. Just as the tayra is about to the make the final, death-dealing bite &ndash THRUNK!! Harpy Eagle&rsquos talons sink into the tayra&rsquos torso! The trio struggles and slips from the branch, but Harpy Eagle&rsquos massive wings quickly catch flight as her talons sink deeper into the tayra. As Harpy Eagle gains altitude, the tayra&rsquos eyes dim and jaw goes slack, and the broken-winged Ghost Bat tumbles back through the canopy to the forest floor. HARPY EAGLE defeats Ghost Bat. Narrated by Dr. Alyson Brokaw.

Chimpanzee (3) v. Mandrill (6) &ndash In our final battle of the evening, two primates in their prime are set to do battle. Both Chimpanzee and Mandrill are social primates. Male chimpanzees spend their entire lives in the community to which they are born, while male sphinx monkeys are more likely to be peripheral to groups or even live alone. No home-court advantage, as tonight&rsquos primate showdown takes place in Lopé National Park in central Gabon in a 9-ha &lsquoisland&rsquo of forest in which Chimpanzee and Mandrill are sympatric! A lone male Mandrill is foraging on the forest floor, while our adult male Chimpanzee arrives accompanied by a subadult male. Chimpanzees routinely hunt monkeys and are known to crush the skull and go for the brain &ndash a large, nutrient dense source of energy. However, this type of hunting would require multiple adult males in order to be successful. Our two primates engage in an aggressive staring contest that is broken when Chimpanzee coughs. After being bitten by White-Winged Vampire Bat in Round 1, has there been zoonotic disease transmission?? Chimpanzee coughs up a fig chunk &ndash no sign of disease. Recognizing Mandrill has larger and sharper canines, Chimpanzee decides to instead climb a tree into the nest of a crowned hawk-eagle, perhaps to steal fledglings or eggs. Crowned hawk-eagle fights back, striking the back of Chimpanzee&rsquos head with its beak, and Chimpanzee quickly descends to the ground. Chimpanzee and his subadult friend move away from the eagle tree and away from the field of battle as Mandrill calmly watches. MANDRILL outlasts Chimpanzee. Narrated by Prof Katie Hinde.

TONIGHT'S #2021MMM ROUND 2 RED IN FUR and TAXONOMY WINNERS: Red Kangaroo, Tapir, Fruit Bat, Hartebeest, Red Wolf, Dugong, Bay Cat, and Brocket. We'll see you back on Monday 3/22 at 8PM Eastern for the rest of Round 2 in the Sea Beasties and Myths & Monsters divisions

&mdash March Mammal Madness (@2021MMMletsgo) March 19, 2021

ANNOUNCEMENT: TOMORROW March 19th at 11AM EDT, join American Museum of Natural History scientists as they guide a LIVE virtual tour of MAMMAL EXHIBITS at the AMNH!

Round 2, Tricksy Taxonomy & Red, in Fur Results: Red Kangaroo, Mountain Tapir, Egyptian Fruit Bat, Red Hartebeest, Red Wolf, Dugong, Bay Cat, and Red Brocket ADVANCE.

Sports Summaries by Prof Kate Lesciotto, Sam Houston State University

Red Kangaroo (1) v. Red Crested Tree Rat (8) &ndash After winning their respective battles by slobbering and boxing, Red Kangaroo and Red Crested Tree Rat find themselves in Judbarra National Park in Australia&rsquos Northern Territory. Red Kangaroo is again enjoying home-habitat advantage and begins grazing on the desert shrubbery as the sun sets and temperatures begin to cool. Red Crested Tree Rat is not a fan of this semi-arid desert but is enticed by some nearby Calomymex ants to begin foraging. Feeling something brush against its tail, Red Kangaroo looks down to see the much smaller Red Crested Tree Rat. Red Crested Tree Rat brings itself up to its full standing height, chest puffed and ready to defend its foraging ground&hellip until it sees Red Kangaroo glaring down at it from 4 ft above. Red Crested Tree Rat channels its inner rodent and runs away from the larger threat. RED KANGAROO intimidates Red Crested Tree Rat. Narrated by Prof Patrice Connors

Mountain Tapir (3) v. Jaguarundi (6) &ndash Both Mountain Tapir and Jaguarundi have interesting activity patterns, with Mountain Tapir being active any time of day, unlike other tapir species that are mostly nocturnal, and Jaguarundi being diurnal and therefore easier to see than other felid species. Our combatants meet in the Sangay National Park in Ecuador. Although not its preferred habitat, Jaguarundi is a habitat generalist and is not disturbed by the unfamiliar location. As Mountain Tapir uses its bristly proboscis to find some tasty greens, its keen sense of smell picks up the scent of a feline predator. Jaguars are frequent predators, and Mountain Tapir is on guard. Nearby, Jaguarundi is also sniffing the air &ndash he detects the rich base notes of tapir but is more interested in the ocelot latrine at the base of a tree. The strong scent indicates that an ocelot has been here very recently. Knowing the ocelots are twice his size and known for intraspecific competition, Jaguarundi decides it would be better to exit the field of battle. Satisfied that there are no jaguars around, Mountain Tapir continues to munch away at the local plants. MOUNTAIN TAPIR ignores Jaguarundi. Narrated by Dr. Anne Hilborn & Dr. Brian Tanis

Egyptian Fruit Bat (12) v. Solenodon (13) &ndash Two underdog titans meet in this battle &ndash Solendon avoided being a treat for Malagasy Striped Civet, and Egyptian Fruit Bat outlasted the socially-motivated Kinda Baboon. Egyptian Fruit Bat most likely reacquired the ability to echolocate that was lost at some point in its ancestry, but instead of using pulses from their larynx, they use tongue clicks for lingual echolocation to locate land and detect large objects. Not to be outdone, Solendon is also able to echolocate! Solenodon also uses a click form of echolocation for orientation in the dark. In tonight&rsquos battle, Egyptian Fruit Bat emerges from his cave to forage in the Mount Carmel Biosphere Reserve in Israel to feed on a variety of fruits, while Solenodon finds itself beneath some fig trees on the slopes of Mt Carmel. Egyptian Fruit Bat lands in the tree and plucks some nearby figs. Eyeing his haul, a female Egyptian Fruit Bat snatches one away as they scramble over this delicious meal. Their scrambling dislodges ripe figs from the branches, which start to rain down on Solendon, who is not pleased by the resulting squishy, sticky mess. Combined with the high-pitched squabbling of the bats above, Solenodon decides to find a more peaceful place to hunt and zigzags away from the field of battle. EGYPTIAN FRUIT BAT drives away Solenodon. Narrated by Dr. Alyson Brokaw

Red Hartebeest (2) v. Red Ruffed Lemur (7) &ndash The fully terrestrial Red Hartebeest, found in grazing herds of up to 300, faces off against the primarily arboreal Red Ruffed Lemur in the Eastern Cape Province, South Africa, in Mkambati Nature Reserve. Lemurs were outcompeted by monkeys on the mainland of Africa, which is why they are only found in Madagascar. Finding herself on the outskirts of the hartebeest herd, Red Ruffed Lemur keeps her eyes on the large horns of Red Hartebeest and begins to sidle towards a nearby stand of trees. Red Hartebeest doesn&rsquot view Red Ruffed Lemur as a threat, but nevertheless pauses to mark his territory with a fresh pile of dung. Red Ruff Lemur deposits her own stinky secretions by using her glands to deposit scent-marks on a tree to mark territorial boundaries and convey information about biological sex and age. Hearing unexpected calls from above, Red Ruffed Lemur looks up to see a troop of vervet monkeys, grunting and giving alarm calls. Realizing these trees are already occupied, Red Ruffed Lemur quickly departs, moving further away from Red Hartebeest and his herd as evolutionary history repeats itself! RED HARTEBEEST displaces Red Ruffed Lemur!! Narrated by Dr. Lara Durgavich

Red Wolf (2) v. Tarsier (7) &ndash Although tricksy to determine whether Red Wolf is an ancient species or more recent hybrid with coyotes, mitochondrial DNA analyses show that the red wolf haplotype clusters among coyote haplotypes rather than grey wolf, but the sample size was small. Tarsier&rsquos tricksy taxonomy has been investigated through nuclear DNA, which shows that tarsiers group with monkeys and apes and is therefore part of Haplorrhinii (monkeys & apes) rather than Prosimians (lemurs & lorises). Deep in the Sabine National Wildlife Refuge of southeast Louisiana, Tarsier is feeling a bit cold but is more perturbed by the lack of large trees to provide cover among the canopy. Scurrying in the tall grasses, Tarsier finds a nutria (aka swamp rat) burrow and hunkers down to wait for nightfall. Red Wolf and its pack are on a usual patrol when the scent of an unfamiliar animal causes them to deviate and approach the burrow to investigate. As Red Wolf approaches, Tarsier&rsquos fight-or-flight instinct kicks in! Using all of its energy, Tarsier takes off in a leaping movement to relocate to another nutria burrow away from the field of battle. RED WOLF defeats Tarsier. Narrated by Dr. Tara Chestnut & Prof Anne Stone

Dugong (1) v. Musk Deer (8) &ndash Both combatants enter tonight&rsquos battle with one thing in common &ndash tusks! Dugong tusks are elongated second incisors, similar to elephant tusks, and are found in all adult males and mature females. Musk Deer&rsquos vampire-like tusks are found in males and range from 7-10 cm in length! Despite these fearsome tusks, Musk Deer populations have declined, partially due to high demand for the musk produced by males to attract mates. As these tusked combatants meet on the field of battle in the Great Barrier Reef along an inner reef not too far from shore, Dugong happily uses his tusks to scrape vegetation off the sea floor. Feeding is the main activity for dugongs, which need to eat up to 70 lbs of sea grass a day. Musk Deer, with hooves adapted for walking on steep ground and climbing slanted trees, is much less happy in this marine environment. Dugong angles his tusks upward, spotting the swimming artiodactyl just above him, and Musk Deer directs his head and tusks downward to notice the dark shape moving in the waters beneath. Deciding that it would be the better part of valor to avoid a fight, Musk Deer swims towards land through the salty, SALTY (crocodile) infested waters to the mainland. DUGONG outlasts Musk Deer. Narrated by Prof Jessica Light & Prof Marc Kissel

Bay Cat (3) v. Red Fox (6) &ndash It&rsquos a cat versus dog(ish) battle tonight! Bay Cat shares its rainforest home with four other cat species, which may be reason why it is so elusive and rarely seen. Red Fox is no stranger to coming up against cats &ndash across the world, Red Foxes are killed by bobcats and two species of lynx. In tonight&rsquos battle, Bay Cat has home habitat advantage in the Batang Ai-Lanjak-Entimau complex in the Bornean rainforest, but Red Fox has a 3kg (

14 stoat) weight advantage. Both combatants dealt some serious carnage in Round 1 and are looking for a place to sleep off even more recent meals. Bay Cat is resting in a cool, shady den under a tree root embankment, while Red Fox snuffles its way to Bay Cat&rsquos doorstep. Red Fox isn&rsquot particularly interested in this cat but does like the look of this nice resting spot. Bay Cat stands up, arches his back, and growls at Red Fox. This Red Fox is from Walnut Creek, California, and knows that even the bravest of its home turf cats would rather run that fight him. Bolstered with confidence, Red Fox creeps forward to press his size advantage &hellip and receives a slash from Bay Cat&rsquos claws across the nose! Red Fox jumps back but quickly rushes in again, baring his gleaming teeth. Bay Cat refuses to back down and delivers a lightening fast one-two-three strike to Red Fox&rsquos muzzle! Bay Cat charges and strikes again, and Red Fox runs off the field of battle. BAY CAT runs off Red Fox. Narrated by Dr. Asia Murphy & Kwasi Wrensford, PhD

Maroon Langur (4) v. Red Brocket (5) &ndash These two combatants could each deal some serious #PlantCarnage &ndash Red Brocket is a true ruminant with a four-chambered stomach that allows fluid washing and microbial fermentation for plant matter digestion, and Maroon Langur is a foregut fermenter with adaptations to digest a fiber-heavy herbivorous diet. However, they are not fighting plants tonight. In the peat swamp Sebangau Forest, Central Kalimantan of Indonesian Borneo, a uni-male, multi-female group of langurs with several infants and juveniles has come to the area to forage. Two female langurs have found a delicious patch of mushrooms, and our male Maroon Langur has gorged on ripe fruit and is resting nearby. Red Brocket enters the arena, at first going completely unnoticed by the langur group. However, Red Brocket is a fan of fungi and takes a shortcut to mushrooms directly through the group of playing primates. A cacophony of alarm calls erupts as the young langurs rush towards their mothers. Maroon Langur rouses from his rest to lead the group a short distance away from Red Brocket before looking back. However, this &ldquoshort distance away&rdquo is officially off the field of battle. RED BROCKET rousts Maroon Langur!! Narrated by Prof Katie Hinde

Antler regeneration: cartilage and bone growth

In the first month after casting, antlers grow relatively slowly however, during the next 2 months longitudinal growth is very rapid and this rate of bone formation represents the fastest described in the mammalian kingdom (Goss, 1983). The longitudinal growth of the antler that occurs in the distal end of each branch (shown schematically in Fig. 7F and histologically in Fig. 9 ) was originally described as a process of modified endochondral ossification by Banks & Newbry (1983). These authors classified the antler tip as consisting of four zones, namely the zones of proliferation, maturation, hypertrophy and calcification, representing the spectrum of bone development.

Histology of the regenerating antler during rapid longitudinal growth. (A) Longitudinal tissue section of antler tip to show macroscopic appearance of regions: v, velvet skin p, perichondrium m, mesenchyme cp, chondroprogenitor region c, cartilage bo, bone po, periosteum. Scale bar = 0.5 cm. (B–J) Hɮ-stained undecalcified paraffin sections of the tissue regions shown in A. (B) Velvet skin. e, epidermis d, dermis h, hair follicle s, sebaceous gland. (C) Fibrous perichondrium. A blood vessel is marked by an arrowhead. (D) Mesenchymal ‘growth zone’. (E) Chondroprogenitor (cp) region. As in the early antler bud, cells start to become aligned in 𠆌olumns.’ However, the vascular spaces are relatively small (arrowhead). (F) Non-mineralized cartilage. Recently differentiated chondrocytes (ch) are arranged in trabeculae separated by larger vascular channels (v). (G) Mineralized cartilage region. Chondrocytes and the vascular channels (v) increase in size in this region. (H) Spongy bone in the mid shaft of the antler that has formed by endochondral ossification. Osteoblasts are marked with an arrowhead. (I) Fibrous (f) and cellular (c) layers of the antler periosteum. (J) Intramembranous bone formation (b) takes place beneath the cellular periosteum (c). Scale bar (B–J), 100 µm.

The mesencymal growth zone

Below the dermis of the velvet skin ( Fig. 9B ) is the perichondrium ( Fig. 9C ), which is continuous proximally with the periosteum that surrounds the shaft of the antler and is the site of intramembranous bone formation. There is an outer fibrous perichondrium where type I collagen mRNA and protein are highly expressed (Price & Faucheux, 2001) and an inner, more cellular zone ( Fig. 9D ). This region of the antler has been variously described by different authors (our group is also guilty of this), and the descriptors include ‘reserve mesenchyme’, ‘hyperplastic perichondrium’, �llular periosteum’ and ‘mesenchyme’. For consistency we now describe this as ‘mesenchyme’ or ‘mesenchymal growth zone’ because cells in this region, like cells in this region of the primary antler, are actively dividing (Matich et al. 2003 Faucheux et al. 2004). In culture these cells proliferate rapidly as monolayers and synthesize type I but not type II collagen (our unpublished observations), and this reflects their in vivo phenotype (Price et al. 1996). However, unlike mesenchymal cells from the developing limb, they cannot be cultured as micromasses they spread out to form monolayers and chondrogenesis is not initiated. Compared with cells in more proximal regions of the antler, cells in this region express only low levels of alkaline phosphatase and this reflects their undifferentiated state (Price et al. 1994 Price, 2005). However, although these cells will differentiate into chondrocytes in more proximal regions, they do express markers of the early osteoblast lineage (our unpublished observations) and in the presence of dexamethasone alkaline phosphatase expression will increase (Faucheux et al. 2001). This indicates that these cells are at least bi-potential, although we have preliminary evidence that they can also differentiate into adipocyte-like cells under the appropriate culture conditions.

In the mesenchymal growth zone there will be a tightly co-ordinated balance between cell growth, cell survival and differentiation into chondroprogenitors, with some signalling pathways inducing proliferation and others inducing differentiation. In recent years our group and others have made some progress in identifying the local factors that may play a role. Several years ago it was first shown that their proliferation in vitro is stimulated by IGF-I and IGF-II and IGF receptors are present in this region of the antler tip in vivo (Price et al. 1994 Sadighi et al. 1994). Furthermore, IGF-I and IGF-II were identified in a screen of antler extracts undertaken some years ago (Mundy et al. 2001). This is consistent with the hypothesis that IGF-I is likely to be the 𠆊ntler growth stimulus’. We have found that FGF-2 also stimulates proliferation of mesenchymal cells from regenerating antlers (Price, 2005), although we have not yet tried immunolocalizing it in regenerating antlers. Members of the FGF family and their receptors have also been identified in the primary antler. A proteome analysis of red deer antler has been recently undertaken but surprisingly neither FGFs, IGFs, IGF binding proteins nor IGF receptors were identified (Park et al. 2004).

The BMP and TGF-β signalling pathways appear to induce a more differentiated state in mesenchymal cells, as our preliminary studies have shown that BMP-2 and TGFβ-1 inhibit the proliferation of mesenchymal cells whereas they induce ALP activity (Price, 2005). BMP-2 and BMP-4 have both been cloned from antlers (Feng et al. 1995, 1997) and Barling and collagues have identified BMP-2, BMP-4 and BMP-14 and their receptors in the primary antler (Barling, 2004b). We have recently immunolocalized TGF-β in regenerating antlers and it appears to act upstream of PTHrP, which, together with the PTH/PTHrP receptor, are synthesized by the majority of mesenchymal cells (Faucheux et al. 2004). Interestingly, we have found that PTHrP has no effect on the proliferation of mesenchymal cells (Faucheux & Price, 1999) and may maintain the undifferentiated state, although the functional significance of its abundance in this region requires further study. We have previously presented several lines of evidence that RA also plays a role in controlling mesenchymal cell growth and differentiation: first, the RA-synthesising enzyme RALDH2 can be immunolocalized in mesenchymal cells, and second, retinol, all-trans-RA and 9-cis-RA were identified in mesenchyme by HLPC and in vitro all-trans-RA dose dependently increased ALP activity in cultures of mesenchymal cells (Allen et al. 2002). However, the effects of RA in this region are likely to be very complex, as reflected in the distinct patterns of expression of the RA receptors RARα, RXRβ, RXRβ and RXRγ.

Antler cartilage

With the naked eye it is possible to identify where chondrogenesis starts in a longitudinal antler section it is where the tissue becomes slightly darker in colour because of an increase in size of the vascular channels ( Fig. 9A ). It is also possible to distinguish that there is a distal region of non-mineralized cartilage whereas more proximally deposition of mineral takes place (Price et al. 1996). The vascularization of antler cartilage is the most striking difference between its anatomy and that of other hyaline cartilages. This abundant blood supply is required to meet the high metabolic demands imposed by rapid tissue regeneration. That the antler provides a valuable model for the study of angiogenesis was proposed recently by Clark et al. (2004), who have identified VEGF and the VEGF receptor in regenerating antler tissues.

Histologically, the boundary between mesenchyme and the zone of chondroprogenitors is not distinct in longitudinal sections, but is a region where cells start to become arranged into columns between which there are vascular spaces ( Fig. 9F ). Previously we have described this as a ‘zone of transition’ because cells at this site are at different stages of differentiation along the chondrocyte lineage (Price et al. 1996). Type IIA collagen mRNA identifies chondroprogenitors in the developing skeleton (Sandell et al. 1994) and this isoform is expressed in the distal antler cartilage whereas type IIB collagen mRNA and protein are expressed throughout the cartilage (Price et al. 1996). Type IIA collagen is not expressed in growth plate cartilage (Sandell et al. 1994), another reason why it is difficult to compare directly the process of endochondral ossification in a long bone with that in antlers. Neither is type I collagen found in the growth plate, whereas it is expressed by antler cells in the ‘transition zone’. Yet another difference between the matrix of antler and mammalian growth plate cartilage is the distribution of type X collagen in the growth plate it is expressed only in proximal hypertrophic chondrocytes (Sandell et al. 1994) whereas in the antler type X collagen can be localized in the majority of chondrocytes.

Non-mineralized cartilage ( Fig. 9F ) provides us with an abundant source of cells for in vitro studies, and culturing them as a micromass helps to maintain the chondrocyte phenotype (Allen et al. 2002 Price, 2005). This provides a useful model for in vitro studies of chondrogenesis however, as will be described below, we also use the model to study antler osteoclasts. To date we have focused on molecules that we have identified in antler cartilage in vivo. PTHrP can be immunolocalized in chondroprogenitors but not in fully differentiated chondrocytes (Faucheux et al. 2004), and in micromass cultures it inhibits differentiation, consistent with its role during limb development (Faucheux, 1999). Indian hedgehog (IHH) and TGFβ-1 are also expressed in antler chondroprogenitors, indicating that these molecules may act with PTHrP in a feedback loop to control differentiation. RA also controls chondrogenesis both all-trans-RA and 9-cis-RA are present in antler cartilage, and in vitro RA inhibits proteoglycan synthesis by chondrocytes, an effect that requires RAR signalling (Faucheux, 1999 Allen et al. 2002). However, RXRβ may mediate the effects of RA in vivo because it is expressed throughout cartilage trabeculae.

General features

The evolution of the class Mammalia has produced tremendous diversity in form and habit. Living kinds range in size from a bat weighing less than a gram and tiny shrews weighing but a few grams to the largest animal that has ever lived, the blue whale, which reaches a length of more than 30 metres (100 feet) and a weight of 180 metric tons (nearly 200 short [U.S.] tons). Every major habitat has been exploited by mammals that swim, fly, run, burrow, glide, or climb.

There are more than 5,500 species of living mammals, arranged in about 125 families and as many as 27–29 orders (familial and ordinal groupings sometimes vary among authorities). The rodents (order Rodentia) are the most numerous of existing mammals, in both number of species and number of individuals, and are one of the most diverse of living lineages. In contrast, the order Tubulidentata is represented by a single living species, the aardvark. The Uranotheria (elephants and their kin) and Perissodactyla (horses, rhinoceroses, and their kin) are examples of orders in which far greater diversity occurred in the late Paleogene and Neogene periods (about 30 million to about 3 million years ago) than today.

The greatest present-day diversity is seen in continental tropical regions, although members of the class Mammalia live on (or in seas adjacent to) all major landmasses. Mammals can also be found on many oceanic islands, which are principally, but by no means exclusively, inhabited by bats. Major regional faunas can be identified these resulted in large part from evolution in comparative isolation of stocks of early mammals that reached these areas. South America (the Neotropics), for example, was separated from North America (the Nearctic) from about 65 million to 2.5 million years ago. Mammalian groups that had reached South America before the break between the continents, or some that “island-hopped” after the break, evolved independently from relatives that remained in North America. Some of the latter became extinct as the result of competition with more advanced groups, whereas those in South America flourished, some radiating to the extent that they have successfully competed with invaders since the rejoining of the two continents. Australia provides a parallel case of early isolation and adaptive radiation of mammals (specifically the monotremes and marsupials), although it differs in that Australia was not later connected to any other landmass. The placental mammals that reached Australia (rodents and bats) evidently did so by island-hopping long after the adaptive radiation of the mammals isolated early on.

In contrast, North America and Eurasia (the Palearctic) are separate landmasses but have closely related faunas as the result of having been connected several times during the Pleistocene Epoch (2.6 million to 11,700 years ago) and earlier across the Bering Strait. Their faunas frequently are thought of as representing not two distinct units but one, related to such a degree that a single name, Holarctic, is applied to it.

Watch the video: A breeding to preserve the musk deer. SLICE (January 2023).