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Ways to Die: Snake Venom
The vast majority of snakes that one encounters in the wild (unless you live in Australia or India) are either non-venomous to humans or want nothing to do with you.
However, should you stumble upon a rattlesnake nest or coral snake hole while texting in the middle of nowhere, there will probably be a combination of different enzymes and polypeptides pumped into your body, via the modified parotid salivary glands (right below the ear in humans) that snakes have evolved over the ages, to disable their prey. Of course, you’re not prey, but you stepped on a snake while texting. It has every reason to envenomate you.
While all snakes have multiple active enzymes in their venom, all snakes dangerous to humans have either neurotoxins or cytotoxins as a significant component in their venom. For the most part, elapids (such as the cobras and mambas) create neurotoxins, while the viperids (such as vipers, adders, and rattlesnakes) create cytotoxins.
Neurotoxins
- Dendrotoxins: Inhibit neurotransmission by blocking the exchange of positive and negative ions across the pre-synaptic neuronal membrane, causing paralysis. Found in some rattlesnakes (such as the Mojave) and mambas.
- Fasciculins: Destroys acetylcholinesterase (AChE) in synaptic clefts of nerves. Without AChE, acetylcholine (ACh) is not broken down, and remains bound to the postsynaptic vesicles of the nerve, leading to constant contraction of the related muscles. This is called tetany or tetanic paralysis. Found only in mambas.
- α-neurotoxins: Very large group of toxins that mimic ACh and bind to post-synaptic vesicles, leading to numbness and paralysis. Found in cobras, kraits, and sea snakes.
Cytotoxins
- Cardiotoxins: Target muscle cells and cause depolarization. If enough of these components reach the heart, the depolarization can cause irregular heartbeat or spontaneous stopping of the heart. Can cause fasciculations in skeletal muscles. Found in the Naja genus, and in King Cobras. Minor but important component of mamba venom.
- Phospholipases: Proteins that target the phospholipid bilayer of cells, causing cellular rupture. Can cause extreme blistering at site of bite. Relatively uncommon, found in the Japanese Habu.
- Hemotoxins: Burst red blood cells (hemolysis), causing thin blood, internal bleeding, and blood clots due to the massive clotting response. Found to some degree in almost all vipers, as well as some cobras.
Images:
Top: Bungaris fasciatus - Banded Krait. An elapid, and the largest of the kraits. Has neurotoxic venom. [source]
Center Right: Hydrophis robusta [now Hydrophis spiralis] - Yellow Sea-Snake. The longest sea snake, at 3 m (9.8 ft). A member of the Hydrophiinae, separate from other elapids. Though they have some of the most toxic venom in the world, bites are extremely uncommon and often unnoticed. [source]
Center Left: Vipera russellii - Russell’s Viper. A particularly aggressive viperid. Necrosis and amputation following envenomation not uncommon, due to hemolysis and local cell damage. [source]
Bottom: Vipera caudisona [now Crotalus horridus] - Timber Rattlesnake. A venomous viperid endemic to the United States. Primarily hemotoxic venom, very low fatality rate, but very painful bites. [source] -
HERE HAVE SOME THEROPOD PELVES for the purposes of comparison.
Dinosaurs, what is even going on with your hips.
(A is Deinonychus, B is Segnosaurus, and C is Tyrannosaurus, for the curious. These may not be entirely proportional, because they are illustrative of general pelvic morphology trends and this paper is due tomorrow so they are MEGA QUICK).
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Thornback ray (Raja clavata) and thornback ray skeleton
Like sharks, rays and skates have fully cartilaginous skeletons, which provide a stable structure but more flexibility than bone. You can see that, much like fish, rays have defined, er, rays, in their fins. The difference is that while fish tend to have a few unconnected rays and a taught tissue between them, the Rajiforms (skates and rays) have many, many rays, which are all connected perpendicularly by collagen. The body is then formed around these rays, which propel the Rajiforms forward in an undulating (wave-like) motion.
A history of the fishes of the British Islands. Jonathan Couch, 1863.
(via mudwerks)
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Nine-Banded Armadillo (Dasypus novemcinctus)
Did you know that the nine-banded armadillo (and a few of its Dasypus cousins) gives birth to identical quadruplets in almost every litter? Shortly after the zygote implants in the uterus, it splits into four (or occasionally three or five) separate embryos, each of which develop their own independent placenta. This means that, unlike in identical human fetuses, blood and nutrients are not shared, and the death of one fetus is unlikely to affect the survival of the others. After the pups are born, they remain in the burrow for approximately three months, and over the next year of their life, slowly wander farther and farther away from their place of birth.
As nine-banded armadillos have few natural predators in their Northern range, this highly effective reproduction strategy means that one female will often produce upwards of 50+ offspring in her relatively short lifetime. Those offspring have been expanding the armadillo’s known range for the past several decades. However, as armadillos are poor at thermoregulation, they’ve just about reached the limit of the area that they can survive in - any farther north, and they would not be able to survive the longer winters.
Images:
Top: Tatusia novem cincta [now Dasypus novemcinctus] - The Nine-Banded Armadillo. From Biologia Centrali-Americana. F. Ducane Godman and Osbert Salvin, 1918.
Bottom: Fetal Nine-banded Armadillo Pups. The American Journal of Anatomy. Vol. III, 1900-1901. “Enamel in the teeth of an edantate.” A. M. Spurgin. -
Limbs of the Cephalopoda
Whether squids, octopuses, and nautilus have “arms” or “tentacles” is often simply a matter of semantics, but the most accepted definitions (from what I’ve found) tend to define the “arm” as a tapered limb, with two rows of suckers along its entire length. “Tentacle” is typically a length of tapered limb with no suckers, leading to a distal club-like appendage, covered in suckers.
One exception would be limbs in the nautilus - they have up to 90 un-suckered limbs, but their limbs are called “tentacles” by those who study them, even without the terminal club.Images:
Top right: Octopus vulgaris and detail of beak and arms
Top left: Detail of tenticular clubs in squid, from the Expedition of the Valdivia
Bottom right: Arm of Illex illecebrosis (Northern Shortfin Squid)
Bottom left: Tentacle of Illex illecebrosis -
Faces of Lorises
1. Nycticebus tardigradus malayanus (Nycticebus coucang spp.- Sunda slow loris. Note: possibly Nycticebus javanicus - the Javan slow loris)
2. Nycticebus tardigradus hilleri (Nycticebus coucang coucang - the Sunda slow loris, type species)
3. Loris gracilis typicus (Loris lydekkerianus lydekkerianus - Gray slender loris)
4. Loris gracilis zeylanicus (Loris tardigradus - Red slender loris)All lorises are endangered or vulnerable due to the pet trade and their use in traditional “medicine”. While these small and nocturnal critters tend to be much more adaptable when humans encroach upon their habitat than other species of primate (making due in the trees humans transplant as opposed to their native foliage, and dealing with the human presence in stride, for example), they’re still all too often thought to “cure” various ailments with their body parts (especially the slow lorises), and traded as pets throughout their native habitat of Southeast Asia, and when they’re successfully smuggled to the rest of the world.
Seriously, people. Their cuteness is so much cuter in the wild. Lorises are freaking adorable, and the hunting strategies of the various species and subspecies are so varied and fascinating that they deserve to stay in a protected natural habitat. I mean, among other reasons to preserve them, obviously…they’re just such cool little omnivores!
Proceedings of the Zoological Society of London, 1904.
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Strix decussata and skulls from other raptors by BioDivLibrary on Flickr.
[Die vergleichende Osteologie /.
Bonn :In Commission bei Eduard Weber,1821-1838..
biodiversitylibrary.org/page/40170760 -
Northern Wolverine - Gulo borealis (now recognized as a sub-population of Gulo gulo luscus)
Check out the huge paws and the distance from the ribcage to the edge of the body - the thick, oily fur, and the fat padding keep the wolverine resistant to frost, and the big paws allow it to “snowshoe” across the winter tundra. Well, that, and they help them take down prey as large as mule deer and moose calves.
Wolverines are the largest (or at least most powerful) carnivores active throughout the year in most holarctic regions of the world.
Vergleichende Osteologie von Christian H. Pander und Eduard d’Alton, 1821-1831.
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Skull of juvenile Bornean orangutan (top) compared to adult Homo sapiens
Like most great apes, Bornean orangutans (Pongo pygmaeus) have large, sharp, canine teeth. However, these do not grow in until the juvenile orangutan loses its milk teeth, a couple years after weaning (typically between 4-6 years of age).
You can see the evolutionary differences in diet between orangutans and humans, simply by looking at the teeth and shape of the skull. The orangutan has large, broad molars, sharp incisors, and mandibular musculature that has a very broad attachment point on the skull. Bornean orangutans are generally vegetarian, feeding on leaves, berries, and even bark at times. The broad molars are necessary for grinding and breaking down roughage in their diet.
While the human skull given is not the best example, we have smaller molars, weaker mandibular muscles, and fairly dull incisors and canines. Homo sapiens evolved as strict omnivores, but with a very distinct difference from our more simian (and even most of our hominid) ancestors - we cooked our food. Though the roughage early humanity consumed was much tougher than what we eat today (unless you eat roots and nutmeats as a primary diet), cooking foods such as meats and roots broke them down before we ate them. Our skulls required less space for jaws and jaw muscles, and we required less energy to eat than ever before.
Die Säugthiere in Abbildungen nach der Natur. J.C.D. Schreber, 1774.
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Lynx canadensis - Canada Lynx
Check out those paws! They’re big and fur-covered, providing a snowshoe-like surface for the lynx to to traipse across the winter snow of Canada. These felids are closely-related to Eurasian Lynx (Lynx lynx) and bobcat (Lynx rufus).
The Newfoundland Lynx (Lynx canadensis subsolanus) subspecies is larger than the mainland species, and has been known to take down caribou calves when snowshoe hares are not around. They’re some of the largest cats that aren’t considered “big cats”.
Quadrupeds of North America. John James Audubon, 1849.
