Posts tagged Herpetology

Rainbow Snake - Farancia erytrogramma

The rainbow snake is a large North American colubrid that lives along the Southeastern coastline of the US. A subspecies that lived in Lake Okeechobee was declared extinct in 2011, but the common rainbow snake (Farancia erytrogramma erytrogramma) is non-threatened at this time.

These guys are non-venomous, highly glossy, and also known as “eel moccasins”, for their habit of eating “conger eel” salamanders. Despite their bright, shiny colors, and their length of over 4 feet long, these snakes are extremely difficult to spot in the wild. They stay under swampy underbrush, are largely aquatic, and hunt their prey at night. Without specific traps or highly skilled herpetologists, the chances of seeing one in the wild are extremely slim, but many herp farms and experienced snake owners like having them around for their aesthetic appeal.

Internal anatomy of the snake

"Arms and legs gone, no ears, only one functional lung, voiceless, eyelids missing…a human being under these conditions would be institutionalized and under constant care…" James A. Peters, Encyclopedia Britannica 15th edition

The internal anatomy of snakes shows their obvious relation to other vertebrates; their organs, tissues, and germ cell layers are all very similar to those of other scaled reptiles (order Squamata), and even to other vertebral species (subphylum Vertebrata).

However, their differences from other vertebrates are even more distinct than their similarities. The body of a snake is long and elongated, like a tube, and certain adaptations have been made along the evolutionary chain in order to fit their organs into this form.

Other adaptations have also been developed in the evolutionary history of the suborder Serpentes, with the result of this highly specialized carnivore. Here are a few of those adaptations:

Lungs: All snakes are essentially one-lunged. Their left lung is usually vestigial, sometimes completely absent, and their right lung is enlarged and elongated, and has much less cartilage in it than other vertebrates. In aquatic snakes, the left lung’s anterior portion still functions, albeit not for gas exchange. It works as buoyancy organ during swimming.

Jaws: The lower jaw of snakes is loosely attached, with ligaments connecting the anterior left and right halves of the mandible. The left and right halves are generally also connected with a relatively loose ligament, allowing separation and movement of both halves. When the snake ingests a large meal, the jaw easily pops out of its hinge, to allow food to enter the esophagus. After swallowing its prey, the snake will “yawn” widely, and snap its mandible back into place.

Spine: Snakes generally have between 200 and 400 vertebrae. The “tail” vertebrae usually make up less than 20% of the total, and are the only vertebrae without ribs attached. The ribs and vertebral column of the snake provide solid anchoring points for the strong muscles required for limbless locomotion, and are necessary much farther down the torso than in other vertebrates.

Skin: It’s not slimy, for one! Despite some snakes looking like they have a sheen to their scales, no snakes secrete “slime” or mucous to coat their skin. Only amphibians and worm-type creatures do that. Snake skin is incredibly flexible, to accommodate the large meals that are consumed, and is comprised of scales, which are a protective extension of the epidermis. Scales also allow snakes to grip the ground or trees they’re climbing. Snake eyes are covered in clear scales, allowing them to be protected without eyelids.

Ears: Obviously, snakes have no external ears. However, they still have inner ears. When soundwaves hit their skin, the vibration is transferred through the muscle and bone, and into the inner ear, where it’s processed. Though the ability to sense directional vibration in snakes is generally highly developed, the sense of “hearing” as humans know it is relatively poor.

Sight: This is one trait that varies widely between snake species. Some are nearly blind, sensing only light and dark, while some can spot prey from far away. No snakes can see in color, but some snakes (the pythons, pit vipers, and some boas) can see infrared images - that is, they can sense the heat radiating from warm-blooded animals, allowing them to hunt prey at night.

Tongues: Snakes do not have a sense of taste, in the way that humans think of “taste”. Instead, their tongues “test” the air for certain compounds, bringing the air particles back into their mouth, into their vomeronasal (Jacobson’s) organ, which can tell if there are predators or prey in the area. Some snakes that live in aquatic environments, such as sea kraits and boas, can also use this sense underwater.

All images: Brehms Tierleben, Allgemeine Kunde des Tierreichs. Dr. Otto zur Strassen, 1913.

Snake info from: Snakes: In Question. Carl H. Ernst, George R. Zug, 1996.

Chelys  fimbriata [now Chelus fimbriatus] - Mata mata
Some people say the Mata mata turtle looks like it’s smiling, because of its unusually-shaped mouth. The Indigenous South American nickname for the turtle, “matamata”, means “I kill”, according to Fritz Jurgen Obst. Whether that eponym meant that the turtle was good to kill and eat or the turtle killed a lot is unknown. The relatively large size and a meat quality similar to the Alligator Snapping Turtle makes the former meaning more probable.
In the wild, Chelus fimbriatus lives in stagnant waters, blackpools, and muddy streams around the Amazon rainforest. Its fringed neck and murky coloration, combined with algae that grows on its carapace, makes this turtle an excellent ambush hunter. When fish come near it, the mouth opens up, and the mata mata “vacuums” them in. This is in contrast to Alligator Snapping Turtles, which are similar ambush predators, but with a different strategy. The tongue of the snapping turtle acts as a lure, and unsuspecting fish swim right into its mouth.
Transactions of the Zoological Society of London, 1885.

Chelys fimbriata [now Chelus fimbriatus] - Mata mata

Some people say the Mata mata turtle looks like it’s smiling, because of its unusually-shaped mouth. The Indigenous South American nickname for the turtle, “matamata”, means “I kill”, according to Fritz Jurgen Obst. Whether that eponym meant that the turtle was good to kill and eat or the turtle killed a lot is unknown. The relatively large size and a meat quality similar to the Alligator Snapping Turtle makes the former meaning more probable.

In the wild, Chelus fimbriatus lives in stagnant waters, blackpools, and muddy streams around the Amazon rainforest. Its fringed neck and murky coloration, combined with algae that grows on its carapace, makes this turtle an excellent ambush hunter. When fish come near it, the mouth opens up, and the mata mata “vacuums” them in. This is in contrast to Alligator Snapping Turtles, which are similar ambush predators, but with a different strategy. The tongue of the snapping turtle acts as a lure, and unsuspecting fish swim right into its mouth.

Transactions of the Zoological Society of London, 1885.

Hey! You spending tonight at home/recovering from a wild party/lollygagging about all day? Here’s something to take a few minutes of your time!

The new layout isn’t up yet, but I have quite a few images on my Flickr photostream already - both natural history and medical.

Check out the Erpétologie générale album. I can never seem to find enough uses for the illustrations over on the blog, but they are fantastic. Frogs and gators and turtles and lizards!

The German orthopedics and the herpetology books aren’t annotated yet, but the references for everything are already loaded.

Effects of the Crotalus adamanteus venom on mesentery of rabbit (top), and pectoralis of pigeon (bottom).
Many venomous snakes have hemotoxic venom, or a hemotoxic component within their venom. These toxins are able to break down red blood cells, disrupt clotting, and cause hemorrhaging due to the blood being thin enough to slip through capillary and tissue walls. Unlike a neurotoxic venom, which kills by paralyzing the diaphragm and suffocating the victim or prey, hemotoxic venom does not kill quickly. The internal bleeding and hemorrhaging of organs and major vessels is extremely painful.
When snakes kill with hemotoxins, they tend to follow their prey until it collapses, before attempting to eat it. However, the majority of the time, it turns out that the prey isn’t dead yet. It’s simply in shock and unable to continue - it would end up dying soon enough, but if the snake isn’t too far behind it, the prey does get eaten alive. 

Snake Venoms: An Investigation of Venomous Snakes, with Special Reference to the Phenomena of Their Venoms. By Hideyo Noguchi M. D., 1909.

Effects of the Crotalus adamanteus venom on mesentery of rabbit (top), and pectoralis of pigeon (bottom).

Many venomous snakes have hemotoxic venom, or a hemotoxic component within their venom. These toxins are able to break down red blood cells, disrupt clotting, and cause hemorrhaging due to the blood being thin enough to slip through capillary and tissue walls. Unlike a neurotoxic venom, which kills by paralyzing the diaphragm and suffocating the victim or prey, hemotoxic venom does not kill quickly. The internal bleeding and hemorrhaging of organs and major vessels is extremely painful.

When snakes kill with hemotoxins, they tend to follow their prey until it collapses, before attempting to eat it. However, the majority of the time, it turns out that the prey isn’t dead yet. It’s simply in shock and unable to continue - it would end up dying soon enough, but if the snake isn’t too far behind it, the prey does get eaten alive. 

Snake Venoms: An Investigation of Venomous Snakes, with Special Reference to the Phenomena of Their Venoms. By Hideyo Noguchi M. D., 1909.

This book has exactly two plates with the nomenclature we use today. :[ And it’s not one that’s been matched to modern nomenclature on binomial indices, yet. 
Oh well. This is an iguana.
Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

This book has exactly two plates with the nomenclature we use today. :[ And it’s not one that’s been matched to modern nomenclature on binomial indices, yet. 

Oh well. This is an iguana.

Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

Gecko feet are incredible. They can hang onto anything, thanks to little rubbery hairs that will suction their bodies to almost every surface.
Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

Gecko feet are incredible. They can hang onto anything, thanks to little rubbery hairs that will suction their bodies to almost every surface.

Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

It’s a natural history kind of day. A reptilian one at that. 
Shell and skull of loggerhead turtle.
Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

It’s a natural history kind of day. A reptilian one at that. 

Shell and skull of loggerhead turtle.

Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

Snake skeleton.
Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

Snake skeleton.

Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

Skull bones, teeth, and fangs of two venomous snake species.
Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.

Skull bones, teeth, and fangs of two venomous snake species.

Erpétologie générale, ou, Histoire naturelle complète des reptiles. A. Duméril, 1834.