Herpetology

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Herpetology
Life Science & Study Event
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Herpetology is an event for the 2018 season in Division B and Division C that deals with the identification and life science of different specimens of amphibians and reptiles.

This article mainly deals with the general concepts of this event. Specific identification info can be found on Herpetology/Identification List.

The official taxonomy list used for this event for the 2018 season can be found here.

Introduction to Herpetology

Amphibians VS Reptiles

While most amphibians are tied to water throughout their lives, reptiles of many species generally entirely terrestrial. The adaptational differences of each represent this difference.

Amphibian Reptile
Eggs Moist and spongy exterior Tough and leathery outer shell
Skin Moist glandular skin Keratinized, rough skin/scales
Reproduction External generally Internal generally
Origin Lobe-finned fishes Amphibians
Feet Often webbed, without claws Clawed, less often webbed
Respiration Lungs, skin, and/or gills Lungs, skin in rare cases.

Internal Anatomy

Circulatory System: consists of two loops.

  • Pulmonary loop - from heart to lungs and back
  • Systemic loop - from heart to body tissues and back

Hearts in all herps other than crocodiles consists of two atria and one ventricle somewhat divided by a septum. Contraction of heart keeps oxygenated and deoxygenated blood separate even though ventricle isn't completely divided. n crocodiles, two atria and ventricles exist.

There are two main ways in which adult amphibians respire:

  • Pulmonary respiration - breathing through lung by positive-pressure breathing
  • Cutaneous respiration - respiration through the skin

Nervous System: brain is similarly sized (relatively) in amphibians and reptiles.

In reptiles, the cerebrum (used for controlling behavior) is larger than amphibians. Optic lobes are also large, due to the fact that many reptiles rely on sight for hunting. Some reptiles and amphibians have nictitating membrane which is a transparent,movable membrane that covers the eyes allowing them to see with their 'eyelids' closed.

Hearing is also important. Sound waves heat the tympanum and then are transferred to the inner ear through the columella. Snakes lack a tympanum and are effectively deaf. They are however able to sense vibrations caused by sound through a touch. They detect these ground vibrations which are transferred to columella by the bones of jaw.

The Jacobson's organ is an extra sense organ in the roof of the mouth of reptiles. This organ is used to detect scents in the air. Reptiles use their forked tongue to gather chemicals from the environment and transfer it to the back of their mouth. These scent chemicals are then analyzed by the brain to find prey by using the two segments of the forked tongue independently gathering scent, and determining in the brain the direction of the scent through the sensitivity on each fork. While reptiles can smell with their nostrils, the jacobson organ is vastly more sensitive and important.

Another 'sixth' sense is present in pit vipers. A heat-sensitive pit beneath eyes allows the snake to detect heat. This allows them to locate warm blooded prey instantly in any light.

Reproduction

Fertilization - the joining of egg and sperm

  • Internal Fertilization - fertilized within female's reproductive tract
  • External Fertilizaqion - fertilized outside body

Reptilian Patterns of Reproduction - division of reproduction methods by how long eggs stay within female and in how eggs are provided with nutrition

  • Oviparity - female's tract encloses egg in tough shell which is then deposited
  • Ovovivoparity - eggs retained in female's body before being either laid shortly before hatching or hatching within body
  • Viviparity - shell is not formed around egg and young mature in female's body; nutrients often delivered by placenta

Behavior

Many behavioral aspects of reptiles and amphibians are due to their thermoregulation strategies. Each of these species are ectotherms (cold-blooded and gaining heat from environment rather than metabolism). This energy saving strategy leads to several behavioral adaptations.

  • Activity - Many ectotherms have optimum temperatures of function (due to the optimum temperatures of enzymes), this results in many organisms in cooler habitats being most active in midday and many organisms in desert habitats to be more nocturnal. The other pros and cons of diurnal/nocturnal are listed below.

Other reasons to be diurnal include easier sight and communication as well as more common prey in some habitats. Reasons to be nocturnal include less competition for food and fewer predators in some habitats.

  • Aestivation - During cold or dry seasons, some organisms 'hibernate' in order to retain energy.

Other aspects of behavior good for review are mating rituals, how they interact with other organisms (aggressive or passive), and how they obtain food.

Conservation

Populations of various reptiles have diminished for several reasons. First of all is their (or their eggs) use as food in many cultures. (Snapping Turtle soup is actually quite tasty.) "Rattlesnake roundups" have occured in some states as recreational activities. Snakes are gathered to be killed by visitors who do so in belief that killing snakes protect public. Every year in Sweetwater, Texas, about 1% of the entire rattlesnake population of Texas is slaughtered. Some attendees claim that this is justified due to the fact that they collect venom, however the venom is useless for most any research as it is not collected in a sterile environment. Some are also gathered for use as folk medicine. Snake venom has use in medical research. Habitat destruction is also hurting various populations.

Amphibian populations have been mysteriously declining for several years. There are several proposed reasons for this decrease. Some believe thinning of the ozone layer increases the amount of UV B radiation that reaches sensitive eggs, embryos, and larvae causing them to die. Herbicides, pesticides, and fertilizers also have killed amphibians when interfering with their natural hormones. Habitat destruction and disease have also lead to a large amount of decrease in population.

One of the largest threats to anurans (frogs and toads) is a lethal fungal infection that has been expanding in prevalence and range in recent year. This disease, known as chrytridiomycosis, is caused by the chrytid fungus Batrachochytrium dendrobatidis. The disease is thought to increase in range with global warming. This disease is responsible for large numbers of frog death, and are among the leading causes of the extinction of several frog species, and possible more to come.

Helpful Hints

1) If they allow a field guide, make your own, and know where everything in it is.

2) Be able to identify quickly, you should be able to do most if not all identification without resources.

3) Do not rely on your field guide, memorize as much as you can.

4) Make flashcards or online quizzes to study.

5) Put post-it flags in your field guide to get to major sections easily.

6) Print out diagrams and helpful pictures if needed, and put them into your field guide.

7) Know where everything is in your field guide, as this will be much quicker than jumping to the index and searching for the page.

8) Some field guides will only have the Western specimens and some will only have the Northeastern. Be sure that you know both Western and Northeastern specimens, along with Central.

Reference

  • National Audubon Society Field Guide to Reptiles and Amphibians: North America
  • Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America, Fourth Edition; Peterson Field Guide to Western Reptiles and Amphibians

Day of the Event

First of all, do not panic. Panicking will only make you go slower and cause unnecessary mistakes. Make sure that both you and your partner are calm and relaxed, confident, and ready to blow away your competition. Bring two pencils and pens, just in case. Make sure you don't speak loudly, talk in hushed tones or whispers. Write neatly and legibly. Be 100% sure that the station you're on is the station you are writing answers for on your answer sheet. Do not spend more than half of the time trying to identify the specimen, go on to the questions and try to figure them out logically.

Sample Questions

Iguana.PNG

1. Identify the family and genus of this lizard

2. What kind of teeth does this species of lizards have?

3. Are these lizards principally herbivores or carnivores?

Whiptail.PNG

1. Identify the family and genus of this lizard

2. What is unique about the way certain species of this lizard produce?

3. What do these lizards eat?

Links

Biological ID Events
Herpetology · Ornithology · Forestry · Entomology · Invasive Species