Dec 05 , 2019
It is estimated that there are more than 8,000 reptiles and 6,000 amphibians inhabiting the Earth. They are as small as a dwarf gecko and as large as a Chinese Giant Salamander or saltwater crocodile. With such diversity, it is easy to see why reptiles and amphibians are such major players in the pet industry. Those keeping reptiles or amphibians as pets are affectionately called “herpers.” The name is derived from herpetology which is a branch of zoology that studies reptiles and amphibians. Herpetology includes turtles, snakes, lizards, tortoises, amphisbaenids, crocodiles, toads, frogs, caecilians, newts, and salamanders. The name “reptile” refers to creeping or crawling animals. The name “amphibian” refers to dual modes of existence—for example, frogs look like fish in their early life and then grow legs as they become adults. At one time, reptiles and amphibians were zoologically classified as reptiles due to their many similarities. It is speculated that reptiles transitioned from amphibians some 50 million years ago, which perhaps explains why there are so many commonly shared characteristics.
Identifying Similarities between Reptiles and Amphibians:
- Ectothermic – Both are ectothermic (cold-blooded) meaning their internal sources of heat are so insignificant that they must rely upon external sources to regulate their body temperature. Body heat regulation is primarily required for operation of their metabolic processes.
- Chordata (animals that possess a spinal column) – Both reptiles and amphibians are vertebrates possessing a central vertebral column.
- Skin color alteration – Skin color alteration by concentrating or dissipating melanin is possible in many amphibians and reptiles. Altering their skin coloration aids in camouflage and can help thermoregulation of body temperature.
- Keen eyesight – Many lizards (reptiles) and frogs (amphibians) have sharp eyesight which is crucial for their precise capture of prey by flicking their tongues.
- Defensive traits – Both reptiles and amphibians use camouflage, biting and inflating of the body to avoid predation. Lizards (reptiles) and salamanders (amphibians) both have the ability to autotomize which is a voluntary removal of the tail as a defensive response. One common defense is mimicry where animals that have no innate defensive protection mimic the bright colors of dangerous animals. For example, a harmless king snake might appear as a venomous coral snake.
Identifying Differences between Reptiles and Amphibians:
- Respiration – All breathing is via lungs; however, aquatic turtles have the ability to do a limited gas exchange underwater primarily during extended periods of cold temperature or inactivity. The condition is called brumation.
- Feeding – Snakes are able to disjoin their upper and lower jaw to accommodate swallowing large prey whole.
- Neck vertebra – Multiple vertebra in the neck, allowing articulation.
- Skin – Dry, scaly, watertight skin. Exposed parts are covered by bony scutes.
- Reproduction – Leathery, soft or hard eggs laid on land or maintained inside the body until hatching. The reptile egg is self-contained and protects the embryo from dehydration.
- Metamorphosis (profound change in form) – Reptiles have no larval stages.
- Longevity – Some tortoises have reportedly lived more than 180 years. The popular smooth green snake (Opheodrys vernalis) are reportedly living up to 15 years in captivity.
- Defense – Three layers of protection are normally used by reptiles.
- Avoidance – This is where the reptile evades danger through playing dead or retreats into a protective shell.
- Warning – This is when the reptile alerts potential predators by releasing a foul small; or they hiss and shake their tail tip like the rattlesnake. Several species of the horned lizard (Phrynosoma) are able to squirt foul tasting blood from their eyes to ward off predators—the dispensing of blood is called ocular autohemorrhaging. When warnings fail, some reptiles attack. Reptiles such as the alligator, snapping turtle, and venomous snakes use strong jaws, claws, venom, and/or whip their enormously powerful tails to subdue attackers or prey.
- Additional sensory organs – Some reptiles possess an additional sense called a vomeronasal organ (also called Jacobson’s organ). This organ is located on the roof of the mouth. It captures chemical molecules for the purposes of locating mates, predators, and prey. It is speculated that some amphibians may also have similar, but convoluted capability. Some snakes have thermoreceptors (sensing heat) located on their face which allows them to find prey in total darkness.
- Respiration – Breathing via gills, lungs or through the skin which is called cutaneous respiration. Their vascularized skin must be moist for this to work. The Lungless salamander (Plethodontidae) conducts respiration through cutaneous means tissues within its mouth.
- Feeding – Amphibians attempt to swallow their food whole but some have exclusive teeth called pedicellate teeth.
- Neck vertebra – Single vertebra in the neck which limits head articulation.
- Skin – Moist, smooth, or rough skin sometimes with sticky mucous glands that secret waterproof coating to keep skin moist. Oxygen and CO2 can be exchanged through their skin.
- Reproduction – Soft eggs normally laid in water or in damp media. The amphibian eggs is a yolk sac enveloped in one or more layers of a clear, jelly-like covering. The egg capsule is permeable to water and gases.
- Metamorphosis (profound change in form) – Most amphibians use gills while developing their lungs. Some salamanders such as the mudpuppy retain their gills throughout their lives which is called neoteny.
- Longevity – The Japanese Giant Salamander lacks natural predators and is speculated to live about 80 years. The American Bullfrog lives about 8 years.
- Defense – AVOIDANCE – Nocturnal activity and aposematic coloration by many amphibians helps avoid predation. WARNING – Slippery skin make it difficult for a predator to grasp. When grabbed, the amphibian secrets a vile tasting, sometimes toxic substance through the skin, in hopes that it leads to immediate rejection by the predator. Tetradotoxin, which is produced and released through the skin by newts, is deadly to reptiles, fish, birds, and mammals ingesting the substance.
- Additional sensory organs – Some amphibians using their lateral line (like a tadpole) may sense water pressure changes to locate prey.