Herpetology: Study Materials on Amphibians and Reptiles

Panther Chameleon (Furcifer pardalis), endemic to Madagascar.
Image courtesy link

-by Aaron S. Johnson

Introduction:

Herpetology is the zoological study of amphibians (frogs, toads, salamanders, newts, caecilians [legless amphibians]) and reptiles (turtles/tortoises, snakes, lizards, amphisbaenians [non-snake, legless squamate clade], crocodilians, tuataras).  A herpetologist is an expert in amphibian and reptile behavior, diet, ecology, taxonomy, physiology, anatomy, evolution, health, conservation, and husbandry.

Amphibians have been around for over 370 million years (m.y.) and reptiles for 310-320 m.y.  Amphibians are the descendants of a fishlike ancestor, whereas reptiles descended from a common amphibianlike ancestor.  Together, reptiles and amphibians are collectively known as "herps" and are the common ancestors of birds and mammals.  

Herps may be ectotherms, but they are voracious eaters of everything humans consider as "pests" and carriers of disease, e.g. insects, arachnids, slugs, rodents.  Needless to say, world ecological systems would collapse without them.  With the decline of amphibians and reptiles due to herbicides, pesticides, pet trade, destruction of the environment, climate change, invasive species, and pathogenic microbes, the importance of these creatures have grown ever more apparent.  Accordingly, modern herpetologists should have expertise in microbiology, chemistry, climatology, conservation, and even business administration, communications, and sociology in order to professionally problem solve as difficult issues arise. 

Sponges Could Have Lived in Oceans Before the Origin of Animals

- by Aaron S. Johnson

Just how much oxygen did animals inhabiting the oceans 635-542 million years ago (mya) need to live?  Lower than one may expect.  Present atmospheric levels could drop as low as 0.5% to 4% and animals, such as the modern day breadcrumb sponge (Halichondria panicea), would have been quite alright, according to researcher Daniel Mills, PhD at the Nordic Center for Earth Evolution at the University of Southern Denmark (1, 2, 3).  His laboratory research has demonstrated that the breadcrumb sponge can survive under these conditions, and therefore, would have been capable of living in the low-oxygenated waters that predated animal life (1). 

The question then becomes, why didn’t animal life evolve sooner?  Generally, the accepted hypothesis is that animal lifestyles couldn’t be supported until ocean oxygen levels dramatically increased.  That increase occurred 635-542 mya, and the first evidence of the animal fossil record lends support to the hypothesis (1). 

Nevertheless, Mills proposes that the complexity of an animal’s biological machinery was purely difficult to develop, and so even if the required minimum oxygen level were available, animal evolution took time to keep pace (3).  Therefore, if surplus oxygen wasn’t wholly the evolutionary catalyst, other mechanisms, such as other ecological and developmental processes, may have promoted the origin of the most primitive animal life (1).  That’s still to be determined.