Amphibians.pdf

Vertebrate diversity Dr Nokubonga Mgqatsa [email protected]  Homework In your own words, write a short summary (not more than a page) of what you have learnt in class this week and submit this on RUConnected (Student notes).  Phylum: Chordata Sub-phylum: Verteb...

Vertebrate diversity Dr Nokubonga Mgqatsa [email protected]  Homework In your own words, write a short summary (not more than a page) of what you have learnt in class this week and submit this on RUConnected (Student notes).  Phylum: Chordata Sub-phylum: Vertebrata Class: Amphibia Order: Anura Family: Pipidae Genus: Xenopus Species: X. laevis Amphibians, reptiles, birds and mammals The early tetrapods and modern amphibians Origin of Tetrapods  Why come ashore? Avoiding predators Possibility of feeding on terrestrial animals (arthropods) Challenges Oxygen content Fluid density Temperature regulation Challenges animals encountered when moving from water to land Oxygen – more abundant in air, and it diffuses much more rapidly through air than through water. Fluid density – there is relatively little support for animals against gravity, life on land requires animals to have strong limbs. Temperature regulation – temperature on land changes faster than it does in water, as such, there can be harsh and unpredictable cycles of freezing, thawing, drying, and flooding in terrestrial environments.  Modern amphibians There are three major groups of amphibians alive today and these include frogs (Anura or Salientia), salamanders (Caudata or Urodela), and caecialians (Apoda or Gymnophiona). More than 7600 species; ~90% are frogs and toads. Most amphibians lay their eggs in water, and they hatch to produce an aquatic larval form that uses gills for respiratory gas exchange. Aquatic larvae lose their gills through a process called metamorphosis. Eleutherodactylus jasperi, from Puerto Rico  Modern amphibians The skin of amphibians is thin, and it requires moisture for protection against desiccation in air. Amphibians are ectotherms and their body temperature matches environmental temperature. Very moist and relatively cool environments. Amphibian species richness: Worldwide  Caecilians: Order Gymnophiona (Apoda) ~ 200 species They have a long, slender body, many vertebrae, long ribs, and no limbs; some have small dermal scales in the skin. Eyes are small, and most species are totally blind as adults. They feed mostly on earthworms and small insects. Pink-head caecilian (Herpele multiplicata)  Salamanders: Order Urodela (Caudata) ~ 700 species Body with head, trunk and tail; no scales In most salamanders, limbs are set at right angles to the trunk, and have fore-and-hindlimbs of approximately equal size. Some aquatic and burrowing forms have rudimentary limbs or no limbs at all. Salamanders are carnivorous, they feed mainly on worms, small arthropods, and small molluscs.  Frogs and toads: Order Anura (Salientia) ~ 6700 species Green tree frog, Hyla cinerea Head and trunk fused together; no tail and no scales American toad, Bufo americanus True toads (family Bufonidae) – short legs, stout bodies, and thick skins usually with prominent warts (while frogs usually have moist slimy skin) The largest anuran Goliath frog, Conraua goliath  The smallest frogs Brazilian gold frog, Psyllophryne didactyla Monte Iberia frog, Eleutherodactylus iberia Reference Chapter 17