Question

Salamanders can use gills, skin, lungs or some combination of the three to complete gas exchange. Based on the phylogeny of salamander families and what you know about the evolution of vertebrates, which gas exchange surface is most ancestral?

A. gills B. lungs C. skin

Answer 1

The Salamanders are amphibians that belong to order Urodela or Caudata. These are similar to ancestral amphibians that lived in aquatic and terrestrial habitats. Most adult Salamanders live on land but young forms are aquatic. They have a tetrapod body containing four limbs and a tail. Most of the salamanders are lungless and these carryout respiration through the skin or through external gills found in aquatic species.

Some terrestrial salamanders contain primitive lungs and few species contain both gills and lungs. Different species of salamanders respire through gills, lungs, skin, and the membranes of mouth and throat. The larval forms respire mainly through gills. The gills appear externally and feathery. The respiration through gills occur by water drawn in through the mouth and flows out through the gill slits.

Some neotenic species like mudpuppy (Necturus maculosus) retain their gills throughout their lives. Most species lose the gills during the metamorphosis. Some terrestrial lungless salamanders like Ensatina undergo direct development and in these, the embryos contain large gills near the egg's surface. Basing on the phylogeny of Salamander families and based on evolutionary history of vertebrates, the gills are ancestral structure and gas exchane surface. Therefore, the option A is correct.