1) Terrestrial members of the salamander family Plethodontidae are referred to as "lungless salamanders" because--wait for...

1) Terrestrial members of the salamander family Plethodontidae are referred to as "lungless salamanders" because--wait for it--they don't have lungs! How do you suspect gas exchange occurs in these animals? How do you think the circulatory system (particularly the heart) might be different from salamanders with lungs? Explain your reasoning

2) Some aquatic animals have no gills when they are young but then develop gills that grow larger as the animal grows larger. Discuss (1) why the young animals do not have gills and (2) why the gills grow larger as the animal grows larger.

Expert Solution

Question 1 How do you suspect gas exchange occurs in these animals?

Ans -Cutaneous respiration is the sole respiratory mode of lungless salamanders (family Plethodontidae) which lack lungs entirely yet constitute the largest family of salamanders.

How do you think the circulatory system (particularly the heart) might be different from salamanders with lungs?

Those amphibians that depend on non-pulmonic respiration have a modified interatrial septum. Lungless salamanders have a septal modification.One study indicates that lungless salamanders have a reduced interatrial septum. Another report indicates that this septum is a sinoatrial valve. Our study suggests that the structure in question is a composite of 1) the sinoatrial valve and 2) a component of the interatrial septum.

Question 2

According to Daniel Pauly, the study’s lead author, as fish grow into adulthood their demand for oxygen increases because their body mass becomes larger. However, the surface area of the gills — where oxygen is obtained — does not grow at the same pace as the rest of the body.

He describes this set of principles that explains why fish are expected to shrink “gill-oxygen limitation theory."

For example, as a fish like cod increases its weight by 100%, its gills only grow by 80% or less. When understood in the context of climate change, this biological rule reinforces the prediction that fish will shrink and will be even smaller than thought in previous studies, researchers said.

gladiator answered 2 years ago

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