Question

Shark Questions:

1. What may be the purpose of counter shading in sharks and other types of fish?

2. What are the functions of the shark liver?

3. Make a flow chart (using arrows) of shark digestion.

4. Why are rugae necessary to shark digestion?

5. Why do you think carnivores have shorter intestines than herbivores; what might be the adaptive advantage?

6. Why does the ovoviviparous reproductive method improve the chances of an individual shark’s survival, but at the same time make the species of shark more vulnerable to overfishing and other environmental problems?

Answer 1

Ans1. Countershading, originally described in the late 1800s, is when one side of an animal is dark and the other is light.

The main purpose is to serve as a form of camouflage.

Example- In fish, such as the Atlantic Bluefin Tuna (Thunnus thynnus), the ventral side (bottom) is light and the dorsal side (top) is dark.

This is useful for fish because the dark dorsal side helps them blend in the with substrate or deeper water below if they are being viewed from above. Then, the lighter dorsal side helps fish blend in with the water (and light backdrop of the sky) above them if you are looking at the from below.

Countershading is seen in fish species in coastal and open ocean habitats.

Figure- Atlantic Bluefin Tuna are one of many pelagic species that exhibit countershading.

However, some species, such as the Nile catfish (Synodontis batensoda), exhibit reverse countershading where the ventral side is dark and the dorsal side is light.

The Nile catfish feeds while swimming upside down in the water column and the reverse countershading helps it camouflage.