Question

Proteus anguinus is an example for
a. Circannual rhythms
b. Effect of light on pigmentation
c. Phototaxis
d. Photokinesis

Answer 1

Hint: Proteus anguinus or the cave salamanders are used to living in the dark environment. This has enabled their body to undergo several changes to adapt to this dark environment around them. They have a pale skin color with a modified vessel.

Complete answer:
> Option (a) Circadian rhythms are endogenously generated biological rhythms having a period length of one day. A circannual rhythm can also be defined as annual. There are many different examples of circannual rhythms, like- the urge to migrate in migratory birds during a particular time in a year, hibernation cycles seen in ground squirrels and moulting in ungulates. Hence, this option is incorrect regarding the cave salamanders.

> Option (c) Phototaxis is incorrect. Taxis are a behavioral response of a cell or an organism towards an external stimulus. Phototaxis is exhibited by phototrophic organisms. They gradually move toward the light source to take advantage of the light energy necessary in photosynthesis, e.g. euglena and other photosynthetic bacteria.

> Option (d) Photokinesis is also incorrect. Several insects move much faster when placed in a direct sunlight, this is known as a photokinesis. This process helps them to spend less time in direct sunlight where they would be at risk of desiccation and predation.

> Option (b) The Proteus anguinus or the cave salamander is a rare amphibian having an unusual appearance. This appearance is gradually shaped by several million years of living in dark caves. Their skin lacks a few pigments which give rise to a white, pasty colored body. They also have a pink hue due to blood capillaries emerging near the skin. This translucency also shows the contours of the internal organs sometimes. So, Proteus anguinus can be considered a good example for the study of effects of light on pigmentation.

Hence, The correct answer is option (B).

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