In males,pelvic fins bear claspers in:

Which of the following statements are not true?
$a$. Dermal scales of fishes form the exoskeleton.
$b$. Cycloid and ctenoid scales have distinct lines of growth which aid in determining the age of the fish.
$c$. Fish scales are never shed.
$d$. The skin in elasmobranchs is covered with placoid scales.
$e$. The development of a placoid scale is not like the development of a tooth.

$S$ - Statement: Shark is an example of cartilaginous fish.
$R$ - Reason: The endoskeleton is made of cartilage.

The heart of a fish is:

What is the location and function of claspers?

The term $Mermaid's$ $purse$ refers to: