GENERAL HISTOLOGY

Detailed explanation-1: -Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. They are found in all oceans, mostly in shallow water but sometimes at depths of many thousands of metres.

Detailed explanation-2: -Pearlfish are slender, eel-shaped fish that often live inside various invertebrates including sea cucumbers. Because a sea cucumber breathes by taking in water through its anus, a pearlfish can wait for the cucumber to open for a breath and swim in.

Detailed explanation-3: -Crabs, fish, turtles, and even some species of shark are natural predators of sea cucumbers.

Detailed explanation-4: -Holothurians are common in the oceans of today; in fact, in certain parts of the deep sea, the ocean floor swarms with vast herds of holothurians. Holothurians are also common in shallow-water habitats such as tidepools.

Detailed explanation-5: -Class Holothuroidea. The class Holothruoidea is better known by as the sea cucumbers. Sea cucumbers are cylindrical echinoderm animals with feathery tentacles at the mouth end of their bodies.