Question

What is a water vascular system? In which group of animals does this system exist? How is it useful to the animal?

Answer 1

Hint: The water vascular system is a type of water based hydraulic system used by marine animals’ echinoderms, such as sea stars, sea cucumbers sea urchins, for locomotion, food and waste transportation, and respiration. It is composed of channels connecting numerous tube feet.

Complete answer:

The water vascular system belongs to the members of phylum Echinodermata. The water vascular system is a distinguishing characteristic of echinoderms like starfishes, sea urchins and sea cucumbers etc.. The water vascular system is a complex hydraulic system used for functions like locomotion, respiration, and removal of food and waste products. It contains the system of perforated plates known as madreporites through which the water enters the body and after circulating the complete route, leaves the body through the tube feet. It also consists of canals connecting various tube-feet. 

Water vascular system is useful to animals in the following different ways.

- Helps in locomotion- One of the major functions of the water vascular system is to help the organisms in locomotion. All echinoderms consist of suctorial podia (also called as tube-feet) by which they stick to the substratum for some time, not permanently. 

- Helps in respiration and in senses-

Ophiuroidea and Holothuroidea the tube-feet are sensory in function. 

Echinoidea (urchins) – podia is present at the aboral side, and are sensory in function.

Spatangoida generally have lobulated shaped podia and are respiratory in function, in which suckers are not present. 

- Helps in excretion- Nitrogenous wastes always flushed out from the minute thin areas on the surface of the body like the walls of podia.

Note: This system is enterocoelic in origin and which begins from the left hydrocele. It shows radial symmetry and is generally equally developed in all types of Echinoderms.

The canal of the water vascular system contains a type of fluid that is albuminous in nature. It also consists of sea water and leukocytes, and some red corpuscles are observed.