Question

In starfish, the upper side contains
A. Mouth
B. Mouth and ambulacral grooves
C. Anus
D. Anus and madreporite

Answer 1

Hint: Starfish belongs to the phylum Echinodermata. All echinoderms are exclusively marine and live at the bottom of the sea. They are also known as bottom dwellers. They are free-living animals. Starfish have a pentamerous radial symmetry and their body parts are arranged along the five axes.

Complete answer:
In starfish, the upper side contains anus and madreporite.
Endoskeleton of echinoderms is made up of calcareous ossicles with overlying skin which gives a spiny appearance to echinoderms. Echinoderms have a tube type of body plan which has evolved along the deuterostomic evolutionary line.
Phylum Echinodermata is divided into five classes:
> Asteroidea: Asterias (Star fish)
> Ophiuroidea: Ophiothrix (Brittle star)
> Echinoidea: Echinus (Sea urchin)
> Holothuroidea: Cucumaria (Sea cucumber)
> Crinoidea: Antedon (Feather star sea lily)
Features of Asteroidea:
> Body is flat and star-like.
> There are five arms which are not sharply marked off from the central disc.
> Oral/ventral/lower surface has mouth and ambulacral grooves.
> Aboral/dorsal/upper surface has anus and madreporite.
> Spines are short.
> Pedicellariae are present. Pedicellariae are a pincer like structure to keep the surface clean.
> Respiration in asteroidea is brought about by dermal branchiae and tube feet.
> Examples of asteroidea are Asterias, Pentaceros and Astropecten.

So the correct answer is option D.

Note: Autotomy is the ability of starfish is to break off a part of its body. Excretory system is absent in the phylum echinodermata. Water vascular system is the most distinctive feature of echinoderms which helps in the locomotion, capture and transport of food and respiration.