What is the function of the ossicles in a starfish?

Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids.

What does the ambulacral groove on a starfish do?

The grooves are called ambulacral grooves and are filled with many soft projections, the suckers of the tube feet. Large spines line the ambulacral groove, and they are used for locomotion.

What are the functions of the tube feet madreporite and ambulacral groove?

The madreporite is an opening to the water vascular system on the aboral surface. A mouth occurs on the oral surface. The ambulacral groove is on the oral surface from which tube feet project through the body wall.

What is unique about the ossicles of echinoids?

A distinguishing feature of the echinoids is that the ossicles imbricate (overlap) and are fused into a globular or discoidal test; its flattened or concave oral side faces the substratum and the aboral side is arched in most species.

What is meant by Ambulacral groove?

ambulacral groove: (Echinodermata: Asteroidea) A groove or furrow bordered by large spines extending along the oral surface of each arm of sea stars, that contain two to four rows of small tubular projections called feet or podia.

Where is the Ambulacral groove located on a starfish?

For example, sea stars or “star fish” have an ambulacral groove on their oral side (underside). This ambulacral groove extends from the mouth to the end of each ray or arm.

What is the difference between open and close Ambulacral groove?

What is an ambulacrum and what is the difference between open and closed ambulacral grooves? A band of tube feet that extend from the mouth along the oral sides of each arm to its tip. When ossicles or other dermal tissue cover these structures it is closed. When the tube feet are out then it is open.

What are the salient features of the echinoids?

1 Answer

  • (1) It includes sea urchins, heart urchins, sand dollars etc.
  • (2) Arms are absent, tube feet are arranged in five bands and bear suckers.
  • (3) Ossicles of the body unity to form a rigid test or corona or case.
  • (4) Pedicellaria are “three jawed”.
  • (5) Anus and madreporite are aboral in position.

What is the function of madreporite?

The madreporite /ˌmædrɪˈpɔːraɪt/is a light colored calcareous opening used to filter water into the water vascular system of echinoderms. It acts like a pressure-equalizing valve.

What is the difference between open and closed Ambulacral groove?

How does the ossicles work?

The ossicles are actually tiny bones — the smallest in the human body. The three bones are named after their shapes: the malleus (hammer), incus (anvil) and stapes (stirrup). The ossicles further amplify the sound. The tiny stapes bone attaches to the oval window that connects the middle ear to the inner ear.