|
Date & Time : 22, November 2024 09:29
General Characteristics of Echinodermata
- exclusively marine and cosmopolitan in distribution.
- Body triploblastic,radially symmetrical,divided into oral and aboral surface.
- Body surface covered with radiating grooves called Ambulacra with five inter ambulacra.
- Mouth usually present on oral surface and anus on aboral surace.
- Blood lacunar system present.
- Sense organs are poorly developed.
- Sexes are usually separate with only a few exceptions
Classification of Echinodermata
A Few Examples
1. Antedon
Common name- feather star or sea-lily.
Distribution- found in all seas.
Habit and Habitat- marine, remain attached to the rocks by cirri.
Food- feed on microscopic living organism.
IDENTIFYING CHARACTERS:-
- Body- consist of calyx (central part), and arms radiated from calyx.
- calyx- differentiated into oral surface and aboral surface.
- Oral surface- contains mouth and anus
- aboral surface- contains arms and cirri.
- Cirri- composed of skeletal ossicles.
- mouth- present in central, surruonded by sensory podia, but no suckers are present.
- Ambulacral grooves- 10 in number, leading into the arms.
- Arms- actually arms are 5 in muber, each arm is divided into two.
- Each arm contain pinnules having gonads.
2.Asterias
Common Name- star fish or sea star.
Distribution- abundant in North Atlantic Coast, found in India and U.S.A.
Habit- marine.
Food- microscopic organisms
IDENTIFYING CHARACTERS-
- Appearance- star shaped, pentagonal.
- Body- differentiated into oral and aboral surfaces.
- Body color- yellow or brown(preserved).
- Arms- 5 in number, and are prolongation of coelom, gonds and alimentation.
- Oral surface- consist of mouth (actinostome).
- Ambulacral grooves- extend from mouth, accomodate a large number of tube feet.
- Aboral surface-consist of conical spines, madreporite plate and pedicellariae.
- Skeleton system- it is only about meshwork of ossicles and closely packed discrete plates.
3. Echinus
Common name:- sea urchin.
Distribution:-found in Atlantic, the Mediterrnean and Pacific waters.
Habit and Habitat:-marine in habit, benthic animal.
IDENTIFYING CHARACTERS:-
- Body covering:- enclosed in corona(rigid) or test is made up of calcareuos plates.
- Body division:- oral and aboral surface.
- Oral surface:- contain mouth
- Mouth:- contain peristome, buccal tube, calcareous ossicles.
- Pedicullariae and spheridia:- located between articulated spines.
- Test:- divided into ambulacral and inter ambulacral zones
- contain spines and tube feet.
- Ambulacral grooves:- closed.
4. Cucumaria
Common name:- sea cucumber.
Distribution:- cosmopolitan, found in Europe, U.S.A. and India.
Habit and Habitat:- marine in habit, like to live partially burried in mud.
Food:- detritus and plankton.
IDENTIFYING CHARACTERS:-
- Body:- elongated horizontally along the oral and aboral axis.
- Body color:- may be whitish, reddish or brown.
- Body wall:- dermo-muscular, having separate ossicles.
- Mouth:-anterior in position.
- Tentacles:- modified tube feet, surrounds the terminal mouth.
- tube feet possesses suckers, either arranged in rows or scattered.
- Body division:- rest of the body is divided into various zones
1.five ambulacral and
2.inter ambulacral zones.
- Ambulacral grooves:- run longitudinally and are covered.
- Genital aperture:- placed between two adjacent inter-ambulacral tentacles near mouth
- single in number.
- Anus:- aboral with respiratory trees.
5. Clypeaster
Common name:- cake urchin.
Habit and Habitat:- marine in habit, like to live partially burried in mud in tropical and sub tropical waters.
Food:- detritus and plankton.
IDENTIFYING CHARACTERS:-
- Body:- flattened and oval,covered with dense brown spines.
- Body color:- reddish or brown.
- Body wall:- dermo-muscular.
- Mouth:- central in position, on the concave oral surface. Teeth or masticatory apparatus present.
- madreporic plate:- petaloid ambulacra enclose the madreporic plate.
- Pedicellariae and spaeridia are present.
- podia:- respiratory in function.
- Ambulacral grooves:- run longitudinally and are covered.
- Genital plates:- fused with central pentagonal plate.
- Aristotle's lantern:- present.
6. Astropecten
Common name:- large star fish
Habit and Habitat:-found in seas below tide line.lives partly buried in sand.
IDENTIFYING CHARACTERS:-
- Body:- star shaped,flattened,has five arms.
- Arms:- flexible,triangular, have tappering tips.
- Body division:- oral and aboral surface.
- Oral surface:- contains mouth.
- Ambulacral grooves:- extend from the mouth and pass along entire arm.
- Tube feet:- Conical structures, project in two rows along each ambulacral groove.
- Aboral surface:- contains madreporite, having numerous minute pores.
- Paxillae numerous short blunt spines on aboral surface.
- Dermal branchiaesmall,soft,hollow,finger like outgrowths arise between paxillae
7. Ophiothrix
Common Name- spiny brittle star
Distribution- found in Atlantic coast.
Habit and habitat- marine in habit.
IDENTIFYING CHARACTERS:-
- Body- consist of central disc and arms.
- Arms-symmetrical and are fused with central disc, five in number.,covered by spines.
- Body division-body is divided into oral and aboral surface.
- Oral surface- consists of mouth with jaws,madreporite,oral shields,podial pores.
- Bursal slits- deep grooves present on base of each arm. Mature sex cells pass through it.
- Shows great power of regeneration of its lost arm.
8. Pentaceros
Common Name- sea pentagon.
Distribution- found in India, Panama, U.K., U.S.A.
Habit and habitat- marine in habit.
IDENTIFYING CHARACTERS:-
- Body- consist of central disc and arms.
- integument- tough, hard and and leathery. It contain spines of different size, and vessicles.
- Arms-symmetrical and are fused with central disc, five in number.
- Body division-body is divided into oral and aboral surface.
- Oral surface- concave and brown in color. containing mouth.
|
