phylum echinodermata clear concept

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Introduction The Coelnterata are tentacle bearing, aquatic, either sedentary or free swimming, radially or biradially symmetrical metazoa with head organs or systems. They have very simple tissue organization, with only two layers of cells. They possess nemtoacysts of intrinsic origin and only one internal cavity, opening only by the mouth. Coelenterata is an obsolete term encompassing two animal phyla, the Ctenophora (comb jellies) and the Cnidaria (coral animals, true jellies, sea anemones, sea pens, and their allies); diverse group of aquatic, invertebrate animals armed with microscopic stinging structures, which encompasses more than 9,000 species. The name comes from the Greek "koilos" ("full bellied"), referring to the hollow body cavity common to these two phyla and enteron (gut or intestine). Some of the examples are corals, sea anemone which are colonial and hydra, jelly fish which are solitary. Cnidarians live in all oceans, and a few species inhabit fresh water.

Welcome to the Presentation of

Phylum : ECHINODERMATA

Presented by : Group D

Illutsrated by:

sv d bIntroductionThe echinoderms are exclusively marine enterocoelous coelomata, triploblastic animals having pentamerous radial symmetry derived from a original bilateral symmetry without definite head or brain with an endoskeleton of calcareous plates or spicules embedded in the skin with a peculiar water vascular system of coelomic origin, pushing out of the body surface, numerous small delicate projections the podia or tube feet, with an ectodermal nervous system without nephridia and with gonads opening directly to the interior by special ducts.The name Echinodermata literally means spines or prickly skinned and refers to the conspicuous spines possessed by their skin. This name was at first used by Jacob Klein for echinods.The Greeks applied the name echinas to the hedgehog as well as the sea urchin; both having a prickly appearance. It was Leukart who first established Echinodermata as a distinct group of animal kingdom.

General Characteristics- The echinoderms are exclusively marine and are among the most common and widely distributed of marine animals.- They occur in all seas from the intertidal zone to the great depths.- Radially symmetrical and nearly always pentamerous.- Body is triploblastic, coelomate with distinct oral and aboral surfaces and without definite head and segmentation.- They are moderate to considerable size but none are microscopic.- Body shape rounded to cylindrical or star-like with simple arms radiating from a central disc or branched feathery arms arise from a central body.

- Surface of the body is rarely smooth, typically it is covered by five symmetrically space radiating grooves called ambulacra with five alternating inter-radii or inter ambulacra.- Body wall consists of an outer epidermis, a middle dermis and an inner lining of peritoneum.- Endoskeleton consists of closely fitted plates forming a shell usually called theca or test or may be composed of separate small ossicles.- Presence of water vascular or ambulacral system is the most characteristic feature. It consists of tubes filled with a watery fluid.

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- Alimentary tract is usually coiled tube extending from the mouth located on the oral surface to the annus on the oral or aboral surface. - Circulatory or haemal or blood lacunar system is typically present.- Excretory system is wanting.- Nervous system is primitive, consisting of networks concentrated into the radial ganglionated nerve cords.- Sense organs are poorly developed.- Sexes are usually separated (dioecious) with few exceptions. Gonads are simple with or without simple ducts.

- Reproduction is usually sexual; few reproduce asexually or by regeneration.- Fertilization is external, while few echinoderms are viviparous.- Development is indeterminate including characteristic larvae which undergo metamorphosis into the radially symmetrical adults.- Radially symmetrical and nearly always pentamerous.- Body is triploblastic, coelomate with distinct oral and aboral surfaces and without definite head and segmentation.- Surface of the body is rarely smooth, typically it is covered by five symmetrically space radiating grooves called ambulacra with five alternating inter-radii or inter ambulacra.- Endoskeleton consists of closely fitted plates forming a shell usually called theca or test or may be composed of separate small ossicles.- Presence of water vascular or ambulacral system is the most characteristic feature. It consists of tubes filled with a watery fluid.Identifying Characters of Echinodermata

- Alimentary tract is usually coiled tube extending from the mouth located on the oral surface to the annus on the oral or aboral surface.- Excretory system is wanting.- Nervous system is primitive, consisting of networks concentrated into the radial ganglionated nerve cords.- Sense organs are poorly developed.- Sexes are usually separated (dioecious) with few exceptions. Gonads are simple with or without simple ducts.

Asterius rubens

Gorgonocephalus

Cucumaria miniata Classsification: Classification of Echinodermata is not universally taken yet. But at present, two format of classification can be seen.One of them is given by G.Ulbaughs (1967). This format is based on the basis of external features of living and extinct species.Other one is given by A.B. Smith (1984). In this format, Phylum Echinodermata is divided into two sub-phylum. Now well discuss about this classification________

Sub-phylum: EleutherozoaClass:Asteroidea

Characteristics:- Starfishes or sea stars.- Arms five or more and not sharply marked off from the central disc.- Tube feet in orally placed ambulacral grooves; with suckers.- Annus and madreporite aboral.- Pedicellariae present.- Free-living, slow creeping, predaceous and scavengerous.

Characteristics:Fossil Pelazoic Sea stars. Platasterias latiradiata is the only living species.

Characteristics:They are living sea stars.Characteristics: - Brittle stars and allies. - Body star like with arms sharply marked off from the central disc. - Pedicellariae absent. - Stomach sac like; no annus. - Ambulacral grooves absent or covered by ossicles; tube feet without suckers. - Madreporite oral. Example: Ophiura, Gorgonocephalus, Asteronyx.

Characteristics: - A single row of plates in each inter ambulacral area.- Without typical lantern.- Madreporite radial.

Example: Single extinct Ordovician genus Bothriocidaris. Characteristics:- Body globular pentamerous, with two rows of inter-ambulacral plates in existing members.- Mouth central.- Aristotles lantern well developed.- Annus central on aboral surface with well developed apical plates.- Madreporite oral.

Example: Palaeodiscus,Melonechinus,Diadema,Echinus.Characteristics:- Body oval or circular, flattened oral-aborally.- Mouth oral or displaced anteriorly on oral surface.- Annus marginal, outside the apical system of plates.- Tube feet generally not locomotor. Example: Echinoneus,Cassidulus,Echinocyamus, Spatangus.Characteristics:- Sea cucumbers.- No arms and no spines.- Body elongate on oral-aboral axis, body wall leathery.- Mouth anterior surrounded by tentacles.- Ambulacral grooves concealed; tube feet with suckers.- Usually with respiratory tree for respiration.

Example: Cucumaria, Holothuria, Molpadia, Synapta.

Sub-Phylum: PelmatozoaGreek word pelmatos means stalk and Greek word zoois means animal. Thats mean Pelmatozoa stands for stalked animal. Their characteristics are stalked and sedentary.

Class:CrinoideaCharacteristics:- Sea lilies.- Body attached during part or whole of life by an aboral stalk.- Mouth and annus on oral surface.- Arms with pinnules.- Tube feet without suckers; no madreporite, spines and pedicellariae.- Ciliated ambulacral grooves on oral surface.Example: Antedon, Neometra.

General Morphology of Star Fish or Sea StarThere are too many varieties of species consist in phylum Echinodermata. Among them Class Anthozoa is rich of species. Metridium marginatum, known as sea-star or star fish under this class, heres some description about this.Classification: Phylum: Echinodermata Sub-phylum: Eleutherozoa Class: AsteroideaOrder: Euasteroidea Family: Forcipulata Genus: Asterius Species: Asterius rubens

Shape :The echinoderms present at a great diversity of organization. The original biradial symmetry is often obscured by a well developed radial symmetry. The most striking characteristic of the group is their pentamerous radial symmetry, i.e. body can be divided into five parts arranged around a central axis. The radially arranged parts are called antimeres, with the mouth at centre.Star fishes have a flattened body which is pentagonal or produced into five, six or even more tapering arms. Bristle stars have a small rounded central disc with five distinct, slender, jointed and flexible arms. Sea urchins are hemispherical while sand dollars are disc like with a cup like central disc bearing five branched arms.

Size:Some fossil and dollars measure only 6mm in diameter, whereas a fossil crinoid had a stem about 22 meters long. However, the living echinoderms are of moderate size. The largest star fish, Pycnopodia helianthoides is about 30 cm. across. The shell of the largest urchins Echinosome hoplacantha has a diameter of 30 cm. One sea cucumber, Synapta maculata, measures about 2 meters in length and 5cm in diameter.

Coloration:Echinoderms adapted various types of color, such as yellow, orange, brown & purple. The body has two surfaces. The upper convex & darker side is called the aboral &a