Thursday, 17 June 2021

Indistinct inter-radial oral madreporite Ophiocoma is commonly

   Indistinct inter-radial oral madreporite Ophiocoma is commonly

Month is very widely distensible, which can swallow bivalves. molluscs, snails and crustaceans very easily. Aboral surface has madreporite in one of the interradii. Skin is soft and somewhat transparent and internal skeleton is seen from outside. Aboral surface contains blunt spines, finger-like dermal branchiae and pedicellariae, In some forms spines are absent. Sexes are separate. The development includes brachiolaria larva. Class II:Ophiuroidea (Gr., ophis = snake + oura = tail + eidos = form) Commonly called as brittle stars. Central disc and arms are sharply demarcated. E.g. Brittle star Example : Brittle Star upper plates central disc spines arms Fig. Brittle star. 

Ophiocoma is commonly found in shallow waters.. Commonly called as brittle star. Body consists of a small, rounded central disc and 5 long slender, kapering arms, which are inserted on the under-surfaces of the disc. Central disk and arms quite distinct. Arms are distinctly marked off from the central disc and do not have prolongations of perivisceral coelom and alimentation. Oral and aboral surfaces are distinctly marked. Oral surface has leathery skin. Anus and pedicellariae absent. Oral surface has a central, pentagonal mouth opening and indistinct inter-radial oral madreporite. The ambulacral covered. grooves There are 10 elongated slits, two on either side of the base of each arm, called as genital bursae m which gonoducts open. 

Three rows of pointed spines are borne on lateral plates. Single row of short tube feet projects on each side between lower and lateral plates. Ossicles of arms are articulating. Class : Echinoidea (Gr., echinos hedgehog + eidos = form) %3D %3D Commonly called as sea urchins and sand dollars. Body disc shaped, egg shaped or heart shaped. E.g. Sea urchin Example : Sea Urchin ambulacra peristome oral tentacles radial or ocular anus genital plate plate teeth periproct- madreporite tube feet spine branchiae tubercles podial poros ambulacral sone or ambulacrum spines interambuacral zone or interambulacrum interambulacra. 

Crinoidea (Gr., crinon = lily + eidos = form) 65 %3D %3D Commonly called as sea lilies. . Body consists of a cup like calyx and cylindrical arms. Tube feet, madraporite and pedicellaria absent. E.g. Feather star Example : Feather star pinnules arms oral surface of central dise calyx mouth anus embulacral aboral cirri grooves Antedon is marine and occurs about 2 fathoms deep and remains attached to rocks by cirri from central disc. Commonly called on sea-lily or feather-star. 

On the aboral side calyx bears a knob-like structure called as Centro-dorsal plate or stalk. The calyx is differentiated into an upper convex oral surface, having mouth and anus and the lower flat aboral surface into which arms and cirri are inserted. On the aboral side calyx bears a knob-like structure, called as stung of the stalk. The oral surface is covered by a leathery skin in which numerous calcareous plates are embedded It is directed upwards.

Common gonopores of successive Proglottids lie alternately

 Testes : Testes are numerous small, spherical bodies scattered throughout the mesenchyme, close to the dorsal surface. It consists following organs. (b) Vasa efferentia : From each testis arises a fine ductule, the vas efferens, which frequently gets interconnected with similar ductules from the surrounding testes. All the vasa efferentia finally unite, approximately in the middle of proglottid, to form a common sperm duct or vas deferens. 

(c) Vas deferens : It is a thick and convoluted tube, extending upto the lateral margin of proglottid, at right angles to it. (d) Cirrus : Outer end of vas deferens forms the lumen of a thick, muscular, eversible, copulatory organ, the cirrus. There is no seminal vesicle. (e) Genital atrium : Cirrus opens into a cup-shaped genital atrium through the male genital pore., Genital atrium, in turn, opens to the exterior through the common gonopore situated at the peak of a tiny protuberance, the genital papilla, in the middle of the lateral margin of Proglottid. Gonopore is provided with a sphincter muscle. 

Common gonopores of successive Proglottids lie alternately on both the sides. Female Reproductive system It consists following organs. (a) Ovary : A single bilobed ovary or germarium lies ventrally in thd posterior part of proglottid. Each lobe of the ovary is dorso- ventrally flattened and consists of a number of radially- arranged germinal cords or follicles.  (b) Oviduct : A short oviduct arises from about the middle of ovarian isthmus. It runs backwards, joins another slender tube, the vagina and then forms a swollen chamber, the ootype.

and nervous systems; and they are formed at the zone of prolife by muscles, excretory vessels and nerve cords. Proglottic independent, self-contained units, each with a complete strobila. The strobila forms the main bulk of the body and co reproductive organs both male and female and a. proglottisation. The proglottids, internally, remain connected to of a series of proglottids arranged in a linear fashion. The st of a mature tapeworm measures about three metres in length 800 to 900 proglottids.

 A proglottid is one complete unit of the linear arrangement of repetition of these units is having a complete set of genitalium and surrounding tissue The neck is followed by the flattened, ribbon-like body small hook FORMS AND FUNCTIONS IN ANIMALS hand rostellum two rows of hooks Scolex biade C handle Suckers neck showing strobilation A large hook blade bas Tape worm : A Scolex and neck; B Scolex in en-face view: C Small hook; D Large hook [2] Neck Behind the Scolex is a thin, small, narrow, unsegmented neck grows continuously and proliferates proglottids by transversef or asexual budding. Therefore this region is variously calle growth zone, area of proliferation, or budding zone etc. [3] Strobila part of ex differentiated into three kinds. 

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