Tuesday, 22 June 2021

The dorsal surface is convex and is covered with setae of different kinds

  The dorsal surface is convex and is covered with setae of different kinds

Aphrodite segms prostoniu palps palp stiff setae dorsal felt. neuropodia iridescent bristles soft setac stiff setae lar. Siridescent bristles ventral creeping sole gment. elytra ventral metameres anus neuropodial setae ad a d ves in Fig. Aphrodite : A. Dorsal View B. Ventral View Aphrodite is marine worm inhabiting the deep water muddy bottoms. Commonly called as sea mouse measuring approximately 12 cm in length and made up of 30 to 35 segments. e bas Body is covered dorsally by felt-like or blanket-like setae arising from the notopodium. 

Shape of the animal is oval, and dorsoventrally flattened. The dorsal surface is convex and is covered with setae of different kinds. Anterior end contains a small head or prostomium, bearing a small median tentacle and 2 lateral palps. Anus is dorsally situated at the more pointed posterior extremity. Parapodial structures are greatly modified. Notopodia contain 3 kinds of setae stiff setae (i) (ii) soft setae, and (iii) iridescent setae.Neuropodial setae are also brown and stiff. 

The soft notopodial setae are modified to form a felt-like covering over the back of the animal, while dorsal cirri become plate-like and are called as elytra, 15 pairs in number. The elytra obtain dissolved oxygen from the sea water circulating around them. Ventral surface is flat, segmented and forming a creeping sole. Each ventral segment or metamere contains stiff setae. Pumping action of the dorsal body wall causes the sea water to be filtered through the dorsal felt into the space below.

 Animal rolls itself with erect stiff setae like porcupine to protect itself from enemies when disturbed. During movement of the animal, color changes from gold to peacock. Class II: Oligochaeta (Gr., oligos = few + chaite = Few setae in each segment. Clitellum present. E.g.

 Earthworm = hair) Example : Earthworm (Pheretima) mouth prostomium.Organ system level of body organization. Jointed legs (appendages) Exoskeleton of dead chitinous cuticle. Body divided into head, thorax and abdomen. Head and thorax often fused to form a cephalothorax. Coelom replaced by haemocoel. 

 Composed of cellular plates consisting of two upper epithelical

Phylum protozoas is divided into two sub-phyla on the basis of organs Phylum : Protozoa Sub phylum Ciliophora sareomastigophora Class Class Ciliata Sarcodina Mastigophora Opalinata Sub phylum A: Sarcomastigophora Locomotory organs are pseudopodia, flagella or none. Cilia absent. Nuclei of one kind. Super Class I: Sarcodina (Rhizopoda) Locomotion by pseudopodia. Nutrition holozoic or saprozoic. Class Rhizopodea Pseudopodia may be lobopodia, filopodia or reticulopodia. Example: Arcella lobopodia ectoplasmie strands nuclei ectoplasm endoplasm pylome food vacuole Fig. Arcella. 

Ceratium apical pore theca nucleus ectoplasım- endoplasm apical spine annulus chromoplast- starch granules pore for posterior passage of ? agellum lateral spine upper epithecal plates annulus II transverse spiral sulcus lower posterior flagellum hypothecal plate A Fig. Ceratium Ceratium is found in fresh water as well as in sea.They are important members of 'ocean meadows' on which other animal feed. Body is green or brown colored. 

Body is composed of cellular plates consisting of two upper epithelical plates and two lower hypothetical plate. Epithelical plates are produced anteriorly as apical spine. Two posterior hypothecal plates are produced on each side as lateral spines. Shell is grooved by transverse groove and a longitudinal groove or sulcus. 

Transverse groove is called as annulus. Each transverse groove nas spiral transverse flagella and longitudinal groove has posterior flagella, each flagellum projects in cytoplasm. : Cycas - L.S. of seed The nucellus is used up. 

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