Annelida (segmented worms) PDF

KINGDOM : ANIMALIA SUBKINGDOM: METAZOA PHYLUM : ANNELIDA ‫شعبة الحلقيات‬ 1-CLASS: Oligocheata ‫طائفة قليلة االشواك‬ Ex. Allolobophora caliginosa ‫دودة ارض‬ 2- CLASS: Polycheata ‫طائفة عديدة االشواك‬ Ex. Nieres...

KINGDOM : ANIMALIA SUBKINGDOM: METAZOA PHYLUM : ANNELIDA ‫شعبة الحلقيات‬ 1-CLASS: Oligocheata ‫طائفة قليلة االشواك‬ Ex. Allolobophora caliginosa ‫دودة ارض‬ 2- CLASS: Polycheata ‫طائفة عديدة االشواك‬ Ex. Nieres ‫دودة الرمل‬ 3- CLASS: Hirudenae ‫طائفة العلقيات‬ Ex Hirudo medicinales ‫العلق الطبي‬ Phylum: Annelida Characterization of the phylum - Bilaterally symmetrical - triploblastic - true coelomate animals - Body metamerically segmented segmentation increases their flexibility and mobility -  Characterization of the phylum - Have chitinous setae or muscular parapodia for locomotion - Have a complete digestive system with mouth and anus - Have a closed circulatory system - Have a well developed nervous system - Excretory system composed of nephridia ; nearly a pair in each segment - Have no true respiratory organs a respiration usually by simple diffusion through humid skin or parapodia - Sexes usually separate some are hermaphrodites and reproduce sexually - Mostly aquatic, marine and fresh water some are terrestrial burrowings , some are parasites  Annelida ‫الديدان الحلقية‬ ‫طائفة قليالت االشواك‬ ‫طائفة عديدت االشواك‬ ‫طائفة العلقيات‬ Class Oligochaeta Class Polychaeta Class Hirudinea (Leeches) Parapodia absent - Parapodia absent - Parapodia present - Having few setae per - No setae - Having many setae per segment segment - having well developed arranged in bundles on parapodia - Clitellum present plays an suckers for attachment - Clitellum absent important role in reproduction - Clitellum appears only during the breeding season  Characterization of the class Oligochaeta Lack parapodia,have few chaetae Hermaphrodite The gonads are confined to a few of the anterior segments Reproduction by copulation and cross fertilization The egg are deposited and develop in special capsules called the cocoons  Characterization of Earthworm (Allolobophora) Earthworms live in damp soil. They abound in the fields and gardens where they build burrows, engulfing earth particles mixed with organic matter which latter they digest, thus aerating the soil. Earthworms are nocturnal, that is, they become active by night, and retire to their burrows during the day  Characterization Earthworm (Allolobophora)  Body of earthworm The annelid body typically has a two-part head, composed of a prostomium and a peristomium followed by a segmented Each segment typically contains circulatory, respiratory, nervous, and excretory structures, as well as a coelom. Chaetae (on the ventral surface) The external body apertures ( mouth, anus, female opening and male opening, spermathecal pores, the dorsal pores, excretory pores or nephridiopores).  Respiration No respiratory organs. O2 and CO2 diffuse directly through the skin , which contains small blood vessels Excretion metabolic wastes pass from cells to coelomic fluid Which passes through excretory tubules called nephridia nephridium lies in 2 segments.its nephrostome in a segment while its nephridiopore in the next one. coelomic fluid drawn by ciliated nephrostome to pass through nephridia , wastes excreted via nephridiopores --Nervous system: It consists of the suprapharyngeal ganglia form a bilobed mass which lies dorsal to the pharynx and the subpharyngeal ganglia also form a bilobed mass which lie below the pharynx. There are two nerve cords are long and ventral in position and extends from the subpharyngeal ganglia backwards to the last segment. It bears a swelling or nerve ganglion in each segment. From each ganglion three pairs of nerves are given off in first and second segments. Reproductive system - When mating, worms become in opposite directions and adhere their ventral surfaces together by mucus secreted by their clitellum. Sperms pass from the male genital openings of each worm (segment 15), via a seminal groove to enter the seminal receptacles of the other worm hen worms separated - Clitellum of each worm secretes a mucous ring.The ring passes forward to segment 14; eggs pass from the female genital openings to the ring. Ring moves forwards to segments 10-11; sperm stored in seminal receptacles I pass into it to fertilize the eggs. As the ring slips off over the anterior end of the worm , its ends close , producing a sealed cocoon Young worms emerge from cocoon after 2-3 weeks.