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Lecture

Anneli

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Department
Biology
Course
BIOL 2030
Professor
Scott Kelly
Semester
Fall

Description
Annelids Annelids Phylum of segmented coelomate worms, commonly called ringed worms. They have a soft elongated body with a muscular body wall, divided into many similar segments, usually separated by septa, and covered with a thin, flexible collagenous cuticle. They possess a blood system, nephridia, and a central nervous system. The annelida contains three main classes: Polychaeta (ragworms, lugworms), Oligochaeta (e.g. earthworms) and hirudinea (leeches) Chlorocruorin Green, haem-containing, oxygen-carrying protein found in the blood of certain polychaete worms Clitellum Swollen glandular portion of skin of certain annelids, such as earthworm, which secretes the cocoon in which an embryonic worm develops Enteronephric With nephridia opening into gut (in oligochaetes) Episphere Heteronomous Segmented into dissimilar segments Metamere A segment of a worm Metamerism Body divided into a serial succession of segments Metanephridia Nephridial tubule with opening into the coelom Nephridiopore External opening of excretory organs (nephridia) in invertebrates Nephridia Excretory organ having function of kidney in invertebrates Nephrostome Opening of nephridial tubule into body cavity Oligochaete Class of annelid worms characterized by possession of a few bristles (setae or chaetae) on each segment and no parapodia, and which includes the earthworms Parapodia Lateral undulating extension of foot in some molluscs, used for propulsion Peristomium Region surrounding the mouth, in ciliate protozoans, starfish, annelid worms, insects, echinoderms, etc. Peritoneal septa Membrane separating the compartments of metameres Peritoneum Membrane partly applied to abdominal walls, partly extending over the organs contained in abdominal cavity, delimiting the peritoneal cavity Polychaetes The bristle worms, a class of mainly marine annelid worms, e.g. ragworms and lugworms. They possess parapodia bearing numerous chaetae which are used for crawling, and have a pronounced head bearing tentacles, palps, and often eyes Prostomium In some annelids and molluscs, the part of the head anterior to the mouth Prototroch Preoral circlet of cilia in a trochosphere larva Pygidium An exoskeletal shield covering tail region of some arthropods, and various structures in the same region in other insects Seta Chitinous hair or bristle, arising from epidermis of many invertebrates, e.g. polychaete and oligochaete annelid worms and insects Telotroch Trochophore Free-swimming top-shaped pelagic larval stage of annelids, bryozoans, and some molluscs, forming part of the zooplankton. It has a ring of cilia around the rim and a terminal ring or tuft of cilia in front of the mouth **Life Table** Oligochaetas: earth worms Polychaeta: have parapodia Body form & structure  Segmented (cephalization)  Prostomium & pygidium: Anterior/Posterior nd  Note: 2 region near anterior NOT trunk segment; it’s a peristomium Youngest segment @ the bottom: segments created @ teloblastic growth zone  Tapeworms more reproductive-focus, these worms here ganglia, digestive system / segment  Episphere  Prostomium, (prototroch – telotroch area  peristomium) o Metamerism body a serial succession of segments (metamere=segments) o Clitellum localized reprod. Structures, seg. 9-15 (body wall  excess mucousswallows up as a cocoon, no clitellum not sexually mature)  Peristoneal septa seperates metameres (each segment a fluid sac)  Well-developed musculature “sheets” (circular muscle & longitudinal muscle)  Homonomous all segments looking identical  Longitudinal  widen & straighten, circular – elongation (using pressure systems) o Controlled very precisely Locomotion: by means of PERISTALTIC CONTRACTION (motion in oligochaete)  Longitudinal muscles contracting  will allow to hold on to side of burrow  Muscles controlled separately  BURROWING HYPOTHESIS (easier to dig if muscles controlled separately)  Seta: hold on to maintain traction  Set of Retractor/Protractor muscles to hold on (pushing setae more/less)  Polychaete locomotion: parapodia, musculature, & coelomic fluid Slow Crawling, fast crawling, swimming Parapodia paddle-like structures Longitudinal muscles packed not sheets Circular muscles sheets, but not very thick; Parapodia – move on/just above substratum
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