MARB 435 1st Edition Lecture 13 Current Lecture Approximately 15 000 species Range from microscopic size to several meters Annelids are segmented Great diversity in lifestyles especially feeding Segmentation A k a metamerism Linear repetition of body units along the anterior posterior axis with the same set of Tagmosis A k a tagmatization Regional specialization of segments for certain functions In earthworms the clitellum plays an important role in reproduction Body Wall These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Cuticle consists of criss crossed collagen fibers Toughen the body wall Often give the body an iridescent sheen Glandular epidermis Often secretes mucus Sometimes secretes a tube Chaetae Bristles consisting of chitin Very different in structure from arthropod bristles called setae Very important taxonomic characters Systematics Class Polychaeta many bristles Class Clitellata is divided into two subclasses Subclass Oligochaeta few bristles Subclass Hirudinea leeches Class Polychaeta The most diverse annelid group in species number at least 8 000 lifestyles and morphology Parapodia Nuchal organs ciliated pits on the prostomium chemosensory organs Primarily marine but some freshwater species Mostly benthic but also some pelagic species Nervous system Can show numerous variations from the general annelid nervous system Brain may be highly developed if the head has many sensory organs Additional ganglia are often associated with the parapodia Nuchal Organs Ciliated pits or slits on the prostomium Chemosensory Best developed in predatory species Variety of shapes and sizes Eyes and ocelli Usually 1 4 pairs on the prostomium Sometimes present in other parts of the body Mostly simple pigment cups but sometimes highly complex lense eyes Family Siboglinidae A k a Pogonophora Don t feed at all but sometimes grow extremely fast So strange that they were once considered a separate phylum Thrive in sulfide or methane rich environments Live in chitin protein tubes No mouth gut or anus as adults but a temporary gut as larvae Trophosome specialized tissue that contains chemoautotrophic bacteria
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