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TAMU MARB 435 - Annelida
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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 feedingSegmentation, 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 reproductionBody WallThese 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 tubeChaetae Bristles consisting of chitin Very different in structure from arthropod bristles (called setae) Very important taxonomic charactersSystematicsClass 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 speciesNervous 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 parapodiaNuchal Organs• Ciliated pits or slits on the prostomium• Chemosensory• Best developed in predatory species• Variety of shapes and sizesEyes 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 eyesFamily 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


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