Invertebrate Zoology Lecture 16 Phylum Annelida Part 3
Invertebrate Zoology Lecture 16: Phylum Annelida, Part 3
Lecture outline § Phylum Annelida, Part 3 «Nervous system/Sensory structures § Class Polychaeta (previous lecture) § Class Clitellata (briefly) «Movement «Reproduction
Nervous System: Class Clitellata (briefly) § § § Overall, similar to Polychaeta Minimal anterior sensory structures Class Oligochaeta « Some with ocelli « Body sensitive to a variety of stimuli § § “Epithelial sense organs” Class Hirudinoidea « Negatively phototactic; some become positively phototactic prior to feeding. « Mammalian blood-suckers respond to high temperatures
Movement § Peristalsis «Facilitated by compartmentalization of coelomic fluid
Movement § Peristalsis (cont. ) «Hirudinoidea § No compartments «Entire body acts as a single segment for “inchworm”-like movement
Movement § Crawling «Common in Class Polychaeta «Antagonistic action of left vs. right side longitudinal muscles (similar to…? ) «Role of parapodia?
Reproduction: Polychaeta § Regenerative ability/asexual reproduction «Example: Chaetopterus and the amazing Segment 14
Reproduction: Polychaeta § Sexual Reproduction: Overview «Most Polychaeta are gonochoristic «Gametes develop from peritoneal cells «Primarily external reproduction § Spawning via coelomoducts, nephridiopores, or body wall rupture
Reproduction: Polychaeta § Epitoky «Transformation of part or all of a nonreproductive benthic polychaete (atoke) into a swimming reproductive form (epitoke) «Key physical changes § Gut dissolves § Gametes packed into coelom § Large eyes develop § Parapodia become paddle-like «Behavior § Orgy on a moonlit night…
Various epitokous forms
Reproduction: Polychaeta § Early development «Classic protostome pattern… § Trocophore larvae «Apical tuft § sensory «Prototroch § ciliary band for movement
More advanced larvae § Segments added from the posterior end (but anterior of pygidium)
Reproduction: Oligochaeta § Sexual Reproduction: Overview «Simultaneous hermaphrodites «Gonads located in a few anterior segments § Note male and female structures
Reproduction: Oligochaeta § Sexual Reproduction: Mating & Fertilization «Alignment «Role of clitellum in mating «Transfer of sperm into spermatheca § Direct (via penis) § Muscular sperm grooves
Reproduction: Oligochaeta § Sexual Reproduction «Formation of cocoon & secretion of albumin (clitellum) «Cocoon movement § Acquires eggs, then sperm «Fertilization within albumin matrix of cocoon § Development «Cocoons deposited «Direct development Clitellum epithelium
- Slides: 15