Ward_Lect30A_Annelida_ppt

Ward_Lect30A_Annelida_ppt - BIS2C Winter 2010 (Ward)...

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Unformatted text preview: BIS2C Winter 2010 (Ward) Lecture 30. Annelida Today’s lecture (3 March) • Mollusca concluded (cephalopods) • introduction to Annelida • major features • biology • within-group diversity Friday’s lectures • Arthropoda Freshwater clams • life cycle includes a larval stage (glochidium) parasitic on fish • mantle edge of some clams mimics small minnow: predatory fish get a mouthful of glochidia instead of a meal A pocketbook mussel ( Lampsilis ovata ) with minnow-mimicking conglutinate More about the glochidium larva of freshwater clams “In most freshwater bivalves, eggs are fertilized internally by sperm entering with incurrent water flow. After fertilization, the eggs develop within the gill tubes [of the clam]… After being discharged, the larvae wait until they contact a passing fish and attach themselves to the gills or skin where they live as parasites for a few weeks before dropping off to begin living independent lives.” Source: http://bioweb.uwlax.edu/zoolab/Lab-5b/Glochidium-Larva.htm Nematocyst-stealing nudibranchs • some sea slugs ingest cnidarian tissue and store undischarged nematocysts in elongate protrusions on their back – ready to fire • the sea slug thus expropriates the defensive mechanism of another animal Solar-powered sea slugs • certain sea slugs feed on algae • they digest most algal tissue but sequester the chloroplasts in their in their body, where they continue to function • kleptoplasty: the stealing of plastids for use as photosynthetic machines Sacoglossan, Placida cf. dendritica , showing the green network of ducts which contain the green chloroplasts from its algal food. From: www.seaslugforum.net Cephalopods – nautiluses, squids, octopuses, cuttlefish, etc. • wholly marine; actively mobile predators • largest and smartest invertebrates • foot modified as tentacles and a siphon • nautilus with shell, in others shell is internal (squid, cuttlefish) or lost (octopus) • locomotion by jet propulsion: siphon expels water from mantle cavity Cephalopods – nautiluses, squids, octopuses, cuttlefish, etc. • capable of learning and memory tasks • can learn by observation of others (experiments with octopuses) The cephalopod eye – single lens eye convergent with that of vertebrates • excellent visual acuity • some common genes ( rhodopsin , PAX6 ) involved in eye development in the two groups • concept of “deep homology”...
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Ward_Lect30A_Annelida_ppt - BIS2C Winter 2010 (Ward)...

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