BIS2C_Lect30_Ward_Annelida_ppt - BIS2C Winter 2012 (Ward)...

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1 BIS2C Winter 2012 (Ward) Lecture 30. Annelida Today’s lecture (9 March) Mollusca concluded (nudibranchs, cephalopods) introduction to Annelida major features biology within-group diversity Monday’s lectures Arthropoda 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: Solar-powered sea slugs sequester alga-derived chloroplasts for use as photosynthetic machines how do they accomplish this, given that the functioning of such organelles in algae requires many nuclear-encoded genes? The sea slug has acquired one or more nuclear-encoded algal genes in its own genome: LGT between in its own genome: LGT between two eukaryotes! Ref.: Rumpho et al. 2008. Proc. Natl. Acad. Sci. USA 105:17867-17871. 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)
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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” (see recent Nature article*) *Shubin, N. et al. 2009. Deep homology and the origins of evolutionary novelty.
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BIS2C_Lect30_Ward_Annelida_ppt - BIS2C Winter 2012 (Ward)...

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