Lecture Notes 7: Annelida

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- budding as preamble to sexual reproduction: epitokes. Epitokes are morphologically-modified stages that are budded off the rear of the vegetative worm. E.g. eunicids - palolo worms budded off parent, which stays in substratum, hind end swims off. Swarms 7 th day after 1 st full moon following autumn equinox. Swarms so large in Fiji / Samoa that they are harvested for food! Spaghetti nights on coral spawning nights! - heteronereids – not epitokes – whole worm metamorphoses into swarmer. Body wall muscles change, gut resorbed, parapodia and chaetae become modified for more effective swimming, especially toward posterior end of worm. (pretty distinct posterior – anterior differentiation in Platynereis dumerilli and Nereis vexillosa, but not much separation in Neanthes brandti). - gonads: peritoneal, primitive metazoan condition. Gametes mature in coelom and released either through gonoducts or by disintegration of worm (e.g. in nereids – body rupture). Development: Spiralian, schizocoelous protostomes. Trochophores Some brood – e.g. sabellid tube brooding Ecology & Diversity: Scolecida Palpata - Aciculata - Canalipalpata SCOLECIDA - tend to have “simple axial buccal organs”, i.e., short, eversible, pad-like pharynxes used for deposit feeding, eversion driven by coelomic pressure, thus tendency of families to have lost septa in anterior segment to allow this, muscular retraction. - mostly unselective, burrowing deposit feeders, without head appendages, free living (though some maldanids make sandy tubes). Arenicolidae - J-shaped tube, surface dimple, eat organic rich accumulations; fecal casts - burrow irrigation Maldanidae - tube-dwelling deposit feeders; live head down in tube, gobble sediment. Simple axial buccal organ like arenicolids. Nor all have tubes, but local Axiothella does, tube of poorly agglutinated, thick layer of sediment. Common in mid False Bay Capitellidae - burrowing, free-living sediment ingestors - earthworms of sea PALPATA – ACICULATA - well-defined clade with many synapomorphies, most strikingly the acicula, antennae, well developed parapodia Onuphidae - tube building omnivores - sister to Eunicidae, very similar, except build parchment tube (which come carry around), and has ceratophores on antennae and palps. - palps antenniform, so with 3 antennae end up with 5 similar “tentacles” on head - Diopatra lunge out at prey from parchment tube - pair of peristomial cirri on peristomium behind prostomium – unique to Eunicidae-Onuphidae - many with large, well developed dorsal gills in anterior segments (good for respiration in tube-confines) Eunicidae
- palps antenniform, + 1-3 antennae = 3-5 similar tentacles on head - pair of peristomial cirri on peristomium behind prostomium – unique to Eunicidae-Onuphidae - rowing raptorial omnivores w/ jaws on ventral pad pharynx Amphinomidae - fire worms; calcified chaetae with venom - caruncle - rowing predators; especially striking in tropics Polynoidae - scale worms; elytra arising from dorsal side of alternate notopodia - lack well developed dorsal cirri on scale-bearing segments; though not clear homology between cirri and elytrae - rowing predators and symbionts Glyceridae – carnivore, especially of crustaceans - Glycera lives in burrow system with multiple entrances, sitting near base of branches, feeling for vibrations with 4 prostomial tentacles and also by chemoreception. Moves up into appropriate burrow to capture prey, via eversible, pharynx armed with 4, hollow, venomous fangs. Venom glands. Especially crustacean predator - lack septae in anterior ~20 segments to accommodate huge eversible pharynx Nereididae - prostomium with paired antennae, palps, peristomium reduced, first segment compound with multiple tentacular cirri - errant, temporary mucus tube, herbivorous, some carnivory, scavenging - paired large jaws in large eversible pharynx look formidable, but mostly used for pulling algae into gut. Platynereis farms Ulva, attaching it to tube, cutting off pieces and in turn attaching those to tube and grazing on growth. In winter, when no Ulva, switches over to eating diatoms PALPATA – CANALIPALPATA Sabellidae - prostomium largely transforms into radiolar crown, which developmentally is homologous to prostomial palps, and seen as arising as such in larvae - ciliary feeding, tentacles with three sets of channels: food, tube-building grains, reject channel - thorax (usually 8 segments) and abdomen, with chaetal inversion - dorsal thoracic and ventral abdominal fecal groove Serpulidae - like Sabellidae, but calc tube - Spirobranchinae within it – tiny, spiral worms that brood, direct dev, ubiquitous Chaetopteridae - in parchment tubes, either U shaped or straight down - some with paired feeding palps, some lost it - major body tagmatization: arms to secrete mucus bag, cup to hold it, major notopodial paddles to drive current - mucus bag feeding, can get tiny particles Spionidae - some of the most abundant polychaetes, enormous densities - tube dwelling, tiny, paired feeding palps, can be used for deposit or suspension feeding or both Terebellidae - spaghetti worms – multiplied palps give spaghetti effect - palps with ciliary track for carrying food; walk out with it upside down
Page 1 and 2: Scolecida - Echiura Clitellata - Ol
Page 3: Resp.: Varied gill structures, thou
Page 7: Dorso-ventrally flattened; Ant. and

Lecture Notes 7: Annelida

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