lochotrophozoa II

1. lochotrophozoaII BIOL240.002 Zoology 13 October 2014

2. Clades and Subclades in Lophotrochozoa Feed using ciliated lophophore Fig. 9.1 p. 176

3. Phylum Cycliophora“wheel bearer”—3 (2) spp. cycliophorans • First sp. described in 1995 • Symbionts on lobster oral appendages • Acoelomate • Ring of cilia around mouth • U-shaped digestive tract • Asexual and sexual reproduction • Former by budding • Latter in dioecious larvae • Sexual stage disperses when lobster molts its exoskeleton (Female larvae are internal) Fig. 9.2 p. 177

4. Phylum Entoprocta“inside anus”—<100 (171) spp. entoprocts • Stalked sessile animals • Most marine • 1 sp. freshwater • Solitary or colonial • Lophophore of ciliated tentacles • Mouth and anus of U-shaped gut both insidelophophore • Pseudocoelom • Pair of protonephridia • Solitary spp.: monoecious • Mostly protandrous • Colonial spp.: dioecious • Brood eggs or viviparous • trochophorelarva Fig. 9.3 p. 178

5. Phylum Ectoprocta“outside anus”—~4000 (5656) spp. bryozoans or moss animals • aka Bryozoa • “moss animals” • Stalked or encrusting sessile animals • Most marine • 1 class of 69 spp. and a few other spp. are freshwater • Most are colonial, with zooids in secreted zooecia • Calcareous, chitinous, or gelatinous • 1 genus solitary • Lophophore of ciliated tentacles that can be withdrawn into the zooecium • Anus of U-shaped gut is outsidelophophore • Nephridia excrete coelomocytes full of wastes • Asexual statoblasts in freshwater spp. • Mostly monoecious • Fertilization internal or external • Many brood in ovicell chambers Fig. 9.4 p. 179 Fig. 9.6 p. 180

6. Phylum Brachiopoda“arm foot”—<300 (393) spp. lamp shells • Marine sessile animals • Much better represented among fossils • Two-valve shell (ventral and dorsal) • Some with fleshy pedicel • Two-armed lophophore • Three-part enterocoelic coelom • Nephridia excrete coelomocytes • Open circulatory system • Mostly dioecious • Mostly external fertilization, but some brood eggs Fig. 9.7 p. 181 Fig. 9.8 p. 181

7. Phylum Phoronida“bearing a nest”—~10 (16) spp. phoronids • Marine worms up to 30 cm • Secrete tubes of chitin that line permanent burrows • Lophophore is two incurved ridges • Anus outside lophophore • Three-part partitioned eucoelom (enterocoely) • Circulatory system largely closed • Two nephridia • Some reproduce asexually via buds or fragmentation • Monoecious or dioecious • Mostly external fertilization • Or, internal via lophophoralspermatophores, with brooding on female lophophore • Ciliated hooded actinotroch larva Fig. 9.9 p. 182

8. Phylum Nemertea“unerring one”—~1300 (1252) spp. ribbon worms • Elongate, mostly marine worms • Hydrostatic rhynchocoel houses proboscis • Shot out at prey/trails/burrows • Neurotoxins delivered via stylet • Rhynchocoel a derived coelom? • Complete digestive system • Nerve cords with transverse nerves • Closed circulatory system • No heart; vessels contract • Several protonephridia • Asexual fragmentation • Mostly dioecious external fertilizers • Some hermaphrodites, some internal, some ovoviviparous Fig. 9.11 p. 183 Fig. 9.10 p. 182

9. Lineuslongissimus • Bootlace worm • Northern European coasts • Up to 55 m in length • Up to 10 mm in width

10. Phylum Mollusca“soft”—<90,000 (41,646) spp. mollusks • Hypodermal mantle with mantle cavity housing gills (lung in some spp.) • Hydrostatic foot • Scraping radula in mouth • Small “true” coelom surrounding heartof open circulatory system • Most with simple nervous system (nerve cords, few ganglia) • Ciliated trochophoreand shelled veliger larval stages Fig. 10.3 p. 189 Fig. 10.6 p. 191 Fig. 10.7 p. 192 Fig. 10.4 p. 189

11. Mollusk Systematics and Taxonomy 270 spp. 4 orders 31 spp. 1 order 585 spp. 8 orders 571 spp. 2 orders 30,242 spp. 16 orders (>8000 spp. not in an order…yet) 132 spp. 1 order 976 spp. 2 orders 8839 spp. 16 orders Fig. 10.2 p. 188

12. Classes Caudofoveata and Solenogastres—caudofoveates and solenogasters“tail pit” “pipe stomach” • Marine • Elongate worm-like bodies • No shell • Some fossil spp. had shells • Formerly united in class Aplacophora • Scales and calcareous spicules in skin • Most have radula (lost in some solenogasters) • Foot is lost in caudofoveates, a vestige in solenogasters • Reduced posterior mantle cavity • Pair of gills in caudofoveates, none in solenogasters • Caudofoveatesdioecious, solenogastersmonoecious Fig. 10.8 p. 192

13. Class Polyplacophora—chitons“bearing many plates” • Marine • Elongate foot with mantle cavity and gills to either side • 8-piece (rarely 7) shell • Scraping radula • Trochophoremetamorphoses into adult form Fig. 10.1 p. 187 Fig. 10.11 p. 194

14. Class Monoplacophora—monoplacophorans“bearing one plate” • Marine “living fossils” • Single shell • Broad, hydrostatic foot • Serially repeated gills, gonads, heart ostia, nephridia, and transverse nerves • True metamerism or pseudometamerism? Fig. 10.9 p. 193

15. Class Gastropoda—snails, slugs, and allies“stomach foot” • 73% of the phylum • Marine, freshwater, and terrestrial • Single-valve shell in most, often coiled • Internal or lost in slugs, nudibranchs • Torsion in larval development brings mantle cavity and anus above head • Radula usually present • Gills in some, lungs in others • Monoecious or dioecious • Copulate or transfer spermatophores • Eggs float, or in masses or capsules • Some freshwater snails are aplacentlally viviparous • Trochophore and veliger larvae Fig. 10.19 p. 199 Fig. 10.22 p. 200

16. Gastropod Torsion Fig. 10.13 p. 195

17. Gastropod Shell and Lung Evolution Fig. 10.14 p. 196 Fig. 10.15 p. 196

18. Class Cephalopoda—cephalopods“head foot” • Squids, cuttlefish, octopi, and chambered nautili • Foot  Head and tentacles • Shell buoyant in nautili, internal in squids and cuttlefishes, and lost entirely in octopi • Swim by ejecting water from the mantle cavity • Eject ink to confuse predators • Closed circulatory system with three hearts • Well-developed camera eyes • Radula and keratinized beak • Spermatophore transfer via hectocotylus arm of male Fig. 10.31 p. 205 Fig. 10.32 p. 206 Fig. 10.35 p. 208

19. Cuvier’s (1807) Hectocotyleoctopodis HANDOUT

20. Class Bivalvia—bivalves“two valves” • Freshwater and marine • Two shells join at dorsal hinge • Adductor muscles hold shell closed • Mostly filter feeders fed by ciliary gill currents in mantle cavity • Incurrent/Excurrentsiphons • Lack radula • Most move slowly via hydrostatic foot • Oysters are sessile • Scallops “swim” using adductors • Generally external fertilization • Yrochophoreand veliger larvae • Parasitic glochidium larva in freshwater spp. Fig. 10.4 p. 201 Fig. 10.30 p. 205 Fig. 10.25 p. 202 Fig. 10.29 p. 204

21. Class Scaphopoda—tusk shells“trough foot” • Marine burrowers, to 25 cm • Curved tubular shell open above and below • Mantle cavity’s respiratory current drawn in and out of top hole by cilia and muscular movements • Foot with captacula (tentacles) emerge from lower opening for feeding in sediments • Radula present Fig. 10.12 p. 194