18 IntestineFecal compactionAnus opens into mantle cavity
19 8. Nitrogenous waste Pair of coelomoducts Open to pericardial cavityDischarge into mantle cavity via nephridioporesProbably not homologous to annelid metanephridia (annelid origin = mesoderm; mollusk origin = ectoderm)
20 Waste product? Ammonia in aquatic molluscs Uric acid in terrestrial molluscs
21 9. Nervous system - varied Polyplacophora (chitons) - decentralized, no gangliaCephalopods - as developed as in vert’sPrimitive gastropods:Nerve ring around esophagus, 2 pair of major nerve cords
22 Reproduction and development Pair of gonads in coelomEggs + sperm into pericardial cavity, outside via coelomoductsFert external in sea waterMolluscs mostly dioecious, some gastropods hermaphroditic
23 Most gastropods, all cephalopods: Sperm transferred to female’s mantle cavityInternal fertilizationHermaphroditic gastropods do reciprocal cross-fertilization
25 Trochophore larvae Archaeogastropoda Polyplacophora Aplacophora Most marine bivalvesDevelops into veliger larvaeFoot, shell, other structures appear
26 Phylogenetic significance of trochophore larvae Hatschik (1878)Present in molluscs, annelids, other phylaPromotes ctenophora - trochophore theory of bilateral animals from radial ancestorsbody shape, apical sense organs, statocysts, nervous systems
27 Problem with ctenophora-trochophore connection Flatworms don’t fitDegenerate annelids?
29 Class PolyplacophoraChitons and oval-flattened beasts - mostly in rocky intertidal zonesAll marine, ~ 800 spp.Mostly cmLargest (30 cm)is Cryptochiton stelleri from N. Pacific coast of N. America = Pacific gumshoe chiton
30 Chiton characteristics: Most feed on algae and micro-organisms on rock surfacesFew are predators on small inverts1. Rudimentary headNo tentacles or eyes
31 Characters 2. Mantle covers dorsal surface 3. Broad, ventral foot Secretes 8-piece shell3. Broad, ventral foot4. Many paired gills in mantle cavity5. Anterior mouth with radula
32 Repro: 6. Dioecious trochophore larvae, no veliger external fert. in sea watermouthGills in mantle cavitymantlefoot
33 Classification of Polyplacophora - 2 orders Order Lepidopleurida: few genera, Hanleya NE coastOrder Chitonida - most chitonsChaetopleura (New England - Fl)Chiton (gulf coast)Katherina (N. Pacific coast)Cryptochiton (N. Pacific coast)MopaliaIshnochiton
34 Class AplacophoraSolenogasters are worm-like molluscs cm longLargest is Epimenia verrucova; 30 cmAll marineMostly deep waters, mSome crawl and feed on hydroids and coralsPoorly known, seldom seen, ~ 250 spp.
35 Characteristics: 1. Worm-like body shape 2. No shell, mantle, or foot 3. Cuticle w/layers of imbedded calcareous spicules4. Ventral surface has longitudinal pedal groove5. Hermaphroditic6. Radula well-developed