Fungi ANIMALIA Choanoflagellates Porifera (sponges) ANIMALIA
Multicellularity Ctenophora (comb jellies)
Cnidaria (jellyfish, corals, sea anemones) Diploblasty Acoela (acoels)
LOPHOTROCHOZOA Rotifera (rotifers) Loss of coelom Platyhelminthes Triploblasty (flatworms) Segmentation Annelida
(segmented worms) PROTOSTOMES
Protostome Mollusca BILATERIA development (snails, clams,
ECDYSOZOA Nematoda (roundworms)
Cephalization, CNS, coelom Arthropoda Segmentation (insects, spiders, crustaceans)
DEUTEROSTOMES DEUTEROSTOMES Radial symmetry Echinodermata (in adults) (sea stars, sand dollars) Deuterostome development Chordata Segmentation (vertebrates, tunicates) General Mollusc Characteristics
• Coelomate, Triploblastic • Protostome (lophotrochozoan) • Cephalization • Complete digestive system • Nephridium • Marine, freshwater, terrestrial
Defining Characteristics of Molluscs
• Mantle with mantle cavity • Shell (except where lost) • Visceral mass • Foot • Radula Ctenidia Radula in Marine Snails
Radula retracted into chamber Odontophore moves forward, radula contacts food
Scanning electron micrograph of Atlanta californiensis radula. Modified from Seapy and Richter (1993)
Mollusc shell layers Figure 12_01
Peristracal spines
From prismatic layer, (shell fractured and protein matrix dissolved away)
From nacreous layer, individual calcareous tablets Open Circulatory System in Molluscs Phylum Mollusca
Class Polyplacophora (chitons) Class Gastropoda (snails) Subclass Prosobranchia Subclass Opisthobranchia Subclass Pulmonata Class Bivalvia (clams, etc.) Class Cephalopoda (octopus, squid, etc.)
Class Monoplacophora
One Gill Class Polyplacophora (Chitons) Figure 12_06 Class Polyplacophora (chiton) Class Polyplacophora Class Gastropoda: nudibranchs (top left and right), terrestrial snail (bottom left), deer cowrie (bottom right)
Subclass Opisthobranchia Subclass Opisthobranchia
Subclass Pulmonata Subclass Prosobranchia Subclass Prosobranchia
Figure 12_11 Figure 12_12 Subclass Opisthobranchia Order Nudibranchia Figure 12_18 Class Gastropoda, Subclass Pulmonata
The results of torsion in a gastropod Hypothetical untorted gastropod
Torsion in Gastropods Class Bivalvia: Scallop Anatomy of a clam Class Bivalvia Bivalve ctenidial structure and counter-current exchange
water flow
hemolymph flow
Figure 12_03
Counter-Current Exchange Figure 12_28 Class Cephalopoda: Squid (top left and bottom left), nautilus (top right), octopus (bottom right) Nautilus
Figure 12_37 Figure 12_38
Architeuthis
Artist’s imagination Loligo opalescens Loligo opalescens Loligo opalescens Loligo opalescens