BIOL 3454 1nd Edition Lecture 16 I II III IV V VI zebra mussels a first discovered in the US in 1988 from black and caspian seas b most likely introduced in ballast water c cause a 40 million dollar impact in US yearly Class Caudofoveata a About 120 species of marine wormlike burrowing animals b Feed on microorganisms and detritus c Has an oral shield d Radula e Dioecious Class Solenogastres a About 250 species b Similar to caudofoveates c But no radula and no gills d Foot is a pedal groove e Hermaphroditic f Usually feed on cnidarians Class Polyplacophora a Chitons sea beaf b 7 or 8 articulated plates c Sensory organs reduced esthestes eyes a photosensitive structure d Live on rocky surfaces in intertidal regions e 3 chambered heart f Can roll up like an armadillo g Clings with a broad foot h Most scrape algae i Some predatory j Pair of osphradia for chemoreception in mantle cavity k Sexes separate l Trochophores become juveniles no veliger stage Class Monoplacophora a Long thought to be extinct b About 25 species c Rounded shell d Resemble limpets but have serially repeated organs evidence of serial metamerism e Probably the sister group to polyplacophora repeated structures probably ancestral to these two groups Class Gastropoda a Most diverse 70 000 species b So big no single term snail slugs limpets conchs whelks periwinkles These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute c d e f g h i j k l m Shells are the chief defense called a valve or univalve Dextral right sinistral left dextral more common and is genetically controlled Many have an operculum or cover that protects the shells aperture opening Gastropod form and function i Exhibit torsion to fit into shell all of the body morphs and changes through twisting ii Ontogenetic changes with age during or after the veliger stage iii 2 step process foot retractor muscle contracts and pulls shell and viscera 90 degrees counterclockwise then digestive tract moves laterally and dorsally iv Torsion functions puts gills and mantle cavity up front allows foot to be pulled in last for protection and puts anus and mouth on same side outside shell v Not a u shaped gut but through torsion have made it out the same shell opening Torsion weirdness i Detorsion occurs in opistobranchs and pulmonates but derive from torted ancestors ii Torsion creates a problem anus opens over head and gills Coiling i Not the same as torsion originated earlier in evolutionary history ii Early gastropod planospiral all whorls in the same plane iii Consipiral shells evolved later symmetrical and unstable mass shifted upwards and backwards iv Some modern gastropods have re evolved planopirality Gastropod defense i Protected by shells distasteful or toxic secretions ii Some eat cnidarians incorporate nematocysts and use them for defense iii Cone shells use a modified radula as a needle to inject toxin some species fatal to humans iv Some use their foot and operculum as a weapon fighting conchs eat in bahammas Gastropod feeding i Very diverse but all have radula ii Most herbivorous Internal form and function i Respiration by ctenidia gills ii Pulmonates lack ctenidia but have a highly vascularized part of the mantle that is a lung opens in a pneumostome iii Usually have a single kidney iv Eyes some with cornea and lens photoreceptors statocysts tactile organs and chemoreceptors Gastropod reproduction i Both dioecious and monoecious ii Some pulmonates shoot a dart into their partners body to stimulate excitement iii Some marine forms enclose their eggs some brood their eggs some attached some drift as plankton Gastropod Taxonomy i Traditionally 3 classes VII VIII IX 1 Prosobranchia marine shells paraphyletic 2 Opisthobranchia sea slugs and hares paraphyletic 3 Pulmonata fresh water and land monophyletic n Most marine o Mantel cavity anterior p Gills in front of hear q Operculum usually present r One part of tentacles s Sexes usually separate Opisthobranchs a See slugs sea hares b Some pelagic open ocean shallow marine water c Partial or complete detorsion d 2 pairs of tentacles second pair modified into rhinophores nose sensory organ e Shell reduced or absent f All monoecious g In sea butterflies foot is modified for swimming h Some feed on cnidarians and keep nematocysts Pulmonates a Most land and freshwater snails b Lost ctenidia c Vascularized mantle is a lung anus and nephridiophore open near pneumatosome d Some detorsion e Monoecious f Aquatic forms with one pair of tentacles g Terrestrial forms with 2 h Posterior pair has eyes Class Cephalopoda a Head foot b Squid octopus nautilus devilfish cuttlefish c All active predators d Modified foot concentrated in head region takes the form of a funnel for jet propulsion e All marine and sensitive to salinity like it high f Shell form and function i Nautilus have a shell with one spaces called gas chambers ii Enables them to have neutral buoyancy divided by transverse septa iii Chambers connected by siphuncle cord of living tissue iv Cuttlefish have a small curved shell v Octopus have no shell g Locomotion i Forcefully expel water from the siphon direction control ii Squid very fast iii Cuttlefish slower iv Nautilus even slower v Octopus usually crawl h Respiration and circulation i Nautiloids one pair of gills all others 2 no cilia on gills require more oxygen than cilia can get i ii One way valves and strong circular muscles keep water going one way iii Entire systemic circuit before blood reaches gills iv Opposite of vertebrates have bronchial hearts at base of gills to increase blood pressure Nervous and sensory systems i Very elaborate systems ii Squid have larges known nerve fibers iii Eyes have statocysts slits always horizontal iv Most colorblind but excellent visual acuity v Many trainable and good at observational learning respond to positive and negative reinforcement