BIOL 3454 1nd Edition Lecture 16I. zebra musselsa. first discovered in the US in 1988 from black and caspian seasb. most likely introduced in ballast waterc. cause a 40 million dollar impact in US yearlyII. Class Caudofoveataa. About 120 species of marine wormlike burrowing animalsb. Feed on microorganisms and detritus c. Has an oral shield d. Radulae. Dioecious III. Class Solenogastres a. About 250 species b. Similar to caudofoveatesc. But no radula and no gillsd. Foot is a pedal groove e. Hermaphroditic f. Usually feed on cnidariansIV. Class Polyplacophoraa. Chitons – sea beaf b. 7 or 8 articulated platesc. Sensory organs reduced – esthestes (eyes) a photosensitive structured. Live on rocky surfaces in intertidal regions e. 3 chambered heart f. Can roll up like an armadillo g. Clings with a broad footh. Most scrape algae i. Some predatoryj. Pair of osphradia for chemoreception in mantle cavityk. Sexes separate l. Trochophores become juveniles (no veliger stage)V. Class Monoplacophoraa. Long thought to be extinct b. About 25 species c. Rounded shelld. 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)VI. Class Gastropodaa. Most diverse 70,000 species b. So big no single term – snail, slugs, limpets, conchs, whelks, periwinklesThese 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. Shells are the chief defense called a valve or univalved. Dextral (right)/sinistral (left) – dextral more common and is genetically controllede. Many have an operculum or cover that protects the shells aperture (opening)f. 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 openingg. Torsion weirdnessi. Detorsion occurs in opistobranchs and pulmonates but derive from torted ancestors ii. Torsion creates a problem – anus opens over head and gills h. Coiling i. Not the same as torsion – originated earlier in evolutionary history ii. Early gastropod planospiral – all whorls in the same planeiii. Consipiral shells evolved later – symmetrical and unstable (mass shifted upwardsand backwards)iv. Some modern gastropods have re-evolved planopiralityi. Gastropod defensei. Protected by shells distasteful or toxic secretions ii. Some eat cnidarians, incorporate nematocysts and use them for defenseiii. 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)j. Gastropod feeding i. Very diverse but all have radulaii. Most herbivorous k. 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 kidneyiv. Eyes (some with cornea and lens), photoreceptors, statocysts, tactile organs, andchemoreceptors l. 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 m. Gastropod Taxonomy i. Traditionally 3 classes1. 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 hearq. Operculum usually present r. One part of tentacles s. Sexes usually separate VII. Opisthobranchsa. See slugs, sea haresb. Some pelagic (open ocean), shallow marine waterc. 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 VIII. Pulmonatesa. Most land and freshwater snailsb. 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 eyesIX. Class Cephalopoda a. Head/footb. Squid, octopus, nautilus, devilfish, cuttlefishc. 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 shellv. Octopus have no shell g. Locomotion i. Forcefully expel water from the siphon (direction control)ii. Squid very fast iii. Cuttlefish sloweriv. Nautilus even slowerv. 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 getii. 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 bloodpressure i. Nervous and sensory systems i. Very elaborate systemsii. Squid have larges known nerve fibersiii. 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