Annelids, Mollusks and Arthropods

Announcements

•There will be a quiz next lab that covers materials from annelids and echinoderms.•Assignment for this lab include page77, 78,79, 80 and 81

This lab.

•definitions•Mollusks•Annelids•Arthropods•Dissection of formaline-fixed earthworm and squid•Examination of Grasshoppers,Crayfish

Phylogeny of protostome matazoans

Mollusks Annelides

Arthropods

Mantle

Veliger larva

Radula

Closed vascular systemTrochophore larva lost

Jointed appendage

Exoskeleton

Metamerism

Trochphore larvaschizocoelom

Protostome mode of developement

Assumed ancestral character:bilateral symmetry, mouth and anus

Definitions * Protostome (Schizocoelomate): multicellular metazoans with a coelom formed by splitting in the mesoderm layer*Trochophore: ciliated larval stage*Metamerism: body segmentation. Coelom in each segment is separated from the other.Segmentation allow better control of body movement and function. *Serially homologous structures share a common origin through segmental duplication.

Definitions*Mantle: skirt-like epidermal enlargement that surround the viscera and is responsible for synthesis of the shell* Radula: tongue-like structure formed by a belt of tissue covered with chitinous teeth.*Setae: chitinous bristles on each segment used for burrowing.*Jointed exoskeleton: hard chitinous plates separated by flexible membranes

Annelids, Mollusks and Arthropods

* Grouped together b/c they evolved three shared derived characters1- Trochophore larva2- Schizocoelom3- protostome mode of development

Mollusks * They evolved1- mantle2- veliger larva (certain type of trochophore)3- radula*They feed on algae using the radula and exchange gases using gills*The foot (ventral mass of muscle) is used for locomotion

Radula heart of a clam mantle

MollusksThey include1-Polyplacophora (chitons) -no distinct head -8 shell plates -large foot2-Gastropoda (snails) -distinct head -spiral shell -U-shaped gut3-Bivalvia (clams, oysters) - two parts shell -filter feeders

Mollusks4-Cephalopoda(octopus, squid) -adapted for free swimming (jet propulsion of water) -muscular mantle -foot modified into multiple arms (8 in case of octopus and 8+2 tentacles in squid) -horny parrot-like beak adapted for predation -squid eyes are analogous to vertebrate eyes - the pen is a chitineous structure homologous to the exoskeleton of the arthropods and anologous to the notochord of vertebrates

Annelids

*they are -metameric scchizocoels -nerves, muscles, nephridial tubes and blood vessels are serially homologous -closed vascular system -appendages on each segment include parapodia and/or setae -well developed digestive system(crop,gizzard, stomach and intestine) -gas exchange through body surface

Annelids

They include1-Polychaeta (marine fanworms)2-Oligochaeta(earthworms)3-Hirudinea(leeches) -lost setae and move by undulatory swimming - it has some therapeutic indications (venous congestion to areas with good arterial supply)

Arthropods

* They are -metameric schizocoel -segmentation is less regular(fused or lost) -lost trochophore larval stage -modification of the appendages (sensing, collection of food, grinding food, defense, transfer of gametes or aeration -ancestral open vascular system -jointed exoskeleton -complex gas exchange organs -serially homologous appendages

Arthropods* They include1-Chelicerata (spider, mites and ticks) -chelicerae -cephalothorax and abdomen2-Crustacea (lobsters, crayfish and crabs) -aquatic -2 pairs of antennae -use mandibles to crush food -gills -head, thorax and abdomen -biramous appendages

Arthropods

3-Uniramia (insects) -unbranched appendages -mouth with pair mandible and two pairs of maxillae -pair of antennae -branching gas-filled tubes -head, thorax and abdomen

What should I do

1- dissect formaline fixed earthworm2- dissect fresh squid3- clams and grasshoppers also available 4-demo (live earthworm, leeches, hissing roaches)5-Sonoran arthropod studies institute cart (bug cart)