Chapter 7- Part 2 Marine Biology

Phylum Mollusca Mollusks

Greatest # of species Body covered by mantle made of calcium carbonate Bilateral symmetry Foot used for locomotion Radula used to feed

Gastropods: Snails Mostly eat algae from rocks- ex. Periwinkles

Continued…… Some snails such as mud snails are deposit feeders

Continued……. Snails such as whelks can be carnivorous preying on clams, worms, or small fish

Continued…… Sea slugs are snails without shells. Often have noxious chemicals or nematocysts for protection

Bivalves: Clams, mussels, oysters Body enclosed in shell Gills filter food and used for breathing Mantle lines the inside of shell

Continued…… Clams use foot to burrow in sand- water enters and leaves shell through siphon

Continued……. Mussels attach themselves by using byssal threads

Continued…… Oysters cement their left shell to a hard surface- often other oysters Pearl oysters are the source of most valuable pearls.

How a pearl is made: Particles merge in between mantle cavity and shell Oyster secretes shiny layers of calcium carbonate to coat irritating particle

Oysters can be forced to make pearls by inserting an irritant in shell (cultured pearl)

Cephalopods: Octopus, squid, cuttlefish Good swimmer Complex nervous system No shell

Arms with suckers to capture prey Eyes on side of head Move by forcing water out of their siphon, or funnel

Octopus 8 arms (2 in to 9 ft in size) bottom dwellers Efficient hunters- crabs, lobsters, and shrimp Radula scrapes away flesh

Some are toxic and their bite can paralyze Live in crevices and even discarded bottles Distract predators by spraying ink

Squid Better adapted for swimming Ten arms Two of the arms are longer and wider for catching prey Sizes range up to 66ft in the giant squid

Cuttlefish Similar to squid except the body is flattened

Biology of Mollusks

Digestion: Separate mouth and anus Radula can be modified from scraping or drilling through flesh Amount and strength of digestive enzymes range depending on matter being digested

Circulatory system: Most mollusks have a open circulatory system- blood flows out of vessels into open space Cephalopods have a closed circulatory system-blood always remains in vessels

Nervous System: Most mollusks have a ganglia Cephalopods have a more advanced brain, similar to humans Intelligent and remarkable learners- some cuttlefish can even change colors

Reproduction: Usually separate sexes Some hermaphrodites In bivalves and some snails-external fertilization Cephalopods and most snails- internal fertilization

Cephalopods do not have larvae- young born from and egg Cephalopods do not have larvae- young born from and egg. Mother usually dies after egg hatches due to lack of food while guarding egg.

Phylum Arthropoda Arthropods

Barnacles, shrimp, lobster, crab, etc. Segmented Bilateral symmetry Jointed appendages Exoskeleton

Molt to grow-old skeleton discarded, animal takes in water to expand itself, grows a new skeleton

Crustaceans: Called the insects of the sea Gills Appendages used to swim, crawl, feed, and mate Two pair of antennae (sensory organs)

Copepods- planktonic, some parasitic Small Crustaceans Copepods- planktonic, some parasitic

Barnacles-filter feeders; live attached to surfaces

Beach hoppers (amphipods)-tail and head curve down, strong jumpers

Isopods- marine version of a roly-poly

Krill- shrimp-like, filter feeders, main food source for many whales, penguins, and fish

Large Crustaceans Decapods- shrimp, lobster, crab (10 legs) Commercial importance 5 pair of walking legs First pair larger for obtaining food and in defense

Shrimps typically scavengers Lobsters tend to be nocturnal (hide during day)- scavenge and catch prey Crabs are scavengers as well Female crab-U shaped abdomen for carrying eggs Male- V shaped abdomen

Small teeth or ridges are found in stomach for grinding Digestion: Small teeth or ridges are found in stomach for grinding Digestive glands help digest and absorb nutrients

Nervous System: Small brain Compound eyes- In decapods at the end of stalks Body posture used for communication: mating, disputes, hunting, etc.

Reproduction: Mostly separate sexes Males directly penetrate females to reproduce Reproduction in decapods takes place directly after molting Can store sperm

Phylum Echinodermata: Echinoderms

Sea stars, sea urchins, sea cucumbers, etc. Larvae –bilateral symmetry Adults-radial symmetry Lack a head

Oral surface/aboral surface Water vascular system Tube feet and ampullae’s are part of this system Madreporite connects internal to the external

*Sea Stars Tube feet (with suckers) found in ambulacral groove Pedicellariae help keep surface clean Eat bivalves, snails, barnacles, etc.

Tube feet lack suckers-feeding Organic matter, small animals *Brittle Star Long arms Tube feet lack suckers-feeding Organic matter, small animals

*Sea Urchins Round, rigid, spines 5 ambulacral grooves with spines grazers Flat version with short spines- sand dollar

*Sea Cucumbers Worm-like No spines Oral/aboral surfaces at each end Tube feet modified and resemble tentacles- used to pick up food

Interesting defense methods: ~ discharge sticky substance through anus ~eviscerate internal organs

*Crinoids Better known as feather stars or sea lilies Deep waters Attached to bottom

*Digestion: Most extend stomach through mouth-digest food- and then pull stomach back in

*Nervous System: No brain Complex behaviors for the absence of a brain- camouflage, reposition itself if moved

*Reproduction: Separates sexes Sperm/egg shed directly into water Spawn all at once to ensure fertilization Asexual reproduction- if central disks is separated it can form into two new organisms (regeneration)