Molluscs

Molluscs/Mollusks Over 200,000 species of molluscs More marine species than any other Phylum Most have soft bodies enclosed in calcium carbonate shell.

Structure Body covered by mantle, thin tissue that secretes the shell Have ventral, muscular foot, for locomotion Have head w/ eyes & sensory organs Radula unique to molluscs ribbon of small teeth used to feed made of chitin (highly resistant carbohydrate)

Body Functions Nervous System - well-defined with a primitive brain; ganglia = “local brains” in different parts of body Circulatory system – blood vessels & 2-chambered heart Digestive system - usually includes a jaw, salivary glands, pharynx, esophagus, stomach, intestine and anus Reproductive system – separate sexes & external fertilization  Respiration system –gills

Types of Molluscs All molluscs have basic body plan but greatly modified depending on class. 3 Main Classes: Cephalopoda (Cephalopods) Gastropoda (Gastropods) Bivalves (Bivalvia)

Cephalopods Name means “head-footed” 650 species, all marine Predators specialized for locomotion Includes: octopus, squid, cuttlefish, & other fascinating molluscs

Class Gastropoda Largest and most varied class of mollusk 90,000 species Gastropod (stomach foot) Foot on ventral side (stomach) Examples: Snails, limpets, abalones, nudibranchs

Snails

Nudibranchs

Class Bivalvia Body compressed and enclosed in a two valved shell Very small head, no radula Gills expanded and folded and used to filter out food particles as well as gas exchange Strong muscles are used to close the valves

Clams Giant Clam

Mussels Oysters Scallops

Arthropoda

Arthropods Arthropoda = jointed foot Largest phylum Includes insects, spiders, centipedes, millipedes and crustaceans Inhabit almost every environment on Earth

Arthropod Characteristics Segmented Body Bilateral symmetry Jointed appendages: mouth parts and legs Compound eyes Exoskeleton: hard, chitonous external skeleton Limits growth Must molt

Classification

Biology of Arthropods Feeding Respiration Circulation Can be parasitic, filter feeders, or detrivores Respiration Do Not have Lungs Tracheal Tubes – extend through body Air transferred through Spiracles Marine arthropods have gills or book lungs Circulation Have ganglia or many hearts run along body

Subphylum Crustacea The majority of marine arthropods Gills Includes: shrimps, lobsters, crabs 68,000 species Gills Skeleton hardened by calcium carbonate Appendages used to swim and/or crawl 2 pairs of antennae = sense “Green” gland = salt regulation Ventral nerve chord Complete digestive system

Subphylum Chelicerata All have pinchers Mouthpart called chelicerates Two body sections: Abdomen & Cephalothorax Nearly all have four pair of legs Include: Spiders, Horseshoe Crabs, Scorpions, Ticks

Insecta (Insects) Body divided into 3 parts: Head, Thorax, & Abdomen Three pairs of legs attached to the thorax Have compound eyes Sense taste & smell Growth involves metamorphosis Eggs  Nymph  Adult Eggs  Larva  Pupa  Adult Form societies: closely related animals; same species

Subphylum Uniramia Insects Have jaws 3 pairs of legs One pair antannae Examples: Centipedes : 1 pair of legs per segment Millipedes : 2 pair of legs per segment

Sea Stars, Brittle Stars, Sea Urchins, Sea Cucumbers, & Crinoids Echinodermata Sea Stars, Brittle Stars, Sea Urchins, Sea Cucumbers, & Crinoids

Echinoderm Characteristics Echinodermata = spiny skin Endoskeleton Secreted within the tissues Water vascular system Madreporite = where water enters Tube Feet Muscular extensions of canals End in Suckers Used for attachment, locomotion, & sensing stimuli Pentamerous symmetry = 5 part Larvae = bilateral symmetry

Behavior Carnivorous, detritus foragers, planktonic feeders Reproduce by Spawning & Asexually Regeneration Protection = Spiny skins and spines Predators: Mollusks Fish Crabs and shrimps Other echinoderms

Ecology and Range Only marine Various habitats Intertidal zone to bottom of the deep sea trenches Sand to coral reefs Cold and tropical seas

Classes of Echinoderms