Chapter 38 Arthropods Subphylum: Crustacea

Characteristics Arthropods have three main characteristics: A tough exoskeleton, made of chitin Jointed appendages A segmented body

Subphylum Crustacea Contains over 40,000 species Crustaceans are abundant in oceans, lakes, and rivers Some crustaceans are Sessile (no movement) move by walking on legs swimming with paddle like appendages Drift with currents

Crustaceans Includes shrimp, lobsters, crayfish, barnacles, isopods, copepods, and water fleas.

External Structure 2 Major Sections: Cephalothorax: Head with 5 segments Thorax with 8 segments Fused together = carpace Abdomen: 7 segments 7th segment = telson

External Features 2 pairs of antennae/feelers Chelipeds-modified claws Mandibles Maxillae Maxillipeds Chelipeds-modified claws Larger claw crushes prey Smaller claw holds and tears food Walking legs Swimmerets Uropod- tail flips

Crayfish A freshwater crustacean A decapod: 10 feet composed of 5 pairs of legs. Shrimps and Crabs are also decapods.

Crayfish parts

Feeding Crayfish are bottom dwellers Eat things such as worms, slugs, bugs and vegetation Minimal effort into hunting but will eat small fish that inhabit the area they live in

Digestion Food  esophagus  stomach intestine  anus teeth made of chitin and calcium carbonate grind the food into a fine paste Paste mixed with enzymes secreted by a digestive gland Move to intestine for digestion and absorption. Indigestible material is excreted through the anus

Crustacean Excretion H20 constantly enters tissues by osmosis Have green glands Eliminates excess water Through pore at base of antennae

Respiration Gills: Extend from base of walking leg into chamber under carapace Legs circulate H2O across gills Permits gas diffusion

OPEN Circulatory System

Nervous System/Response Brain that consist of ganglia Receive nerve impulses from eyes & antennules Ventral nerve cord Sense vibrations and chemical in water Small sensory hairs on exoskeleton

Reproduction Male deposits sack filled with sperm on the underside of the females belly Female release eggs to sperm Embyro free swimming naupilus  molts  adult 3 pairs of appendages single eye