Arthropods and Echinoderms

Defining characteristics of Arthropods

Jointed appendages and an exoskeleton

Chitin

Structural sugar, it is what the exoskeleton is made of

Simple eyes

used for light sensing

Compound eyes

used for image formation

Decapods

Specific group of crustaceans who possess 10 legs

Crab abdomen variation among sexes

U-shaped females, V-shaped males

Barnacle feeding

They are sessile filter feeders, using their cirri to grab food.

Uniramia

insects, centipedes, millipedes

Chelicerata

Horseshoe crabs, spiders, scorpions, mites etc.

Trilobita

trilobites (extinct), early arthropods

Crustacea

a large class of arthropods, including crabs and lobsters

Pereopod

walking legs

Antennae

A feeler that senses touch, taste or smell. On the head.

Mandible

Chewing structure in arthropods

Uropod

The tail appendage in crustaceans

Pleopod

swimming limb of a crustacean

Maxilliped

Specialized appendage used to hold food

Maxilla

Appendage that passes food into the mandible

Horseshoe Crab

A bottom-dwelling marine chelicerate. Not a true crab.

Copepod

A small planktonic arthropod, uses large antennae to swim. A key member of the food chain.

Barnacle

a marine crustacean which attaches itself permanently to a variety of surfaces

Amphipod

small crusraceans with a curved body that is flattened sideways

Isopod

a laterally flattened crustacean with 14 legs, common scavenger

Lobster

A decapod, usually with large claws. Commonly used for food.

Brachyuran (true) crabs

True crabs; reduced abdomen; one pair of pincers; Football shaped

Hermit (anomuran) crabs

Not true crabs, hide their soft abdomens in abandoned gastropod shells

Molting

Process in which an arthropod sheds its exoskeleton and manufactures a larger one.

Disadvantages of exoskeletons

Weight; Also requires molting which leaves the animal vulnerable.

Pentaradial Symmetry

circular body plan that can be divided into 5 equal parts. Adult echinoderms have this.

Deuterostome development

Advanced development found in echinoderms and chordates. Can repair embroyos.

Water Vascular System

system of fluid-filled tubes used by echinoderms in locomotion, feeding, and respiration

Order of the water vascular system

madreporite, stone canal, ring canal, radial canal, ampullae, tube feet (podia)

Sea star feeding

uses two stomachs. one pushed out of body to capture prey, one for digestion.

Pedicellaria

pincerlike appendages on echinoderms used for protection and cleaning

Asteroidea

True sea stars. Organs extend into arms, move with tube feet.

Ophiuroidea

brittle stars. No organs in arms, move with snakelike motions.

Echinoidea

sea urchins and sand dollars. Have spines.

Crinoidea

sea lilies and feather stars

Holothuroidea

sea cucumbers