Phylum Arthropoda Notes

arthropoda - “jointed feet”

paired, jointed appendages

joints allow for MOVEMENT

bilateral symmetry

body is segmented (sets of repeated units)

3 main REGIONS (head, thorax, abdomen)

segmentation within the thorax and within the abdomen

Compound eyes

• bundle of visual units

• each unit forms a portion of the total image

• poor image resolution (blurry)

• wide field of view

Open circulatory system

• blood flows freely within body cavities where it makes direct contact with all internal tissues and organs.

• heart but no blood flows outside blood vessels

exoskeleton

• rigid, external covering that protects soft tissue underneath

• made of chitin and calcium carbonate

• exoskeleton does not grow with them

• MOLT - arthropods must shed their exoskeleton to grow

proportion of arthropods to other animals

• 85% of all known animal species are arthropods

• about one million arthropod species have been described, of which most are insects

anatomy of a crayfish

• antennules (short) and ANTENNA (long) - taste/touch

• chelipeds - legs that bear the largest claws (catch food, defense)

• walking legs - 4 pairs

• cephalothorax - fused head and thorax

• carapace - exoskeleton that covers the cephalothorax, gills underneath

• abdomen - (“the tail”) behind cephalothorax, 6 segments, contains swimmerets and a tail fan

• swimmerets - under abdomen, used for swimming and carrying eggs (female)

ESCAPING PREDATORS

• they propel themselves backwards with flips of the abdomen and tailfan

tailfan

• located at end of the end (telson and uropods)

• TELSON - middle paddle

• UROPODS - two pairs, either side of telson

• works with the abdomen to move the crayfish backwards

copepods, barnicles, amphipods, isopods, krill, lobsters, crabs, shrimp, hermit crabs

copepods

1 to 2 mm long

single, bright red eye (mostly)

planktonic (drifting)

1st pair of antennae long

important part of the food chain

amphipods

compressed, curved bodies

sand fleas/sand hoppers

usually eat decaying matter but can bite

isopods

same size as amphipods but flat on top instead of curved

some species are parasites of fish (fish lice)

barnacles

live attached to surfaces

rocky, intertidal areas

bodies enclosed in thick plates

CIRRI - featherly legs used to filter feed

lie on their backs

FUN FACT! can stretch their penis to reach neighboring barnacles

decapods

• decapoda means “10 legs”

• largest crustaceans

• shrimps, lobsters, crabs, crayfish

• commercially important food source

• eyes on stalks that move independently

krill

small, decapod crustaceans (6 cm in length)

common in polar waters

feed on phytoplankton

vital food source for ______, penguins, and fish

determining the sex of a crayfish

MALES - 1st pair of swimmerets are rigid and long

FEMALES - 1st pair of swimmerets are thin and feathery

communication

communicate through chemical signals by peeing out of their face!

use postures to settle disputes over territory and in courtships.

crabs

in crabs, abdomens are fused under the body

females have a rounded abdomen

males have a t-shaped abdomen (jimmies)

sponge crab - a female carrying her fertilized eggs on her abdomen

it is illegal in the state of NJ to have in your possession a sponge crab

life cycle of a crab

fertilized eggs hatch into planktonic larvae

larvae go through metamorphosis to become juveniles

molt 20 times into adulthood

females mate after final molting