Animal diversity 2: arthropods, molluscs, annelids, dissection

Ecdysozoa

Supergroup of protostomes; characterized by periodic molting of their exoskeleton. Include the roundworms and arthropods.

Ecdysis

molting

Arthropoda

Chelicerates, crustaceans, insects, myriapods

Arthropod circulatory system

Open, hemolymph flows through hemocoel

Hemolymph

In invertebrates with an open circulatory system, the body fluid that bathes tissues.

Arthropod exoskeleton

made of chitin

Chelicerates

1. Sea spiders and horseshoe crabs

2. arachnida

Chelicerae

pair of mouthparts in chelicerates that contain fangs or pinchers

Pedipalps

pair of mouthparts in chelicerates that are usually modified to grab prey

Arachnida

spiders, scorpions, ticks, mites

Arachnid and crustacean body plan

cephalothorax and abdomen

Total number of arachnid appendages

6 pairs total, chelicerae, pedipalps, and 4 pairs of walking legs

Crustaceans

1. Lobsters, crayfish, crabs, shrimp

2. copepods and barnacles

crayfish

19 body parts, antennae, mouthparts (maxillipeds), claws (chelipeds), 4 pairs of walking legs, swimmerets, telson (tail)

External crayfish anatomy

Internal crayfish anatomy

insects

Bees, butterflies, fleas, grasshoppers, true bugs, etc

Insect body plan

head, thorax, abdomen

Insect Anatomy

Modified mouthparts, antennae, 3 pairs of walking legs, wings are extension of cuticle

Insect tracheal system

a network of air tubes that branch throughout the body

Spiracles

breathing tubes of insects located on abdomen

complete metamorphosis

Insect development consisting of four stages: egg, larva, pupa, and adult

incomplete (gradual) metamorphosis

Insect development consisting of three stages: egg, nymph, and adult

Myriapods

centipedes and millipedes

Centipedes

segmented bodies, 1 pair of legs per segment, predators with a pair of venomous claws

Millipedes

A terrestrial arthropod that has two pairs of short legs for each of its numerous body segments and that eats decaying plant matter.

Detritivore

organism that feeds on plant and animal remains and other dead matter

Mollusca

Lophotrochozoan: chitons, gastropods, bivalves, cephalopods

Mollusc circulatory system

Open except for cephalopods

Mollusc Anatomy

Visceral mass, muscular foot, shell, mantle

visceral mass

area beneath the mantle of a mollusk that contains the internal organs

Muscular foot

used for movement

Mantle

Secretes shell

Chitons

8 plates

Gastropods

Snails and slugs

Bivalves

clams, oysters, mussels

Umbo

oldest part of the shell of a bivalve from which the shell grows

Layers of clam shells

Periostracum (outer layer), prismatic layer (middle layer), nacre (mother of pearl), iridescent inner layer

Clam anatomy

Cephalopods

Squids, octopi, nautilus

Pen (squid)

Inner shell

Radula

feeding structure

beak (squid)

diverticulum (squid)

the ink sack of a mollusc, you saw one in the squid.

Annelida

Annelid circulatory system

Closed

septae

Divisions between segments

Setae

Aka chaetae, bristles on each segment

Clitellum

Band of thickened, specialized segments in annelids that secretes a mucus ring into which eggs and sperm are released

How many hearts in an earthworm

5

Dissection tools

Blunt probe, dissecting pins, dissecting scissors, scalpel

Locophore

Ciliated tentacles for feeding

trocophore larva

Distinctive larval stage observed in some lophotrochozoan animals, including some annelids and molluscs.

Ocular tentacle in snails and slugs

Snail anatomy

carapace

hard outer covering or case of certain organisms such as arthropods and turtles

Squid anatomy