Phylum Arthropoda

General

Characteristics •Arthropod = “jointed foot”

•Exhibit bilateral symmetry

•Segmented animals

•Segments bear paired,

jointed extensions

(appendages) such as

legs and antennae

•Presence of chitinous exoskeleton made of hardened plates (sclerites) which must be shed as organism grows

• Exoskeleton

– Protection

– Support

– Points of muscle

attachment

–Gas exchange

–Water regulation

•Integument (outermost

body layer of an

organism) is composed

of three principle

layers

•Integument layers

–Epidermis (cellular layer)

–Basement membrane (acellular layer below the epidermis)

–Cuticle (acellular layer above the epidermis)

•Basement membrane- thin sheet of collagen

–Supports cells of epidermis and separates it from underlying tissues

•Cuticle- made up of chains of polysaccharide (chitin) embedded in a protein matrix

–Cuticle can be separated into three distinct layers

•Cuticle layers- epicuticle,

exocuticle, and endocuticle

•a trichogen cell produces a

non-perforated seta, a

tormogen cell produces the

socket

•Epicuticle contains the wax layer, which prevents water loss

–Outermost layer

•Exocuticle- layer of

sclerotized cuticle

–Provides rigidness

of cuticle

•Endocuticle- unsclerotized layer that connects sclerites

–Pliable

–Can be reabsorbed into body before molting (ecdysis)

•Open circulatory system

–Only blood vessel usually being a tubular structure dorsal to the alimentary canal with lateral openings in the abdominal region

•Tubular

alimentary canal,

with mouth and

anus

Some comparisons in excretory

systems

•Excretion in insects

usually by means of

malphighian tubules

that empty into the

alimentary canal

Excretion in marine arthropods

occurs across gills and

antennal/green glands.

Vertebrate Kidneys

•Respiration via gills, or trechae and spiracles

•No cilia

•Separate sexes

Subphylum Chelicerata

•Greek chele = claw and keras = horn

•Spiders, mites, scorpions, sea spiders, and horseshoe crabs

•Antennae absent

and pincerlike

mouthparts called

chelicerae are

present

Class Meristomata

•Horseshoe Crabs

•Physical characteristics

• Compound eyes

–10 eyes

•5 Prs. of book gills

•6 Prs. of legs

Class Pycnogonida

•Means “all legs”

•Sea spiders

•Long proboscis used to

feed on soft inverts

•Digestive system ends

in legs; diverticulae,

or “blind pouch”

•Head has ovigers, on

which eggs are carried.

•Males carry eggs

Subphylum Crustacea

•Crustaceans