Arthropods

Bio 313

Abundance

82% of all animal species

Body plan

Segmented, usually organized in head, thorax, and abdomen (or variation)

skeleton

external, made mostly of chiton

Marine chelicerata

Horseshoe crabs

horseshoe crabs

benthic, predators (dig up clams and worms)

Prosoma

Cepalothorax, biggest region that contains head and appendages

carapace

covers/protects the prosoma

opisthoma

spined, segmented abdomen that contains gills

hinge

connects the prosoma and opisthoma

book gills

5 pairs, housed in branchial chamber, each contains >100 lamellae (gas exchange)

telson

tail, used for locomotion and self righting

lobes/ridges

help distinguish different segments

gizzard

mechanically grinds food

proventriculus

works with crop to store food

ocelli

detect light, used to time spawning

compound eye

form images, navigation

chelicera

first appendage pair, used for handling food

walking legs

walking

pedipalps

first pair of walking legs, in males have claspers for mating

mouth

eating

chilaria

flap like appendages on underside that help guide food towards mouth

gnathobase

jaw like structures that help with grinding food

Horsehoe crab protein

limulus amebocyte lysate

Horseshoe crab reproduction

smaller males hook onto females for external fertilization

trilobites

molt their way to adulthood

Sea Spiders (marine chelicerata)

pycnogonida class

Horseshoe crab class

merostomata

Sea Spiders diet

hydroids, worms, nudis, anenomes

Sea spiders reproduction

external fertilization, usually in pairs, males brood for several weeks/months

cephalon

sea spider head region

chelicera (sea spider)

claw like apendages on cephalon used for handling prey

proboscis

sucks up prey

palp/pedipalp (sea spiders)

physical sensing of evironment

ovigers

pairs of legs, usually on males used to carry egg masses

abdomen (sea spiders)

hosts the anus

ocular tubercle

hosts the eyes

trunk

the segmented body, in most species 3 or 4 segments, each with a pair of legs

sea spiders digestion

gut extends into all legs, undergoes peristalsis to move gut materials around

sea spider respiration

no gills, lungs, or tracheae, instead oxygen diffuses across cuticle of legs into blood

sea spider circulation

heart is small and weak, blood pumped as gut undergoes peristalsis

crustacea subphylum

11 classes

thecostraca class

barnacles, all marine/estuarine, 1/3 are true parasites, 2/3 are free living sessile organisms

barncale plates

have an “extra” exoskeleton of calcareous plates that open and clsoe to expose cirri (feeding and respiration) and allow for reproduction and excretion

goose barnacle connecting structure

softer, flexible, peduncle, which allows for movement and for main body (capitulum) to sway in water

acorn barncale connecting structure

no peduncle, barnacles plates are directly cemented to surface

cirri

six pairs of feathery limbs, covered in cetae (sensory hairs) that are used for feeding and movement

plates

hard, protective, outer calcium carbonate structures that close for protection and open to expose cirri

two types of plates

scutum and tergum

cement gland

secretes cement to attach the barnacle to a substrate

peduncle

stalk like structure in goose barnacles that serve as attachment to substrate and hosts ovaries

capitulum

main body, separate from peduncle

antennae

initial, primary attachment, cement is secreted around the antennae to fortify attachment (absent in goose barncales)

scutum

bigger plates, anterior/dorsal side

tergum

smaller plates, posterior/ventral side

thecostraca reproduction

cypris larvae settle face down, mainly internal reproduction between hermaphrodites that use very long penis to explore local mating env

thecostraca feeding

beating/moving cirri create current to increase particle capture (filter feeding), cirri retract into capitulum and food particles transferred from larger cirri to smaller cirri, then mouth