Arthropod quiz prep 1: Chelicerates and Barnacles

Chitin

Material that makes up the arthropod exoskeleton

Molting

Process whereby arthropods shed and regrow their exoskeleton; required for growth

Crustacea

Arthropod subphylum characterized by four antennae, typially 10 legs, and a cephalothorax (fused head and thorax)

Head, thorax, abdomen

Typical three segments of the arthropod body, in order from front to back

Hexapoda

Arthropod subphylum characterized by two antennae, six legs, and three body segments (head, thorax, abdomen)

Myriapoda

Arthropod subphylum characterized by two antennae, many legs, a distinct head and a segmented trunk (fused thorax and abdomen)

Chelicerata

Arthropod subphylum characterized by no antennae, 4-5 pairs of walking legs, and a first leg pair featuring a claw or similar structure

Merostomata

Class of horseshoe crabs

Gizzard

(Merostomata) structure that mechanically grinds food

Proventriculus

(Merostomata) structure that works with the crop to store food

Ocelli

(Merostomata) structures that detect light and are used to time spawning

Compound eye

(Merostomata) structure that forms images and is used for navigation

Chelicera

(Merostomata) first appendage pair, used for handling food

Walking Legs

(Merostomata) structures used for walking

Pedipalps

(Merostomata) first pair of walking legs, features claspers for mating in males

Chilaria

(Merostomata) flap-like appendages on the underside that help guide food toward the mouth

Gnathobase

(Merostomata) jawlike structures that help with grinding food

Tribobite

(Merostomata) name of the larval stage (very adorable)

Pycnogonida

Class of sea spiders

Pycnogonid reproduction

External fertilization in pairs, the male catches and broods the fertilized eggs

Cephalon

(Pycnogonida) head region

Chelicera/Chelifores

(Pycnogonida) claw-like appendages on the cephalon used for handling prey

Proboscis

(Pycnogonida) sucks up prey

Palps/Pedipalps

(Pycnogonida) structures for physical sensing of the environment

Ovigers/Ovigerous Legs

(Pycnogonida) pairs of legs, usually found only in males, used to carry egg masses

Abdomen

(Pycnogonida) structure that hosts the anus

Ocular Tubercle

(Pycnogonida) structure that hosts the eyes

Trunk

(Pycnogonida) the segmented body; in most species 3-4 segments but some may have 5 or 6

Pycnogonid Digestion

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

Pycnogonid Respiration

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

Pycnogonid Circulation

small, weak heart, blood largely pumped by peristalsis of the gut

Pycnogonid Gonad Storage

unfertilized eggs stored in legs of female, fertilized eggs stored on ovigers (egg legs, leggs if you will) of male

Cirri

(Thecostraca) feathery limbs used for feeding and respiration, and for movement while larval

Thecostraca

Class of barnacles

1/3 true parasites, 2/3 free living

Thecostraca parasitism rates

Mostly Balanus

Acorn barnacle genus

Mostly Lepas or Pollicipes

Gooseneck barnacle genus

Acorn barnacle attachment

No peduncle, barnacle plates cemented directly to the substrate

Goose barnacle attachment

Softer, flexible peduncle which allows the main body to sway in the water, still secretes cement from cement glands for attachment

Capitulum

(Thecostraca) main body

Cetae

(Thecostraca) sensory hairs found on the cirri

Scutum

(Thecostraca) bigger, more anterior/dorsal plates

Plates

(Thecostraca) hard, protective outer calciul carbonate structures that close for protection and open to expose the cirri. Two types: scutum and tergum.

Tergum

(Thecostraca) smaller, more posterior/ventral plates that are a little more mobile