Exam 2 Terms

chitin

a nitrogenous polysaccharide bonded with protein in order to make the hard exoskeleton in arthropods

malpighian tubule

nauplius

ancestral larval stage of crustaceans

lyriform organ

specialized structures used in Arachnida for vibrational detection

radula

a scraping mechanism used in feeding of Gastropods with teeth-like projections

torsion

in Orthogastropods, where the body and internal structures undergo twisting in order to fit into a shell

stellate ganglion

found in Crustaceans, part of the nervous system to control motor activity, sensory input/output - typically in a star-like shape

chromatophore

Used in cephalopods for color changing patterns in foraging, communication, and defense

ophiopluteus

the free-swimming larva form of brittle stars (Ophiuroidea) that exhibits bilateral symmetry

echinopluteus

free-swimming larval stage of sea urchins & sand dollar (Echinoidea) with bilateral symmetry

notochord

a flexible, rod-like structure that runs along the dorsal side of the body, allowing efficient movement, a defining characteristic of phylum Chordata

enterocoely

deuterostomate developments where the coelom forms from enteric pouches

polytomy

a pattern found on a phylogenetic tree where one ancestral lineage splits into 3 or more descending lineages at one point, usually as the result of insufficient data

Ecdysozoa

includes arthropods and nematodes because they share an ancestor with a molted cuticle

sclerotization

A process found in Arthropods where the cuticle, outer covering, becomes hardened and stiff to protect them from dessication and predators

holometabolous

insects which undergo complete metamorphosis at adulthood

megalops

crustacean larval stage for Decapods

pedipalp

specialized appendages near the mouth in phylum Arthropoda, specifically important in Class Arachnida, positioned behind chelicerae for sensory, feeding, defense, and reproduction in males

zebra mussel

freshwater mussel native to Eastern Europe (Black Sea, Caspian Sea, Aral Sea)

• - invaded western European waters in 1700s

• - arrived in US in ballast water of European ships bringing cargo to the Great Lakes mid-1980s

• - clogs intake pipes, sewers, ship bottoms because it attaches to vegetation and other rmolluscs

nacreous layer

characteristic of phylum Mollusca; made of calcium carbonate and proteins to protect the shell from cracking and produces pearls

trochophore

larval stage common to polychaete annelids and molluscs

Aristotle’s lantern

mouth structure found in regular sea urchins (echinoids) that contains 5 teeth

brachiolaria

second larval stage in starfish (Asteroidea) that develop from bipinnaria to become bottom-dwelling

lophophore

a u-shaped set of ciliated tentacles used in filter feeding

myomeres

segmented muscle blocks separated by connective tissue to power locomotion like swimming in chordates

schizocoely

protostomate development where the coelom forms from split in mesoderm

clade

group of organisms that includes a single common ancestor and all of its descendants forming a complete branch of a phylogenetic tree

Lophotrochozoa

Includes molluscs and annelids because they share an ancestor with trochophore larva

ecdysone

molting hormones released once environmental cues stimulate the CNS

spiracle

small openings found in arthropods that regulate gas exchange and respiration

zoea

another crustacean larval stage for decapods

book lungs

characteristic of class Arachnida, a series of thin plates arranged like the pages of a book to provide extensive surface for gas exchange

odontophore

within the radular membrane that has muscles to protract and retract the radula in feeding

hypostracum

in arthropods and molluscs, it is the innermost layer of the cuticle that lies above the hypodermis (arthropods) or mantle (mollusca) for support

glochidia

freshwater clam larvae specialized for temporary parasitism on gills of fish

podia

in echinoderms, they are small branched projections from the body wall that function like gills to allow animals to absorb oxygen form water

doliolaria

larval stage of class Crinoidea, barrel-shaped and emerges from the auricuaria larval stage

pedicle

characteristic of Brachiopods, that is, a specialized stalk-like or fleshy appendage that allows them to attach to the substrate

tadpole larva

larval stage for Urochordates

radial cleavage

indeterminate development of cells

synapomorphy

a shared, derived characteristic by 2 or more taxa that is present in their most recent common ancestor (defines clades)

protostomate

spiral cleavage with determinate (mosaic) development (cells have pre-determined fate)

• - mouth forms first

metamorphosis

ommatidium

found in phylum Arthropoda, it is a tiny, complete ‘eye subunit’ within a compound eye which is made up of 100s of these units

biramous

appendages found in Crustaceans that have a secondary structure or gill that aids in respiration

spinneret

a specialized structure found in the class Arachnida, where silk glands produce silk and is excreted through these, where the air hardens it for practical usage

ctenidia

characteristic of phylum mollusca, they are specialized comb-like gills for respiration, gas exchange, and filter feeding

cerrata

specialized appendages for feeding on Cnidarians where they sequester their nematocysts for defense

veliger

Larval stage of gastropods and bivalves

• - has a velum for swimming & feeding

• - torsion stage in gastropods

bipinnaria

free-swimming larval stage in most starfish (Asteroidea), typically transforms into brachiolaria larva which has additional arms for adhering to things

auricularia

free-swimming larval stage for sea cucumbers (Holothuroidea)

zooid

an individual living unit within the colonial organism that are encased in the zooecium and can be specialized for different functions

tunic

a rough outer covering that surrounds the body of the animal to provide protection, characteristic of phylum urochordata

spiral cleavage

determinate development of cells

symplesiomorphy

shared ancestral trait that is found in 2 or more groups (ie. bilateral symmetry)

deuterostomate

radial cleavage with indeterminate (regulative) development of cells (anus forms first)