Key Terms

amoebocyte
sponge cell with multiple functions, including nutrient delivery, egg formation, sperm delivery, and cell differentiation
Annelida
phylum of vermiform animals with metamerism
archenteron
primitive gut cavity within the gastrula that opens outward via the blastopore
Arthropoda
phylum of animals with jointed appendages
biramous
referring to two branches per appendage
captacula
tentacle-like projection that is present in tusks shells to catch prey
cephalothorax
fused head and thorax in some species
chelicera
modified first pair of appendages in subphylum Chelicerata
choanocyte
(also, collar cell) sponge cell that functions to generate a water current and to trap and ingest food particles via phagocytosis
Chordata
phylum of animals distinguished by their possession of a notochord, a dorsal, hollow nerve cord, an endostyle, pharyngeal slits, and a post-anal tail at some point in their development
clitellum
specialized band of fused segments, which aids in reproduction
Cnidaria
phylum of animals that are diploblastic and have radial symmetry
cnidocyte
specialized stinging cell found in Cnidaria
conispiral
shell shape coiled around a horizontal axis
corona
wheel-like structure on the anterior portion of the rotifer that contains cilia and moves food and water toward the mouth
ctenidium
specialized gill structure in mollusks
cuticle (animal)
the tough, external layer possessed by members of the invertebrate class Ecdysozoa that is periodically molted and replaced
cypris
larval stage in the early development of crustaceans
Echinodermata
phylum of deuterostomes with spiny skin; exclusively marine organisms
enterocoelom
coelom formed by fusion of coelomic pouches budded from the endodermal lining of the archenteron
epidermis
outer layer (from ectoderm) that lines the outside of the animal
extracellular digestion
food is taken into the gastrovascular cavity, enzymes are secreted into the cavity, and the cells lining the cavity absorb nutrients
gastrodermis
inner layer (from endoderm) that lines the digestive cavity
gastrovascular cavity
opening that serves as both a mouth and an anus, which is termed an incomplete digestive system
gemmule
structure produced by asexual reproduction in freshwater sponges where the morphology is inverted
hemocoel
internal body cavity seen in arthropods
hermaphrodite
referring to an animal where both male and female gonads are present in the same individual
invertebrata
(also, invertebrates) category of animals that do not possess a cranium or vertebral column
madreporite
pore for regulating entry and exit of water into the water vascular system
mantle
(also, pallium) specialized epidermis that encloses all visceral organs and secretes shells
mastax
jawed pharynx unique to the rotifers
medusa
free-floating cnidarian body plan with mouth on underside and tentacles hanging down from a bell
mesoglea
non-living, gel-like matrix present between ectoderm and endoderm in cnidarians
mesohyl
collagen-like gel containing suspended cells that perform various functions in the sponge
metamerism
series of body structures that are similar internally and externally, such as segments
Mollusca
phylum of protostomes with soft bodies and no segmentation
nacre
calcareous secretion produced by bivalves to line the inner side of shells as well as to coat intruding particulate matter
nauplius
larval stage in the early development of crustaceans
nematocyst
harpoon-like organelle within cnidocyte with pointed projectile and poison to stun and entangle prey
Nematoda
phylum of worm-like animals that are triploblastic, pseudocoelomates that can be free-living or parasitic
Nemertea
phylum of dorsoventrally flattened protostomes known as ribbon worms
osculum
large opening in the sponge’s body through which water leaves
ostium
pore present on the sponge’s body through which water enters
oviger
additional pair of appendages present on some arthropods between the chelicerae and pedipalps
parapodium
fleshy, flat, appendage that protrudes in pairs from each segment of polychaetes
pedipalp
second pair of appendages in Chelicerata
pilidium
larval form found in some nemertine species
pinacocyte
epithelial-like cell that forms the outermost layer of sponges and encloses a jelly-like substance called mesohyl
planospiral
shell shape coiled around a vertical axis
planuliform
larval form found in phylum Nemertea
polymorphic
possessing multiple body plans within the lifecycle of a group of organisms
polyp
stalk-like sessile life form of a cnidarians with mouth and tentacles facing upward, usually sessile but may be able to glide along surface
Porifera
phylum of animals with no true tissues, but a porous body with rudimentary endoskeleton
radula
tongue-like organ with chitinous ornamentation
rhynchocoel
cavity present above the mouth that houses the proboscis
schizocoelom
coelom formed by groups of cells that split from the endodermal layer
sclerocyte
cell that secretes silica spicules into the mesohyl
seta/chaeta
chitinous projection from the cuticle
siphon
tubular structure that serves as an inlet for water into the mantle cavity
spicule
structure made of silica or calcium carbonate that provides structural support for sponges
spongocoel
central cavity within the body of some sponges
trochophore
first of the two larval stages in mollusks
uniramous
referring to one branch per appendage
veliger
second of the two larval stages in mollusks
water vascular system
system in echinoderms where water is the circulatory fluid
zoea
larval stage in the early development of crustaceans

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Biology 2e for Biol 111 and Biol 112 Copyright © 2023 by Mary Ann Clark; Jung Choi; and Matthew Douglas is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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