OpenStax Biology 2e Chapter 28 Invertebrates

amoebocyte

sponge cell with multiple functions, including nutrient delivery, egg formation, sperm delivery, and cell differentiation

Annelida

phylum of vermiform animals with metamerism

Arthropoda

phylum of animals with jointed appendages

cephalothorax

fused head and thorax in some species

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

cuticle (animal)

the tough, external layer possessed by members of the invertebrate class Ecdysozoa that is periodically molted and replaced

Echinodermata

phylum of deuterostomes with spiny skin; exclusively marine organisms

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

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

mantle (also pallium)

specialized epidermis that encloses all visceral organs and secretes shells

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

Mollusca

phylum of protostomes with soft bodies and no segmentation

Nematoda

phylum of worm-like animals that are triploblastic, pseudocoelomates that can be free-living or parasitic

osculum

large opening in the sponge's body through which water leaves

ostium

pore present on the sponge's body through which water enters

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

schizocoelom

coelom formed by groups of cells that split from the endodermal layer

seta/chaeta

chitinous projection from the cuticle

siphonophore

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

water vascular system

system in echinoderms where water is the circulatory fluid