Term
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Definition
Sponges
No symmetry (irregular shapes)
Come in various sizes
Completely sessile (non-motile)
Benthic (chill on the bottom)
Fouling (Attach to shit)
Body usually has a sponge, friable (brittle) texture |
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Term
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Definition
Sea anemones, corals, jellyfish, hydroids
Radial body symmetry
No head, no left-right/top-bottom, or front-back
Body directions are oral or aboral
Multiple tentacles with stinging cells
Body usually soft, may have skeleton
Planktonic (floating) or benthic; may be sessile |
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Term
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Definition
Comb Jellies
Bilaterally symmetrical
May look radially symmetrical
No head, use oral-aboral for orientation
Body texture is jelly-like
Swim with rows of cilia
Planktonic |
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Term
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Definition
Flatworms
Bilaterally symmetrical
Orientation is anterior-posterior, left-right, dorsal-ventral
Soft body; no skeleton
Bery flat, up to a few cm long
Benthic & motile |
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Term
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Definition
Ribbon Worms
Soft, very elongated bodies
May exceed 1m long but <1cm thick
All benthic & motile |
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Term
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Definition
Rotifers
All Microscopic, very common
Semi-rigid, vase-shaped body
Use cilia at head to move
Most motile, benthic, or planktonic
Most commonly observed in freshwater (though they also live in saltwater) |
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Term
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Definition
Segmented worms
Soft body made of repeated segments
In marine worms (class Polychaeta), most segments have paired appendages (parapodia)
Wide range of sizes (up to 1m long)
Most live in burrows/build tubes
Most are benthic, some are sessile
Often dominate marine benthic biomass |
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Term
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Definition
Snails, bivalves, chitons, & cephalopods
Soft, unsegmented bodies, usually with a shell
Shape, position, & number of shells can differ
Body can be large
Occupy all habitats & modes of existence |
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Term
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Definition
Moss animals
Colonies formed of very small zooids (connected individuals)
Colonies vary widely in appearance, texture, & size
Often confused with hydroids (Phylum Cnidaria) |
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Term
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Definition
*Hydroids vs Bryozoans
Both can form colonies that resemble moss/coral
Distinguishable under a microscope
Difficult to tell apart in the field |
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Term
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Definition
Roundworms
Mostly microscopic, except for parasites
Ubiquitously in all ecosystems
Cylindrical body
No circular muscles in body wall
Thus, body can only move by curling/uncurling
Very characteristic movement |
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Term
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Definition
mostly subphylum Crustacea - amphipods, shrimps, crabs, etc
Body of dissimilar segments
Paired, jointed appendages
Rigid exoskeleton
All sizes, all habitats, all lifestyles |
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Term
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Definition
Seastars, Urchins, Sea Cucumbers
Five-rayed radial symmetry as adults (typically)
Oral-aboral orientation
Body wall includes calcium-rich (?) elements
E.g. shell-like bits, spines
Mostly benthic, motile
May reach large sizes |
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Term
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Definition
Sea Squirts, Humans
Most “invertebrate” chordates are sea squirts (subphylum Tunicata)
leathery/jelly-like body wall, sac-like body
Benthic and sessile, or planktonic
May be solitary or colonial |
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