Survey of Aquatic Invertebrates

Lifestyles

of the

Spineless and Gilled

Phylum Porifera the Sponges

• Asymmetrical • Sessile - attached to submerged rocks, sticks,

logs, or aquatic vegetation• Vary from marble-sized to elongated masses and

can grow to be thin or thick encrusting layers. • Their structure is supported by spicules, tiny

needle-like structures made of silicon that are distributed throughout the sponge body.

• Sensitive indicators of pollution. • Filter feeders• Little is known about them!

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Phylum Cnidaria, Class Hydrozoa the Hydra

• Radial Symmetry

• Carnivorous, kill with nematocysts (stinging cells)

• Somewhat sensitive to pollution

• May reproduce sexually orasexually

Phylum Platyhelminthesthe Flatworms

• Bilateral Symmetry

• Have 3 layers

• lack coelom, anus, circulatory and respiratory systems

• Very tolerant of pollution

Phylum Annelidathe Segmented Roundworms

• have external segments that correspond with repeated digestive and reproductive organs. • include leeches, aquatic earthworms, tubifex

worms and bristle worms • Very tolerant of pollution• Hermaphroditic; reproduce sexually by means of exchange

of gametes

Phylum Mollusca

• Bilateral Symmetry

• Specialized Foot

• Mantle

• Radula

• 2 Aquatic Classes– Pelecypoda (Bivalvia – clams, mussels)– Gastropoda (snails)

Freshwater Bivalves

Freshwater Bivalves – Life History

• Freshwater mussels feed by filtering algae and small particles from the water.

• Most are somewhat sensitive to pollution.• Most species have a larval stage that is parasitic on

fish. • Larvae are released by the female mussel and must

locate a certain fish species or die.• They usually attach to the host fish's gills or fins

where they remain for a few weeks or months. • Larval mussels rarely harm infected fish under

natural conditions. • If essential fish species are removed from the

habitat, mussels will not be able to reproduce.

Freshwater Bivalves – their life cycle illustrated

Bivalves can tell us alot about history!

http://www.texasbeyondhistory.net/jbwhite/musselmania/flash.html

Class Gastropoda – the Snails

• May be carnivorous or herbivorous.• Hermaphroditic• Most are highly tolerant of pollution.• May or may not possess an operculum, or

“lid” that it can close its shell with. • When looking at the shell’s opening with

the narrow end up, the opening may be on the right of the spiral (dextral) or to the left (sinistral)

Class Gastropoda – the Snails

• Planorbid Snails – coiled flat, no operculum • Lymnaeid Snails – dextral, no operculum• Physid Snails – sinistral, no operculum

Bithynid Snail

Dextralstiff operculum, with well-centered concentric rings

Viviparid Snail

Dextral – flexible operculum, with off-center concentric rings.

Hydrobiid Snail

Dextral – has flexible operculum with multispiral rings

Pleurocerid Snail

Dextral – very flexible operculum that recedes deep into shell, paucispiral rings

Planorbid Snail

Coiled flat, no operculum

Lymnaeid Snail

Dextral, no operculum

Physid Snails

sinistral, no operculum

Phylum Arthropoda• Bilateral Symmetry• Jointed Appendages• Exoskeleton of chitin• Most important aquatic groups – • Arachnida Crustacea Insecta (very tolerant) (somewhat tolerant) (variable tolerance)

Water Mites Scuds Water Bugs (tolerant) Water Spiders Isopods Water Beetles (sensitive) Seed Shrimp Odonate nymphs (varies) Grass Shrimp Plecoptera nymphs

Crayfish (extremely sensitive) Ephemeroptera nymphs

(extremely sensitive)

Megaloptera nymphs (sensitive) Diptera larvae (very tolerant)

Phylum Chordata • Bilateral symmetry• Possess notochord, chambered heart,

closed circulatory system• Includes vertebrates.• Some “quasi-vertebrate” examples:

– Lampreys

– Tadpoles

No paired fins, no jaws. Gill slits, cartilage skeletonOur native Southern Brook Lamprey (Ichthyomyzon gagei, pictured) has a larval stage that is a detritivore; adults are ephemeral, do not eat.

All larval amphibians are very primitive in that they lack jaws, paired fins. All are Detritivore until they get hind legs, and jaws, then become predaceous.

Bufo valliceps Gulf Coast Toad

Rana catesbianaBullfrog

Rana sphenocephalaSouthern Leopard Frog

Rana clamitansBronze Frog

http://www.bgsd.k12.wa.us/hml/jr_cam/macros/amc/index.html

http://www.ncsu.edu/sciencejunction/depot/experiments/water/tutorial/tutorialmacro.html

http://rock.geo.csuohio.edu/norp/bmi.htm

http://www.cod.edu/people/faculty/chenpe/RiverWatch/MBI_calculator.html