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Phylum
Porifera (sponges)
Cnidaria (hydra & jellyfish)
Platyhelminthes (flatworms)
Gastrotricha (gastrotrichs)
Rotifera (rotifers)
Nematoda (nematodes)
Mollusca (snails/bivalves)
Annelida (oligochaetes/leeches)
Bryozoa (moss animals)
Tardigrada (water bears)
Arthropoda (arthropods)
Major Aquatic Invertebrate Taxa
Review of major invert classifications
--Radially symmetrical animalsPhylum: Cnidaria
--Bilaterally symmetrical animals
Acoelomates – animals that lack a body cavity: Phylum: Platyhelminthes
Pseudocoelomates – animals that have a body cavity but no peritoneum.
Phlya: Gastrotricha, Nematoda, Rotifer
Coelomates – animals with internal body cavity lined with peritoneum.
Pinacocytes: ‘skin cells’, thin, leathery and tightly packed.
Choanocytes: striking resemblance to choanoflagellates(a single-celled protist). Their function is to create active pumping of water and major site of nutrient uptake.
Archaeocytes: These cells are “totipotent”. They can change into all of the other types of cells. Ingest and digest food caught by choanocyte collars.
Schlerocytes: Create and excrete spicules.
General physiology
Reproduction
--All sponges can reproduce sexually
--Generally monoecious and produce eggs and sperm at different times.
--Produce flagellated parenchymella larva that exit via exhalent current.
--Larval motility is the principal dispersal mechanism
--Sponges have great powers of regeneration
Feeding
--Sponges feed on fine particulate material in the inflowing water.
--Food particles generally range from 5- to 50 µm and are phagocytized by archeocytes.
--After digestion is complete, the archeocytes and associated wastes are expelled into the water.
Phylum: Cnidaria
Class Hydrozoa (only freshwater rep)
over 3,000 species
only 14 freshwater speciesClass Cubozoa (sea wasps)Class Scyphozoa (jellyfishes)Class Anthozoa (sea anemones and corals)
polyp medusa
Dimorphism in Cnidaria
Reproduction
--Cnidarians reproduce both asexually and sexually. Medusa are produced by budding of polyps but not vice versa.
--Generally dioecious and reproduce sexually during warmer periods.
--Embryos develop into ciliated free-swimming larva called planula.
Crespedacusta bowersi – the only freshwater “jellyfish”
Feeding
--Cnidarians are carnivorous but have limited powers of movement.
--Essential to the feeding process are thin, flexible ‘tentacles’.
--Nematocysts are specialized cells located on tentacles that aid in capture of prey.
--Amino acids released by prey can trigger the tentacles to ‘bend’ toward the mouth by ciliary action.
--Common foods of Hydra include invertebrates and sometimes small fish.
Nematocycts – Food, protection, anchoring
Phylum
Porifera (sponges)
Cnidaria (hydra & jellyfish)
Platyhelminthes (flatworms)
Gastrotricha (gastrotrichs)
Rotifera (rotifers)
Nematoda (nematodes)
Mollusca (snails/bivalves)
Annelida (oligochaetes/leeches)
Bryozoa (moss animals)
Tardigrada (water bears)
Arthropoda (arthropods)
Major Aquatic Invertebrate Taxa
Review of major invert classifications
--Radially symmetrical animalsPhylum: Cnidaria
--Bilaterally symmetrical animals
Acoelomates – animals that lack a body cavity: Phylum: Platyhelminthes
Pseudocoelomates – animals that have a body cavity but no peritoneum.
Phlya: Gastrotricha, Nematoda, Rotifer
Coelomates – animals with internal body cavity lined with peritoneum.
--Rhabdoids: Cells that produce mucus and poison for prey immobilization/predator deterrence.
--Neoblasts: Small, ameboid like cells that initiate regeneration of lost parts.
Identification of planarians
Nutritive cells
Simple intestine
3-lobed intestine
Many-lobed intestine
Acoela Neorhabdocoela Tricladids Polycladids
Reproduction
--Most turbellarians are monoecious.
--Penal stylets (Penis) that can be used for both reproduction and defense.
--Embryos develop into a free-swimming, ciliated stage called Muller’s larva. Short-lived, nonfeeding stage.
--Can produce asexually by fission, fragmentation or both.
Life history and ecology
Some species are univoltine:
produce one generation a year
Most turbellarians are multivoltine:
produce several generations a year
--Widely distributed in N. America
--Occur in both lakes and streamsStream-dwelling species more
differentiated than lake species
--Species diversity increases in temperate areas 20 to 60 species per lake
Feeding
--Effective predators on other invertebrates including rotifers, nematodes, cnidarians, bryozoans, small crustaceans, annelids and other turbellarians.
--Turbellarians use ‘slime’ to entangle prey. They use a muscular protrusible pharynx to help ingest prey.
Phylum
Porifera (sponges)
Cnidaria (hydra & jellyfish)
Platyhelminthes (flatworms)
Gastrotricha (gastrotrichs)
Rotifera (rotifers)
Nematoda (nematodes)
Mollusca (snails/bivalves)
Annelida (oligochaetes/leeches)
Bryozoa (moss animals)
Tardigrada (water bears)
Arthropoda (arthropods)
Major Aquatic Invertebrate Taxa
Review of major invert classifications
--Radially symmetrical animalsPhylum: Cnidaria
--Bilaterally symmetrical animals
Acoelomates – animals that lack a body cavity: Phylum: Platyhelminthes
Pseudocoelomates – animals that have a body cavity but no peritoneum.
Phlya: Gastrotricha, Nematoda, Rotifer
Coelomates – animals with internal body cavity lined with peritoneum.