Transcript Ch 12 - Blastocoelomates and Other Phyla

Phylum Rotifera
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> 1,800 described species
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< 1 mm
Complex, variety of body forms
Solitary
Pseudocoelomate
Generally freshwater
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Rotifer Anatomy
Rotifer body
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Head, trunk, foot
Ciliary organ on anterior end = corona
Complete gut
Protonephridia
Tendency to constant cell number
Pharynx modified with internal jaws
Posterior
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Elongate foot
Cuticular annuli with telescoping action
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“toes” for attachment
Rotifer Anatomy
Locomotion
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Some can change shape by “telescoping” action
Some sessile as adults
Hydrostatic skeleton
Most rotifers swim and crawl
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Cilia
Digestion
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Complete digestive tract
Mouth --> buccal tube -->Pharynx (mastax)
-->Salivary gland -->Gastric gland
-->Stomach -->Intestine
-->Nephridioduct -->Cloaca -->Anus
Circulation, Gas Exchange
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No special organs for internal transport or
gas exchange
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Coelomic fluid
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aided by muscles
small size reduces diffusion and transport tissues
Osmoregulation
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one pair of flame bulbs
protonephridia
empties into cloaca
Nervous System and Sense
Organs
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Bilobed mass of gangli
Nerves connect to body
Chemoreceptors, mechanoreceptors
Reproduction
 Parthenogenesis
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 If
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Development from egg w/o fertilization
= most rotifers female
Adaptation for freshwater habitats with severe
disturbance
males exist -- copulation
or hypodermic impregnation
Phylum Acanthocephala
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Spiny – head worms
1200 species
All gut parasites of vertebrates
Phylum Acanthocephala
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Life cycle requires intermediate host –
usually arthropod
Fig. 10.18 Pechenik
Cyst out w/feces
Snail eaten by turtle
Adult worm in turtle intestine
Cyst eaten by ostracod
Ostracod eaten by snail
Phylum Acanthocephala
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Constant number of cells
No respiration organs
No digestive organs
Pseudocoelom
Phylum Acanthocephala
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Proboscis for attachment to intestinal
wall
Dioecious
Fertilized eggs develop
in pseudocoelom of
female
To acanthor stage