UNIT : 1 LIVING WORLD
Biology and its branches; relationships with other sciences; scientific methods in biology; historical
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PHYLUM ROTIFERA Philodina
Rotifera- Latin word meaning â€śwheel-bearerâ€ť ( rota =wheel + fero =to bear).
composed of several ciliated tufts around the mouth that in motion resemble a wheel
Structure of Philodina ; a live Philodina
2000 species throughout the world.
- freshwater inhabitants
- epizoic or parasitic
- benthic â€“ swim or creep on vegetation
Range in size â€“ 40 Âµ m- 3mm in length.
- most are between 100-500 Âµm long.
Some have beautiful colors, most are transparent.
The morphology is very diverse, but their body is cylindrical or spherical.
Floaters - globular & saclike
Creepers & swimmers â€“ elongated and wormlike
Sessile - vaselike
PHYLUM ROTIFERA Variety of form in rotifers
Morphology of rotifers:
Head : bearsÂ a ciliated crown or corona ,
locomotion and feeding .
The cilia create currents of water toward the mouth- draw in small planktonic food.
Trunk : contains visceral organs.
Foot : segmented (when present).
Ringed with joints that can telescope to shorten (in some sp.).
The 1-4 toes secrete a sticky substance from the pedal glands for attachment.
Used by both sessile and creeping forms.
Digestive system- complete
Omnivorous: feed by sweeping minute organic particles / algae forward the mouth by the beating of the coronal cilia.
Carnivorous (some sp.)- feed on protozoa & small metazoans- capture by trapping or grasping.
Trappers - funnel-shape area around the mouth to capture prey.
Hunters - trophi that can be projected & used like forceps to seize prey.
Pharynx ( mastax ) fitted with a muscular portion that is equipped with hard jaws ( trophi )- sucking & grinding up food particles.
Absorption occurs in the stomach.
Female rotifers (have 1 or 2 syncytial ovaries (germovitellaria) .
Produce yolk as well as oocytes.
Rotifers are dioecous, but males are unknown in many species.
(Dioecous- having male & female organs in separate individuals).
Divided into 3 classes:
PHYLUM ROTIFERA class order
Class Seisonidea (most primitive) :
? & ? similar in size and form
Single genus: Seison
Epizoic on gills of a crustacean
Seisonidea : females produce haploid eggs that must be fertilized and develop into either males or females.