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are gathered and used for hatching into the nauplius for feeding young of
fishes. Other examples are A pus and Branchipus.
Sub-class Ostracoda
In this group, the unsegmented and laterally compressed body is enclosed
in a bivalved carapace, which gives them a superficial resemblance to tiny
transparent clams. Example Cypris.
Sub-class Copepoda
It includes a vast number of small Crustacea, playing an important role in
the economy of the sea, because they constitute the main link in the food
chain between diatoms and the larger animals.
They have an elongated segmented body, bearing usually five pairs of
limbs, and a posterior abdomen without appendages. The free-living forms
are found in both fresh and sea waters and form one of the most numerous
items of plankton. Others are parasitic forms which have undergone a
fantastic degeneration. The Branchiura are external parasites on fishes and
have a flat, shield-like body with large compound eyes (e.g. Argulus)
Sub-class Cirripedia
These are shrimp-like animals, enclosed in a calcareous shell. The young
are free-swimming, but as they grow they become permanently attached.
They are popularly known as goose barnacles (Lepas) and acorn barnacles
(Balanus). The Rhizocephala are extremely degenerate forms, mostly
parasites of crabs and hermit crabs. A tumour- like part attached to the
abdomen of the host extends as a network of filaments within the host.
Sub-class Malacostraca
These are highly developed animals. The thoracic and abdominal
appendages are different. Paired compound eyes are present. The
FAUNA 187