Ostracods are small crustaceans, their size ranges from about 0.05 - 2mm long and inhabit a
wide range of habitats, they are mainly found in freshwater, marine and
brackish environments. Ostracods are mainly found
living on the sea floor (benthic), although some are found floating in
surface waters (planktonic). Diagram 1 at the bottom of the page shows
a diagram of an ostracod.
A distingishing feature that ostracods
have is a
bi-valved calcified carapace which is hinged at the upper margin (often
found fossilized), which encloses the soft bodied parts. Adductor
muscles are attached to this carapace and are used to open and close
it. They have apendages which can drop out and can use for walking,
swimming, reproduction or feeding.
The soft bodied parts can be divided
into two main parts the head
(cephalon) separted by the thorax (between the head and abdomen) by a
slight constriction.
They can reproduce both sexually and
asexually and
display sexual diamorphism, the male and females carapaces are differnt
shapes.
- Females
tend to be more squat than the males and have a brood pouch to brood
their young in.
Photograph 1. of a female
Leptocythere lacertosa.
Taken
from Recent British Intertidal Ostracoda.
- Males
are more elongate then females and half of their case is taken up by
the male reproductive organ.
Photograph 2. Of a male
Leptocythere lacertosa. It
is clear to see that compared to the female it is more elongate.
Taken
from Recent British Intertidal Ostracoda.
They grow like
other crustaceans by moulting (ecdysis). They have 9 moult stages and
by the 9th moult stage they are an adult.
One way ostracods can be divided is based on the features of their carapace.
Pelagic forms tend to have a smooth carapace and may have
long
powerful swimming appendages. Benthic ostracods can burrow into the
substrate, so tend to have carapaces that are smooth, robust and
occassionaly elongate.
They display a range of eating habits
being scavengers, filter-feeders, detritivores or herbivors.
