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<= Lateral (side) view
of Daphnia sp. (typical cladocera).
The lateral view is more commonly seen and more useful for identification
than the dorsal or ventral views.
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Dorsal (back) view =>
of Scapholeberis sp. (typical cladocera)
Live free-swimming organisms frequently orient themselves dorsal
side up (so this is what you see looking down at them through
a microscope) - a few orient ventral side up. Identification
is difficult with this view. Removing liquid from the slide may
help to tip them to one side.
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Carapace |
![Photo of Daphnia with carapace outlined in red.](Images/DaphniaAnatCarapace.jpg) |
Cladocera have a bivalve carapace. Usually the carapace completely
covers the animal with only appendages (antennae and postabdomen)
extending outside its protection. In a few families, the carapace
is reduced to cover only the brood pouch area.
Other important carapace
features
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Brood Chamber |
![Photo of Daphnia with brood chamber outlined in red.](Images/DaphniaAnatBrood.jpg) |
Female cladocera have a brood pouch or brood chamber lying along
the dorsal side of the body within the carapace. The brood chamber
contains eggs, epphippia (resting eggs) or young. Eggs and/or
young are typically released when the mother molts.
Male cladocera can be particularly difficult to identify and
to distinguish from juvenile or non-gravid (pregnant) females.
Males are usually smaller, usually have larger first antennae,
and have a hook on their first legs (true legs are located on
the ventral surface within the carapace and are very difficult
to observe via typical light microscopy).
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![Photo of Daphnia with head outlined in red.](Images/DaphniaAnatHead.jpg) |
Head
The cladoceran head may or may not be separated
from the body along the dorsal surface of the carapace but is
typically separated by a deep indentation along the ventral surface.
The ventral-posterior angle of the head may or may not be extended
to form a rostrum (beak). Nearly all cladocera (all Great Lakes
species except Monospilus dispar) have a single large
compound eye located near the center of the head. Cladocera may
or may not have a much smaller ocellus (eyespot) located near
the compound eye.
Other important
head features
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![Photo of Daphnia with ventral margin of the rostrum outlined in red.](Images/DaphniaAnatRostrum.jpg) ![Photo of Daphnia with the Compound eye outlined in red.](Images/DaphniaAnatEye.jpg) ![Photo of Daphnia with the Ocellus highlighted in red.](Images/DaphniaAnatOcellus.jpg)
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![Photo of Daphnia with a 1st antenna outlined in red.](Images/DaphniaAnat1stAntennae.jpg) |
Antennae
Cladocera have two pairs of antennae. The second
antennae are used for swimming and gathering food and are typically
much larger than the first antennae (or antennules). 1st antennae
contain sensory organs - they may be extremely small and hidden
by the rostrum (as in this Daphnia) or nearly as large as the 2nd
antennae. Except for the family Macrothricidae, the second antennae
are attached anterior to the first antennae.
Additional
1st antennae forms
Additional
2nd Antennae forms |
![Photo of Daphnia with the 2nd Antennae highlighted in red.](Images/DaphniaAnat2ndAntennae.jpg) |
![Photo of Daphnia with the intestine outlined in red.](Images/DaphniaAnatIntestine.jpg) |
Post-Abdomen
Cladocerans have a relatively simple digestive
system consisting of a mouth (located anteriorly beneath the rostrum)
and an anus (located posteriorly in the postabdomen) connected
by a simple intestine. In only a few taxa is the intestine convoluted
(coiled). Fine-scale characteristics of the postabdomen or foot
including spines, projections and claws are very important to cladoceran
species identification.
Additional post-abdomen
characteristics |
![Photo of Daphnia with the post-abdomen outlined in red.](Images/DaphniaAnatPA.jpg) |
Tail |
![Photo of Daphnia with the tail spine outlined in red.](Images/DaphniaAnatTailSpine.jpg) |
The most typical cladoceran
tail is a spiny projection of the carapace. A number of species
have setae (hairs) projecting from the carapace or body which appear
as a tail. Only a few groups have true tails (projection of the
body rather than the carapace) -- these are usually segmented.
Additional
Tail Forms |
A quick note about
sizes...Cladocerans are part of a group called Macrozooplankton.
As the name implies, they are the largest of the free-floating
(plankton) species ranging in size from about half a millimeter
to over a centimeter. Males are typically smaller than females
and juveniles (young) are of course smaller than the adults. Click
here to see some photos of typical Great Lakes cladocerans scaled
to size and to access tables listing maximum sizes (or adult ranges)
for all Great Lakes cladoceran species.
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Cladoceran Sizes - |