The Autecology of Eudiaptomus cf drieschi (Poppe & Mrazek 1895 ...

3. Results
3.1 Descriptive taxonomy (General)
The diaptomid copepods are members of the most common group of freshwater, filter
feeding calanoids, the Diaptomidae. There are over 400 species in about 50 genera.
They play an important role in freshwater ecosystems as food for fish and invertebrate
predators. As is typical in crustacean morphology, the diaptomid metasome (prosome)
or cephalothorax is divided into a head and thorax, and the urosome is made up of the
abdominal and genital segments. The urosome terminates with a pair of structures called
caudal rami, which end in caudal setae (Williamson 1991). The metasome may have
between 4 to 6 segments depending on the species. The head bears the first antenna or
antennules, second antenna, mandibles, maxillules, and maxillae. The thorax has the
maxillipeds, four pairs of swimming legs and a pair of modified 5 th legs. Diaptomids are
sexually dimorphic. The female 5 th legs are symmetrical and well developed (Fig. 2a),
while the male 5 th legs are highly asymmetrical and modified for reproduction (Fig. 2b).
The setation and armature of the male right anntenule is also of key significance in
species identification (Fig 2c-d). The first antennae posses both chemoreceptors and
mechanoreceptors that function in feeding, locomotion, and reproduction. They are not
flexible and are raised or relaxed by increased or decreased blood pressure.
The shape and armature of the female genital and last thoracic segment are
important morphological features for distinguishing between species (Fig 2e). The
female genital segment is composed of 3 fused segments. The antennules of the male
diaptomids are asymmetrical, the right antennula is geniculate for grasping the female
during copulation (Fig 3b). It is made up of 21-22 segments that can be divided into
three sections.