ORDER
Calanoida
FAMILY
Diaptomidae
TAXONOMY
Onychodiaptomus sanguineus Forbes, 1876, North America.
OTHER COMMON NAMES
None known.
PHYSICAL CHARACTERISTICS
Body length up to 0.08 in (2.1 mm) for both sexes. Body gymnoplean; with posterolateral corners of prosome produced into spinous processes. Antennules long, 25-segmented in female; male antennule geniculate on right side only; antenna with eight-segmented exopod. Swimming legs 1–4 all biramous, with three-segmented rami; middle exopodal segment without spine on outer margin. Fifth legs biramous in female. Male fifth legs asymmetrical, right leg with claw for grasping female and left leg for transferring spermatophore during mating.
DISTRIBUTION
Canada and United States. (Specific distribution map not available.)
HABITAT
Shallow ponds, including temporary waters and small lakes.
BEHAVIOR
Typically only one generation per year. Life cycle consists of six naupliar stages, followed by five copepodid larval stages before final molt into adult. Produce resting (diapause) eggs that can lie in the sediment for considerable periods before hatching; eggs were still viable after up to 300 years in the sediment bank of a New England (United States) pond.
FEEDING ECOLOGY AND DIET
A small particle feeder that generates water currents by the slow swimming movements of antennae and maxillipeds and captures food particles in laminar flow fields. Herbivorous, with diet including wide range of minute unicellular phytoplankton such as diatoms.
REPRODUCTIVE BIOLOGY
Mating takes place in water column. Sexually receptive female releases pheromones as she swims, leaving trail that is followed by male. Once in close proximity, male grasps female using strongly geniculate right antennule. Single spermatophore transferred during copulation, using tip of fifth leg. Diaptomids lack seminal receptacles, so spermatophore discharges its contents over female's genital area to form an attached spermatophoral mass. Attached spermatophoral mass effectively prevents further inseminations and is displaced when the egg sacs are extruded. After hatching of eggs and release of sacs, another copulation is required before another batch of eggs can be produced.
CONSERVATION STATUS
Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
Diaptomids form middle link in food chain leading from phytoplankton up to commercially important fish species in freshwater habitats.
