Copepoda
Reproduction and development

Calanoids, cyclopoids, poecilostomatoids and harpacticoids are sexually dimorphic. Fertilization is by copulation when the male transfers one or more spermatophores to the female's genital somite. Then sperm is transferred through the female's copulatory pore and stored in seminal receptacles. Fertilized eggs are released through the gonopores that represent the oviduct openings. Eggs are held together by outer membranes and form single or paired egg sacs. In harpacticoids, calanoids, cyclopoids and poecilostomatoids true egg sacs are present, however the majority of calanoids free-spawn their eggs into the water column (Huys and Boxshall, 1991; Huys et al., 1996). Precopulatory mating before copulation is usual. The male grasps the female with the prehensile A1 (harpacticoids, calanoids) and also usually with the P5 (calanoids). In cyclopoids the male has both A1 geniculated, therefore it grasps the P4 of the female in a ventral to ventral orientation. In poecilostomatoids the A1 are non-geniculated, but Mxp are sexually dimorphic and used for holding the female during copulation (Huys and Boxshall, 1991). It is considered that upon chemical stimulation the male performs a distinctly different swimming behavior — "searching movements" or "mate-seeking behaviour" — and these movements bring him into close proximity to a potential mate. The review of literature on mating behaviour of calanoids is given by Blades-Eckelbarger (1991). Recently the mating behaviour of cyclopoids and calanoids was observed using video-computer motion analysis techniques. It was proposed that mating behaviour (encounter-pursuit-capture and copulation) can be compared to predatory behaviour (encounter-attack-capture and ingestion) (Buskey, 1996).

The fecundity of a female depends on the species, the amount and quality of food eaten, season, hydrographic conditions and latitudinal zone. The developmental rate of eggs depends on temperature and may prolong from 1 day to several months. Diapause eggs are known for calanoids (e.g. Uye, 1985; Marcus, 1996). Nearly all free-living copepods have 12 developmental stages: 6 naupliar and 6 copepodite stages, the sixth being the adult. The first nauplius has 3 pairs of appendages: A1, A2 and Md. The sixth naupliar stage has all appendages up to P2 present although the posterior limbs are vestigial. The duration of each naupliar stage is very short (from few hours to few days). The period between moults from one copepodite (or copepodid) stage to another may be much longer. The fifth copepodite stage of some calanoid species may live longer than others. They may feed intensively and store lipids, especially in those calanoids whose adult stages have reduced oral parts. Some species of Calanus may have one generation per year in the northern areas, but the same species in warmer waters may have two generations per year. Continuous breeding is characteristic of tropical copepods; in temperate regions breeding cycles strongly vary (Davis, 1984). Generally, copepods exhibit a wide variety of life histories.