(^) Halocyprid feeding is at least partly predatory. Larger Conchoecia grab copepods or
other prey with the mandibular palps that swing out ventrally through the opening
between the valves. Prey are swung in against the blades at the base of the mandibles,
then sliced into serial sections and swallowed. The valve margins bear glands, the
secretion from which can make a filtering surface across the valve opening. This can
be found in the gut in an accordion fold containing food particles. There are other,
more prominent glands near the shell edge, some of which in some species eject
bioluminescent blobs of mucus as decoys as the ostracod departs to escape from a
predator.
(^) Male ostracods deliver sperm to females through a penis. Females of pelagic groups
carry eggs internally until hatching, which occurs at a relatively advanced stage
compared to copepods. Juveniles (“ostracodites”) are small versions of the adult form.
In mesopelagic layers, there are larger (to ∼2 cm) forms of the genus Gigantocypris
(Cypridinidae) in which the shell is nearly spherical. Unlike the eyeless halocyprids,
these have elaborate visual systems. Holoplanktonic ostracods are oceanic, only
occasionally being mixed shoreward over continental shelves and rarely washing into
estuaries. Some epibenthic, tropical cypridinids of the genus Vargula swim above
tropical grass beds and reefs at night, producing luminescent mating displays.
Copepoda
(^) Copepods usually dominate the mesozooplankton in respect to numbers and biomass
in all marine waters. The abundant, free-living orders are Calanoida (Plate 6.9),
Cyclopoida (family Oithonidae), Poecilostomatoida (families Oncaeidae,
Corycaeidae, and Sapphirinidae), and Harpacticoida. Huys and Boxshall (1991) have
reviewed copepod anatomy, anatomical variation, and phylogeny, and Boxshall and
Halsey (2004) provide a guide to copepod systematics. Claude Razouls and
colleagues maintain a website with documentation for each of the 2462 currently
accepted planktonic species (http://copepodes.obs-banyuls.fr; Diversity and
Geographic Distribution of Marine Planktonic Copepods), complete in French and