Seed Shrimp — Class Ostracoda

A myodocopoid ostracod.

Ostracods (ostracodes="having a shell"), also known as seed shrimp, are crustaceans that range in size from less than 0.1 cm to 3.2 cm and are enclosed in a hinged, shield-like plate (carapace) consisting of two valves. They are the oldest known crustaceans in the fossil record because their shells preserve well. They are numerous and widespread, with approximately 28 species occur in the marine environment of the Canadian Arctic.

Although lacking distinct segmentation, the ostracod body generally has seven pairs of appendages. The first two pairs function as sensory antennae; the third, fourth, and fifth pairs comprise the mouthparts; the sixth pair distinguishes males from females; and the last pair functions in cleaning.

Some ostracods are capable of swimming, employing their antennae for locomotion, but many species simply crawl over the ocean bottom or burrow into it. Most are scavengers, detritus feeders, or filter feeders, although a few are predators or parasites. Ostracods serve as an important link in food webs between producers (algae) and consumers (fish).

After fertilization, developing ostracod eggs are either deposited on the substrate or brooded between the female's valves until they hatch as juveniles. Those that are deposited hatch as a larva and proceed through six moults – shedding of the skeleton – before reaching maturity.