Biology of the uncommon dreissenid bivalve Mytilopsis leucophaeata (Conrad, 1831) in central Chesapeake Bay

The dark falsemussel Mytilopsis leucophaeata (Conrad, 1831) (Dreissenidae) is an uncommon epifaunal bivalve of oligohaline–mesohaline habitats in Chesapeake Bay. It is small and weakly attached to different substrates by its byssi, but is presumably somewhat protected from predators by its habit of living within byssate clumps of hooked mussels Ischadium recurvum (Rafinesque, 1820) attached to eastern oysters Crassostrea virginica (Gmelin, 1791). It is less active than I. recurvum in terms of crawling from under encumbrances or moving and reattaching when detached from a substrate. Its extensible inhalant siphon should enable it to obtain food and oxygen from the water column even when confined within I. recurvum clumps or its own single-species clumps. In terms of egg size and the timing of larval development, it shares a number of characteristics with the freshwater dreissenids Dreissena polymorpha and D. rostriformis bugensis and with I. recurvum. Given the limited numbers of M. leucophaeata that seem to be the rule in its native habitat, there are questions, so far unanswered, as to how the population persists, how its spawning is coordinated and how successful is fertilization when widely separated individuals do spawn.