Occurrence of first crab instars of the Atlantic ghost crabOcypode quadrata(Decapoda: Brachyura: Ocypodidae) along the coast of Maine, U.S.A.

Abstract

Adult populations of Ocypode quadrata have not been reported north of Cape Cod, Massachusetts, but their megalopae, which invade sandy beach habitats, have been recovered recently from the coasts of Massachusetts and Maine. Two megalopa specimens were reported from Maine beaches at Kennebunkport and Kennebunk in 2012. More recently in September 2014, a specimen was collected from Pemaquid Beach, Bristol, Maine, ~ 96 km north of the Kennebunkport-Kennebunk region. Herein, we also report the occurrence of three specimens of first crab instars from Goose Rocks Beach, Kennebunkport, collected on October 2–3, 2014. These juvenile crabs were found slightly above the tide line of the previous high tide, where they were preserved and measured (mean carapace width x carapace length = 6.34 ± 0.38 mm x 5.64 ± 0.34 mm; mean carapace width/carapace length ratio = 1.13). This is the first evidence for megalopa to first crab metamorphosis of ghost crabs in the cold waters beyond Cape Cod. Conformation of survival of early crab instars of O. quadrata, a primarily southern latitude brachyuran, to adulthood in Gulf of Maine waters requires further collections and experimentation.