As more crabs settle in these eastern seagrass beds, the population density of crabs gets too high to sustain them, and some will migrate across the sound to other habitats. For juvenile blue crabs in Pamlico Sound, this includes three main habitats: dense seagrass beds along the soundside of the Outer Banks and dominating the eastern shore, a combination of patchy ephemeral seagrass beds, and the more pervasive shallow marsh-adjacent habitat (“shallow detrital habitat” or SDH) that dominates the western shores of Pamlico Sound.ĭuring years with limited direct hurricane impacts, juvenile crabs will enter the sound through both Oregon Inlet and Hatteras Inlet and will settle into the adjacent dense seagrass beds. This unique geography, while complicating migration, also provides a bounty of different habitat choices. The western shore of the sound is equally distinctive, containing a vast mosaic of marshland, marine forests, and draining freshwater rivers. Pamlico Sound is characterized by a wide and shallow basin, which is separated from the ocean on its eastern shore, by a chain of barrier islands, with only a few narrow inlets allowing limited contact with marine waters. ![]() After the they locate their home estuary, they search for an optimal habitat, before they then settle outside the water column and undergo their last transition into an “instar.” At this stage, they resemble a much smaller version of the adult blue crab.Įntering back into Pamlico Sound and finding a suitable habitat is difficult due to the unique geography of the sound. Megalopa ride the changing wind patterns that mark late summer and early fall back west towards the coast. Right before each blue crab journeys back to its home estuary, it changes body shape and becomes a “megalopa.” In this stage, juveniles become more crablike, growing small claws and legs, yet retaining the large head spikes and shrimp-like tail. After hatching, these zoea travel east out into the open ocean, where they grow and molt for about a month. Zoea hatch from eggs held on their mother’s abdomen, usually at the mouth of estuary, or, as is the case of the zoea I study on the Pamlico Sound, at the numerous inlets that punctuate the Outer Banks. Blue crabs, like many marine invertebrates, have what scientists refer to as a complex lifecycle, which means that they go through drastic changes in body shape and location as they age, similar in some ways to a caterpillar turning into a butterfly.Īs “zoea” during the first stage of their life cycle, blue crabs are a little larger than the tip of a pencil and look a bit like aliens, with three large spikes protruding from their heads, a huge eye spot, and a shrimp-like tail. ![]() However, while many are familiar with the adult blue crab, few know about their strange juvenile stages.
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