Dardanus guttatus is common on lagoon, pinnacle and seaward reefs at Kwajalein. One of the larger marine hermit crabs, it is able to occupy larger shells including those of some of the large finger shells, Lambis truncata. Like Ciliopagurus strigatus, it has a flattened body, enabling it to take advantage of shells with narrow apertures that many crabs cannot fit into. It grows much larger than C. strigatus, so it has unfettered access to the larger cone and cowry shells that otherwise would remain unused after the snails that make the shells die. The turquoise "kneepads" are an easy character to use to identify this species. The first one is in a Conus marmoreus that measured about 14cm.
This one inhabits a Strombus lentiginosus shell.
The Cypraea tigris cowry occupied by the crab below measured at least 85mm.
The hermit below has found an unoccupied Chelycypraea testudinaria shell.
In Conus litteratus.
The next photo shows the turquoise patch on the back behind the eye stalks.
This one has found a Conus crocatus.
The Strombidae also have narrow apertures well suited to this hermit, and some of the species are among the largest snails on the reef. Below a Dardanus guttatus has commandeered a fresh Lambis scorpius shell.
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The one below has a fresh Lambis lambis finger shell.
This one has an older Sinustrombus taurus in a Halimeda patch on a lagoon reef.
The crabs get large enough to inhabit the empty shells of Lambis truncata, which can grow to at least 30cm long at Kwajalein.
The little tiny hermit over on the right side of the aperture of this large Lambis truncata has its sights set pretty high. I don't know if the crab would have the strength to even move that large heavy shell, but sometimes you just have to take what is available.
Created 10 August 2018