Rediscovery of the sponge crab Cryptodromia fallax (Latreille in Milbert, 1812) (Decapoda: Brachyura: Dromiidae) at Mauritius, with the description of a new genus and the confirmation of an unusual seaweed-carrying camouflage mode

Abstract

AbstractCryptodromia fallax (Latreille in Milbert, 1812) has been serendipitously found again on the island of Mauritius, almost 200 yrs after its discovery. The new material provides new information about the structure of the female sternum, providing stronger evidence that a new genus, Alcockdromiagen. nov., is required. Observations show that this crab cuts out and carries pieces of seaweed in the manner of a paraglider, rather than pieces of sponge normally carried by dromiid crabs. The crab uses Ulva lactuca Linnaeus, a green alga, and Lobophora variegata (J.V. Lamouroux), a brown alga. This discovery shows that the last two prehensile dromiid pereopods, which are used to carry soft camouflage, are multi-purpose, having only minor structural differences allowing them to carry seaweeds.