Two new species of brittle-stars (Echinodermata: Ophiuroidea) from an anchialine cave in Cozumel Island, Mexico

Cozumel Island is a Caribbean island with a karstic topography dating from the Pleistocene (~122,000 years old) ( Wilhelm & Ewing, 1972), which has promoted the formation of sinkholes (cenotes), including anchialine caves (a... [ view full abstract ]

Cozumel Island is a Caribbean island with a karstic topography dating from the Pleistocene (~122,000 years old) ( Wilhelm & Ewing, 1972), which has promoted the formation of sinkholes (cenotes), including anchialine caves (a sinkhole with a connection to the sea). Many marine taxa have been reported living in anchialine caves, but echinoderms were first reported in 2007 (Mejia-Ortiz et al., 2007) for the anchialine cave ‘Aerolito de Paraiso’, Cozumel Island. Up to 2013, 26 species have been reported from this cave. The existence of several new species was suggested by the analysis of mitochondrial DNA but further analyses are required to determine the species boundaries more accurately. We focused on two brittle-stars found in the anchialine system. Material from several major collections was examined and Ophionereis sp. records were restricted to this cave, in which it is very abundant throughout the entire system. Ophiolepis sp. specimens were found occurring in the Atlantic Ocean and Gulf of Mexico. Morphological diagnostic external characters were easily identified for the later species, whereas the external morphology of Ophionereis sp. closely resembles that of O. reticulata (Say, 1825), except for colouration patterns and arm length –disc diameter ratio. Moreover, several colouration patterns were identified within the cave, but COI data suggests all these to be the same species. A multi-locus approach is being developed as it is known that single gene trees may not be representative of the species phylogeny.