Mexican anchialine fauna — With emphasis in the high biodiversity cave El Aerolito

Abstract Anchialine ecosystems are one of the least studied in the world since they are very difficult to access, their bibliography is scant and widely scattered, and studies rarely specify actual locations. Mexico is one of the richest countries for these ecosystems, as it has a huge number of cenotes (sinkholes) just in the Yucatan Peninsula. Here we present a thorough checklist of all the species occurring at El Aerolito cave system, Cozumel, Quintana Roo, which has been identified as one of the richest and most biodiverse of the world. Indeed, it holds 100 species (53 as new records), classified within 10 phyla, from which Porifera, Echinodermata and Annelida are the richest groups in contrast with the rest of the subaquatic caves in the world where the dominant phylum is Arthropoda. An exhaustive review of all anchialine Mexican fauna is presented as context, which includes records dating as far back to 1938, half of them just from the last decade. Total records add up to 335, including 47 common names and uncertain records, classified into 171 operational taxonomic units, 108 identified to species level, 33 of which are endemic to cave environments (stygobite), while another 30 species are presumed stygobites. Half of the Mexican anchialine cave systems have records for only one to three species, five have more than 10 records, while only three anchialine cave systems include representatives of more than two phyla. Unfortunately, and despite the scarce information, 12 of the species enlisted are already cataloged in some extinction category by the current national regulation (NOM-059) or on the Red List of the IUCN. Nine of them are in the highest categories of concern, calling for further understanding about these ecosystems in order to develop effective regulations and concurrent management programs for their protection.