Search for: All records

Etisine crabs are some of the most abundant cryptobionts in Indo-West Pacific coral reef systems. Despite their ecological importance and abundance in museum collections, several recent systematic studies have indicated family- to subspecies-level taxonomic problems. One such case involves the former chlorodielline genus Soliella Lasley, Klaus & Ng, 2015 (treated here as part of Etisinae), which currently comprises two valid species and three available names that have been in flux in recent literature. The validity of these taxa has only been cursorily discussed. To resolve species limits and distributions, a thorough morphological examination of hundreds of specimens was conducted, including scanning electron microscopy of male gonopods, along with analysis of sequence data of the mitochondrial marker cytochrome c oxidase subunit I (COI) from 84 exemplars across the distribution of the genus. The status of two species that have Indian Ocean versus Pacific Ocean distributions with overlap in the Indo-Australian Archipelago and adjacent regions is confirmed. While external morphology is not reliable for identification, a few discrete, although slight, differences in gonopod morphology were found, and these results are consistent with a “pseudocryptic species” designation. Speciation conforms to a previously published etisine model of allopatric differentiation followed by subsequent divergence of gonopod morphology upon secondary sympatry. This pattern, the biogeography of the two species, and the term “pseudocryptic species” are discussed. 

Abstract Xanthid crabs of the genus TweedieiaWard, 1935, are among the most beautiful decapod cryptofauna in Indo-West Pacific coral reefs, with an ornate arrangement of granules and setae, in combination with an eye-catching color pattern. The genus and three recognised species (T. odhneri (Gordon, 1934), T. laysani (Rathbun, 1906), and T. brevidactylaDai & Yang, 1998) are revised, and new diagnoses and figures are provided. The COI barcoding gene of 38 specimens was sequenced and used to generate maximum likelihood and neighbor-joining trees. Tweeedieia brevidactyla is here synonymized with T. odhneri. Tweedieia now comprises only two species, differentiated by morphological characters and sequence data. Tweedieia odhneri ranges from the western Indian Ocean to the Hawaiian Islands and French Polynesia, while the rare T. laysani is only recorded from the Hawaiian Islands. These crabs appear to favor clear, oligotrophic, oceanic waters and are common on oceanic islands and rare around continents and large islands of Australasia.