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Taxonomy of the semiterrestrial crab Lepidothelphusa cognettii (Nobili, 1903) (Crustacea: Decapoda: Brachyura: Gecarcinucidae), with descriptions of five new species from Sarawak, Malaysia, Borneo
Abstract
The taxonomy of the semiterrestrial gecarcinucid crab Lepidothelphusa cognettii (Nobili, 1903) from Borneo is revised. The identity of L. cognettii s. str. is clarified and five new species: L. flavochela, L. limau, L. loi, L. padawan and L. sangon, are described from southwestern Sarawak, Malaysia. The species are characterised by their diagnostic live colours, structures of their carapaces, chelae, male abdomens and male first gonopods. They also occupy geographically discrete ranges, sometimes with different habitats.
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RADEMACHER, Monika & Oliver MENGEDOHT (2011): Krabben-Fibel. Die schönsten Krabben für das Aquaterrarium: 1-96. (Dähne Verlag, Ettlingen).
Im Rahmen des Wirbellosen-Booms der vergangenen Jahre haben sich auch die Krabben einen festen Liebhaberkreis in der Aquaristik erobert. Die Autoren sind im deutschsprachigen Raum die bekanntesten Praktiker in Bezug auf Haltung, Pflege und Vermehrung von Krabben. In dieser handlichen Fibel findet der interessierte Leser endlich alle wichtigen Informationen und zu diesen faszinierenden und farbenfrohen Lebewesen.
A new species of cave crab, Stygothelphusa antu new species, is described from limestone formations in Temurang, Sarawak, Malaysia. The new species is the most highly adapted to a cavericolous lifestyle among the four known species of Stygothelphusa, having a pale body pigmentation, reduced eyes and elongated pereopods. In contrast, the other three species have normal eyes that almost completely fill the orbits. The new species also differs from its congeners by a number of carapace, pereopod and gonopod characters.
The phylogeny of the Asian freshwater crabs of the family Gecarcinucidae is investigated using the
mitochondrial large subunit rRNA gene and the nuclear encoded histone 3 gene. The results confirm
the monophyly of the Gecarcinucidae. A division into two families, Gecarcinucidae and Parathelphusidae,
is not supported. Therefore, and in consideration of the unresolved family relationships,
all Old World freshwater crabs are assigned to one superfamily, the Potamoidea. The evolution of
structures of the second gonopod within the Gecarcinucidae is shown to involve convergent reduction
of a complex-type groove to a simple-type groove or its complete absence. Gecarcinucids
without a frontal triangle are shown to form a paraphyletic group. Thus, these morphological characters
are of minor importance for clarifying phylogenetic relationships within the Gecarcinucidae.
Genetically, the Gecarcinucidae can be differentiated and separated into seven monophyletic lineages
and an assemblage of as yet unresolved Indian groups. We identify the Malay Peninsula and
Borneo (particularly Sabah and Sarawak), where representatives of four of these lineages occur, as
a hotspot of gecarcinucid diversity. In agreement with our phylogenetic results, an early radiation
of the Gecarcinucidae on the Indian subcontinent is postulated along with several dispersal events
from Sundaland into the Malesian (Malaysian) Archipelago.
A new genus of cave-dwelling freshwater crab, Stygothelphusa, is described from Sarawak, Borneo, with Potamon (Thelphusa) bidiense Lanchester, 1900 as type species. This species was synonymised with Thelphusula melanippe by Bott (1970) and regarded as a separate species of Thelphusula by Holthuis (1986). Its distinctive carapace, leg and gonopod features however, warrant the establishment of a separate genus for it. A neotype for the type species is also designated.
Freshwater ecosystems in the tropics host a diverse endemic fauna including freshwater crabs, but the rapid loss and deterioration of habitat means that many species are now under imminent threat. Studies on freshwater fish and amphibians suggest a third to half of the species in some tropical freshwaters is either extinct or endangered, but the status of the freshwater crabs is not known. Freshwater crabs, with 1280 species, represent one-fifth of all the World’s brachyurans. We therefore undertook a comprehensive IUCN Red List assessment of the freshwater crabs, which was the first time that such a study had been attempted on a global scale for any group of freshwater invertebrates. The conservation status of all known species from the Americas, Africa, Europe, Asia, and Australasia revealed unexpectedly high threat levels. Here we show that about one-sixth of all freshwater crab species have an elevated risk of extinction, only one-third are not at-risk, and although none are actually extinct, almost half are too poorly known to assess. Out of 122 countries that have populations of freshwater crabs, 43 have species in need of protection. The majority of threatened species are restricted-range semi-terrestrial endemics living in habitats subjected to deforestation, alteration of drainage patterns, and pollution. This is illustrated with a case study of one such species found in Singapore. This underlines the need to prioritize and develop conservation measures before species decline to levels from which they cannot recover. The proportion of freshwater crabs threatened with extinction is equal to that of reef-building corals, and exceeds that of all other groups that have been assessed except for amphibians. These results represent a baseline that can be used to design strategies to save the World’s threatened freshwater crab species.
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