Sundathelphusa tuerkayi, a new species of gecarcinucid freshwater crab (Crustacea: Brachyura) from Lombok Island, Indonesia

A new species of the freshwater crab genus Sundathelphusa Bott , 1969 is described from the Indonesian island of Lombok. Sundathelphusa tuerkayi, new species, appears to be most closely related to Sundathelphusa aruana (Roux, 1911), which is known for certain only from the Aru Islands, but diff ers from it and all other congeners by a unique combination of morphological characters. Th e new crab hosts a small ectosymbiotic temnocephalid fl atworm, possibly belonging to the genus Temnosewellia Damborenea and Cannon, 2001 (Platyhelminthes: Temnocephalida). key words Crabs, Gecarcinucidae, South-East Asia, temnocephalid worm, symbiosis.


IntroductIon
The Indonesian island of Lombok is inhabited by three known species of true freshwater crabs, all belonging to the family Gecarcinucidae: Sundathelphusa aruana (Roux, 1911), Parathelphusa lombokensis Bott, 1970, and Parathelphusa quadrata Ng, 1997 (Bott, 1970;Ng, 1997), the latter two species being endemic to the island. Sundathelphusa aruana, first described from the Aru Islands to the west of West Papua, was first reported from Lombok by Bott (1970).
A re-examination of Bott's (1970) specimens from Lombok, as well as fresh material collected in 2014, leads the authors to conclude that the taxon reported as "Sundathelphusa aruana" actually represents a different species, here recognised as new to science. The description of this new species and comparisons with its closest congener S. aruana form the basis of the present paper.

MaterIal and Methods
The material examined is deposited in the Naturhistorisches Museum Basel, Basel, Switzerland (NMB); Senckenberg Naturmuseum, Frankfurt-am-Main, Germany (SMF); and Zoological Reference Collection of the Lee Kong Chian Natural History Museum, National University of Singapore, Singapore (ZRC). Measurements, in mm, are provided only for adult crabs and are of the maximum carapace width and length, respectively. The terminology used follows that of Ng (1988  Description of male holotype. Carapace transversely ovate, inflated, broader than long, widest at anterior half, dorsal surface distinctly convex longitudinally and transversely, smooth or with scattered pits, regions visible; antero-and posterolateral regions covered with distinct short oblique striae; cervical groove shallow but prominent; H-shaped gastric groove deep (Figs. 1A, 2A). Epigastric cristae distinct, raised, rounded,

A new species of Sundathelphusa from Indonesia
Nauplius, 24: e2016026
Variation. The carapaces of smaller specimens tend to be less inflated, with the branchial regions less swollen (Fig. 1A, C). Large male and female specimens have these regions prominently swollen (Figs. 2A, 3A). The chelipeds of large males also have more inflated chelae with long curved fingers that gape even when closed (Fig. 3C). Smaller males have smaller chelae with straighter fingers (Fig. 1C). The lateral margins of male abdominal somite 6 also varies, with those of large males distinctly concave (Fig. 3E), versus almost straight in smaller males (Fig. 1B).

A new species of Sundathelphusa from Indonesia
Nauplius, 24: e2016026 posterior half more mottled and reticulate with uneven cream patches; dorsal surfaces of chelipeds orangebrown with patches of reddish-brown; ventral surface of chela palm and fixed finger yellow; dorsal surface of ambulatory legs cream with reddish-brown specks and patches; ventral surfaces pale yellow to cream (Fig. 1).
Etymology. The new species is named after our late friend and colleague, Michael Türkay, for his numerous contributions on taxonomy of decapod crustaceans. He

A new species of Sundathelphusa from Indonesia
Nauplius, 24: e2016026 was a wonderful host and always facilitated our visits to SMF with great enthusiasm -he will be sorely missed.

Distribution.
The new species appears to be endemic to Lombok Island in central Indonesia, where it is presently known from Sembalun, Praya, Suranadi and Lombok Barat, at altitudes ranging from about 200 m to just over 1000 m.
Biological notes. All crabs collected near Suranadi were found in the dense vegetation fringing banks of a small stream, about two metres wide (with some

A new species of Sundathelphusa from Indonesia
Nauplius, 24: e2016026 wider pool-like areas), with a weak to moderately strong current. Crabs from Lombok Barat were found hiding under rocks in a fairly large pool under a waterfall, about 0.2-0.5 deep. An ectosymbiotic temnocephalid flatworm, possibly belonging to the genus Temnosewellia Damborenea and Cannon, 2001 (Platyhelminthes: Temnocephalida) characterised by the presence of five cephalic tentacles (Fig. 6), was found on at least three crab specimens. The flatworm attaches its conspicuously yellow-greenish eggs symmetrically to the posterior branchiostegal region of the cephalothorax, just above the coxae of the second and third ambulatory legs (Figs. 1A, 6C). The taxonomy and biology of this flatworm remain to be studied.
Remarks. Roux (1911: p. 91) described Potamon (Geotelphusa) aruanus based on numerous specimens from three localities in Kobroor in the Aru Islands: Seltoutti, Manoumbai and Sungei Kololobo. Bott (1970: p. 75) selected a male from Manoumbai as lectotype and a paralectotype male from Kololobo ( Fig. 2B) was examined for the present study (see also Chia and Ng, 2006) Fig. 2B; Chia and Ng, 2006: fig. 42A); the G1 is proportionately more slender, with the distal part of the subterminal segment noticeably narrower (Fig. 4A) (the G1 is proportionately stouter, with the distal part of the subterminal segment wider in S. aruana, cf. Chia and Ng, 2006: fig. 43A, B); and finally, the terminal segment of the G1 is stouter, with the tip truncate ( Fig. 4A-C) (the terminal segment being evenly conical, more slender and with a sharp tip in S. aruana, cf. Chia and Ng, 2006: fig. 43A-D). These differences are consistent in the good series of male specimens examined and are also valid for females when non-sexual characters are involved.
With regard to the other species of Sundathelphusa occurring in central Indonesia, S. tuerkayi, new species, differs from Sundathelphusa cassiope (De Man, 1902) from Sulawesi in having a relatively lower epibranchial tooth; the lower postorbital cristae; the relatively longer, more slender ambulatory legs; and the proportionately longer male abdominal somite 6; however, their G1 structures are superficially similar (De Man, 1902: pl. 20, fig. 18;Chia and Ng, 2006: figs. 39A, 40); from Sundathelphusa minahassae (Schenkel, 1902), also from Sulawesi, by a more transversely ovate carapace, with the striae on the dorsal surfaces being less prominent; the relatively longer ambulatory legs; and a more curved G1 (cf. Chia and Ng, 2006: figs. 39B, 41); and from Sundathelphusa rubra (Schenkel, 1902) from Sulawesi by the anterior parts of the carapace less prominently swollen; longer ambulatory legs; and in possessing a much longer G1 terminal segment, which is very short in S. rubra (cf. Chia and Ng, 2006: figs. 42B, 44).