Gecarcinautes goodmani, Cumberlidge & Boyko & Harvey, 2002

Cumberlidge, Neil, Boyko, Christopher B. & Harvey, Alan W., 2002, A new genus and species of freshwater crab (Crustacea, Decapoda, Potamoidea) from northern Madagascar, and a second new species associated with Pandanus leaf axils, Journal of Natural History 36 (1), pp. 65-77 : 71-76

Gecarcinautes goodmani n. sp.

(®gures 4±6) Gecarcinautes n. sp. cf. antongilensis antongilensis ( Rathbun 1905) Harvey and Boyko, 1998: 145 ±146.

Material. HOLOTYPE: male adult/subadult (cw 23.0, cl 17.6, ch 6.8, fw 4.7 mm) (FMNH 4651), Station ForestieÁre de Tampolo, Province de Toamasina, Madagascar (17 ss 17 ¾ 2 ² S, 49 ss 24 ¾ 5 ² E), 10 m, in leaf axils of Pandanus , coll. S. M. Goodman, 4.iv.1997. PARATYPES: adult/subadult female (cw 23.5, cl 18.4, ch 8.0, fw 5.4 mm), juv. male (cw 12.6, cl 10.6, ch 4.2, fw 3.1 mm) ( FMNH 4651), male (cl 16.5 mm) ( AMNH 17530), ovigerous female (cl 18.1 mm) ( AMNH 17530a), Station ForestieÁre de Tampolo, Province de Toamasina, Madagascar (17 ss 17 ¾ 2 ² S, 49 ss 24 ¾ 5 ² E), 10 m, in leaf axils of Pandanus , coll. S. M. Goodman, 4 April 1997; ovigerous female (cl 20.3 mm) ( AMNH 17830), near tributary of Manantenina River (14 ss 26.0 ¾ S, 49 ss 45.7 ¾ E), 775 m, in leaf axils of Pandanus , 100 km north-west of Manantenina, Province d’Antsiranana, ReÂserve Naturelle InteÂgrale de Marojejy , Madagascar, leg. S. M. Goodman, 15± 22 October 1996.

Diagnosis. Outer margins of dactylus, propodus of P2 to P5 with thick covering of velvet-like hair.

Description. Based on holotype male from Station ForestieÁre de Tampolo, Province de Toamasina, Madagascar, cw 23.0 mm ( FMNH 4651). Carapace outline heart-shaped, elongated (cl/fw 3.76), high (ch/fw 1.46), widened anteriorly (cw/fw 4.9), tapering sharply posteriorly. Anterolateral carapace regions heavily granulated with short carinae; branchial, semi-circular, urogastric, cardiac, grooves deep; cervical grooves deep, long, ending before meeting postorbital crests. Epigastric crests in line with epibranchial teeth; postorbital crests incomplete, marked by interrupted series of granules; epigastric crests clearly separated from postorbital crests; front sharply deēxed, almost vertical, meeting lower margins of antennulular fossae; frontal margin indented, margin thin, smooth, raised; front very narrow, about one- ®fth cw (fw/cw 0.2). Exorbital, epibranchial teeth distinct, triangular, pointed; epibranchial tooth about half as large as exorbital tooth; anterolateral margin between exorbital, epibranchial teeth short, lacking intermediate tooth; anterolateral margin with seven small pointed teeth behind epibranchial tooth, posterior end of anterolateral margin of carapace continuous with posterolateral margin. Eyestalk normal width, length (not reduced), cornea normal size (not reduced); suborbital margin raised, granulated. Suborbital, subhepatic regions of carapace sidewalls smooth, pterygostomial region, anterior sternum, third maxilliped smooth, with short, sparse hairs under magni®cation. Vertical sulcus on sidewall granular, running from base of epibranchial tooth to epimeral sulcus, separating suborbital region from hepatic region, sidewall clearly divided into three parts.

Mandibular palp two-segmented, terminal segment bilobed, with medium-sized anterior process (about 0.5 Ö terminal segment) at junction between segments. Third maxilliped exopod short, reaching only to lower lateral corner of merus; exopod ¯agellum medium length, ischium with deep vertical groove. First sternal sulcus s1/s2 barely visible; second sternal sulcus s2/s3 deep, horizontal; third sternal sulcus s3/s4 deep at edges, angling inward as faint groove almost meeting anterior margin of sterno-abdominal cavity on sternite s4. Episternal sulci s4/e4, s5/e5, s6/e6, s7/e7 smooth, all lacking visible groove. Last ®ve segments of abdomen (a3 to a7) tapering inward, forming long triangle, a3 widest, telson (a7) narrowest; telson with straight sides, triangular, not bell-shaped; a6 long, slightly longer than width of distal margin of a6. Sternal sulcus s4/s5 meeting a7 about one-third along length of segment; s5/s6 meeting a6 about one-third along length of segment; s6/s7 meeting a5 about onethird along length of a5. Terminal article of gonopod 1 relatively short (ratio of length of terminal article to subterminal segment 0.33). Longitudinal groove on terminal article wide near junction, narrowing sharply distally, clearly visible on ventral, superior sides, not visible on dorsal side; lateral, medial folds on ventral terminal article equal in height, width; terminal article slim, cone-shaped, almost straight, directed slightly outward, tapering to slightly upcurved tip with clear apical opening; subterminal segment of gonopod 1 with distinct triangular shoulder on external margin near junction with terminal article. Suture marking junction between terminal article and subterminal segment of gonopod 1 distinct on dorsal side but barely visible on ventral side. Wide dorsal membrane on dorsal side of junction between terminal article and subterminal segment of gonopod 1. Gonopod 2 longer than gonopod 1; gonopod 2 terminal article ¯agellum with rounded tip, shorter than subterminal segment, ratio length terminal article to subterminal segment 0.7.

Dactylus of right, left chelipeds relatively narrow (one-quarter height of palm), straight, upper margin granulated; ®nger of propodus one-third height of palm, lower margin of propodus of cheliped slightly indented. Fingers of propodus with four large teeth interspersed by series of smaller teeth, closed ®ngers enclosing long interspace. Anterior, posterior inferior margins of ischium of pereiopod 1 smooth. Inferior margins of merus of pereiopod 1 each lined by row of small rounded teeth; single large meral tooth on distal margin; superior surface of merus rough, ®nely granulated. Inner margin of carpus of pereiopod 1 with two pointed teeth: ®rst carpal tooth large, second carpal about half as large as ®rst carpal tooth. Inner margins of propodi of P2 to P5 smooth with tufts of hair. Merus, carpus, propodus, dactylus of P2 to P5 elongated, walking legs long, slender: ratio of total length of P2/cw to P5/cw 1.22, 1.57, 1.92, 1.20 respectively. Outer margins of dactylus, propodus of P2 to P5 with thick covering of velvet-like hair.

Size. Largest specimen is an ovigerous female, cw 27.5 mm.

Colour. Frontal region of carapace chocolate brown, gastric, hepatic regions of carapace dark red-purple, branchial regions lilac, cardiac region gray, intestinal region gray-purple; anterolateral margin teeth pale orange-tan; orbital, anterior margins dark orange. Cornea black, eyestalk dark red-brown. Dorsal surface of dactylus of cheliped deep red-brown, becoming pale orange ventrally, lateral surface of dactylus pale orange-tan; ®xed ®nger of cheliped pale orange-tan; dorsal surface of merus dark orange/red-brown, grading to pale orange/yellow ventrally; carpus dark orange/red-brown, lateral and dorsal surface of merus mottled tan to red-purple; all tubercles on cheliped pale tan. Walking legs brown-lavender, dactyli dark brown-orange distally. Colour varies noticeably with size. Carapace, pereiopods of smallest specimen gray-violet; dactyli of walking legs yellow, propodus yellow distally, grading into gray-violet; dactylus and propodus of cheliped uniform brilliant yellow. Chelipeds of medium sized specimens with regions of pale orange which become rich mahogany in large specimens.

Distribution. Madagascar. Gecarcinautes goodmani is found at diOEerent elevations, always in association with Pandanus leaf axils. The exact nature of the distribution of this species on the island remains unknown, because Pandanus habitats have not been well sampled over the whole of Madagascar.

Type locality. Station ForestieÁre de Tampolo, Province de Toamasina, Madagasca r (17 ss 17 ¾ 2 ² S, 49 ss 24 ¾ 5 ² E), 10 m elevation, in leaf axils of Pandanus .

Sympatric taxa. One male (cl 36.0 mm) and four females (cl 18.8±24.8 mm) ( FMNH 4652) of Gecarcinautes cf. goudoti (H. Milne Edwards 1853) were collected from pitfall traps close to the type locality of G. goodmani . Gecarcinautes goodmani is therefore sympatric with G. cf. goudoti in at least part of its range, although these two species do not appear to share the same ecological niche.

Diagnosis. Epigastric crests posterior to supraorbital margins, separated by narrow midgroove; outer margins of dactylus, propodus of walking legs with thick covering of velvet-like hair; inner margin of propodus of walking legs smooth, with tufts of hair.

Comparisons. Gecarcinautes goodmani can be distinguished from Marojejy longimerus by the suite of generic-level characters described above under Marojejy . Gecarcinautes goodmani was collected in the same locality and the same habitat as G. cf. goudoti, but the larger body size, highly ināted, smooth carapace, smooth anterolateral carapace margins, smooth dactyli of P2±P5, and normal sized walking legs of G. cf. goudoti immediately distinguish it from G. goodmani .

Gecarcinautes goodmani resembles G. antongilensis in its heart-shaped carapace, narrow front, anterior process on the terminal segment of the mandibular palp, and extremely long walking legs. In addition to the nominate subspecies, Bott (1965) erected the taxon G. antongilensis vondrozi , which he considered to have a smaller, ¯atter, less grooved carapace, a wider front, less well de®ned epigastric crests, and smaller teeth on the anterolateral margin of the carapace compared to the nominate form. During the present study, we examined the male holotype of G. antongilensis from Baie d’Antongil, Madagascar (MNHN BP 5033), as well as the male holotype of G. a. vondrozi from Vondrozo, at an elevation of 100±800 m, pointe de Farafangana, Madagascar (MNHN BP 5038) collected by M. Decary, ix.1926. Characters of the ®rst and second gonopods, mandibles, sternum, abdomen, dorsal carapace, carapace sidewalls, chelipeds and walking legs of G. a. vondrozi correspond well with the type of G. antongilensis , and set this specimen apart from G. goodmani . The diOEerences between G. a. vondrozi and the nominal species that were cited by Bott (1965) as justi®cation for the establishment of a new taxon are well within the range of intraspeci®c variation and do not, in themselves, warrant the recognition of a separate taxon. Therefore G. a. vondrozi is considered here to be a junior objective synonym of Gecarcinautes antongilensis (new synonymy).

Gecarcinautes goodmani can be distinguished from G. antongilensis as follows. In G. antongilensis , the epigastric crests are advanced and lie in line with the supraorbita l margins and are separated by a wide midgroove; the inner margin of the propodus of pereiopods P2±P5 is distinctly toothed; and the outer margins of the dactylus and propodus of P2±P5 lack the thick covering of velvet-like hair characteristic of G. goodmani .

Remarks. It is di cult to reach conclusions regarding the range of this species on the island because our specimens of G. goodmani were collected from two geographically distinct regions and two diOEerent elevations. Some species of freshwater crabs from West Africa ( Globonautes macropus, Cumberlidge, 1991 Cumberlidge and Sachs, 1991 ) and Sri Lanka ( Ceylonthelphusa scansor, Ng, 1995 ) have been reported to be able to climb trees and to utilize unusual habitats in the rain forest such as tree holes. It would therefore be extremely interesting to evaluate the ecological relationships between G. goodmani and Pandanus palms, because this interesting ecological specialization has not been reported before for any species of freshwater crab.

Etymology. The new species has been named for Dr Steven M. Goodman of the Department of Zoology, Field Museum of Natural History, Chicago, USA, to recognize his extensive and diverse contributions to the conservation of the biodiversity of Madagascar.