Marojejy longimerus, 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 : 67-71

Marojejy longimerus n. sp.

(®gures 1± 3)

Material examined. HOLOTYPE: male adult (cw 23, cl 15.1, ch 7.45, fw 5.9 mm) ( AMNH 18345 ), under rocks, at source of Andranomifototr a river (14 ss 26 ¾ 8 ² S, 49 ss 44 ¾ 1 ² E), 1,875 m, 11 km north-west of Manantenina, Province d’ Antsiranana, ReÂserve Naturelle InteÂgrale de Marojejy , Madagascar, leg. E. Quinter, 13± 19 November 1996 . PARATYPES: subadult female (cw 15.1, cl 11.3, ch 5.4, fw 4.5 mm), juv. male (cw 11.1, cl 8.4, ch 4.5, fw 3.1 mm) ( AMNH 17833 ) ; four males (cl 13.0± 14.7 mm), ®ve females (cl 12.2±14.2 mm) ( FMNH 4656 ), under rocks, at source of Andranomifototr a river (14 ss 26 ¾ 8 ² S, 49 ss 44 ¾ 1 ² E), 1,875 m, 11 km north-west of Manantenina, Province d’Antsiranana, ReÂserve Naturelle InteÂgrale de Marojejy , Madagascar, leg. E. Quinter, 13± 19 November 1996 ; ovigerous female (cl 13.1 mm) ( AMNH 17831 ), three males (cl 12±14.2 mm) ( AMNH 17834 ), along tributary at head of Andranomifototr a River (14 ss 26 ¾ 4 ² S, 49 ss 44 ¾ 5 ² E), 1,625 m, 10.5 km northwest of Manantenina , Province d’Antsiranana, ReÂserve Naturelle InteÂgrale de Marojejy , Madagascar, leg. E. Quinter and S. M. Goodman, 6± 12 November 1996 .

Diagnosis. As for genus.

Description. Based on holotype, an adult male from Marojejy , Madagascar, cw 23.0 mm ( AMNH 18345). Carapace ovoid outline, high (ch/fw 1.26), extremely wide anteriorly (cw/fw 3.8), tapering sharply posteriorly; posterior margin straight, relatively wide (0.33 cw). Anterolateral regions of carapace granular, rest of dorsal carapace smooth; semi-circular, urogastric, cardiac grooves shallow; cervical grooves deep, long, ending before meeting postorbital crests. Epigastric crests lying posterior to epibranchial teeth; postorbital crests low, indistinct, aligned with, but not joined to, epigastric crests; postorbital crests fading laterally before meeting epibranchial teeth; front slightly indented, margin thin, raised, smooth; front moderately deēxed, not meeting inferior margin of antennulular fossae; epistomial tooth triangular, deēxed, granulated. Exorbital angle low, lacking tooth, continuous with anterolateral margin. Epibranchial tooth reduced to small granule; anterolateral margin between exorbital angle and epibranchial tooth short, lacking intermediate tooth; anterolateral margin granular, curving sharply outward, posterior end curving inward, not continuous with posterolateral margin of carapace. Eyestalk tapering sharply distally, cornea very reduced; suborbital margin smooth. Subhepatic, pterygostomial regions of carapac e sidewall granulated, suborbital region smooth. Vertical sulcus on carapace sidewall granular, curving, running from base of epibranchial tooth to epimeral sulcus, separating suborbital from subhepatic region, dividing carapace sidewall into three parts.

Mandibular palp two-segmented, terminal segment bilobed, with medium-sized anterior process (about 0.5 as large as terminal segment) arising from junction between segments. Exopod of third maxilliped medium length, reaching to midpoint of merus; exopod with distinctly reduced, but still substantial, ¯agellum; ischium with faint, shallow, vertical groove. First sternal sulcus s1/s2 short but visible; second sternal sulcus s2/s3 deep, completely crossing sternum, s2 distinctly lower than s3. Sternal sulcus s3/s4 consisting of two short notches at edges of sternum, continuing over s4 as shallow, barely visible, v-shaped groove whose point meets granulated anterior margin of sterno-abdominal cavity midway along s4. Anterior sternum appearing smooth, but sparse short hairs visible under magni®cation. Episternal sulci s4/e4, s5/e5, s6/e6, s7/e7 smooth, all lacking visible groove. Sternite s5 with pair of sternal knobs (`bouton-pressions ’ of Guinot, 1977). Last ®ve segments of adult male abdomen (a3 to a7) forming triangle, a3 widest, telson (a7) narrowest. Telson with straight sides, triangular, not bell-shaped; a6 long, almost as long as width of distal margin of a6. Sternal groove s4/s5 meeting a7 close to junction between a7/a6; s5/s6 meeting a 6 in middle of segment, s6/s7 meeting a5 just short of a5/a6 junction.

Terminal article of gonopod 1 relatively short (ratio of length of terminal article to subterminal segment 0.3), 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 cone-shaped, almost straight, directed slightly outward; slim, tapering to upcurved tip with clear apical opening; subterminal segment of gonopod 1 with distinct, raised, rounded shoulder on external margin near junction with terminal article. Junction between terminal article and subterminal segment of gonopod 1 not clear on ventral side, but marked by deep sulcus dorsally; gonopod 1 with broad dorsal membrane. Gonopod 2 longer than gonopod 1; terminal article of gonopod 2 ¯agellum shorter than subterminal segment (ratio length terminal article to subterminal segment 0.7).

Merus, carpus, propodus, dactylus of P1 all elongated, chelipeds both extremely elongated: ratio of total length of chelipeds (from ischium to dactylus) to cw (P1/cw) 2.7 (right), 2.3 (left). Dactylus of right, left chelipeds relatively slim (one-third height of palm); upper margin of dactylus smooth; ®nger of propodus slim (one-third height of palm), lower margin of propodus of cheliped slightly indented. Finger of propodus with large, fused molar tooth in proximal region, rest of propodus and dactylus with series of small teeth, closed ®ngers leaving long, narrow interspace. Inner margin of inferior face of ischium of pereiopod 1 with two small teeth; outer margin smooth. Inner margin of inferior face of merus of pereiopod 1 lined by row of small uneven teeth, outer margin lined by small even teeth; low, faint tooth in middle of distal margin; superior surface of merus rough, granulated. Inner margin of carpus of pereiopod 1 with two large teeth, second about half size of ®rst; ®rst carpal tooth broad, triangular, blunt, second carpal tooth small, low, blunt. Merus, carpus, propodus, dactylus of P2 to P5 all elongated, walking legs slender: ratio of total length of P2/cw to P5/cw 1.36, 1.47, 1.53, 1.23 respectively. Inner margins of propodi of P2 to P5 smooth.

Size. Largest known specimen is the male holotype, cw 23 mm.

Colour. Carapace, eyestalks, chelipeds uniformly pale orange. Merus of cheliped with dark brown wash, ®ngertips pale white. Merus, carpus of walking legs pale white with pale orange mottling; mottling decreasing on propodus and dactylus.

Distribution. Madagascar.

Type locality. Andranomifototr a river (14 ss 26 ¾ 8 ² S, 49 ss 44 ¾ 1 ² E), 1,875 m, 11 km north-west of Manantenina , Province d’Antsiranana, ReÂserve Naturelle InteÂgrale de Marojejy , Madagascar .

Comparisons. Marojejy longimerus is super®cially similar to other small long-legged crabs found in Madagascar ( Gecarcinautes , Madagapotamon and Skelosophusa ) but can be distinguished from these taxa by the characters discussed above for the genus.

Remarks. The ReÂserve Naturelle InteÂgrale de Marojejy is a 60,000 ha reserve in north-east Madagascar, north of Andapa, that includes the Marojejy mountains and consists of a continuous steep climb from 100 m to over 2100 m. The vegetation in the reserve includes closed canopy forest, mountain woodland, and ericoid bush, and palms, ferns, orchids and balsams are abundant. Some of the fauna, including lemurs, birds and insects, is endemic to the reserve ( Jolly et al., 1984).