Geosesarma nigripes, Ng & Wowor & Daisy, 2024

Ng, Peter K. L., Wowor, & Daisy, 2024, Two new species of vampire crabs (Crustacea: Decapoda: Brachyura: Sesarmidae: Geosesarma De Man, 1892) from Java, Indonesia, Raffles Bulletin of Zoology 72, pp. 469-478 : 473

Geosesarma nigripes , new species

( Figs. 1E–H , 3 , 4D–F , 5J–R )

Material examined. Holotype: male (12.3 × 11.3 mm) ( MZB Cru 5720), Cikukun hamlet, Adimulya village , Wanareja District, Cilacap Regency, Central Java, Indonesia, coll. Achmad Sofyan, transferred from Achmad Rian Dietra, June 2022 . Paratype: 1 male (12.7 × 11.9 mm) ( ZRC 2023.0321 ), same data as holotype ; 1 male (13.3 × 11.8 mm), 10 females (10.8 × 9.9 mm – 14.5 × 13.1 mm), 12 ovigerous females (11.8 × 11.0 mm – 12.8 × 12.4 mm) ( MZB Cru 5721) , 2 females (13.9 × 12.8 mm, 12.7 × 11.8 mm), 1 ovigerous female (11.8 × 11.3 mm) ( ZRC 2023.0562 ), same locality and collector as holotype, early July 2023 ; 34 males (11.5 × 9.9 mm – 13.8 × 12.6 mm), 2 females (11.5 × 10.3 mm – 13.3 × 11.4 mm), 1 ovigerous female (12.5 × 11.1 mm) ( MZB Cru 5732) , 20 males (10.7 × 9.6 – 15.1 × 13.8 mm), 2 females (12.3 × 11.1 mm, 15.0 × 12.6 mm) ( ZRC 2023.0567 ), same locality and collector as holotype, 28 November 2023 .

Diagnosis. Carapace subsquarish, slightly trapezoidal with posterior part wider than anterior part, lateral margins gently diverging posteriorly ( Fig. 3A, B ); dorsal surface with distinct regions, anterior regions with numerous small rounded granules ( Fig. 3A, B ); front deflexed, frontal lobes very broad with almost truncate margins, separated by broad median concavity; postfrontal cristae sharp ( Fig. 3A–C ); external orbital tooth triangular, directed obliquely outwards, tip extending beyond anterior part of lateral carapace margin, first epibranchial tooth triangular, low, visible, separated from margin by shallow notch, second epibranchial tooth small but visible ( Fig. 3B ). Ischium of third maxilliped subtrapezoidal, merus ovate, wide; exopod relatively slender, with long flagellum that extends beyond merus width ( Fig. 5J ). Outer surface of palm of adult male chelae with low granules and rugae; inner surface finely granulated but without distinct transverse comb-like ridge; dorsal margin of dactylus with 5 or 6 evenly spaced tubercles, each with chitinous tip ( Fig. 3D–F ). Ambulatory legs with relatively stouter meri (fourth leg length-to-width ratio ca. 3.0), with sharp subdistal spine on dorsal margin; ventral margins of propodus and dactylus of adult first ambulatory leg with scattered stiff setae ( Fig. 3A, G ). Male pleon wide, triangular; especially somite 6 relatively wide; telson subtriangular with rounded tip, slightly shorter than broad (length-to-width ratio ca. 0.8); somite 6 with convex lateral margins ( Figs. 4D , 5K ). G1 relatively slender; subdistal part of outer margin of stem before chitinous distal part rounded, outer margin of junction between stem and chitinous distal part concave, long; chitinous distal part bent about 45º along longitudinal axis, elongate, tapering, distalmost part conical in lateral view, subspatuliform in mesial view ( Fig. 5L–Q ). Vulva on anterior part of somite 6, with raised vulvar cover, directed mesially ( Fig. 4F ). Preserved egg size 1.8 × 1.6 mm – 1.6 × 1.5 mm in diameter.

Notes on habitat. Geosesarma nigripes , new species, lives among wet bushes with stony substrates along streams in lowlands in Central Java Province at about 40 m asl.

Colour. Carapace pale cream to pale yellow, with posterolateral regions dark purple to almost black; frontal surfaces of cephalothorax dark brown to almost black; H-shaped grooves dark brown; eyes iridescent orange to yellow; chelipeds orange; ambulatory legs dark purple to almost black ( Fig. 1E–H ).

Etymology. The species is named after its black ambulatory legs; from the Latin “nigra” for black and “pes” for legs. The name is used as a noun.

Figures

Fig. 1. Live colouration of males. A–D, Geosesarma riani, new species; E–H, G. nigripes, new species. All specimens not preserved. Photographs: A, E, F, Achmad Rian Dietra; B, Oliver Mengedoht; C, D, G, H, Chris Lukhaup.

Fig. 3. Geosesarma nigripes, new species, holotype male (12.3 × 11.3 mm) (MZB Cru 5720), Central Java. A, overall dorsal habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, outer view of right chela; E, dorsal view of right cheliped; F, submarginal view of dactylus of right chela; G, left fourth ambulatory leg.

Fig. 4. A, Geosesarma riani, new species, holotype male (12.8 × 11.8 mm) (MZB Cru 5717), West Java; B, C, G. riani, new species, paratype female (13.2 × 11.8 mm) (MZB Cru 5719), Central Java; D, G. nigripes, new species, holotype male (12.3 × 11.3 mm) (MZB Cru 5720), Central Java; E, F, G. nigripes, new species, paratype female (15.0 × 13.3 mm) (MZB Cru 5721), Central Java. A, D, male thoracic sternum and pleon; B, E, female pleon; C, F, sternopleonal cavity showing vulvae.

Fig. 5. A–I, Geosesarma riani, new species, holotype male (12.8 × 11.8 mm) (MZB Cru 5717), West Java; J–R, G. nigripes, new species, holotype male (12.3 × 11.3 mm) (MZB Cru 5720), Central Java. A, J, left third maxilliped; B, K, pleon; C, L, left G1 (ventral view); D, M, left G1 (dorsal view); E, N, distal part of left G1 (ventral view); F, O, distal part of left G1 (dorsal view); G, P, distal part of left G1 (mesial view); H, Q, distal part of left G1 (outer lateral view); I, R, left G2. Scales: A, C, D, I, J, L, M, R = 0.5 mm; B, K = 1.0 mm; E–H, N–Q = 0.2 mm.