Geosesarma garutense Ng & Wowor 2022, n. sp.
Creators: name: Ng, Peter K. L.
name: Wowor, Daisy
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Sesarmidae
Geosesarma
Geosesarma garutense

description: Geosesarma garutense n. sp.
(Figs. 1–4)
Type material. Holotype: male (10.7 × 9.5 mm) (MZB Cru 5387), West Java Province, Garut Regency, Banyuresmi District, Ds. Sukaratu, Kp. Patrol, S. Cimanuk, 7°10’52.7”S 107°56’13.1”E, coll. Y. Y. Goh, 1–2 July 1997. Paratypes: 8 males, 5 females (MZB Cru 5388), 8 males, 6 females (largest 10.5 × 9.5 mm) (ZRC 2021.0586), data same as holotype.
Diagnosis. Carapace transversely rectangular, lateral margins almost parallel, wider than long, anterior regions with small low granules (Figs. 1A, B); front deflexed, frontal lobes broad with gently convex margins, separated by short, shallow median concavity; postfrontal cristae sharp (Figs. 1B, D); external orbital tooth triangular, directed obliquely outwards, tip not extending beyond anterior part of lateral carapace margin, separated from margin by deep V-shaped cleft, first epibranchial tooth low, subtruncate, separated from margin by shallow concavity, second epibranchial tooth not clearly visible, just discernible as very low lobe (Fig. 1A, B). Third maxilliped ischium ovate; exopod slender, without any trace of flagellum (Fig. 1C). Adult male cheliped palm with small granules and rugae on outer surface, inner surface granulated, with low transverse ridge of low granules but not comb-like; dactylus dorsal margin with 8–10 tubercles on proximal one-third, with 2 or 3 tubercles medially, those on distal half very low, barely visible (Figs. 1F–H, 2A, B). Ambulatory legs short, stout, with relatively slender meri with sharp subdistal spine on dorsal margin, surfaces slightly rugose to almost smooth; ventral margins of propodus and dactylus of adult first ambulatory leg with scattered long setae (Figs. 1A, 2C). Male pleon broadly triangular; telson triangular with rounded tip and convex margins, as long as broad; somite 6 with convex lateral margins (Figs. 1E, 2D). G1 relatively short, stout, outer margin almost straight; chitinous distal part bent 70–80° along longitudinal axis, long, subspatulate in lateral view, broad in mesial view; tip subtruncate when viewed dorsally (Figs. 2E–H, 3A–E).
Etymology. The species name is after the area of occurrence of the new species, Garut Regency.
Habitat. The type locality, Cimanuk stream, is a small river with rocky substrates at an altitude of 698 m asl (Statistik Daerah Kabupaten Garut 2021). This is a relatively flat agricultural area consisting of rice fields and gardens with irrigation. People who live along the river use it as water source for their agricultural land and fishponds. The location is in the middle part of Cimanuk River, with the headwaters in the Mandalagiri-Puncakgede mountain range in Ds. Simpang, Cikajang District, Garut Regency. This regency is surrounded by Mt. Karacak (1838 m asl), Mt. Cikuray (2821 m asl), Mt. Papandayan (2622 m asl), and Mt. Guntur (2249 m asl). Overall, the type locality is considered relatively low in altitude (Statistik Daerah Kabupaten Garut 2021).
Remarks. The new species is very distinct from known Javanese congeners in that the carapace is relatively wider and rectangular in shape, the exopod of the third maxilliped does not have a flagellum, the ambulatory legs are short and stout, and the G1 is relatively short and stout, with the chitinous distal part spatuliform.
The combination of characters in G. garutense n. sp. is unusual. All the known species of Geosesarma from Java, including the highland species, have a well-developed flagellum on the exopod of the third maxilliped; G. garutense n. sp. is the only species that lacks one (Fig. 1C). The good series of specimens on hand confirms this character is constant for this species, even for juveniles. In addition, the absence of a flagellum on the exopod of the third maxilliped is normally associated with Southeast Asian species that have a quadrate carapace, longer and more slender ambulatory legs, and a proportionately stouter G1 with a relatively shorter sharply bent chitinous distal part which is subconical in shape. The only species with similar characters to G. garutense n. sp. is G. aurantium Ng, 1995 from Sabah, Malaysian Borneo; but in this species, the G1 has the chitinous distal part more prominently flared and wider distally (cf. Ng 1995: fig. 3). The structure of the tubercles on the dorsal margin of the dactylus of the adult male chela is also unusual in G. garutense n. sp., with the proximal one-third possessing a cluster of sharp tubercles before forming a row of lower sharp tubercles which becomes faint just before the tip (Figs. 1G, H, 2A, B); rather than forming a distinct row of tubercles which gradually becomes smaller distally. In this respect, the male chela most closely resembles that of G. rouxi from eastern Java, but the carapace and G1 structures of the latter species are very different (cf. Ng & Wowor 2019: fig. 22F–H).
There appears to some correlation with the structure of the G1 and where the crabs occur in Java. The G1 of species of Geosesarma occurring in the lowlands is invariably more slender, with the chitinous distal part bent and spatuliform to various degrees. The G1 distal part of G. bicolor from Ujung Kulon on the westernmost coast, G. dennerle and G. hagen, both from Cilacap, a coastal town in south of Central Java Province, are long and slender, and sharply bent at about 45° along the longitudinal axis (cf. Ng & Davie 1995: fig. 2I–M; Ng et al. 2015: figs. 2F–I, 4C–G, J–M). All three type localities are between 0–100 m asl (Kecamatan Lumbir dalam angka 2021; Kecamatan Sidareja dalam angka 2021). Two other species of Geosesarma from slightly higher altitudes of 170–800 m asl in western Java (G. noduliferum and G. lebak) have the G1 chitinous distal part sharply bent at about 45° along the longitudinal axis, although the structure is relatively less slender than those of the first three species (cf. Ng & Wowor 2019: figs. 4D–F, H–J, 6D–H, 7B–E).
At intermediate altitudes of 580–700 m asl in western Java, two species are present: G. sukabumi and G. garutense n. sp., both of which have the G1 relatively stouter with the chitinous distal part bent at about 70–80° along the longitudinal axis (Ng & Wowor 2019: fig. 10B–E; Figs. 2E–H, 3A–E). Noteworthy is that the G1 chitinous distal part of G. sukabumi and G. garutense n. sp. is relatively shorter and wider than those of G. noduliferum and G. lebak.
The G1s of the five highland species of Geosesarma from Java (altitudes above 1000 m asl) show more variation, although all are relatively shorter and stouter than those from lowlands. The G1 chitinous distal part of G. robustum is stout and bent at about 45° along the longitudinal axis (Ng & Wowor 2019: fig. 12B–F), while those of G. confertum and G. cikaniki are less bent (ca. 40°) (cf. Ng & Wowor 2019: figs. 21B–D, 15B–E). The G1 chitinous distal part of G. sekop is bent at about 30° (Ng & Wowor 2019: fig. 18B–F, H–I) and that of G. rouxi bent at about 20° (Ng & Wowor 2019: fig. 23B–F). The length of the G1 chitinous distal part varies with species, it is relatively longer in G. confertum and G. sekop and very short in G. rouxi. That being said, the chitinous distal G1 of the highland Geosesarma are always broad and robust, more so than those from lowland and intermediate altitudes.
description: Published as part of Ng, Peter K. L. & Wowor, Daisy, 2022, Geosesarma garutense n. sp., a new species of vampire crab (Crustacea, Brachyura, Sesarmidae) from Garut in western Java, pp. 145-150 in Zootaxa 5159 (1) on pages 146-150, DOI: 10.11646/zootaxa.5159.1.8, http://zenodo.org/record/6771091