Leptarma reunionense Shahdadi & Schubart 2020, n. sp.
Creators: name: Shahdadi, Adnan
name: Schubart, Christoph D.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Sesarmidae
Leptarma
Leptarma reunionense

description: Leptarma reunionense n. sp.
(Figs. 4– 6, 7E, 8A, 9A, 10E)
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Parasesarma plicatum — Poupin (2009: 132, Fig. p. 36); not Parasesarma plicatum (Latreille, 1803).
Material examined. Holotype: male (11.8×9.92) (UF12356), Réunion. Paratype: 1 male (11.6×9.8) (UF12354), Réunion Island.
Diagnosis. Carapace subrectangular, slightly broader than long, front deflexed, almost straight in dorsal view, median post-frontal lobes wider than lateral ones, lateral carapace margin slightly concave. Eye with short and stout eyestalk, wider than long, corneal part slightly wider. Male chela large, robust, upper surface of palm with two oblique pectinated crests, dorsal surface of dactylus bearing 9 or 10 low, rounded, asymmetric tubercles, with longer distal slope, proximal ones positioned at middle of dorsal face of dactylus with oblique keel. Ambulatory legs relatively long, third pair longest, total length (basis-dactylus) ca. 1.8 times carapace width; male pleon triangular, somite 2 medially longer than lateral edges. G1 stout, straight; apical corneous process long, tip truncate, bent at an angle of about 65° to vertical axis, aperture terminal.
Description. Carapace subrectangular, slightly broader than long (cw/cl = 1.17), greatest width between exorbital angles; carapace surface smooth; front ca. 0.55 times carapace width, deflexed, almost straight in dorsal view; post-frontal lobes prominent, median lobes wider than lateral ones, separated by deep furrow; dorsal carapace regions well indicated, gastric region demarcated, cardiac region separated from intestinal region, lateral branchial ridges prominent; upper orbital border smooth, lower orbital border finely granulate; anterolateral margin with sharp exorbital angle, lateral margin slightly concave, edged with row of short setae. Eye with eyestalk short, stout, wider than long, corneal part slightly wider (Figs. 4A, 5A, 6A).
Male chela large (palm length/cw ca. 0.68) (Figs. 4B, 5A), robust (palm width/length ca. 0.61) (Figs. 4B, 5C); merus with granulate dorsal border, no distinct subdistal spine, ventral border granulate, anterior border granulate, with distinct subdistal spine, accompanied by several spines distally, inner face smooth with longitudinal row of setae, anterior face smooth, outer face with rows of fine granules; upper surface of palm with 2 oblique pectinated crests, distal (primary) crest composed of 13-16 teeth; secondary crest well developed, with 6-8 teeth, both crests terminating at inner end in 1-2 granule(s) and several granules on outer side (Fig. 5E); outer surface of palm with fine granules (rows of fine granules on the proximal half) except for smooth, punctate fixed finger (Fig. 5C); inner surface of palm granular except area facing carpus and distal half of finger; no vertical ridge, dactylus slightly curved downward and inward, dorsal surface bearing 9 or 10 low but distinct, rounded tubercles, distinct to tip, tubercles asymmetric with distal slope longer distal slope, proximal ones positioned at middle of dorsal face of dactylus with oblique keel; small pointed granules on inner side, cutting edge of both fingers with a series of variably sized teeth (Fig. 5 C–F).
Ambulatory legs flattened dorso-ventrally, relatively long, third pair longest, total length (basis-dactylus) ca. 1.8 times carapace width, tufts of long setae scattered along prpodi and dactyli, merus with anterior margin crenulated, ca. 2.26 times as long as wide, propodus ca. 2.8 times as long as wide, dactylus ca. 0.8 times length of propodus (Figs. 4A, 6A).
Male pleon triangular (Figs. 4B, 5G), with telson almost as long as basal width, as long as somite 6; somite 6 longer than others; somites 4 and 5 trapezoidal, somite 3 widest, laterally convex, somite 2 medially longer than lateral edges (Fig. 5H).
G1 stout, rather long, straight; apical corneous process long, tip truncate, bent at angle of about 65° to vertical axis, arched in cross section, aperture terminal (Figs. 5B, 6 B–E).
Female. No female specimen was examined.
Color. The specimens preserved in ethanol do not show any coloration. According to the photo in Poupin (2009, p. 36), the carapace and pereiopods are light brown with black clouds, chela brighter, fingers yellow.
Habitat and distribution. No information to be found on label. According to Poupin (2009: 35) the crab lives in mangrove and muddy swamps of estuaries.
Etymology. The name is derived from the region of occurrence (type locality) of the species, Réunion Island.
Remarks. Among other Leptarma, the new species resembles most L. liho and L. jamelense, both from South East Asia, in general appearance (Fig. 7E, F), chelar (Figs. 8 A–C, 9A–C) and G1 morphology (Fig. 10 E–G). The new species, however, has a wider carapace compared to the other two species, i.e. cw/cl ca. 1.2 in the new species vs. 1.1 in L. liho and L. jamelense. In dorsal view, the front is more sinuous in L. liho (Fig. 7F) and L. jamelense compared to the almost straight front of the new species (Fig.7E). The new species also differs from the two other species in chelar dactylar tubercles (9-10 rounded tubercles in the new species (Fig. 9A) vs. 12-14 oval tubercles in L. liho (Fig. 9B) and L. jamelense (Fig. 9C)). The new species also has G1s with slightly longer apical corneous processes, compared to the other two similar species (Fig. 10 E–G).
The new species shows phylogenetic association (Fig. 1A) and some morphological resemblance to the species pair L. moluccense and L. paucitorum. The new species, however, has a wider carapace compared to these two species (Fig. 7G, H), i.e. cw/cl ca. 1.2 in the new species, while it is less than 1.1 in the other two species. They also differ in chelar dactylar tuberculation and G1 morphology. The new species has more tubercles (9-10) than L. moluccense and L. paucitorum (6-8) (Figs. 8D, E, 9D, E) and G1s with longer apical corneous process (Fig. 10H, I).
Leptarma reunionense n. sp. also resembles L. aurifrons in general appearance as well as in chelar morphology. L. reunionense n. sp., however, differs from L. aurifrons in G1 morphology, which has longer and more bent corneous process (see Li et al., 2019: Fig. 3E, F).
description: Published as part of Shahdadi, Adnan & Schubart, Christoph D., 2020, Two new species of Leptarma (Decapoda, Brachyura, Sesarmidae) from the Western Indian Ocean with notes on their phylogeny, pp. 439-456 in Zootaxa 4816 (4) on pages 445-453, DOI: 10.11646/zootaxa.4816.4.2, http://zenodo.org/record/3954577