Melothelphusa apiaka, Pedraza, Manuel, Tavares, Marcos & Magalhães, Célio, 2016

Pedraza, Manuel, Tavares, Marcos & Magalhães, Célio, 2016, A new genus of freshwater crab of the tribe Kingsleyini Bott, 1970 (Crustacea: Decapoda: Brachyura: Pseudothelphusidae) with description of a new species from Mato Grosso, Brazil, Zootaxa 4173 (1), pp. 94-100 : 96-99

Melothelphusa apiaka n. sp.

( Figs. 1A–E ; 2A–C; 3A–D)

Type material. Holotype: male (cl 18.8 x cw 27.8), Brazil, Mato Grosso, Apiacás , [9º34’S, 57º23’W], altitude 220 m, G. Skuk & V. Xavier coll., 10–15 February 1997 ( MZUSP 32914 ) . Paratypes (same date as holotype unless otherwise stated): 1 male (cl 17.2 x cw 26.3), 3 females (cl 20.6 x cw 32.8; cl 18.5 x cw 28.3; cl 20.3 x cw 32.2) (MZUSP 32915); 1 male (cl 16.1 x cw 24.3), 2 females (cl 14.1 x cw 21.2; cl 17.2 x cw 25.8) (INPA 2183); 1 male (cl 19.2 x cw 28.9); 3 females (cl 21.6 x cw 32.8; cl 19.9 x cw 30.9; cl 16.4 x cw 25.4), Ana Maria Ramos-Costa coll., 15–17 February 1997 (MZUSP 32916): 1 male (cl 18.8 x cw 27.5); 2 females (cl 19.5 x cw 29.5; cl 22.5 x cw 35.0), Ana Maria Ramos-Costa coll., 15–17 February 1997 (INPA 2184): 1 male (cl 18.9), dry, carapace partially damaged, Brazil, Mato Grosso, Juruena [probably Juruena River, near Juruena , 10º22’S 58º20’W], 7–18 June 1997, G. Skuk coll. ( INPA 2185 ) ; 1 male (cl 14.5 x cw 20.5), Brazil, Mato Grosso, Juruena, G. Skuk coll., 7–18 June 1997 (MPEG 1742).

Comparative material. Brasiliothelphusa tapajoense : male holotype, Brazil, Pará, Monte Cristo, Tapajós river , Expedição Permanente da Amazônia leg. 20–28 July 1973 ( MZUSP 6550 ) ; 2 males, 2 females paratypes, Brazil, Pará, Monte Cristo, Tapajós river , Expedição Permanente da Amazônia leg. 20–28 July 1973 ( MZUSP 6378 ) .

Type locality. Apiacás [9º34’S, 57º23’W], altitude 220 m, Mato Grosso, Brazil.

Distribution. Presently known only from northern Mato Grosso, Brazil, in the interfluvial area between the Juruena and São Manuel Rivers.

Diagnosis. Mesial process of G1 large, subquadrate; mesial side of apical plate smooth, devoid of spines; subapical bulge noticeable in sternal view; subapical bulge and crest of sternal lobe both covered by abundant spinules.

Description of holotype. Carapace cervical groove nearly straight, faint, ending just before anterolateral margin. Post-frontal lobules obsolete; median groove indistinct; fronto-orbital region width less than half maximum width of carapace (18.84/27.83). Anterolateral margin fringed with minute anteriorly-directed tubercles almost evenly spaced. Posterolateral margin, smooth, poorly defined. Frontal margin carinate, straight in frontal view. Supraorbital margin lined with small granules laterally. Infraorbital margin slightly crenulated, moderately marginated, straight mesially. Exorbital angle moderately prominent, obtuse. Inner orbital tooth poorly developed, narrow, subtriangular, lobe-like. Mxp3 dactylus rather flattened ventrally, mesial surface markedly setate; propodus and carpus subclinical, nearly equal in size. Mxp3 ischium subquadrate, mesial edge setate, dentate, teeth squarish, corneous; ischium lateral margin slightly convex. Mxp3 exopod noticeable, reaching to about 0,5 times length of lateral margin of ischium (left exopod lost in holotype). Epistome upper margin straight, strongly carinate; lower margin deeply sinuous to receive folded mxp3 palp, large triangular epistomial tooth in center filling gap between joining palps; scarcely pubescence.

Merus of major cheliped subtriangular in cross-section, upper, mesial margins distinctly crenulated. Carpus upper surface smooth; mesial margin crenulated, strong acute tooth medially. Propodus massive, mesial, lateral surfaces smooth; dorsal, ventral surfaces with line of small tubercles. Movable finger slightly curved downwards, lateral, mesial, dorsal surfaces with punctations arranged in longitudinal subparallel lines. Cutting edges of fingers with small, massive teeth; fingers fully closing. P2–P5 meri, carpi, propodi massive, dactyli slightly laterally compressed, with 5 longitudinal rows of strong acute spines: 3 dorsal, 2 ventral; propodi with minute scattered spines dorsally, ventrally, smooth mesially; carpi minutely spinous dorsally, punctate laterally, smooth mesially, ventrally; meri crenulate dorsally, otherwise smooth.

Thoracic sternal sutures 4/5 to 6/7 well marked, ending just before reaching median line of thoracic sternum; median line prolonging between sternites 7 and 8, deeper at interception with sternal suture 7/8; episternites 4-6 triangular posteriorly, episternite 7 posteriorly truncate. Sterno-abdominal cavity strongly pubescent; tubercle of abdominal holding system minute, placed near sternal suture 5/6.

Male abdomen triangular in shape, tapering progressively from third somite onward, margins scarcely pubescent, sutures between somites well distinct, complete. Telson broadly triangular, lateral margins distinctly crenulated.

G1 robust, proximal half slightly convex in lateral view. Marginal suture straight. Lateral suture deep, extending 2/3 of gonopod length. Marginal process short, strongly curved to spermatic channel, apex truncated. Field of apical spines open, almost as wide as long. Opening of spermatic channel delimited by crest of abdominal lobe and marginal process. Crest of sternal lobe strongly curved, covered with abundant small spinules. Apical plate short, subquadrate in abdominal view, mesial side smooth, devoid of spines, bearing two distinct lobes distally (abdominal, sternal); sternal lobe small, uniformly rounded; abdominal lobe narrow; apical plate provided with prominent transversal keel in abdominal view, partially covering marginal process in abdominal view. Subapical bulge noticeable in sternal view, rounded, covered with small spinules. Mesial process large, subquadrate, arising from sternal surface, continuous with apical plate, spine-like distally, slightly oriented to abdominal side.

G2 distinctly slender, distal 3/4 tapered; tip flattened, with numerous short spinules on sternal surface.

Etymology. The species is named after the Indian tribe Apiaká . The specific epithet is used as a noun in apposition.

Remarks. Melothelphusa apiaka n. sp. and M. dardanelosensis n. comb. are unique in the tribe Kingsleyini as follows: they both have a G1 with a short marginal process that is strongly curved toward the spermatic channel which has a truncated apex (fig 2B); field of apical spines of G1 semicircular in shape, open (figs. 2B; 3B); the opening of spermatic channel of G1 delimited by both the crest of abdominal lobe and marginal process (figs. 2B, C; 3B); and the apical plate provided with strong, keel-like process, running transversally on the abdominal surface of G1 (figs. 2A, B; 3A, B, D). However, M. apiaka n. sp. differs from M. dardanelosensis n. comb. in having: (i) the mesial process of G1 distinctly subquadrate (figs. 2C; 3C) (while the mesial process is subtriangular in M. dardanelosensis n. comb.); (ii) the mesial side of apical plate of G1 devoid of spines (figs. 2A; 3A) (while the mesial side of apical plate is furnished with a distinct triangular spine in M. dardanelosensis n. comb.); (iii) well developed subapical bulge in sternal view of G1 (figs. 2B, C; 3B–D) (while the subapical bulge is absent and subapical region is smooth in sternal view in M. dardanelosensis n. comb.); (iv) the crest of the sternal lobe and the subapical bulge of G1 abundantly covered with spinules (figs. 2 A–C; 3A–D) (while all regions of the G1 are devoid of spinules in M. dardanelosensis n. comb.).

Figures

FIGURE 1 A – E. Melothelphusa apiaka n. sp., male holotype, cl 18.8 mm, cw 27.8 mm (MZUSP 32914). A, habitus, dorsal view. B, cephalothorax, ventral view. C, cephalothorax, frontal view. D, E, lateral view of right and left chelipeds, respectively. Abbreviations: CxP 4, coxa of pereopod 4; G 1, gonopod 1; G 2, gonopod 2; St 4 – 8, thoracic sternites 4 to 8. Scale bars A – E, 10 mm.