Macrophthalmus (Mareotis) fusculatus, Rahayu, Dwi Listyo & Nugroho, Dharma Arif, 2012

Rahayu, Dwi Listyo & Nugroho, Dharma Arif, 2012, The Indonesian species of Macrophthalmus Desmarest, 1823, with the description of a new species (Crustacea: Decapoda: Brachyura: Macrophthalmidae), Zootaxa 3158, pp. 20-36 : 27-32

Macrophthalmus (Mareotis) fusculatus n. sp.

( Figs. 4–7 )

Type material. Holotype: male (8.69 x 12.02 mm) ( MZB Cru 3273), Ajkwa I., Papua, Indonesia, 17.05.2001. Paratypes: same data as holotype, 2 males (7.45 x 9.64, 7.64 x 9.27 mm), 1 female (6.36 x 8.54 mm), 2 ovig. (8.00 x 9.82, 8.54 x 10.18 mm) ( ZRC 2011.1001); 2 males (7.45 x 9.09, 7.18 x 10.36 mm), 3 ovig. (7.27 x 8.54, 8.18 x 10.18, 1.82 x 9.64 mm) (RCLA-C.B.0262); 2 males (7.45 x 9.27, 8.00 x 10.00 mm), 1 female (6.73 x 8.55 mm), 2 ovig.. (8.00 x 9.64, 8.91 x 10.36 mm) ( MZB Cru 3274).

Other material examined. 17 males (4 x 5.27 – 8 x 9.82 mm), 16 females (4.36 x 5.27 mm – 6.91 x 8.73 mm), 1 ovig. (7.09 x 8.54 mm) ( MZB Cru 3275), Ajkwa, Papua, 17.05.2001; 2 males (6.54 x 8.18 mm – 8.36 x 10.36 mm), 3 females (5.63 x 6.91mm – 6.72 x 8.54 mm), 1 ovig. (8.00 x 9.27 mm) ( MZB Cru 3331), Ajkwa I., Papua, 26.03.2007; 3 males (6.36 x 7.82 mm – 7.64 x 9.27 mm), 3 females (5.64 x 6.91 mm – 8.91 x 10.73 mm), 7 ovig. (6.72 x 8.18 mm – 7.45 x 9.82 mm) ( MZB Cru 3332), Ajkwa I., Papua, 22.06.2008; 16 males (5.27 x 6.00 mm – 7. 45 x 9.64 mm), 14 females (5.45 x 6.73 mm – 7.64 x 9.27 mm) ( MZB Cru 3333), Kamora, Papua, 6.05.2003; 2 ovig. (8.2 x 10.8 –9.7 x 13.1 mm) (RCLA-C.B.0267), Otakwa, Papua, 09.07.2008; 6 males (6.91 x 8.73mm – 9.09 x 11.27 mm), 1 female (7.45 x 9.27 mm) (RCLA-C.B.0263-0264), Ajkwa I., Papua, 30.05.2001 and 19.03.2008; 4 males (5.82 x 6.91 – 9.82 x 12 mm), 3 females (7.09 x 9.09 – 8.91 x 10.09 mm) (RCLA-C.B.0265), Wai I., Papua, 26.06.2008; 5 males (6.91 x 8.36 – 8.18 x 10 mm) (RCLA-C.B.0266), Ajkwa, Papua, 21.06.2008; 6 males (7.64 x 9.73 mm – 9.45 x 11.82 mm), 10 females (6.36 x 7.82 mm – 9.27 x 11.45 mm), 3 ovig. (8.00 x 9.82 mm – 8.54 x 10.91 mm) ( ZRC 2011.1002) Ajkwa, Papua, 5.06.2001, 0 1.04.2008 and 22.06.2008.

Description. Carapace moderately wide ( Figs. 4 A, 6A), rectangular, greatest width at point anterior to insertion of third pereopod. Margin of carapace granular, setose. Three anterolateral teeth, first two distinct, third indistinct. Exorbital angle large, broad-based, subrectangular, directed outwards; separated from second tooth by wide, U-shape incision. Second lateral tooth large, wider than preceding tooth, directed outwards, projecting beyond first tooth; separated from third lateral tooth by small but distinct incision. Third anterolateral tooth small but distinct. Dorsal surface of carapace sparsely granular; granules more conspicuous on branchial region, less so on cardiac, gastric regions; granular ridges on posterolateral region present. Central region of epistome distinctly concave ( Fig. 6 C).

Front narrow ( Figs. 5 B, 6B), 0.15 times distance between external angles, slightly deflexed, constricted between bases of ocular peduncles, margin smooth, thinly rimmed, with deep median furrow. Upper orbital border moderately sinuous with minutely granular margin. Ocular peduncles relatively stout, not reaching to exorbital angle. Lower orbital margin with regular tubercles along whole length.

Third maxillipeds ( Fig. 4 B) separated by median hiatus, not completely covering buccal cavity when closed; median length of ischium about 1.6 merus length; merus, ischium with setose inner margins.

Chelipeds subequal ( Fig. 5 A, C, 6E, F), moderately elongated, stout; both longer than second pair of pereopods. Fingers relatively short. Movable finger slightly curved, outer surface smooth; upper margin with dense, fine setae, continue to cover entire inner surface; cutting margin subproximally with large, quadrangular, crenulated tooth, row of sharp, small teeth distally. Immovable finger not deflexed, lower margin slightly sinuous; outer surface smooth; inner surface with dense, fine setae on upper half; cutting margin with raised row of crenulated tooth occupying distal three quarter. Palm slightly elongated, upper, lower margins finely granular, outer surface smooth, without longitudinal ridge near lower margin; inner surface smooth, covered with fine setae on upper half. Carpus with row of small granules on proximal upper margin, lower margin finely granular, few setae on upper, lower margins; outer surface somewhat centrally smooth, finely granular towards margin; inner surface with sparse setae. Merus slightly elongated, inner margin setose; upper margin with row of small granules; outer margin finely granular. Outer surface with scattered granules; inner, lower surface setose.

Pereopods relatively stout. Dactylus shorter than propodi. Outer, inner surface of carpi, propodi of second to fourth pereopods with dense fine setae. Meri elongated; upper, lower margin of meri of second to fourth pereopods with row of small granules, subdistal tooth, outer, inner surface with sparse fine setae; meri of fifth pereopod with subdistal tooth.

Male abdomen moderately narrow ( Fig. 4 B, 7B). Third somite without transverse ridge, lateral margin of sixth somite slightly sinuous, distal margin of telson truncate ( Fig. 7 A). Male first gonopod (G1) with terminal process elongate, slightly curved ( Fig. 7 D – F).

Females similar to males in all non-sexual characters. Chelipeds smaller than in males ( Fig. 6 D), palm shorter than finger, row of setae on upper, lower chela, 2 rows of setae on inner surface of palm, outer surface of cheliped smooth. Abdomen wide ( Fig. 7 C), third somite without transverse ridge. Genital papillae (Fig) situated slightly proximal to suture between sternites of fifth and sixth thoracic somites, without transverse groove; operculum oval, directed mesially.

Live coloration. Generally dark brown, usually covered with mud.

Etymology. From the Latin fuscus, for “ brown,” for the dark brown color of individuals.

Remarks. The new species is included in the subgenus Mareotis because of the moderately wide carapace, which has a narrow front with constricted bases, the central concavity of the epistome, the broad based external orbital angle, and the greatest carapace width is at a point anterior to the insertion of the third pereopod and not across the first or second anterolateral teeth. Several characters, however, are shared with the subgenus Venitus , i.e. granular carapace surface, absence of a longitudinal or transverse row of granules or hairs on the branchial region, and the presence of a differentiated tooth on the cheliped dactylus.

Macrophthalmus fusculatus n. sp. most closely resembles M. definitus in the shape of the male abdomen, which is narrow, with the sixth somite having a sinuous margin, and the male G1 with a long, curved apical process. The differences are on the shape of the carapace, which is divergent posterolateraly, the presence of tubercles on the gastric, cardiac and intestinal regions, and the absence of longitudinal row of granules or hair on the branchial region, and the absence of a transverse ridge on the third somite of the male abdomen in M. fusculatus n. sp., while in M. definitus the lateral margin of the carapace posterior to the third antrolateral tooth is parallel to the midline, the gastric, cardiac and intestinal regions are smooth and shiny, two short granular rows are present on the branchial region, and the abdomen having a transverse ridge on the third somite. Furthermore, in M. fusculatus n. sp. the male chelipeds are moderately elongated, with dense, fine setae on the upper half of inner surface of the palm and fixed finger and on the entire inner surface of the dactylus, whereas in M. definitus the male chelipeds are not elongated and the inner surface of the palm and fingers are covered entirely by dense setae.

This new species is also similar to M. (Venitus) barnesi Serène, 1971 in the shape and granulation of the carapace, which is divergent posterolateraly and granular on the gastric, cardiac, branchial, and a small portion of the hepatic regions. These two species are easily distinguished by the form of the external orbital angle, which is quadrangular, directed forward in M. fusculatus n. sp but subtriangular and directed upwards in M. barnesi n. M. fusculatus n. sp. the upper half of the inner surface of the palm and fixed finger and the entire inner surface of dactyl of the chelipeds are covered by dense, fine setae, whereas in M. barnesi the inner surface of the palm and dactyl have a row of sparse long setae situated close and parallel to the upper margin; a row of sparse long setae is also found on the inner surface of fixed finger close and parallel to the cutting margin ( Barnes 1971).

Habitat. Mudflats on upper part of intertidal region in mangrove forest.

Geographical distribution. Known only from Papua, Indonesia.

Figures

FIGURE 4. Macrophthalmus (Mareotis) fusculatus n. sp. Holotype, male (8.69 x 12.02 mm) (MZB Cru 3273). A. Overall view; B, ventral view.

FIGURE 5. Macrophthalmus (Mareotis) fusculatus n. sp. Holotype, male (8.69 x 12.02 mm) (MZB Cru 3273), A, Chelipeds; B, front; C, inner face of left cheliped.

FIGURE 6. Macrophthalmus (Mareotis) fusculatus n. sp. A – C, E, F, Holotype, male (8.69 x 12.02 mm) (MZB Cru 3273). D, paratype, female (6.73 x 8.54 mm) (MZB Cru 3274). A, carapace; B, front; C, epistome; D, female cheliped; E, male cheliped, outer face; F, male cheliped inner face. Scale 1 mm.

FIGURE 7. Macrophthalmus (Mareotis) fusculatus n. sp. A − F, Holotype, male (8.69 x 12.02 mm) (MZB Cru 3273). G, H, paratype, female (6.73 x 8.54 mm) (MZB Cru 3274). A, telson; B, male abdomen; C, D, male G 1, right; E, F, apical part of male G, right 1; G, female abdomen; H, female gonopore, right. Scale: A, B, G 1 mm; C − F, H, 0.5 mm.