Macrophthalmus ( Euplax ) leptophthalmus (H. Milne Edwards, 1852 )

Macrophthalmus ( Euplax) leptophthalmus (H. Milne Edwards, 1852) View in CoL

( Figs. 2A–D, 3A–C, 4A–C, 5A–C)

Euplax leptophthalmus H. Milne Edwards, 1852: 160 View in CoL [ type locality: “ Chili ” (certainly incorrect, probably India; see Mendoza & Ng, 2007)]; Trivedi et al., 2018: tab. 1 (list) ( India); Pati et al., 2018: 41, tab. 15 (list) ( India); Sasaki, 2023: 15153 (list).

Euplax leptophthalma – Rathbun, 1910: 593 (list); Porter, 1913: 317; Porter, 1917: 159; Rathbun, 1918: 423; Garth, 1957: 107.

Euplax leptophthalma – Boschi, 2000: 81, appendix (list) (Perú- Chilean Province); Retamal & Moyano, 2010: 316, tab. 1 (list) ( Chile).

Macrophthalmus gastrodes View in CoL – Kemp, 1915: 228, fig. 9, pl. 12, fig. 5 ( Orissa, India); Kemp, 1919: 394 ( Orissa, India).

Macrophthalmus leptophthalmus View in CoL – Barnes, 1966: 370, pl. 24, figs. 3, 4; Barnes, 2010: 36, 37 (key).

Macrophthalmus ( Venitus) leptophthalmus View in CoL – Barnes, 1977: 269, fig, 1 ( Orissa, India); Ng et al., 2008: 238 (list).

Macrophthalmus ( Euplax) leptophthalmus View in CoL – Mendoza & Ng, 2007: 677, figs. 1–2; Ng et al., 2008: 237 (list); Barnes, 2010: 36 (key).

Macrophthalmus ( Venitus) gastrodes View in CoL – Ng et al., 2008: 238 (list).

Not Macrophthalmus ( Euplax) leptophthalmus View in CoL : Kishino et al., 2011: 14, figs. 1–3 (Amami Island, Ryukyus) (= Macrophthalmus ( Euplax) dagohoyi Mendoza & Ng, 2007 View in CoL ); Koyama et al., 2022: 64, fig. 1 (Kyushu, Japan) (= Macrophthalmus ( Euplax) dagohoyi Mendoza & Ng, 2007 View in CoL ); Nunobe et al., 2023: 35, fig. 1 (Shikoku, Japan) (= Macrophthalmus ( Euplax) dagohoyi Mendoza & Ng, 2007 View in CoL ).

Material examined. 6 males (24.4 × 19.5, 24.0 × 18.9, 23.7 × 18.9, 21.5 × 17.0, 19.3 × 16.0, 18.6 × 15.3 mm) (NCHUZOOL 17222), Vellar River , India, coll. M. Prema, September–December 2020 ; 2 males (23.4 × 18.8, 19.1 × 15.7 mm) ( ZRC 2024.0599 View Materials ), Vellar River , India, coll. M. Prema, September–December 2020 ; 1 male (18.1 × 14.8 mm) (NCHUZOOL 17290), Vellar River , India, coll. M. Prema, September 2020 ; 1 male (24.3 × 19.5 mm) (NCHUZOOL 17291), Vellar River , India, September–December 2020 ; 1 female (18.9 × 15.8 mm) (NCHUZOOL 17292), Vellar River , India, coll. M. Prema, September–December 2020 ; 4 males (23.4 × 18.9, 21.8 × 17.3, 19.0 × 16.2, 18.7 × 15.7 mm) (NCHUZOOL 17296), Vellar River , India, coll. M. Prema, September–December 2020 ; 4 males (23.5 × 18.9, 21.6 × 17.6, 19.7 × 16.8, 18.8 × 15.4 mm) ( ZRC 2024.0600 View Materials ), Vellar River , India, coll. M. Prema, September–December 2020 ; 4 males (19.5 × 16.5, 18.9 × 16.6, 18.4 × 16.2, 16.5 × 14.3 mm) (CASAU-1051), Vellar River , India, coll. M. Prema, 13 November 2023 ; 2 males (20.4 × 16.9, 22.4 × 16.5 mm) (CASAU-1052), Vellar River , India, coll. M. Prema, 10 November 2022 ; 2 males (19.4 × 16.4, 16.8 × 14.0 mm) (CASAU-1052), Vellar River , India, coll. M. Prema, 22 September 2022 .

Diagnosis. Carapace ( Fig. 2A–C) subquadrate, almost circular, 1.2–1.3 times wider than long; surface granular, with scattered, short setae. Supraorbital margin ( Fig. 3A–C) slightly backward-sloping. Anterolateral margin ( Fig. 3A–C) granulated, setose, with 3 relatively well-defined teeth (including exorbital tooth). First tooth (exorbital tooth) broadly to acutely triangular; second tooth broad, lobular or subrectangular, with rounded to acutely angular tip, directed upwards and outwards; U-shaped incision between first and second teeth narrow, pronounced, deep; third tooth distinct, small, bluntly triangular, directed upwards and outwards. Front moderate in width. Eyestalk ( Fig. 3A–C) slightly curved, more-or-less uniform in width throughout its length, cornea less inflated. Male chelipeds subequal. Merus inner and outer margins with fringe of long setae. Inner surface of carpus with dense long setae; outer surface smooth. Palm short, inflated; upper margin and inner surface with thick mat of setae. Ambulatory legs ( Fig. 2A–C) long, slender. Male pleon ( Fig. 4A–C) tapering gradually toward telson, tip of telson rounded anteriorly. G1 ( Fig. 5A–C) relatively stout; subdistal region gently tapered, short and gently curved.

Habitat. Subtidal muddy bottoms of the estuaries ( Kemp, 1915). In the Vellar River estuary, Tamil Nadu, India ( Fig. 6A, B), M. leptophthalmus and M. latreillei specimens were collected using fishing nets at depths of 4– 10 m.

Size. Largest male CW 24.4 mm (NCHUZOOL 17222); largest female CW 18.9 mm (NCHUZOOL 17292).

Distribution. India ( Kemp, 1915; Mendoza & Ng, 2007; this study). East coast of India; so far known from Chilka Lake in the north and Vellar River in the south (Fig. 1).

Remarks. The type locality of M. leptophthalmus was indicated as “ Chili ” in South America (H. Milne Edwards, 1852: 160). Others have suggested that the type locality is likely not Chile, but rather India ( Mendoza & Ng, 2007: 677), particularly since Macrophthalmus and Macrophthalminae are not known from the eastern Pacific ( Barnes, 1967, 2010), and a synonymised species, M. gastrodes Kemp, 1915 , has its type locality in Chilka Lake in Orissa, India. From this, it can even be surmised that the “ Chili ” in the original label/s of the types of M. leptophthalmus may have been a misspelling of “Chilka” (P.J.F. Davie, pers. comm.). Subsequent studies focusing on the region around Chile, such as Boschi (2000) and Retamal & Moyano (2010), have not provided any specimen collection data for M. leptophthalmus , with the authors basing this record solely on H. Milne Edwards’ original report (H. Milne Edwards, 1852). In contrast, apart from records in the western Pacific (which were actually M. dagohoyi , see later), M. leptophthalmus has only been reliably recorded in India (see the synonymy list above for details).