Eleotris diamsoi, Mennesson & Keith, 2020

Mennesson, Marion I. & Keith, Philippe, 2020, Eleotris (Teleostei: Eleotridae) of the Indian Ocean: an overview with the description of three new species, Cybium 44 (3), pp. 185-203 : 199-200

Eleotris diamsoi sp. nov. Mennesson, Keith & Feunteun

( Figs 1D , 2, 7; Tabs VI-VIII)

Material examined

One male and one female collected from Madagascar with a size range of 61-64.6 mm SL.

Holotype. – MNHN-IC-2020-0068, male (64.6 mm SL), Sahana River , Madagascar; 7 July 2008; Diamsoi coll.; tag 13004.

Paratype. – MNHN-IC-2020-0067, female (61 mm SL), Ankazofotsy River , Madagascar; May 2010; Diamsoi coll.; tag 13016 .

Diagnosis

The species is distinguished by: second, third and fourth suborbital free neuromast rows on cheek extending ventrally past horizontal row d (‘2.3.4’ pattern) ( Fig. 1D ); row os connected with row oi at ventro-posterior margin of operculum (‘closed’ pattern); 16 pectoral fin rays; 63 scales in lateral series; a small body depth at anal and second dorsal fins origin (15-18% SL).

Description

Scale counts in Eleotris diamsoi sp. nov. and related species are given in table VI, ray counts in table VII and morphometrics in table VIII. Below, the holotype counts are given first followed in brackets, if different, by the paratype counts.

The body is elongated. The body depth at anus is 15 (18% SL) and the caudal peduncle depth is 12 (14% SL). Predorsal length 44 (47% SL) and preanal length 63 (66% SL).

The head 32 (33% SL) is broad and depressed, the snout is pointed. Eyes high on head. The mouth is quite large, as jaw length is 10 (11% SL), and oblique, the posterior margin of upper jaw reaches the vertical through the two thirds of the eye. Upper and lower jaws with multiple rows of small inwardly curved teeth, larger on outer row; a few caniniform teeth in anterior position on lower jaw.

Dorsal fins VI-I,8; D1 separate from and smaller than D2; spines not elongated. Anal fin I,8 and directly opposite to second dorsal fin. Pelvic fins separate, I,5. Pectoral fins 16. Caudal fin pointed with 15 branched rays.

Cycloid scales on top of head, nape, cheek, operculum, pectoral fin base, prepelvic region, and abdomen. Ctenoid scales covering flanks. No lateral line canals. 63 scales in lateral series, 36 (38) in predorsal series, 18 in transverse back series, 17 (23) in transverse forward series and 14 in zigzag series.

A downward pointing spine at the posterior margin of the preoperculum is covered with skin. Gill opening is moderately broad, extending to below the preoperculum. Tubular anterior nares overhanging one third of upper lip, posterior nares open pits.

Cephalic lateralis: Adults with five transverse suborbital free neuromast rows of which second, third and fourth suborbital free neuromast rows on cheek extending ventrally past horizontal row d (‘2.3.4’ pattern); row os connected with row oi at ventro-posterior margin of operculum (‘closed’ pattern) ( Fig. 1D ).

Urogenital papilla in females rounded, elongated and tapered in males.

Colour in life Unknown.

Colour in preservation ( Fig. 7 )

Male and female similar. Head and preoperculum beige. Back and flanks brownish. A big brown dot at the base of the pectoral fins. Abdomen and gular region yellowish. Anal and first and second dorsal fins spotted with spots aligned on rays. Caudal fin brownish, with several yellow spots. Pelvic and pectoral fins whitish.

Comparison

Eleotris diamsoi differs from the other species sequenced that occur in the area studied by having a high % of divergence in COI gene (9.9-14.9%).

Eleotris diamsoi n. sp. differs from the other species of the Indian Ocean with a ‘2.3.4’ pattern by several characters. It differs from E. soaresi in having 16 pectoral fin rays versus 17-18, more scales in lateral series (63 versus 50-56) and in zigzag series (14 versus 12-13), and a smaller body depth at anal fin origin (15-18 versus 20-21). It differs from E. valadei , this paper, in having 16 pectoral fin rays versus 18, fewer scales in predorsal series in males (36-38 versus 45-50), fewer scales in transverse forward series (17-23 versus 27-30) and a smaller body depth at anal fin origin (15-18 versus 19-24).

Distribution

Currently known only from Madagascar. It was found in sympatry with E. pellegrini and E. sahanaensis (this paper).

Ecology Unknown.

Etymology

The new species is named after the MNHN ‘Diamsoi’ program which enabled to collect the specimens in Madagascar.

Figures

Figure 1. – The five different cephalic neuromast patterns in Eleotris.

Figure 7. – Eleotris diamsoi n. sp., Ankazofotsy, Madagascar (© P. Keith).