Giuris yahayai, Keith & Mennesson, 2020

Keith, Philippe & Mennesson, Marion I., 2020, Review of Giuris (Teleostei: Eleotridae) from Indo-Pacific islands, with description of three new species, Cybium 44 (4), pp. 331-349 : 337-340

Giuris yahayai n. sp. Keith & Mennesson

( Figs 1-2 , 10 ; Tabs III-IV)

Material examined

Thirteen specimens from Madagascar, Mayotte and Moheli ( Comoros), totalling 4 males, 3 juveniles (not measured) and 6 females; size range 38-178 mm SL, largest male 115 mm SL, largest female 178 mm SL.

Holotype. – MNHN 2018-0715 , male (115 mm SL), Gouloué , Mayotte Is., Comoros, 13 Nov. 2003, Arda coll.; tag 12190.

Paratypes. – MNHN 2006-0602 , 1 male and 1 female (110-130 mm SL), Mjawatché , Mohéli Is., Comoros, 31 Oct. 2005, Keith et al. coll . MNHN 1902-0269 , 1 female (126 mm SL), Madagascar, Grandidier coll. MNHN 1966- 0951 , 2 females (161-178 mm SL), Mararano , Marohago , Madagascar, Majunga Prov., Kiener et Therezien coll. MNHN 2015-0362 , 1 male (97.5 mm SL), Mtsangacheli , Mayotte Is., Comoros, 12 Nov. 2003, Keith & Arda coll. MNHN 2015-360 , 1 juv. (21 mm) Sahana , Madagascar, 7 Jul. 2008, Diamsoi coll. MNHN 2015-0361 , 2 juv. (33.3- 38 mm) Manahara , Madagascar, 6 Jul. 2008, Diamsoi coll. MNHN 2018-0716 , 1 male and 2 females (93.4-113.5 mm SL), Gouloué , Mayotte Is., Comoros, 13 Nov. 2003, Arda coll. ; tags 12191, 12192, 06801.

Diagnosis

The new species has 14 pectoral rays, a large body depth at anus (26-36% SL) and at first dorsal fin (26-39% SL), and a great number of scales in transverse forward series (17- 20).

Description

The scale and ray counts are given in table III and morphometrics in table IV. Below, the holotype counts are given first, followed in brackets, if different, by the paratypes’ counts.

The body is more ovoid than elongated, but the body depth at anus is high 30 (26-36% SL) as at first dorsal fin 34 (26-39% SL), which give a humped look to several specimens, generally the larger ones ( Fig. 2B ). Caudal peduncle depth 17 (16-20% SL). Predorsal length 46 (44-50% SL) and preanal length 62 (60-68% SL).

The head 32 (31-36% SL) is depressed, the snout is convex. The anterior nostrils are short, not reaching upper margin of upper lip. The mouth and the jaw length (10 (9-12% SL)) are small with inwardly curved teeth set on both jaws and larger on outer row. Posterior end of maxillary extending from to below around anterior margin of eye to 1/3 of the eye. Lips with numerous internal short and generally bifid papillae. Several specimens with numerous external papillae on mentum, snout, inferior lip and between nostrils. Eye small, diameter 5 (4-6% SL) and interorbital length 15 (14-16% SL).

Dorsal fins VI-I,8-9 with no filamentous rays. The first dorsal fin is with second, third and fourth rays longer. Anal fin I,9 directly opposite to the second dorsal fin. The caudal fin is with 15 branched rays and its posterior margin is rounded. Pelvic fins separate, I,5. Pectoral fins 14, with the posterior margin rounded. Lateral scales 29 (29-32), with ctenoid scales on flanks and caudal peduncle. Cycloid scales from snout to top of head and anterior part of D1, on operculum, on base of pectoral fins and on belly extending to anus. Scales of top of head and back bigger than those of belly. Scales in transverse back series 11 (10-12), in transverse forward series 20 (17-20), in predorsal 17 (16-18) and in zigzag 8 (8-9). 11(11-15) scales around the eye (ENO). 25 vertebrae.

Absence of oculoscapular canal and supratemporals and presence of a short preopercular canal with the pores N’ and O’.

Cephalic sensory papillae system developed as described by Akihito et al. (1988).

Males with a rounded/triangular urogenital papilla with distal tip rounded. The females have bulbous urogenital papilla with fimbriate projections around distal opening.

Colour in preservation

Male and female slightly similar. Background of body dark brown on the back to clear brown on the flanks. Top and middle of head brownish, inferior part greyish with 3 slim brown stripes radiating from the eye to the cheeks and operculum. Several small brown spots in two or three rows along the longitudinal scales, from pectoral base to hypural base. Belly whitish. The dorsal fins are brown with a white distal stripe. Pectoral, pelvic, caudal and anal fins greyish. Several old specimens entirely whitish ( Fig. 2B ).

Colour in life

Males. – ( Fig. 2A ) Male with background of body dark brown on the back to clear brown or greyish on the flanks. Top and middle of head brownish, inferior part greyish with 3 thin dark red stripes radiating from the eye to the cheeks and operculum, the highest one continuing on the pectoral base. Several small red spots in two or three rows along the longitudinal scales, from pectoral base to hypural base and mixing with slight blue or green pattern. Belly whitish. The dorsal fins are brown with a yellow distal stripe. Pectoral fins hyaline with a black dot at the base. Pelvic fins hyaline with a yellow distal margin. The anal fin is brownish with a yellow distal stripe. Caudal fin greyish to hyaline.

Females. – Background of body greyish on the back to top of head. Head with 3 thin red stripes radiating from the eye to the cheeks and operculum, the highest one continuing on the pectoral base. Several small slight red spots in two or three rows along the longitudinal scales, from pectoral base to hypural base and mixing with slight blue or green pattern. Belly whitish to greyish as the lower part of the flanks. The dorsal fins are brown. Pectoral fins hyaline with a black dot at the base. Pelvic and anal fins hyaline. Caudal fin greyish to hyaline.

Ecology

Giuris yahayai occurs in lower parts of coastal streams and ponds connected to rivers, usually in riverbank vegetation and in shelters over rocky or gravel bottoms. It is omnivorous. It is thought to be amphidromous as some other species of the family ( Keith et al., 2006).

Distribution

Giuris yahayai is currently known from the Comoros archipelago (Mohéli, Mayotte) and Madagascar.

Etymology

The new species is dedicated to our friend and colleague Ibrahim Yahaya from Comoros (CNDRS) in recognition of his work on the fauna of this archipelago.

Comparison

Giuris yahayai differs from the other species sequenced by having a high percentage of divergence in COI gene (7.7- 13%) (Tab. II) and by a combination of characters including a greater body depth at anus (26-36 vs. 16-27% SL) and a greater body depth at first dorsal fin (26-39 vs. 19-27% SL), more scales in transverse forward series (17-20 vs. 11-16), a greater caudal peduncle depth (16-20 vs. 13-17% SL) and by a duller pattern in males.

Figures

Figure 1. – Bayesian tree of the cytochrome c oxidase subunit (COI – 495 bp) for sequenced specimens of Giuris. Numbers at each node represent posterior probabilities.

Figure 2. – A: Giuris yahayai n. sp., male, MNHN 2006-0602, paratype, Mohéli, Comoros; LS 110 mm (Photo P. Keith). B: G. yahayai n. sp., female, MNHN 1966-0951, paratype, Madagascar (MNHN, Photo P. Keith).

Figure 10. – Distribution of Giuris species.