Giuris caussei, 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 : 342-343

Giuris caussei n. sp. Keith, Mennesson & Lord

( Figs 1 , 4 , 10 ; Tables III-IV)

Material examined

Two specimens from New Britain ( Papua New Guinea), totalling 1 male and 1 female; size range 60.7-74.3 mm SL.

Holotype. – MNHN 2019-0240 , female (74.3 mm SL), Water Lily Hole , Nut , West New Britain, Papua New Guinea, 23 Oct. 2018, Keith , Lord , Causse, Amick et al. coll.; tag 6827.

Paratype. – MNHN 2019-0241 , male (60.7 mm SL), same data as holotype; tag 17737 .

Diagnosis

The new species has always 14-15 pectorals rays, a medium body depth at anus (16-21% SL), a great interorbital length (13-15% SL) and 11-12 scales in transverse forward series.

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. The body depth at anus is 16 (21% SL), at first dorsal fin 25 (22% SL), and the caudal peduncle depth is 16 (14% SL). Predorsal length 50 (% SL) and preanal length 63 (64% SL).

The head 37 (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 (% SL) are small. Inwardly curved teeth set on both jaws and larger on outer row. Posterior end of maxillary extending to below around anterior margin of eye. Lips with numerous internal short papillae. Eye diameter 4 (6% SL) and interorbital length 15 (13% SL).

Dorsal fins VI-I,8-9 without 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 13 branched rays and its posterior margin is rounded. Pelvic fins separate, I,5. Pectoral fins 14 (15), with the posterior margin rounded. Lateral scales 29, 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 on top of head and back bigger than those on belly. Scales in transverse back series 9, in transverse forward 12 (11), in predorsal 16 (15) and in zigzag 9. 12 (11) 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

Males and Females similar. Background of body dark brown to black on the back. Top of head brownish, lateral part brownish to greyish with 3 thin dark stripes radiating from the eye to the cheeks and operculum. Flanks beige to yellowish from pectoral base to hypural base. Belly whitish. The first and second dorsal fins and the anal fin are brownish. Pectoral and pelvic fins greyish to hyaline. Caudal fin brownish to greyish ( Fig. 4 ).

Colour in life Unknown.

Ecology

The species occurs mainly in the vegetation of ponds and swamps. It is omnivorous. It was found in sympatry with G. aporocephalus and G. margaritaceus .

Distribution

Giuris caussei is known from Papua New Guinea (New Britain).

Etymology

The new species is dedicated to our friend Romain Causse, from MNHN, for his dedication to ichthyology and the invaluable help he provides both in the field and in the laboratory.

Comparison

Giuris caussei differs from the other species sequenced by having a significant percentage of divergence in COI gene (2.5-11.4%) (Tab. II). Moreover it differs from G. yahayai by a combination of characters including fewer scales in transverse forward series (11-12 vs. 17-20), a smaller body depth at anus (16-21 vs. 26-36% SL) and a smaller body depth at first dorsal fin (22-25 vs. 26-39% SL). It differs from G. viator in having fewer scales in transverse forward series (11-12 vs. 14-15) and in transverse backward series (9 vs. 10-12). It differs from G. tolsoni in having fewer scales in transverse forward series (11-12 vs. 13-16), a greater interorbital length (13-15 vs. 9-12% SL), and 14-15 pectorals rays vs. always 14 rays. It differs from G. margaritaceus in having fewer scales in transverse forward series (11-12 vs. 13-14) and more scales around the eye (11-12 vs. 8-11). It differs from G. charpini in having 14-15 pectorals rays vs. 13-14 and more scales in transverse forward series (11-12 vs. 13-14). It differs from G. aporocephalus in having a smaller body depth at anus (16-21 vs. 20-25% SL). It differs from G. laglaizei in having more scales around the eye (11-12 vs. 6-8), a smaller body depth at anus (16-22 vs. 23-27% SL) and a greater interorbital length (13-15 vs. 10-12% SL).

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 4. – Giuris caussei n. sp., male; MNHN 2019-0241, paratype, New Britain, Papua New Guinea; LS 60.7 mm (MNHN, Photo P. Keith).

Figure 10. – Distribution of Giuris species.