Ophiocara aporos rigonis Whitley, 1938

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 : 343-344

Ophiocara aporos rigonis Whitley, 1938

Material examined

Syntype. – AMS A.17837, Lillesmere Lagoon , Burdekin River, Queensland, Australia .

Others. – Ophiocara aporos rigonis, Whitley, 1938 . Holotype: AMS IA.5785. Paratypes. – AMS IA.5787 (1), IA.5789 (1). Freshwater creek near Rigo, Papua New Guinea. MNHN 2019-0242 , male (92.3 mm SL), Water Lily Hole , Nut , New Britain, Papua New Guinea, 23 Oct. 2018, Keith , Lord , Amick , Causse et al. coll.; tag 17730. MNHN 2019-0245 , 4 females, same data as MNHN 2019-0242; tags 6826, 6828, 6829, 6830. MNHN 2019-0243 , 2 males and 2 females, same data as MNHN 2019-0242; tags 17731, 17732, 17733 &17734. MNHN 2019-0244 , male, [extracted from MNHN 2016-229 ], Kolobangara Is., Zamba riv., Solomon Islands, 9 Nov. 2015, Keith, Lord, Boseto, Marquet et al. coll. MNHN 2019-0252 , 2 males and 2 females, New Britain, Papua New Guinea, 2015, Amick coll.; tags 6049, 6050, 16801 & 16802.

Diagnosis

The species generally has 15 pectorals rays, a medium body depth at anus (20-26% SL), 11-13 scales in transverse forward series and a specific colourful reddish pattern in mature male and a brownish poorly coloured pattern in female.

Description

The scale and ray counts are given in table III and morphometrics in table IV.

The body is more ovoid than elongated. The body depth at anus is 21-26% SL, at first dorsal fin 20-25% SL, and the caudal peduncle depth is 13-16% SL. Predorsal length 44-51% SL and preanal length 62-67% SL. Size: up to 22 cm SL.

The head 31-36% SL is depressed, the snout is convex. The anterior nostrils are short, not reaching upper margin of upper lip. The mouth and jaw length 9-11% SL are small. Inwardly curved teeth set on both jaws and larger on outer row. Posterior end of maxillary extending before or to below around anterior margin of eye. Lips with numerous internal short papillae. Eye diameter 4-7% SL and interorbital length 13-16% SL.

Dorsal fins VI-I,8 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 13 branched rays and its posterior margin is rounded. Pelvic fins separate, I,5. Pectoral fins mostly 15 (3 specimens with 14), with the posterior margin rounded. Lateral scales 28-30, 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 8-10, in transverse forward 11-13, in predorsal 15-18 and in zigzag 8-10. Scales around the eye 9-14 (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. – Background of body dark brown on the back. The flanks are greyish to brownish. Each scale underlined by a dark grey dot. Belly greyish as the isthmus. Top of head brownish, lateral part greyish with 3 dark brown stripes radiating from the eye to the cheeks and operculum. The first and second dorsal fins as the anal, pelvic, pectoral and caudal fins are brownish.

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

Colour in life

Males. – Two patterns. (1) Background of body greyish on the back. A bluish or greenish tinge along midline from the pectoral fin base to the caudal peduncle. The flanks have several, orange to reddish dots from pectoral base to hypural base, giving a certain shine to the fish. Belly whitish. Top of head greyish, lateral part yellowish with 3 dark brown to black stripes radiating from the eye to the cheeks and operculum, the highest continuing on the pectoral base which is yellow. The first and second dorsal fins as the anal fin are greyish with a reddish stripe at the distal part. Pectoral fins greyish to hyaline. Pelvic fins greyish to hyaline with a red distal margin. Caudal fin brownish with reddish base ( Fig. 5A ). (2) Background of body brownish to orange on the back but colourful on the flanks. Blue along midline from the pectoral fin base to the caudal peduncle. The flanks are orange to reddish and each scale is underlined by a dark red dot. Belly bright yellow or orange as the isthmus. Top of head brownish, lateral part orange to bright red with 3 dark red stripes radiating from the eye to the cheeks and operculum, the highest continuing on the pectoral base which is bright yellow. Lips orange. The first and second dorsal fins as the anal fin are dark red to dark brown with an orange stripe at the distal part and a lighter red one at the base. Pectoral fins brownish. Pelvic fins brown with a red distal margin. Caudal fin brown ( Fig. 5B ).

Females ( Fig. 5C ) – Background of body brownish to black on the back. Top of head brownish, lateral part greyish with a yellowish tinge. Three thin brown stripes radiating from the eye to the cheeks and operculum, the upper one continuing on the pectoral base, which is yellow with a black superior spot. Flanks greyish to yellow from pectoral base to hypural base; each scale is underlined by a greyish dot. Belly whitish. The first and second dorsal fins as the anal fin are brownish with a reddish stripe at the distal part. Pectoral fins greyish to hyaline. Pelvic fins greyish to hyaline with a red distal margin. Caudal fin brownish.

Ecology

The species occurs mainly in the vegetation of ponds, lakes, swamps, and in the lower parts of rivers. It is omnivorous and feeds on filamentous algae, small crustaceans and aquatic insects. It was found in sympatry with G. caussei (present paper) and G. margaritaceus .

Distribution

Giuris aporocephalus is known from Australia, Papua New Guinea and the Solomon Islands.

Comparison

Giuris aporocephalus differs from the other species sequenced by having a significant percentage of divergence in COI gene (2.5-11.3%) (Tab. II) and by the colourful pattern of the male. Moreover it differs from G. yahayai by a combination of characters including fewer scales in transverse forward series (11-13 vs. 17-20), a smaller body depth at anus (20-25 vs. 26-36% SL) and a smaller body depth at first dorsal fin (21-25 vs. 26-39% SL). It differs from G. viator in having always 15 pectorals rays vs. always 14 rays, fewer scales in transverse forward series (11-13 vs. 14-15) and zigzag series (8-9 vs. 9-10). It differs from G. tolsoni in having always 15 pectorals rays vs. always 14 rays, and a greater interorbital length (13-16 vs. 9-12% SL), and fewer scales in transverse forward series (11-13 vs. 13-16). It differs from G. margaritaceus in having fewer scales in transverse forward series (11-13 vs. 13-14) and zigzag series (8-9 vs. 9-10), more scales around the eye (10-14 vs. 8-11), and always 15 pectorals rays vs. 14-15. It differs from G. charpini in having always 15 pectorals rays vs. 13-14, and more scales in transverse forward series (11-13 vs. 13-14). It differs from G. caussei in having a greater body depth at anus (21-25 vs. 16-21% SL). It differs from G. laglaizei in having more scales around the eye (10-14 vs. 6-8), fewer scales in transverse back series (8-10 vs. 9-11) and a greater interorbital length (13-16 vs. 10-12% SL).

Figures

Figure 5. – A: Giuris aporocephalus, male; in MNHN 2019-0243 (tag 17734), New Britain, Papua New Guinea; LS 61.3 mm (Photo P. Keith). B: G. aporocephalus, male; in MNHN 2019-0252, New Britain, Papua New Guinea; LS 143 mm (Photo P. Amick). C: G. aporocephalus, female; in MNHN 2019-0252, New Britain, Papua New Guinea; LS 143 mm (Photo P.Amick).