Hemibagrus pluriradiatus ( Vaillant, 1892 )

Hemibagrus pluriradiatus ( Vaillant, 1892) View in CoL

( Fig. 38 View Fig )

Macrones pluriradiatus Vaillant, 1892: 126 (type locality: Nam- Tiong-Kong, a small tributary of Song Da, Lai Chau province, northern Vietnam); Vaillant, 1904: 462, Pl. 23 Fig. 2 View Fig (additional locality information: area of Lai-Chau or Muong-Lai: Nam Tiong Kong, a stream whose source is near Na-Ho village, first left-hand tributary of Nam Ma on which Pou-Fang [22°18'N 100°06'E] is located); Chu, 1986: 131, Fig. 87.

Mystus pluriradiatus View in CoL - Jayaram, 1954: 555; 1978: 226, Fig. 1 View Fig ; Cheng & Zheng, 1987: 217, Fig. 1089; Cui, 1990: 165, Fig. 169; Gao, 1990: 316, Fig. 191; Zheng & Dai, 1999: 70, Fig. 34 View Fig (in part); Zhou et al., 1999: 117; Jayaram & Sanyal, 2003: 97, Fig. 21 View Fig ; Yang & Zhang, 2006: 416, Fig. II-238.

Mystus (Mystus) pluriradiatus View in CoL - Jayaram, 1966: 446.

Mystus planiceps View in CoL (in part) - Desoutter, 1975: 451.

Hemibagrus pluriradiatus View in CoL - Mo, 1991: 132; Kottelat, 2001a: 51, Fig. 103 (Figure mislabelled Pelteobagrus pluriradiatus ); 2001b: 122, Fig. 330; Ferraris, 2007: 90.

(?) Hemibagrus chiemhaoensis Nguy n, 2005: 627, Fig. 46 View Fig (type locality: Gam River, Chiem Hoa district , Tuyen Quang province)

(?) Hemibagrus songdaensis Nguy n, 2005: 629, Fig. 47 (type locality: Van Yen, Yen Chau, Son La province)

(?) Hemibagrus taybacensis Nguy n, 2005: 625, Fig. 45 View Fig (type locality: Lai Chau)

Material examined. — CHINA: ZRC 54068, 1 ex., 90.0 mm SL, Guangxi province: Napo county, market at Baihe . VIETNAM: MNHN 1892–48 View Materials , holotype, 155.6 mm SL, Lai Chau province: Nam-Tiong-Kong, a small tributary of Song Da ; AMNH 211146 View Materials , 3 ex., 110.1–149.4 mm SL, Ha Giang province: Duc River, Thanh Thuy village at Chinese border ; AMNH 211251 View Materials , 4 ex., 78.5–146.5 mm SL, Ha Giang province: Ha Giang fish markets ; AMNH 211252 View Materials , 2 ex., 117.0–122.0 mm SL, Ha Giang province: Vi Xuyen district, Bac Trao River at big bridge downstream from camp 1 in broad pools .

LAOS: CMK 15305, 2 ex., 140.8–161.4 mm SL, Houaphan province: Houay Taungoua, small stream entering Nam Xam in Ban Houataungoua .

Diagnosis. — Hemibagrus pluriradiatus differs from H. centralus in having the adipose fin in contact with the base of the last dorsal-fin ray (vs. separated by a distance of 5.8–8.5% SL) and smaller interorbital distance (28–31% HL vs. 31–34), from H. hainanensis in having the adipose fin in contact with the base of the last dorsal-fin ray (vs. separated by a distance of 10.1–10.4% SL) and a larger eye (diameter 14–21% HL vs. 13–14), from H. imbrifer in having a brown (vs. grey) body in life, a shorter adipose-fin base (35.3–39.2% SL vs. 38.4–44.2), and sensory pores on body not easily visible (vs. relatively large sensory pores arranged in vertical columns along the sides of the body), and from H. variegatus in having fewer gill rakers on the first gill arch (16 vs. 19–21), a shorter post-adipose distance (9.1–10.9% SL vs. 12.9–14.1), and a uniform (vs. mottled) brown body in life.

Description. — Biometric and meristic data as in Table 24. General description as for genus. Head depressed and broad, body moderately compressed. Interorbital distance 28–31% HL. Eye diameter 14–21% HL. Dorsal profile rising evenly but not steeply from tip of snout to origin of dorsal fin, then sloping gently ventrally from there to end of caudal peduncle. Ventral profile horizontal to origin of anal fin, then sloping dorsally to end of caudal peduncle. Adipose fin with long base, about 3.0 times length of anal-fin base (35.3–39.2% SL) and origin in contact with base of posteriormost dorsal-fin ray. Post-adipose distance 9.1–10.9% SL. Dorsal spine stout, without serrations on posterior edge. Pectoral spine stout, with 12–14 large serrations on posterior edge. Caudal-peduncle depth 7.6–9.0% SL. Caudal fin forked; upper lobe rounded with principal ray produced into a filament, lower lobe rounded posteriorly. Sensory pores on body not prominent. Rakers on first gill arch 16. Maximum recorded size 212 mm SL ( Cui, 1990).

Colour. — Preserved specimens with dorsal and lateral surfaces of head and body uniform brown, lateral line cream; ventral surface of head and body dirty white; adipose fin and all fin rays brown; inter-radial membranes of all fins hyaline.

Distribution. — Known from the Song Da and Song Hong (Red River, Yuanjiang) drainages in southern China, northern Vietnam and northern Laos, as well as Hainan Island and the Beilun River, which drains the southern face of the Shiwandashan Range at the border of southeastern China with Vietnam ( Fig. 39 View Fig ).

Habitat and biology. — Hemibagrus pluriradiatus is found in fast-flowing streams with sand or gravel substrate and shows a marked preference for deep pools (R. Schelly, pers. comm.; MK pers. obs.). It is a euryphagous species that feeds on a wide range of food items, including small fishes (mainly loaches), aquatic insect larvae, aquatic and terrestrial insects, molluscs, annelids, crustaceans, fish eggs, frogs, rotifers, cladocerans, copepods, macrophytes and algae ( Du et al., 2010).

Remarks. — The identity of H. pluriradiatus has been particularly problematic, a problem somewhat exacerbated by the paucity of material. Kottelat et al. (1998) discussed the validity of H. pluriradiatus and commented on the synonymy of this species by various Chinese authors (e.g. Ni & Wu, 1986; Cui, 1990). They concluded that H. pluriradiatus is a valid species and that H. pluriradiatus reported by Cheng & Zheng (1987), Gao (1990) and Cui (1990) from southern China, and the H. elongatus of Ni & Wu (1986) from Hainan Island are all conspecific with the holotype of H. pluriradiatus . They also commented that H. centralus is either the same as or very closely related to H. guttatus , but this conclusion was based solely on the figures in the original description ( Mai, 1978) before the problem with Mai’s figures came to light (see remarks under H. vietnamicus ).

Hemibagrus chiemhaoensis was described from the Song Gam [which flows into the Song Hong (Red River) via the Song Lo], Chiem Hoa district, Tuyen Quang province. Nguy n (2005) considered this species to be most similar to H. pluriradiatus , distinguishing it from the latter by differences in the following characters: eye shape (oval in H. chiemhoaensis vs. rounded in H. pluriradiatus ); the relative positions of the anterior and posterior nares (said to be further apart in H. chiemhoaensis ); the distance of the posterior nare from the tip of the snout (smaller than the distance from the posterior nare to the anterior orbital margin in H. chiemhaoensis and larger than the distance from the posterior nare to the anterior orbital margin in H. pluriradiatus ); the width of the mouth (three-quarters of head width in H. chiemhoaensis vs. equal to head width in H. pluriradiatus ); contact between the base of the last dorsal-fin ray and the adipose fin (present in H. chiemhoaensis vs. absent in H. pluriradiatus ); the morphology of the dorsal spine (distal third non-osseous with its posterodistal margin with 3–4 serrations in H. chiemhoaensis vs. distal half non-osseous with a smooth posterodistal margin in H. pluriradiatus ); the morphology of the anterior margin of the pectoral spine (weakly serrate in H. chiemhoaensis vs. smooth in H. pluriradiatus ); the shape of the caudal-fin lobes (rounded in H. chiemhoaensis vs. sharply tapering in H. pluriradiatus ); the extent of the maxillary barbels (to the middle of the pelvic fin in H. chiemhoaensis vs. beyond the anal fin in H. pluriradiatus ); and the shape of the vomerine tooth band and teeth (tooth band strongly curved and teeth of noticeably different sizes in H. chiemhoaensis vs. tooth band gently curved and teeth of approximatel the same size in H. pluriradiatus ). The stated differences between H. chiemhoaensis and H. pluriradiatus appear to be very slight and might presumably be the result of fixation or intraspecific variation. The shape of the eye, while diagnostic for some catfishes (e.g. Ng, 1999), is dependent on fixation and length of time spent in preservative in the case of bagrid catfishes: there is a tendency for the eyes to shrink and assume a more rounded shape in specimens that have been stored in alcohol for some time. We measured the distance between the posterior nares, the snout and the anterior orbital margin in our specimens of H. pluriradiatus , and could find the character state for H. chiemhoaensis (the distance of the posterior nares from the snout smaller than the distance from the posterior nares to the anterior orbital margin) present in some of the material we examined. Contrary to the account in Nguy n (2005), the adipose fin is in contact with the base of the last dorsal-fin ray in H. pluriradiatus . Furthermore, our examination of Hemibagrus indicates that the anterior margin of the pectoral spine frequently bears a series of low bumps (but not distinct serrations), especially in larger specimens. These low bumps on the anterior margin of the pectoral spine are thus most likely to be the “serrations” referred to in the original description. Because all Hemibagrus possess the bumps on the anterior margin of the pectoral spine, this cannot be considered a diagnostic character. Lastly, all of the caudal-fin lobes of the H. pluriradiatus specimens we have examined are gently rounded (particularly the lower lobe), and none are sharply tapering, as claimed in Nguy n (2005). Therefore there are only the following characters that may be useful in distinguishing H. chiemhoaensis from H. pluriradiatus : mouth width, dorsal-spine morphology, maxillary-barbel length, and the shape of the vomerine tooth band and teeth. We have not examine sufficient material to fully understand intraspecific variation in these characters, but we note that many of these stated differences are slight and are likely to be the result of intraspecific variation. Despite the illustration of H. chiemhoaensis in the original description (Nguy n, 2005: Fig. 46 View Fig ) being very crudely retouched with a pen, it is referable to H. pluriradiatus as far as we can see. Based on the distribution of H. chiemhoaensis , our examination of material from the Song Hong [Red River] drainage and the information discussed above, we consider H. chiemhoaensis a junior synonym of H. pluriradiatus pending the availability of additional material from the Song Hong [Red River] drainage for study.

Hemibagrus songdaensis was described from Van Yen, Yen Chau district, Son La province (which lies within the Song Da drainage). Some of the diagnostic characters for this species are not immediately clear in the original description. In the account for this species, it is said to be distinguished from H. guttatus (the only species it is directly compared with) in having the body without black spots, branchiostegal membranes not overlapping, palatal teeth continuous, dorsal spine serrated on both margins, and adipose fin very thin. However, both the original description and the key for Hemibagrus in Nguy n (2005) indicate that it is the pectoral spine that is serrated on both margins. Our examination of Hemibagrus indicates that the anterior margin of the dorsal spine is always smooth, while the anterior margin of the pectoral spine frequently bears a series of low bumps (but not distinct serrations), especially in larger specimens. These low bumps on the anterior margin of the pectoral spine are thus most likely to be the “serrations” referred to in the original description. Because all Hemibagrus possess the bumps on the anterior margin of the pectoral spine, this cannot be considered a diagnostic character. The other key diagnostic character would be the absence of black spots on the body (all members of the H. guttatus species group possess black spots on the body), which is a feature also seen in H. pluriradiatus . Although the illustration in the original description (Nguy n, 2005: Fig. 47) shows a fish with a longer adipose-fin base, we note that this feature is heavily and crudely retouched with a pen, rendering the accuracy of the illustration highly questionable. Based on the distribution of H. songdaensis , our examination of material from the Song Da drainage and the information discussed above, we consider H. songdaensis a junior synonym of H. pluriradiatus pending the availability of additional material from the Song Da drainage for study.

Hemibagrus taybacensis was described from Lai Chau (which lies within the Song Da drainage). This species is said to resemble H. wyckioides in body shape and colour (Nguy n, 2005), but the photograph accompanying the original description (Nguy n, 2005: Fig. 45 View Fig ) shows a species with an adipose fin that spans nearly all of the postdorsal distance (this is despite the heavy and crude retouching with a pen, as with a number of photographs in this work). Given that H. wykioides has a shorter adipose fin that spans only about half the postdorsal distance and that the illustration in Nguy n (2005) shows a fish similar to H. pluriradiatus , we consider H. taybacensis a junior synonym of H. pluriradiatus pending the availability of additional material from the Song Da drainage for study.

The species identified as Hemibagrus sp. A in Kottelat (2001a: 52, Fig. 105) is clearly a member of the H. pluriradiatus species group, as it possesses a long-based adipose fin that spans most of the postdorsal distance and a uniformly grey body. It appears to have a deeper caudal peduncle than H. pluriradiatus , but as this material is unavailable to us for further study, we are unable to comment further on its taxonomic status. The figured specimen had been collected in the Song Gam in Chiem Hoa (22°11'07.4"N 105°16'18.2"E), Chiem Hoa district, Tuyen Quang Province, Vietnam.

A comparison of specimens from northern and central Vietnam and Hainan Island reveals significant morphological differences among all three populations and therefore, the conspecificity of H. pluriradiatus of Vaillant with that reported from Hainan Island by various authors (as postulated by Kottelat et al., 1998) is highly doubtful. The results of this study show that the three populations represent three distinct species: H. centralus from central Vietnam, H. hainanensis from Hainan Island, and H. pluriradiatus from northern Vietnam.