Pseudobarbus afer (Peters, 1864)

Chakona, Albert & Skelton, Paul H., 2017, A review of the Pseudobarbusafer (Peters, 1864) species complex (Teleostei, Cyprinidae) in the eastern Cape Fold Ecoregion of South Africa, ZooKeys 657, pp. 109-140 : 117-119

Pseudobarbus afer (Peters, 1864) Figures 5a, 6a, 7a

Barbus (Capoeta) afer Peters, 1864; Günther 1868; non Boulenger 1911; non Gilchrist and Thompson 1913; Barnard 1938, 1943; Jubb, 1965, 1967.

Barbus anoplus (non Weber, 1897): Boulenger 1911; Gilchrist and Thompson 1917.

Barbus vulneratus (non Castelnau, 1861): Gilchrist and Thompson 1913 (in part, species from the Baakens and Swartkops Rivers).

Barbus senticeps Smith, 1936; Barnard 1938, 1943.

Barbus asper non Boulenger, 1911: Barnard 1943; Jubb 1965; Smith and Smith 1966.

Pseudobarbus afer : Skelton 1988 in part (distributed from the Baakens to the Sundays River systems).

Syntypes.

ZMB 5413, 3 unsexed, 78, 89, 92 mm SL, original locality uncertain, but probably the Swartkops River system ( Jubb 1965).

Topotypic specimens.

SAIAB 203790, Pseudobarbus afer , 8 unsexed, 42.1-54.2 mm SL, Waterkloof River, - 33.7149528S, 25.2783833E, Groendal Wilderness, Swartkops River system, collected by A Chakona, W Kadye and B Ellender, 4 March 2015; SAIAB 97364, 2 males, 76.2-78.7 mm SL, Groendal Wilderness, Swartkops River system, - 33.7000S, 25.2800E, collected by ER Swartz and B Ellender, 20 April 2010; SAIAB 97366, Pseudobarbus afer , 6 unsexed (31.9-70.8 mm SL), Groendal Wilderness, Swartkops River system, - 33.7000S, 25.2900E, collected by B Ellender, 13 April 2010.

Etymology.

afer means African (citizen).

Diagnosis.

Pseudobarbus afer differs from Pseudobarbus burchelli , Pseudobarbus burgi , Pseudobarbus skeltoni and Pseudobarbus verloreni by possession of a single pair of oral barbels. Possession of fewer and larger scales separates Pseudobarbus afer (29-35, mode 32 scale rows along the lateral line) from Pseudobarbus quathlambae (> 60 scale rows along the lateral line) and Pseudobarbus asper (> 35 scales along the lateral line). Lack of a mid-dorsal stripe and a relatively deeper head and body profile separates Pseudobarbus afer (mean head depth: 71.8 % HL (range: 66.5-78.2%); mean body depth: 25.3% SL (range: 22.5-31.6%) from the more slender bodied Pseudobarbus tenuis (average head depth: 65.9 % HL (range: 61.1-71.2%); average body depth: 22.4 %SL (range: 18.8-26.8%)). Lack of prominent black spots and patches on the body distinguishes Pseudobarbus afer from Pseudobarbus phlegethon . Pseudobarbus afer most closely resembles Pseudobarbus senticeps , Pseudobarbus swartzi sp. n., and Pseudobarbus asper . Barbel length and the number of scale rows along the lateral line separates Pseudobarbus afer from these three species. Short barbels which do not reach the vertical through the posterior margin of the eye and a higher number of lateral line scales (29-35, mode 32) distinguishes Pseudobarbus afer from Pseudobarbus senticeps whose barbels reach or surpass the vertical through posterior edge of eye and has fewer and larger scales (lateral line scales 25-30, mode 29; caudal peduncle scales 10-12, mode 11; Figure 4 a–c). Pseudobarbus afer further differs from Pseudobarbus senticeps by lack of a blotch of pigment at the base of the caudal fin, while the lateral stripe in Pseudobarbus senticeps terminates in a triangular blotch at the base of the caudal fin (Figure 6a). Pseudobarbus afer differs from Pseudobarbus swartzi sp. n. by possession of fewer scale rows along the lateral line (29-35, mode 32 vs 34-37, mode 36 in Pseudobarbus swartzi ; Figure 4a) and fewer scales around the caudal peduncle (12-16, mode 12 vs 13-17, mode 16 in Pseudobarbus swartzi ; Figure 4b). Pseudobarbus afer has a distinct mesh-like pigmentation pattern below the lateral line which further separates this species from Pseudobarbus swartzi which lacks discernible pigmentation pattern on the latero-ventral scales (Figure 6a, d). Pseudobarbus afer s.s is separated from Pseudobarbus asper by possession of fewer and larger scales (lateral line scale series 29-35, mode 32 vs 35-45, mode 37-40; caudal peduncle scale rows 12-16, mode 12 vs 16-22, mode 18-20).

Description.

Morphometric and meristic data summarised in Table 4 are based on three syntypes and 68 specimens (43-82 mm SL) from the Sundays, Swartkops and Baakens River systems. General body shape and colouration are shown in Figures 5a, 6a, 7a.

Body fusiform, more or less laterally compressed, with dorsal profile generally more convex than ventral profile. Body deepest around the anterior bases of the dorsal and pelvic fins. Caudal peduncle length is almost twice its depth. Head length sub-equal to body depth, snout slightly blunt, mouth sub-terminal and sickle shaped, with a single pair of simple short maxillary barbels. Barbel length shorter than orbit diameter, barbels do not surpass the vertical through posterior margin of pupil. Eyes moderately large, located dorsolaterally, closer to tip of snout than to the posterior margin of gill cover, orbit diameter shorter than snout length.

Tuberculation . Mature breeding males develop large conical tubercles on the snout and head dorsum. The bilateral clusters on the snout include 2-4 tubercles. Scattered tubercles on dorsal surface of head smaller than those on the snout. Minute tubercles develop in bands on the dorsal surface of pectoral fin rays and a row along the free edge of latero-dorsal scales.

Scales. 29-34 scale rows along the lateral line to end of hypural plate (point of flexure), 1-2 more scales to base of caudal fin. Of the 68 specimens examined, only 13 had 29 -30 scale rows along the lateral line and only five specimens had 35 lateral line scale rows. The rest of the specimens (50) had 31-34 scale rows along the lateral line. Four to six scale rows between lateral line and anterior base of dorsal fin (dorsal fin origin), 3-5 scale rows between lateral line and pelvic fin origin, 3-5 scale rows between lateral line and anal fin origin, 14-16 pre-dorsal scale rows (from posterior edge of head to anterior base of dorsal fin), 12-16 circumpeduncular scales. Triangular naked patch between the gill covers and anterior base of pectoral fins, ventral scales between pectoral fin origin and pelvic fin origin reduced and embedded. Axillary scales of pelvic fin not prominent or elongate. Scales between posterior edge of head and dorsal fin origin embedded and smaller than flank scales.

Fins. Dorsal fin situated almost in the centre of the body (excluding caudal fin), origin slightly behind vertical through origin of pelvic fin, with 3-4 unbranched rays and 6-7 branched rays, distal margin straight to slightly concave, tip of depressed dorsal fin reaches within 1-2 scales to vertical through posterior base of anal fin. Pectoral fins fan-shaped, larger in males than females, with 14-17 rays, often reaches and surpasses base of pelvic fin in males, reaches 2 scales to base of pelvic fin in females. Pelvic fin with 8-9 rays, origin slightly in front of dorsal fin origin, tip of depressed pelvic fin does not reach anterior origin of anal fin, except in mature males. Anal fin with 3 simple rays and 5 (rarely 6) branched rays, distal margin almost straight to slightly convex, origin closer to anterior base of pelvic fin than caudal fin base. Caudal fin is obtusely forked, with a mode of 10+9 principal rays.

Osteology. Total vertebrae including Weberian apparatus 36-39 (mode 37), predorsal vertebrae including Weberian apparatus 11-13 (mode 12), precaudal vertebrae including Weberian apparatus 18-20 (mode 19), caudal vertebrae including Weberian apparatus 17-19 (mode 18).

Colouration (live and fresh specimens). Refer to Figure 5a for general live colouration. Dorsum grey-black, sides and belly silvery white, base of fins bright red in adults. Vague dark mid-lateral band from behind the head to the base of the caudal fin.

Colouration (preserved). The bright red pigmentation on base of fins and silvery colouration fades in preservative (Figure 6a). Dorsum and flanks above lateral line dark greyish. Belly off-white to yellow in most specimens. Band of pigment around centre of scales, basal segment of exposed area of scales without pigment, leaving a lighter band along distal edges of scales, producing a mesh or net-like pattern which is more pronounced on dorso-lateral scales (Figure 6a).

Distribution.

Pseudobarbus afer s.s. (referred to as the 'Mandela lineage’ by Swartz et al. 2007) occurs in three isolated river systems (the Sundays, Swartkops and Baakens) which discharge into Algoa Bay near Port Elizabeth (Figure 7). Remnant populations of this species are highly fragmented, persisting in only a few less degraded upland tributaries that have not been invaded by alien species ( Ellender et al. 2011).

Conservation status.

Once common and widely distributed throughout the Sundays, Swartkops and Baakens River systems, Pseudobarbus afer suffered severe decline in distribution and abundance, mainly due to invasion by alien predators and competitors, deterioration of water quality and loss of critical habitat. Consequently, this species (referred to as Pseudobarbus afer (Peters, 1864) by Tweddle et al. 2009) was listed as Endangered during the most recent IUCN assessment of the status and distribution of freshwater fishes in southern Africa ( Tweddle et al. 2009). Invasion by alien fish was identified as the single most important threat to this species. Long-term persistence of this species in the Baakens River system is uncertain as the entire catchment of this system has been heavily urbanised and the river is now heavily infested with non-native species, particularly Tilapia sparrmanii and Pseudocrenilabrus philander (personal observations, March 2014). There is urgent need for comprehensive surveys to determine the status of the Baakens population and identify measures to prevent its eradication. The conservation status of Pseudobarbus afer s.s is being reassessed as part of a national program that is assessing the conservation status of all freshwater fishes of South Africa.