Pseudobarbus senticeps (Smith 1936)

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 : 120-123

Pseudobarbus senticeps (Smith 1936) Figures 5b, 6b,c

Barbus senticeps Smith, 1936.

Barbus afer : Jubb 1963, 1965.

Pseudobarbus afer : Skelton 1988.

Holotype.

SAIAB 304, male, 65.7 mm SL, Assegaaibosch River, Krom River system.

Topotypic material.

SAIAB 200302, 9 unsexed, 23-83 mm SL, Assegaaibos River, Krom River system, - 33.9452778S, 24.3139167E, collected by R Bills, V Bills and D Naran, 12 August 2014. SAIAB 121815 (formerly AMG 2651), 29 unsexed, 45-75 mm SL, Assegaaibosch River, - 33.9413889S, 24.3188889E, Krom River system, collected by PH Skelton and J Stephenson, 20 January 1975.

Etymology.

' senticeps ' refers to the thorny or prickly appearance of the head (sentis a thorn, bramble, and ceps, head) of sexually mature males due to the development of distinctly pointed tubercles on the snout, along the inner edges of the nares and orbits and head dorsum (see Figure 6b).

Diagnosis.

Possession of a single pair of oral barbels separates Pseudobarbus senticeps from Pseudobarbus skeltoni , Pseudobarbus verloreni , Pseudobarbus burgi and Pseudobarbus burchelli . Possession of fewer and larger scales separates Pseudobarbus senticeps (25-30, mode 29) from Pseudobarbus quathlambae (> 60 scale rows along the lateral line), Pseudobarbus asper (35-45; mode 37-40), Pseudobarbus swartzi sp. n. (34-37, mode 36) and Pseudobarbus tenuis (32-37, mode 35-36). There is overlap (although uncommon) in lateral line scale series between Pseudobarbus senticeps , Pseudobarbus afer (29-35, mode 32) and Pseudobarbus phlegethon (29-37, mode 35). A lateral stripe which terminates in a triangular blotch at the base of the caudal fin and longer barbels (reaching or surpassing vertical through the posterior edge of the eye) further separate Pseudobarbus senticeps from Pseudobarbus afer (barbels do not surpass vertical through the centre of the eye). Body colour pattern distinguishes Pseudobarbus senticeps from Pseudobarbus phlegethon . Pseudobarbus phlegethon is characterised by prominent black spots and patches on the body, which are lacking in Pseudobarbus senticeps .

Description.

Morphometric and meristic data summarised in Table 4 are based on the holotype and 29 topotype specimens (45-79.3 mm SL). General body shape and colouration are shown in Figures 5b, 6b, c.

A moderately laterally compressed, fusiform species. Cross-section of body between pectoral and pelvic fins ellipsoid. Dorsal profile of body, in lateral view, convex from snout tip to dorsal fin origin, straight and descending from dorsal fin origin to caudal fin insertion. Ventral profile, in lateral view, more or less straight or slightly convex from snout tip to anal fin origin, slightly concave and ascending from origin of anal fin to caudal fin insertion. Body deepest around anterior bases of dorsal and pelvic fin origins, progressively becoming narrower from anal fin origin towards the caudal fin. Caudal peduncle length almost twice as its depth, cross-section ellipsoid. Snout blunt or obtusely pointed. Mouth terminal, sickle shaped, its corner not reaching vertical through anterior margin of eye. A single pair of well developed, long and slender maxillary barbels present, barbel length longer than orbit diameter in most specimens. Eyes moderately large (23.5-29.5% HL), dorso-laterally positioned, and located closer to tip of snout than posterior margin of gill cover. Orbit diameter shorter than snout length.

Tuberculation . Mature breeding males develop prominent conical tubercles on the snout, along the nares and dorsal edges of the eyes. Bilateral clusters on snout include 2-4 tubercles in mature ripe males. Smaller, scattered tubercles develop on the head dorsum. A band of fine tubercles along dorsal surface of each of several anterior pectoral fin rays of mature breeding males.

Scales. Lateral line with 25-30 scales to end of hypural plate, 1-2 more scales to base of caudal fin. Four to five scale rows between lateral line and dorsal fin origin, 3-4 rows between lateral and pelvic fin origin, 3-4 scale rows between lateral line and anal fin origin, 12-15 pre-dorsal scale rows, 10-12 circumpeduncular scales. Breast scales reduced and embedded, giving a naked appearance to the region between the isthmus and base of pelvic fins. Elongated or triangular pelvic axillary scales absent. Scales between the nape and dorsal fin origin reduced and embedded.

Fins. Dorsal fin with 3-4 unbranched rays and 7 branched rays, origin slightly posterior to pelvic fin origin. Tip of adpressed dorsal fin reaches within 2-3 scales to vertical through posterior base of anal fin, distal margin straight. Pectoral fin with 13-15 rays, fan shaped, larger in males than females, tip of adpressed pectoral fin 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, outer margin slightly convex, its tip reaching anterior origin of anal fin when depressed in males and reaches 2-3 scales to anal fin origin in females. Anal fin with 3 simple rays and 5 branched rays, distal margin almost straight to slightly convex or straight, origin closer to anterior base of pelvic fin than base of caudal fin. Caudal fin is forked, with 10+9 principal rays.

Osteology. Total vertebrae including Weberian apparatus 35-38 (mode 37), predorsal vertebrae including Weberian apparatus 11-13 (mode 12), precaudal vertebrae including Weberian apparatus 18-19 (mode 19), caudal vertebrae including Weberian apparatus 16-18 (mode 18).

Colouration (live and fresh specimens). Refer to Figure 5 for general live colouration. Dorsum and sides dark brown, belly and underparts off-white or silvery, operculum metallic gold, base of fins bright red. Vague lateral stripe terminating in a triangular blotch at the base of the caudal fin.

Colouration (preserved). Dorsal surface of alcohol preserved specimens dark grey or black, sides and belly lighter. Distinct black lateral stripe from posterior margin of operculum terminating into a black triangular blotch of pigment at the base of the caudal peduncle. Red pigmentation at the base of fins disappears in preserved specimens (Figure 6b).

Distribution.

Pseudobarbus senticeps (referred to as the 'Krom lineage’ by Swartz et al. 2007, 2009) is endemic to the Krom River system which discharges into St Francis Bay (Figure 7). The species has a restricted known distribution range, surviving in a few relatively unimpacted and uninvaded tributaries of the Krom River system (Figure 7).

Habitat.

Pseudobarbus senticeps inhabits perennial mountain streams with clear to peat stained water, cobble and pebble substrates.

Conservation status.

Pseudobarbus senticeps (referred to as Pseudobarbus sp. " afer Krom" by Tweddle et al. 2009) was listed as Critically Endangered during the IUCN assessment of the status and distribution of freshwater fishes in southern Africa ( Tweddle et al. 2009). Invasion by alien fish (particularly Micropterus spp.) was identified as the major threat to this species. Further studies are required to more accurately assess the distribution, ecology and biology of this species.