Enteromius pallidus (Smith, 1841)

Martin, Melissa B. & Chakona, Albert, 2019, Designation of a neotype for Enteromiuspallidus (Smith, 1841), an endemic cyprinid minnow from the Cape Fold Ecoregion, South Africa, ZooKeys 848, pp. 103-118 : 106-111

Enteromius pallidus (Smith, 1841) Figs 3, 4

Barbus (Pseudobarbus) pallidus Smith, 1841: no pagination, pl. 11 (fig. 2). Type locality: Defined in the original description as "various parts of the Cape Colony", but it is likely to be the Baakens River which is closest to the former British Army base, Fort Fredrick, where Andrew Smith, who was an army surgeon, would have been based at the time when he described this species.

Barbus hemipleurogramma Boulenger, 1911, fig. 126. Type locality: Baakens River, Port Elizabeth, Cape Province, South Africa; Bertin and Estève 1948.

Barbus pallidus : Barnard 1943; Lévêque et al. 1984; Skelton 1993; Engelbrecht and van der Bank 1996; Seegers 1996, Farm 2000; Skelton 2001; Muller et al. 2015; Chakona et al. 2015.

Enteromius pallidus : Hayes and Armbruster 2017.

Material examined.

Neotype (Fig. 3A, B): In compliance with Article 75.3.7, the neotype was deposited at the South African Institute for Aquatic Biodiversity (catalogue no. SAIAB 207086) for future reference. The neotype is an adult female, 51.4 mm standard length (SL), collected on 3 November 2018 by Albert Chakona, Wilbert Kadye and Melissa Martin using seine netting, Baakens River system at Targetklooff downstream of bridge on the road to Walmer, (33°58'12"S, 25°35'40"E), altitude 20 m, Port Elizabeth, South Africa.

Additional material. South Africa: Port Elizabeth: SAIAB 207084, (n= 6; 2 adult females, 1 adult male, 4 sub-adults), 17.1-36.1 mm standard length (SL), collection details similar to neotype (Fig. 4 A–D).

South Africa: Eastern Cape: Port Elizabeth: SAIAB 200091; (n=38 juveniles and sub-adults, 17.1-36.1 mm standard length (SL), collected from the Baakens river on 4th April 2014 by Albert Chakona and Roger Bills downstream of low water bridge on the road to Green Acres, (33°57'28.1"S, 25°33'36.8"E).

South Africa: Eastern Cape: Port Elizabeth: SAIAB 127772; (n=2 gravid females, 46.8 and 47.6 mm standard length (SL), collected on 22 October 1981 by D. Heard from the Baakens River system, (33°58'S, 25°37'E).

Neotype designation for Enteromius pallidus (Smith, 1841).

The generic status of the diploid Smiliogastrini minnows, currently placed in Enteromius , is the subject of ongoing investigation because this genus is polyphyletic ( Yang et al. 2015, Ren and Mayden 2016, Hayes and Armbruster 2017). Detailed revision of the taxonomic statuses of the species belonging to this genus is plagued by a number of challenges, particularly similar body morphology, ambiguous type locality details and lack of extant type material for a number of species. This hinders accurate resolution of species identities, resulting in exaggerated geographic distribution ranges for many of the species (see Skelton, 2001). Without primary type specimens and better resolution of species identities and their distribution ranges, it would be difficult to resolve the bigger questions of the generic status and relationships of diploid smiliogastrins. Within southern Africa, a number of species in the genus Enteromius are in need of taxonomic revision as many are perceived to have broad geographic ranges, such as the case of E. pallidus . There are no extant types for this species, the illustration does not provide clear diagnostic characters to objectively associate it with E. pallidus or for comparisons with other species, and the species has a vague type locality description. The designation of a neotype is therefore essential to facilitate ongoing taxonomic revision of the "goldie barb" complex in southern Africa and for the broader evaluation of the phylogenetic relationships and generic placements of Enteromius species across the African continent. There is therefore an explicit need for the designation of a neotype (Art. 75.3 of ICZN).

All qualifying conditions (Art. 75.3 of ICZN) are met. The neotype is designated to clarify the taxonomic status of the species (Art. 75.3.1). Enteromius pallidus was described by Smith, who provided an illustration for a specimen with a brief description of the colour and form of the species, and a vague type locality defined as "clear streams in various parts of the Cape colony". Although Smith provided an illustration, there is no evidence within the text that he established a holotype or any expression of the equivalent. In compliance with Article 75.3.4 of the ICZN, the authors conducted a comprehensive search for the types, and it was established that extant types for E. pallidus are unlikely to be in existence. This was based on correspondences with Prof. Paul Skelton at the South African Institute for Aquatic Biodiversity (SAIAB), who confirmed that he examined and measured all the types of southern African freshwater fishes in 1981 at the British Museum of Natural History (BMNH). He searched for Smith’s Barbus pallidus but found no trace of any record or specimen(s). The authors also contacted the curator at the British Museum, James Maclaine, who indicated that Andrew Smith’s types of E. pallidus are not at the BMNH. While according to Article 73.1.4, Smith’s (1841) illustration would be considered to represent the holotype of E. pallidus , unfortunately the illustration does not provide clear details to extract diagnostic features for the species.

In compliance with Articles 75.3.2 and 75.3.3, a diagnosis, redescription, and comparison of E. pallidus and the other congeners in southern Africa are presented below. Following Barnard (1943), the original specimens used for the description of E. pallidus could have come from a river system near Port Elizabeth, probably the Baakens River. We therefore chose a specimen from the Baakens River system for the neotype designation (in compliance with Article 75.3.6), because it is closest to the 1820's British army camp (Fort Frederick), where Andrew Smith is likely to have been based during the time when he made the description.

Diagnosis.

Enteromius pallidus can be identified by the slightly convex dorsal surface; posterior barbel 2.0 to 3.0 times the length of anterior barbel; a slightly prominent snout; an incomplete lateral line; deep translucent light brown to golden sheen with the presence of irregular and scattered spots in mature adults; and the presence of 3-7 bold spots above the lateral line in juveniles and sub-adults.

Comparison with congeners in southern Africa.

The species belongs to the group of Enteromius species in southern Africa that is characterised by a simple and flexible unbranched primary dorsal fin ray. Distinguished from E. amatolicus (Skelton, 1990), E. anoplus (Weber, 1897), E. annectens (Gilchrist & Thompson, 1917), E. toppini (Boulenger, 1916) and E. radiatus (Peters, 1853) by possession of two pairs of prominent and long barbels (vs single pair and/or minute oral barbels in other species). Distinguished from E. lineomaculatus (Boulenger, 1903), E. viviparus (Weber, 1897) and E. unitaeniatus ( Günther, 1867) by absence of distinct chevron markings on the lateral line (vs presence of conspicuous chevron markings on the lateral line in the other three species), and from E. bifrenatus (Fowler, 1935) by absence of a distinct lateral stripe and absence of black tubular markings around lateral line pores (vs presence in E. bifrenatus ). Distinguished from E. anoplus , E. amatolicus , E. annectens , E. unitaeniatus , E. bifrenatus , E. gurneyi ( Günther, 1868), E. motebensis (Steindachner, 1894), E. radiatus , E. toppini , E. treurensis (Groenewald, 1958) and E. viviparus by the presence of scattered black spots on the body, particularly in juveniles (vs absence of scattered black spots in the other species). Lateral pigmentation pattern of E. pallidus is closely similar to that of E. brevipinnis and E. neefi (Greenwood, 1962), but it is distinguished from these two species by having an incomplete lateral line (vs complete lateral line in both E. neefi and E. brevipinnis ). Enteromius pallidus is further separated from E. neefi by absence of wavy lines along the scale rows (vs. presence of conspicuous wavy lines along the scale rows in E. neefi ), and from E. brevipinnis by lack of black pigmentation around the borders of the scales (vs presence of distinct black pigmentation around the scales in E. brevipinnis , giving a mesh-like pattern on the lateral side of the fish).

Figures 3, 4 show the general body features of E. pallidus as an adult female (neotype), adult male and juvenile. Morphometric and meristic data for the neotype and additional (topotypic) material are presented in Table 1.

Neotype description

(Article 75.3.3.). (Fig. 3A, B). Body fusiform, moderately compressed laterally; with four visible, irregular spots above lateral line. Dorsal profile slightly convex from tip of snout to origin of dorsal fin; anterior-projection slightly pronounced; body depth greatest between dorsal fin and anal fin origin, tapering from posterior margin of dorsal fin base to base of caudal fin. Ventral profile slightly concave, curving downwards from operculum to origin of pelvic fin base, slightly tapering to posterior end of anal fin base, then slightly concave to caudal fin.

Head relatively small and slightly projected; 0.2 times standard length, head length sub-equal to body depth. Eye relatively large and round; located dorsolaterally, closer to tip of snout than distal margin of operculum, interorbital space slightly convex. Snout rounded, shorter than post-orbital length; sub-equal or less than eye diameter; nuptial tubercles absent.

Mouth inferior; upper jaw sub-equal to lower jaw. Lip simple and thin; lower lip unretracted. Two pairs of barbels; rostral (anterior) barbels minute, reaching past posterior end of nostril, 0.3 times length of eye diameter; maxillary (posterior) barbels 3.0 times longer than rostral barbels, reaching beyond vertical through middle of eye.

Dorsal fin with 3 simple unbranched and 7 branched rays; distal margin almost straight; origin centered vertically with origin of pelvic fins. Pectoral fin with 1 simple unbranched and 7 branched rays; posterior edge gently rounded, not reaching pelvic fin origin. Pelvic fin with 1 simple unbranched and 5 branched rays; posterior edge gently rounded, almost reaching anus; origin midway between pectoral fin origin and anal fin origin. Anal fin with 3 unbranched and 5 branched rays; distal margin almost straight; origin inserted closer to origin of pelvic fin than base of caudal fin. Caudal fin bifurcate; with two pairs of 1 simple unbranched ray, 8 or 9 branched rays on each lobe.

Scales moderately large, radiately striated. Lateral line incomplete, with 4-13 (mode 9) perforated scales, 23-31 (mode 26) lateral scale series; 3-5 (mode 4) scale rows between dorsal fin origin and lateral line; 2-5 (mode 3) scale rows between pelvic fin origin and lateral line; 2-3 (mode 2) scale rows between lateral line and anal fin origin; 12 circumpeduncular scale rows; 7-14 (mode 10) predorsal scale rows, embedded in skin, smaller than flank scales. Scales between posterior base of pectoral fins and anterior base of pelvic fins smaller than flank scales and embedded.

Coloration.

In life, the colour for both adult breeding males and females is deep greenish-brown with a golden sheen dorsally, golden-yellow laterally and silvery ventrally (Figs 3A, B; 4A, B). Fins are translucent-yellow. The neotype thus represents E. pallidus sensu Smith (1841) based on the consistent similarities in colour pattern as defined in the original description (Art. 75.3.5). Juveniles appear brown laterally and silvery ventrally. Black spots are present above the lateral line, with juveniles and sub-adults having bold or more prominent spots in comparison to adults which tend to have fewer and often less conspicuous spots or blotches. All the juveniles and sub-adults examined (46 in total) had at least 3 bold spots above the lateral line (4C and 4D) on both sides (range 3-7 bold lateral spots). At least one bold spot is consistently found within the pre-dorsal region, pre-anal and caudal regions, a dark spot is always present on vertical through dorsal fin insertion and at the base of the caudal peduncle. Alcohol preserved specimens appear either plain silvery, or dusky grey dorsally and laterally and cream-yellowish ventrally (Figs 3B; 4B, D). The black spots become more prominent in preserved specimens. Black pigmentation at the anterior base of the anal fin is more prominent in juveniles and sub-adults compared to adults.

Reproduction.

There have been no dedicated studies on the breeding biology of E. pallidus , but spawning is likely to begin in summer (October - November) based on the general pattern of other congeners ( Cambray and Bruton 1984; Skelton 2001), and other cyprinid minnows in the CFE ( Cambray 1994). We have also observed presence of several gravid females and males with breeding coloration (prominent golden-yellowish sheen) during field surveys conducted during the summer period.

Distribution and habitat.

Enteromius pallidus is endemic to the eastern Cape Fold Ecoregion (CFE) of South Africa where it is distributed from the Krom to the Great Fish river system (Fig. 2). Rivers in this region are characterized by variable flow regimes, with mountain tributaries generally flowing throughout the year, while some main-stem sections of the rivers recede into a series of disconnected pools during the dry season ( O’Keeffe and de Moor 1988). The species inhabits pools within both perennial and seasonal streams with clear or moderately turbid water as well as rocky to fine (silt and mud) substrates. The species often favours river sections with emergent aquatic vegetation and woody riparian vegetation.