Enteromius werneri (Boulenger, 1905)

Moritz, Timo, Dayem, Zuheir Nour El, Abdallah, Mohammed Abakar & Neumann, Dirk, 2019, New and rare records of fishes from the White Nile in the Republic of the Sudan, Cybium 43 (2), pp. 137-151 : 145

Enteromius werneri

Enteromius werneri ( Boulenger, 1905) is currently placed in synonymy with E. stigmatopygus ( Boulenger, 1903) , following the work of Banister (1987) on small African barbs. Lévêque (1989) confirmed the view that E. werneri just represents adult specimens of E. stigmatopygus . Banister argued that the arrangement of gill-rakers, pharyngeal teeth and the positioning of lateral flank spots justify synonymizing both species. However, size, shape and arrangement of pharyngeal teeth are highly diagnostic features in cyprinids. The pharyngeal teeth in fig. 13 ( E. stigmatopygus ) and fig. 17 ( E. werneri ) in Banister (1987) differ markedly. The same applies for the extent, size and arrangement of gill rakers on the ceratobranchial arch shown in his figures 12 ( E. stigmatopygus ) and 16 ( E. werneri ).

Moreover, Boulenger (1903) already indicated in his first account (here erroneously as Barbus miolepis , a then already preoccupied taxon name) and his subsequent description ( Boulenger, 1905), that only the first 3 to 6 scales of the lateral line series are pored in Enteromius stigmatopygus , while in E. werneri the lateral line series is always complete with pored scales reaching the tail ( Fig. 4C, E ). Comparison of the type series of both species at the NHM London confirmed this feature ( Fig. 4 A-B). There are also more obvious morphological differences between both species: Banister explicitly mentions that Boulenger apparently overlooked the minute posterior barbels in three (juvenile) syntypes of E. stigmatopygus (0.6-1.0 mm long). At this life stage and in specimens below 19 mm SL, the barbels are often weakly developed or even absent. However, Banister (1987) failed to mention that the majority of the syntypes of E. werneri have two pairs of well-developed barbels, which is one of the most striking morphological features when comparing figures 10 and 14 in Banister (1987) work. Moreover, already in the small syntypes of E. werneri (approx. 20 mm SL) the posterior barbels reach beyond the centre of the eye and in specimens above 30 mm SL they can reach the posterior margin of the eye. Another striking difference in the colouration pattern not mentioned by Banister (1987) is the positioning of lateral flank spots in E. stigmatopygus compared to E. werneri : while E. stigmatopygus displays a prominent dark spot at the insertion of the anal-fin base ( Fig. 4E, F ), E. werneri clearly lacks a black marking of the anal-fin base ( Fig. 4 A-D). Based on the diagnostic features mentioned above which clearly distinguish E. werneri and E. stigmatopygus , we reject the synonymy of E. werneri with E. stigmatopygus and treat E. werneri as a valid species. Enteromius werneri was recorded from beach seining at Al Jabalayn and Aba Island ( Fig. 4D ) together with the similar looking E. perince ( Rüppell, 1835) ( Fig. 4G, H ). The distribution range of E. werneri is presently unclear. Reports from the Chad Basin ( Blache, 1964) might represent this species,

but reports from the Niger River by Daget (1954) likely refer to E. sublineatus ( Daget, 1954) ( Lévêque, 1989) .

Figures

Figure 4. – Enteromius werneri and similar looking species. A: E. werneri, syntype, 22.4 mm SL, BMNH 1907.12.7.1328-1332, Lake No; B: E. werneri, syntype, 31.2 mm SL, BMNH 1907.12.7.1335, White Nile at Gondokorro; C: E. werneri, drawing from Boulenger (1907); D: E. werneri, live, ~30 mm SL, White Nile at Kosti, not preserved; E: E. stigmatopygus, drawing from Boulenger (1907); F: E. stigmatopygus, live, 30 mm SL, Bougouriba River, Burkina Faso; G: E. perince, 22.7 mm SL, determined as E. stigmatopygus by Bailey, BMNH unreg.; H: E. perince, live, ~30 mm SL, White Nile at Kosti, not preserved.