Chiloglanis fortuitus, Schmidt, Bragança, and Tweddle, 2023

Schmidt, Ray C., Bragança, Pedro H. N., Friel, John P., Pezold, Frank, Tweddle, Denis & Bart, Henry L., 2023, Two New Species of Suckermouth Catfishes (Mochokidae: Chiloglanis) from Upper Guinean Forest Streams in West Africa, Ichthyology & Herpetology 111 (3), pp. 376-389 : 379-382

Chiloglanis fortuitus, Schmidt, Bragança, and Tweddle , new species

urn:lsid:zoobank.org:act:5DAB9826-ADEE-42B5-84A8-934D5CCF4511

Figure 5 , Table 1

Holotype.— SAIAB 202292 , 35.0 mm SL, Liberia, St. John River drainage, Nimba County, Dayea River, above Yekepa , 7.5793338N, 8.5168898W, D. Tweddle, 30 March 2012.

Diagnosis.— Chiloglanis fortuitus is distinguished from all known species of Chiloglanis , including all species in the Upper Guinean Forest, except C. disneyi , C. microps , C. niger , and C. orthodontus , in having 18 mandibular teeth in the functional row (vs. 6–15 teeth; Table 1 ). Chiloglanis fortuitus is easily distinguished from C. disneyi , C. microps , and C. niger in having longer mandibular barbels whereas these are absent or reduced in the latter species. Chiloglanis fortuitus is distinguished from C. orthodontus in having a more robust oral disc and its length equal to its width versus length much shorter than width (Friel and Vigliotta, 2011). Chiloglanis fortuitus is further distinguished from C. orthodontus in having a longer dorsal spine (12.8 versus 4.1–7.8 % SL) and shorter maxillary barbels (7.2 versus 9.4–14.8 % SL).

Description.— Morphometric measurements and meristics for holotype summarized in Table 1 . Dorsal, lateral, and ventral views ( Fig. 5 ) illustrate body shape, fin shape and placement, oral disc size and shape, and maxillary and mandibular barbel lengths.

Moderate-sized Chiloglanis , maximum standard length observed 35.0 mm in one male specimen. Body dorsally depressed anteriorly and laterally compressed posteriorly. Pre-dorsal convex, sloping ventrally towards posterior nares, pre-orbital convex. Post-dorsal body sloping ventrally towards caudal fin. Post-anal profile concave, pre-anal profile horizontal. Small unculiferous tubercles present on body, concentrations of tubercles higher near head. Lateral line complete, arising at level of orbit and sloping ventrally to midlateral alongside of body towards caudal peduncle. Urogenital papillae presumed sexually dimorphic; males with elongated urogenital papilla.

Head depressed. Gill membranes broadly united. Gill openings restricted, opening near pectoral-fin origin to horizontal level of orbit. Occipital-nuchal shield covered and visible through skin. Eye moderate in size, located post mid-head length, horizontal axis longest, without free margins. Anterior and posterior nares equidistant, positioned mid-snout. Naris with raised rims, posterior naris with elongated anterior flap.

Mouth inferior, upper and lower lips united to form oral disc. Oral disc moderate in size, length equaling width and covered in papillae. Barbels in three pairs; maxillary barbel originating from posterolateral region of disc, unbranched, moderate in length, 7% of SL. Lateral and medial mandibular barbels moderate, incorporated into lower lip and positioned on both sides of midline cleft on posterior margin of oral disc. Lateral barbel 5% of SL, less than twice length of medial barbel. Primary maxillary teeth ‘‘S’’ shaped with exposed brown tips. 72 teeth in four scattered rows on ovoid tooth pads. Secondary premaxillary teeth scattered on posterior surface of premaxillae. Tertiary teeth small and needle-like, near midline of dorsal edge of tooth plate. Mandibular teeth in one to two rows, ‘‘S’’ shaped and grouped near midline. Functional (anterior) row with 18 brown-tipped teeth.

Dorsal-fin origin just posterior to anterior third of body. Dorsal fin with small spinelet, spine, and four rays. Dorsal spine moderate to short in length, reaching 13% of SL. Adipose fin medium length, reaching 17% of SL; margin convex with small notch posteriorly. Caudal fin forked with rounded lobes, lower lobe longer than upper lobe, count i, 7, 8, i. Anal-fin origin posterior to origin of adipose fin, margin convex, count iii, 6. Pelvic-fin origin at vertical between dorsal and adipose fins, margin convex, reaching beyond anal-fin origin, count i, 6. Pectoral fin with smooth spine, reaching 16% of SL, count I, 7. Postcleithral process in holotype short and pointed.

Coloration.— Coloration of preserved specimen in Figure 5 . In dorsal view, dark brown with mottled areas of medium brown. Lighter areas between nares and orbits, at origin of dorsal fin, at origin and terminus of adipose fin, and at caudal peduncle. In lateral view, specimen with yellow-buff color with overlying medium and dark brown blotches. Dark area more prevalent dorsal to midline, extending ventrally at origins of pelvic and anal fins. Dark brown melanophores scattered across body, more readily visible ventral to midline, prominent on sides of belly. Ventral surface yellow-buff colored with few melanophores scattered near pelvic and anal fins. Oral disc and barbels cream colored.

Pectoral and dorsal spines pigmented distally, rays cream to translucent. Dorsal base of pectoral fin lightly marked by triangular area of dark brown melanophores, band of melanophores at mid-length. Dorsal fin with area of melanophores near base and mid-length. Anal fin with melanophores at base and mid-length. Pelvic fin cream with few melanophores at base and band at mid-length. Adipose fin cream to translucent with dark brown markings from region just posterior of origin to its posterior third. Caudal fin cream to translucent with dark brown areas near base, mid-length, and distal end on upper and lower lobes; lighter areas forming circular marking on upper and lower lobes.

Etymology.— The specific epithet is ‘‘fortuitus,’’ referring to the fortuitous aspect of collecting this one specimen at the type locality. The collector, D. Tweddle, sampled fishes at 36 localities in the upper St. John River drainage in Liberia and collected 69 specimens of Chiloglanis at ten of these localities. Additionally, the lot that contained C. fortuitus was one of the three lots borrowed by the lead author to aid with the description of C. tweddlei ( Schmidt et al., 2017) . The discovery and formal description of C. fortuitus is fortuitous in several aspects.

Distribution.— Chiloglanis fortuitus is only known from the type locality in the Dayea River above Yekepa in Nimba County, Liberia (Supplemental Fig. B; see Data Accessibility). The site looked natural, yet it had been severely impacted many years earlier by the iron ore mine upstream. It was fast flowing, of uniform depth with a bottom of gravel with small rocks, with very little natural structure (e.g., woody debris and large boulders) likely due to previous mining activities. It is interesting that this species was not collected at the other ten localities in the region that contained C. tweddlei . As with other members of Chiloglanis that are found in streams in the Upper Guinea Forests, when two species co-occur within a drainage, they usually utilize different microhabitats ( Schmidt et al., 2017). Additional collection efforts in the upper St. John River drainage in Guinea and Liberia may yield additional specimens and populations of C. fortuitus .

Remarks.— Species descriptions based on a single specimen are not ideal though in this case it is warranted. This species is morphologically distinct from congeners in the region ( Fig. 2 ), and the number of mandibular teeth and morphology of the oral disc and barbels, characters used in the taxonomy of species of Chiloglanis , clearly separate it from all other known species of Chiloglanis . In sampling fishes at 36 localities, the collector was only able to get one specimen of C. fortuitus . Another lot from the St. John River drainage, USNM 193949, collected in the 1950s, contained 17 specimens all of which were determined to be C. tweddlei . This species is seemingly rare within the drainage and we don’t know when, or even if, additional specimens of C. fortuitus will be collected. Additionally, this area is under intense pressures from the mining industry and all species present face an uncertain future. Indeed, the type specimen was collected in a stream that had previously been disturbed by iron ore mining. Formally describing this species is an important step in recognizing and conserving the freshwater biodiversity in the Upper Guinean Forests.

Chiloglanis fortuitus resembles species of Chiloglanis that are in the short-spine group referenced in Schmidt et al. (2016, 2017). The discovery of this new species within the St. John River suggests that additional species of Chiloglanis , and other taxa, remain to be discovered and described from the region. This is especially likely for rivers in the region (e.g., Rokel, Jong, Sewa, and Mano) where collections of freshwater taxa are still lacking. While collecting this specimen was fortuitous, depositing the specimen and the others collected during an environmental impact assessment into natural history collections is what allowed this species to be discovered and described. Other new species have been collected and formerly described from similar surveys in the region ( Pezold et al., 2016, 2020). We encourage practitioners in this field to continue the practice of depositing specimens collected during assessments in natural history collections so that the specimens will be available to researchers.

Figures

FIG. 5. Dorsal, lateral, and ventral views of the holotype of Chiloglanis fortuitus, SAIAB 202292, 35.0 mm SL, Liberia, St. John River drainage, Nimba County, Dayea River, above Yekepa, 7.5793338N, 8.5168898W. Scale bar equals 2 mm. Photographs by P. H. N. Bragança.

FIG. 2. Plots of PC1 to PC2 (A) and PC2 to PC3 (B) from principal component analysis of 45 log-transformed measurements from 114 specimens of the short-spine taxa from the Upper Guinean Forests. Holotype of Chiloglanis fortuitus denoted by star.

Tables

Table 1. Morphometric measurements and meristics for holotype of Chiloglanis fortuitus. Standard length expressed in mm. All other measurements expressed in percent SL.

Holotype
Morphometrics
Standard length (mm)	35.0
Head length	32.0
Head depth (maximum)	20.4
Body depth at anus	17.0
Occipital shield width (minimum)	4.3
Prepectoral length	32.0
Predorsal length	43.4
Prepelvic length	62.6
Preanal length	75.7
Eye diameter (horizontal)	4.6
Orbital interspace	7.6
Snout length	22.3
Premaxillary tooth-patch width	13.3
Premaxillary tooth-patch length	3.4
Mandibular tooth row width	4.0
Anterior nares interspace	5.0
Posterior nares interspace	5.0
Maxillary barbel length	7.2
Medial mandibular barbel length	3.0
Lateral mandibular barbel length	5.1
Mouth width	10.3
Oral disc width	21.1
Oral disc length	21.4
Upper lip length	5.3
Lower lip length	9.7
Pectoral-spine length	16.6
Pectoral-fin length	18.3
Width at pectoral-fin insertion	26.6
Length of postcleithral process	11.8
Pelvic-fin length	11.4
Depth at dorsal-fin insertion	23.4
Dorsal-spine length	12.8
Dorsal-fin length (longest ray)	14.3
Dorsal-fin base length	10.7
Dorsal fin to adipose-fin length	18.3
Adipose-fin base length	17.1
Adipose fin to caudal-ped length	12.0
Adipose-fin height	2.9
Anal-fin length (longest ray)	11.4
Anal-fin base length	7.8
Lower caudal-fin lobe length	24.0
Upper caudal-fin lobe length	19.4
Fork length	15.2
Caudal-peduncle depth (maximum)	10.5
Caudal-peduncle length	17.1
Meristics
Mandibular tooth rows	1
Mandibular tooth count (total)	18
Mandibular tooth count (functional anterior row)	18
Mandibular tooth count (posterior replacement row)	—
Primary premaxillary teeth (total)	72
Pectoral-fin count	I, 7
Pelvic-fin count	i, 6
Dorsal-fin count	II, 4
Anal-fin count	iii, 6
Caudal-fin count	i, 7, 8, i