Chiloglanis frodobagginsi, Schmidt, Friel, Bart

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 : 382-386

Chiloglanis frodobagginsi, Schmidt, Friel, Bart , and Pezold, new species

urn:lsid:zoobank.org:act:02157426-E35A-4ABB-BEF4-85047A68B5C8

Figure 6 , Table 2

Chiloglanis batesii . — Paugy and Roberts, 1992 (in part): 502– 511; Paugy and Roberts, 2003 (in part): 197–207.

Chiloglanis micropogon .—Daget, 1954 (in part): 307–308; Daget, 1959 (in part): 682–683; Daget, 1962 (in part): 115.

Chiloglanis cf. micropogon .— Schmidt et al., 2016: 201–204.

Chiloglanis sp. aff. micropogon .— Schmidt et al., 2017: 301– 336.

Holotype.— TU 203552, 24.1 mm SL, Guinea, Niger River , North of Faranah, on road N29, 10.283828N, 10.769258W, 2013 Guinea expedition team, 29 January 2013.

Paratypes.— AMNH 263794, 4, 23.1–25.7 mm SL, AUM 59751, 8, CUMV 97679, 8, TU 203527, 4, 24.8–25.3 mm SL, Guinea, Niger River drainage, Mafou River, on road N2 ~ 80 km South of Faranah, 9.530728N, 10.401998W, 2013 Guinea expedition team, 28 January 2013 ; AUM 59554 , 19 , CUMV 97678, 18, TU 203348, 19, 20.6–24.1 mm SL, FLMNH 249106, 5, 20.0– 24.6 mm SL, Guinea, Niger River drainage, Tinkisso River, below Tinkisso Dam, 10.7 27938N, 11.168558W, 2013 Guinea expedition team, 12 January 2013 ; CUMV 97680 , 6 , TU 204171, 4, 19.2–24.3 mm SL, collected with holotype ; SAIAB 203746 , 9 , 19.9–23.3 mm SL, USNM 437542, 9, 22.1–38.1 mm SL, Niger River drainage, Tinkisso River, at dam, 10.728N 11.178W, B. Samoura and others, 7 April 2003 ; TU 204157, 1, 20.4 mm SL, Guinea, Niger River drainage, Tinkisso River, at dam, 10.727938N 11.168558W, F. Pezold and others, 18 January 2003 .

Non-type material examined.— AMNH 264623, 1, 26.3 mm SL, Guinea, Niger River drainage, Tinkisso River, at Toumania, 10.579028N, 10.472738W, F. Pezold and others, 16 May 2003 ; CUMV 98653, 1, 19.4 mm SL, TU 204170, 1, 20.1 mm SL, Guinea, Moa River drainage, Masseni River, about 3 miles north of Konesseridou, 8.72048N, 9.524368W, 2013 Guinea expedition team, 26 January 2013 ; MRAC 2016.029.P.52-63, 12, 20.0–27.0 mm SL, Guinea, Niger River drainage, Tinkisso River, at Bissikrima, 10.838N, 10.928W, B. Samoura and others, 8 April 2003 ; USNM 437545, 5, 22.2–23.5 mm SL, Guinea, Niger River drainage, Niger River, north of Faranah, F. Pezold and others, 26 May 2003 .

Diagnosis.— Chiloglanis frodobagginsi is distinguished from all known species of Chiloglanis in the Upper Guinean Forests, and most of the other described species (except C. disneyi , C. harbinger , C. marlieri , C. micropogon , C. microps , C. mongoensis , and C. niger ) by the very reduced, or absent, mandibular barbels on the oral disc. Chiloglanis frodobagginsi can be distinguished from C. disneyi , C. harbinger , C. marlieri , C. microps , C. mongoensis , and C. niger in having fewer mandibular teeth in one row (10–12 versus 16–20, 26–30, 26–28, 16–18, 28, and 16–20 respectively). Chiloglanis frodobagginsi is distinguished from C. batesii in having two prominent papillae on the roof of the oral cavity; versus the absence of papillae in C. batesii . This species is further distinguished from C. batesii in having shorter and more blunt mandibular teeth arranged in bunched rows; versus sharper, more elongate, and disordered mandibular teeth. Chiloglanis frodobagginsi also has a fleshy unpapillated ridge posterior to the mandibular teeth versus several large papillae in C. batesii (Friel and Vigliotta, 2011) .

A unique combination of characters distinguishes C. frodobagginsi from the closely related C. micropogon and C. cf. micropogon from Central Africa. As compared to C. micropogon from the Lualaba River, C. frodobagginsi has a larger eye diameter (4.2–6.5 versus 4.7–5.5 % SL; Supplemental Fig. A; see Data Accessibility), longer maxillary barbels (3.8–7.2 versus 3.4–6.5 % SL; Supplemental Fig. A; see Data Accessibility), a narrower mandibular tooth row (1.6–2.8 versus 2.4–3.1 % SL; Supplemental Fig. A; see Data Accessibility), a longer distance between dorsal fin and adipose fin (14.4–21.5 versus 14.9–18.8 % SL; Fig. 4A ), and a shorter anal-fin base length (8.0–10.8 versus 9.7–12.7 % SL; Supplemental Fig. A; see Data Accessibility). Chiloglanis frodobagginsi is further distinguished from C. micropogon in having fewer premaxillary teeth (36–70 versus 62–103) scattered in three rows versus four ( Fig. 4B ; Table 2). While the ranges of these measurements and counts overlap, these distinctions hold true when comparing similar sized species ( Fig. 4 ; Supplemental Fig. A; see Data Accessibility). Compared to Chiloglani s cf. micropogon from the Benue, Ndian, and Cross River basins Chiloglanis frodobagginsi has a narrower occipital shield (3.0–4.0 versus 4.0–5.4 % SL), a shorter dorsal fin to adipose fin distance (14.5–21.5 versus 19.3–24.2), and a narrower mandibular tooth row (1.6–2.8 versus 1.8–3.2 % SL).

Description.— Morphometric measurements and meristics for holotype and 21 paratypes summarized in Table 2. Dorsal, lateral, and ventral views ( Fig. 6 ) illustrate body shape, fin shape and placement, oral disc size and shape, and maxillary and mandibular barbel lengths.

Small to moderate-sized Chiloglanis , maximum standard length 38.1 mm. Body dorsally depressed anteriorly and laterally compressed posteriorly. Pre-dorsal convex, sloping ventrally towards posterior nares, pre-orbital convex, sharply angling towards tip of snout pre-nares. Post-dorsal body sloping ventrally towards caudal fin. Post-anal profile shallowly concave, pre-anal profile horizontal to slightly convex. Small unculiferous tubercles present on body, concentrations of tubercles higher near head. Lateral line complete, arising at dorsal level of orbit and sloping ventrally to midlateral alongside of body towards caudal peduncle. Urogenital papillae sexually dimorphic; males with elongated urogenital papillae, females with reduced papillae, separated from anus by shallow invagination.

Head depressed. Gill membranes broadly united. Gill openings restricted, opening near pectoral-fin origin to horizontal level of mid-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 naris set farther apart than posterior naris, positioned mid-snout. Nares 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, slightly wider than long and covered in papillae. Maxillary barbel originating from posterolateral region of disc, unbranched, moderate in length, reaching 7% of SL. Lateral and medial mandibular barbels absent or very reduced. Two prominent papillae on roof of oral cavity. Primary maxillary teeth ‘‘S’’ shaped with exposed brown tips. 36–70 teeth in three 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 toothplate. Mandibular teeth in one to two rows, curved and bunched near midline. Functional (anterior) row with 12 brown-tipped teeth. Distinct, slightly concave rectangular fleshy ridge posterior to mandibular teeth.

Dorsal-fin origin just posterior to anterior third of body. Dorsal fin with small spinelet, spine, and five to six rays. Dorsal spine medium to short in length, reaching 13% of SL. Adipose fin medium length, reaching 19.6% of SL; margin convex. Caudal fin forked with rounded lobes, lower lobe longer than upper lobe, count i, 7, 8, i, no sexual dimorphism observed in examined specimens. Anal-fin origin posterior to origin of adipose fin, margin convex, count iii, 5–7. Pelvic-fin origin at vertical between dorsal and adipose fin, margins convex, reaching beyond anal-fin origin, count i, 6. Pectoral fin with smooth spine, reaching 15.6% of SL, count I, 8–9. Postcleithral process shorter and bluntly pointed, no sexual dimorphism noted in specimens examined.

Coloration.— Typical coloration of preserved specimens in Figure 6 . In dorsal view, specimens medium brown with mottled areas of light brown. Lighter areas on tip of snout anterior to nares, at origin of dorsal fin, at origin and terminus of adipose fin, and on caudal peduncle. White or cream unculiferous tubercles scattered across body, more concentrated near head. In lateral view, specimens with yellow-buff color with overlying medium brown blotches. Dark area more prevalent dorsal to midline, but extending ventrally at origin of pelvic and anal fins. Dark brown melanophores scattered across body, more readily visible ventral to midline, absent on belly. Ventral surface yellow-buff colored with few melanophores scattered near anus and origin of anal fin. Oral disc and barbels cream colored.

Pectoral and dorsal spines pigmented distally and 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 mid-length. Pelvic fin cream with few melanophores at base and band at mid-length. Adipose fin cream to translucent with dark brown markings at origin. Caudal fin cream to translucent with dark brown areas near base and at mid-length.

Etymology.— Chiloglanis frodobagginsi is named after another diminutive traveler, Frodo Baggins, a fictional character well known from J. R. R. Tolkien’s The Lord of the Rings series. Roughly 3,000 miles (4,800 km) separate C. frodobagginsi in the upper Niger River drainage and C. micropogon , the sister species, found in the Congo River basin. Another seemingly closely related species, Chiloglanis cf. micropogon , is found in the southern Benue drainage and in several small coastal rivers about 3,000 km from the upper Niger River drainage (e.g., Cross and Ndian Rivers). It is unclear whether these species are descended from a more widespread species, or the result of dispersal from the Congo River basin into the Niger River drainage, via the Benue River, and then up to the headwaters of the Niger River. This was an incredible journey for such a small and seemingly non-vagile fish.

Distribution.— Chiloglanis frodobagginsi occurs in the upper Niger River drainage in Guinea and further downstream in the Niger River near Bamako ( Fig. 1 ; Daget, 1959). This species was collected in several tributaries to the Niger River in Guinea and also collected in the upper reaches of the Moa River drainage (Masseni River), a coastal river drainage. Only two specimens were collected in the Moa River drainage and no tissues were retained. Given that most species of Chiloglanis in the region are restricted to individual river drainages and since the Moa River drainage is on the other (i.e., west) side of the Guinean Range from the Niger River drainage, this population may be a distinct species. For this reason, these specimens were not included in the type material for C. frodobagginsi . In the Tinkisso River, C. frodobagginsi was collected below the waterfall over small gravel in the middle of the channel. Chiloglanis waterloti is also found in the Tinkisso River, but this species is usually associated with woody debris or large rocks.

Remarks.— The affinity between Chiloglanis frodobagginsi and C. micropogon was first reported in research on fishes in the upper Niger River drainage (Daget, 1954, 1959). The large distance between the populations in the upper Niger River and the Lualaba River ( Congo River drainage) warranted further examinations of these specimens (Daget, 1959). Daget sent specimens from the upper Niger River to Max Poll for comparison to those that Poll described as C. micropogon from the Congo River drainage ( Poll, 1952; Daget, 1959). Poll noted some variation between the different populations, but it wasn’t enough to readily distinguish one from the other (Daget, 1959). Daget also noted their diminutive size and rarity relative to the co-occurring specimens of C. waterloti (Daget, 1954) . Herein we noted another aspect of these specimens that wasn’t directly noted: the apparent lack of an elongated upper caudal-fin lobe and an elongate and spatulate postcleithral process in males. An examination of the type specimen of C. micropogon and the sketch of the holotype clearly shows an elongated upper caudal-fin lobe ( Poll, 1952, fig. 3, page 228). The larger specimens collected in recent expeditions were mostly females, and none of the males collected showed an elongated upper caudal-fin lobe. More specimens of C. frodobagginsi are needed to better understand if this species also displays those sexually dimorphic characteristics, or if the lack of sexual differentiation can be a useful trait in distinguishing both species. Chiloglanis frodobagginsi is also genetically distinct from C. micropogon with a divergence observed of 3.6% in cytochrome b and 6.2% in Growth Hormone intron 2 ( Schmidt et al., 2016).

Populations of Chiloglanis cf. micropogon in the Benue, Cross, and Ndian Rivers have only been relatively recently collected (e.g., in the 1970s and 1980s) and were unknown to Daget and Poll at the time of their comparisons of upper Niger and Lualaba River specimens. In examining these specimens, they clearly concur with C. micropogon , but also differ in some respects ( Fig. 3 ). Some specimens showed the sexual dimorphism attributed to C. micropogon (e.g., an elongated upper caudal-fin lobe and an elongated and spatulate postcleithral process), but most of the specimens examined did not have these traits. Many of these collections and subsequent identifications took place before many of the species in the region were described ( Roberts, 1989) and cataloged under superficially similar species names C. niger and C. disneyi . Additional populations from the Benue and the smaller coastal drainages in Central Africa are needed to fully resolve the relationships within the C. micropogon complex.

Figures

FIG. 6. Dorsal, lateral, and ventral views of Chiloglanis frodobagginsi holotype, TU 203552, 24.1 mm SL, Guinea, Niger River drainage, Niger River, North of Faranah, on road N29, 10.283828N, 10.769258W. Scale bar equals 2 mm. Photographs by S. Raredon.

FIG. 4. Reduced-major axis regression of distance from dorsal fin to adipose fin (as a percentage of standard length) on log-transformed standard length (A). Reduced-major axis regression of log-transformed total number of premaxillary teeth on log-transformed standard length (B). Chiloglanis frodobagginsi (open circle), Chiloglanis frodobagginsi from the Moa River (filled circle), Chiloglanis micropogon (open square), and holotype of C. frodobagginsi (black star).

FIG. 1. Localities of species of Chiloglanis discussed in this study. Rivers of the Upper Guinean Forests enlarged from outlined region in the inset map of West and Central Africa. River drainages outlined in white lines. White circles are localities where no Chiloglanis were collected. Locations of Chiloglanis frodobagginsi (black circles), holotype of C. frodobagginsi (black star), type locality of Chiloglanis fortuitus (black triangle), and comparative Chiloglanis micropogon and Chiloglanis cf. micropogon (black squares).

FIG. 3. Plots of PC1 to PC2 from principal component analysis of 35 log-transformed measurements from 47 specimens (A) and PC2 to PC3 (B). The holotype of Chiloglanis frodobagginsi is noted by the black star. Refer to Supplemental Table B (see Data Accessibility) for component loading values.