Chiloglanis carnatus Mutizwa, Braganca & Chakona, 2024

Mutizwa, Tadiwa I., Kadye, Wilbert T., Braganca, Pedro H. N., Bere, Taurai & Chakona, Albert, 2024, Hidden in the riffles: A new suckermouth catfish (Mochokidae, Chiloglanis) from the middle Zambezi River system, Zimbabwe, ZooKeys 1197, pp. 57-91 : 57

Chiloglanis carnatus Mutizwa, Braganca & Chakona sp. nov.

Material examined.

Holotype. Zimbabwe • ♂, stored in 70% ethanol, 46.8 mm SL, Fig. 9A-E ; Mukwadzi River near bridge on the road to Mutorashanga, Manyame River sub-catchment, middle Zambezi River system, Mashonaland West Province, 17.42485°S, 30.58542°E; 30 Jun. 2016; A. Chakona, W. Kadye and T. Bere; SAIAB 236631; genseq-1 COIPP156890 . Paratypes. Zimbabwe • 5 ♀, stored in 70% ethanol, 36.5-45.5 mm SL; near bridge on the road to Mutorashanga, Mukwadzi River, Manyame River sub-catchment, middle Zambezi River system, Mashonaland West Province, 17.42485°S, 30.58542°E; 30 Jun. 2016; A. Chakona, W. Kadye and T. Bere; SAIAB 211346; genseq-2 COIPP156891 to PP156895 . Zimbabwe • 6 ♀, 35.5-45.1 mm SL, 7 ♂, 36.5-48.9 mm SL, stored in 70% ethanol; near bridge on the road to Mutorashanga, Mukwadzi River, Manyame River system, middle Zambezi Basin , Mashonaland West Province, 17.42444°S, 30.58453°E; 11 Apr. 2019; A. Chakona, W. Kadye and T. Bere; SAIAB 211349 .

Diagnosis.

Chiloglanis carnatus sp. nov. is readily distinguished from its congeners in southern Africa (i.e. C. anoterus , C. bifurcus , C. emarginatus , C. fasciatus , C. paratus , C. pretoriae and C. swierstrai ) by the presence of a dorsal fin that has a basal portion covered by a fleshy skin, a character which is absent in the other species. Chiloglanis carnatus possesses ten closely packed mandibular teeth, that further distinguishes it from C. fasciatus that has eight closely packed mandibular teeth; C. bifurcus and C. emarginatus that have eight widely spaced mandibular teeth; C. anoterus , C. paratus , and C. pretoriae that have 12 closely packed mandibular teeth; and C. swierstrai that has 14 closely packed mandibular teeth. Chiloglanis carnatus possesses a deeply forked caudal fin that readily separates it from C. pretoriae and C. emarginatus that have emarginate caudal fins, and from C. anoterus that has a caudal fin with extended median rays in males and emarginate in females. Chiloglanis carnatus possesses a caudal fin with an upper lobe that is shorter than the lower lobe. This distinguishes it from C. bifurcus that has a caudal fin with an upper lobe that is longer than the lower lobe. Chiloglanis carnatus has an oral disc with a well-developed mid-ventral cleft that distinguishes it from C. swierstrai that possesses an oral disc without a mid-ventral cleft. Chiloglanis carnatus possesses a smooth skin with a few tubercles occasionally found on the head that separates it from C. fasciatus that has its entire dorsal and lateral body surfaces mostly covered by small tubercles. Chiloglanis carnatus has a dorsal spine with crenate anterior and posterior margins that distinguish it from C. paratus that has a dorsal spine with a serrated posterior margin.

Description.

Morphometric proportions and meristics are summarised in Table 7 . Holotype meristic counts are given in parentheses.

Body shape. Anterior portion of body slightly compressed dorsally, becoming laterally compressed from pelvic fin insertion to caudal peduncle. Body greatest depth at dorsal-fin insertion. Pre-dorsal profile convex, sharply slopping from snout to posterior nostril, gently from nostril to dorsal-fin origin. Post-dorsal profile about straight from dorsal-fin base to adipose-fin origin, becoming gently concave from adipose-fin origin to caudal fin. Ventral profile gently convex from region just posterior to oral disc to anal-fin origin, becoming gently concave from anal-fin origin to caudal fin.

Head. slightly depressed dorsally. Oval eye dorsally positioned, ~ 1/2 distance between snout and gill opening. Interorbital distance greater than distance between nostrils. Anterior and posterior nostrils closer to the eye than snout. Distance between anterior nostrils slightly greater than distance between posterior nostrils. Posterior nostril medially positioned relative to orbit. Anterior nostril with posterior flap; posterior nostril with anterior flap. Occipital-nuchal shield not visible through skin. Gill opening above pectoral fin insertion.

Oral disc. Mouth inferior; large upper and lower lips combined to form oral disc (see Fig. 9E, K ). Oral disc width greater than length. Upper and lower lips with pronounced roundish papillae, largest papillae concentrated around mid-ventral cleft of lower lip. Three pairs of barbels. Maxillary barbel unbranched, originating from lateral region of oral disc, extending to posterior region of oral disc. Lateral mandibular barbel longer than medial mandibular barbel, both incorporated into lower lip. Shallow cavity above lower lip.

Dentation . Pre-maxillary teeth arranged in three or four rows; variable number of teeth (43-69). Up to 5+5 closely packed mandibular teeth; central teeth projecting higher than outer teeth forming a gentle arc; replacement tooth row emerges anteriorly to the functional row.

Fins. Dorsal-fin ray count 5-7 (6), originating in anterior 1/3 of body, posterior to pectoral-fin origin. Dorsal fin basal portion covered by a fleshy skin prominent in large adult males and females with ~ ¾ of the dorsal spine and the first two rays also covered by fleshy skin (Fig. 10 ). Dorsal spine length ~ 80% of longest dorsal fin ray length. Dorsal spine with dentate anterior and posterior margins. Pectoral-fin ray count 6-8 (8), origin anterior to gill opening; pectoral spine anterior margin smooth; dentate posterior margin; pectoral spine length ~ 80% of pectoral fin length. Adipose fin origin preceded by anterior tissue flange; rounded (Fig. 10 ). Caudal fin forked, lower lobe longer than upper lobe. Anal-fin ray count 12 or 13 (13), origin posterior to origin of adipose fin; terminating just before end of adipose-fin; rounded. Pelvic-fin ray count 6 or 7 (7), origin posterior to midpoint between end of dorsal-fin and adipose-fin origin; rounded.

Skin. Skin smooth with occasional tubercles present, concentrated on dorsal and lateral surface of head. Lateral line complete; originating anterior to dorsal fin at same horizontal level of orbit and sloping ventrally until it lies mid-laterally along body.

Sexual dimorphism. Urogenital opening situated adjacent to origin of anal fin. Urogenital papillae sexually dimorphic; elongated in males; reduced and separated from anus by shallow invagination in females.

Colouration. Overall body background colouration brown with yellowish ventral surface. Anterior portion of body dark brown becoming paler towards posterior. Small dark melanophores scattered across entire dorsal and lateral sides. Six yellowish brown blotches on lateral surface of body; two vertically arranged posterior to end of adipose fin; one above origin of anal fin; two above pelvic fin origin; and one below dorsal fin origin. Basal 1/3 of fins pale to dark brown with medium and posterior portion of fins gradually becoming translucent. Dark blotch cuts vertically across caudal peduncle lobes.

Vertebral counts. Total vertebrae 29 or 30 (29), abdominal vertebrae 11-13 (12), caudal vertebrae 16-18 (17).

Etymology.

The specific epithet Chiloglanis carnatus means fleshy, referring to the dermal tissue covering the base of the dorsal fin of some of the larger specimens of this species and the general robust body structure of this species compared to its regional congeners.

Distribution.

Chiloglanis carnatus was collected from two sites in the Mukwadzi River near the bridge on the Mutorashanga Road. The Mukwadzi River is a perennial river that originates from wetlands (dambos) on the eastern side of the Great Dyke. This river flows in a north-western direction cutting through the Great Dyke before it joins the Manyame River. The Great Dyke is a major intrusion of mafic and ultramafic rocks that have vast ore deposits, including gold, silver, chromium, platinum, nickel, and asbestos. The rich mineral deposits have resulted in the establishment of many mines along the Great Dyke. The sites where C. carnatus was collected were in a communal area surrounded by rural communities on the western slope of the Great Dyke. The substratum at the sites was composed of bedrock, cobbles and gravel, and the riparian vegetation was dominated by Syzygium Gaertner, 1788 and Phragmites Adanson, 1763. At these sites C. carnatus co-occurred with native fish species that include Labeo cylindricus Peters, 1852, Opsaridium zambezense (Peters, 1852), Enteromius trimaculatus (Peters, 1852), Tilapia sparrmanii Smith, 1840, Clarias gariepinus (Burchell, 1822), and Labeobarbus marequensis (Smith, 1841) as well as the non-native species Serranochromis jallae (Boulenger, 1896) and Micropterus salmoides ( Lacepède, 1802).

Figures

Figure 9. Holotype of Chiloglanis carnatus sp. nov., SAIAB 236631 male (A-E) and female paratype specimen SAIAB 211346 (F-K). Scale bars: 1 cm.

Figure 10. Comparison of the dorsal and adipose fins of Chiloglanis carnatus sp. nov. and the type specimens of the valid southern African species A Chiloglanis carnatus sp. nov. (SAIAB 236631) specimens have an extended dermal tissue covering the base of the dorsal fin that distinguishes them from B C. swierstrai (SAIAB 186247) C C. bifurcus (SAIAB 120160) D C. emarginatus (SAIAB 120117) E C. fasciatus (SAIAB 204928) F C. paratus (SAIAB 186248) G C. pretoriae (SAIAB 30011) H C. anoterus (SAIAB 186246). Scale bars: 1 cm.