Rhabdalestes
The species of this genus lack small conical teeth in the inner mandibular tooth row. The inner premaxillary teeth have rather numerous cuspids aligned on the same plane. Depending on species, and on individuals within species, the lateral line may be complete or incomplete. Body form is slender fusiform.
This genera is distinguished from all other Petersiini by the combination of the following characters::
Synonyms
Petersius Boulenger, 1899 (partim)
Micralestes Boulenger, 1899 (partim)
Micralestes (Rhabdalestes) Hoedeman, 1951
Micralestes (Rhabdalestes) Hoedeman, 1956
Hemigrammopetersius (Rhabdalestes) Géry, 1977
Type species: Rhabdalestes tangensis
Petersius tangensis Lönnberg, 1907 by original designation of Hoedeman, 1956.
Currently, eight species are assigned to the genus Rhabdalestes.
Key to species.
1 35-37 scales along lateral line; 12-14 scales around the caudal peduncle.........................................................................2
22-29 scales along lateral line; 10 scales around the caudal peduncle.............................................................................4
2 Lateral line incomplete; 16 gill rakers on lower limb (ceratobranchial) of first gill arch............................................R. leleupi
Lateral line complete; 14-15 gill rakers on lower limb (ceratobranchial) of first gill arch.......................................................3
3 Well-marked band of melanophores present above anal fin; flanks with slignt dark band, more distinct backward................
...........................................................................................................................................................R. rhodesiensis
No band of melanophores present above anal fin; flanks without dark band......................................................R. tangensis
4 Lateral line incomplete..........................................................................................................................R. brevidorsalis
Lateral line complete...................................................................................................................................................5
5 12 gill rakers on lower limb (ceratobranchial) of first gill arch........................................................................R. maunensis
13-19 gill rakers on lower limb (ceratobranchial) of first gill arch......................................................................................6
6 17-19 gill rakers on lower limb (ceratobranchial) of first gill arch; 27-28 scales along lateral line.............................R. aeratis
13-17 gill rakers on lower limb (ceratobranchial) of first gill arch; 24-27 scales along lateral line.........................................7
7 4 (exceptionally 6) outer premaxillary teeth with 3-5 cusps; 13-17 anal fin branched rays; a black spot on the dorsal fin tip...
.......................................................................................................................................................R. septentrionalis
5-7 outer premaxillary teeth with 5 cusps; 18-19 (exceptionally 17) anal fin branched rays; no black spot on the dorsal fin tip
.....................................................................................................................................................................R. yokai
Discussion concerning the species to the genus Rhabdalestes (after Ibala Zamba & Vreven, 2008)
Poll (1967a) and Paugy (1984) recognised seven Rhabdalestes species: R. eburneensis, R. leleupi, R. loennbergi, R. maunensis, R. rhodesiensis, R. septentrionalis and R. tangensis. According to Paugy (1990b) the character provided by Géry (1977) to diagnose R. loennbergi from R. septentrionalis, i.e. a black versus a hyaline point of the dorsal fin, was not convincing. Therefore, he synonymised R. loennbergi with R. septentrionalis. Rhabdalestes eburneensis was transferred to the genus Micralestes due to the presence of two inner mandibular teeth (Paugy, 1990b). In addition to the absence of two inner mandibular teeth, R. yokai is distinguished from R. eburneensis by having 25-26 pored lateral line scales (vs 27-29) and in missing a black spot at the top of the longest dorsal fin rays (vs spot present).
Hemigrammopetersius brevidorsalis and Alestopetersius smykalai have been transferred to the genus Rhabdalestes by Paugy (1990b) and have therefore been included in the differential diagnosis of R. yokai. However, unfortunately Paugy (1990b) gave no detailed justification for this transfer. According to Stiassny & Schaefer (2005), the transfer of A. smykalai to the genus Rhabdalestes might have been motivated by the fact that this species is only known from the Niger whereas all other Alestopetersius are endemic to the Congo River basin. However, according to Stiassny & Schaefer (2005) R. smykalai has elongated dorsal and anal (the latter not confirmed by our observations) fins in males, features lacking in Rhabdalestes but typical for many Phenacogrammus, Nannopetersius and Alestopetersius. Therefore, Stiassny & Schaefer (2005) did not further compare their new species, i.e. R. aeratis, with R. smykalai.
Despite the absence of inner mandibular teeth, Géry (1995) described and placed Micralestes ambiguus within the genus Micralestes, which is characterised by the presence of inner mandibular teeth, based on habitus and morphometric similarities to members of the M. argyrotaenia group. This seemingly natural group of tree species, i.e. M. argyrotaenia, M. congicus and M. lualabae, is characterised by relatively high number of 30-32 lateral line scales and a lateral band (Géry, 1995). The species name ambiguus, means changeable, uncertain, doubtful or of double meaning (Brown, 1956), and as such refers to the difficulty of placing the species in the proper genus (Géry, 1995). Despite the similarities of M. ambiguus with Rhabdalestes, the new species is readily distinguished from M. ambiguus by the fewer gill rakers on the lower limb of the first branchial arch (13-14 vs. 16) and a longer prepelvic distance (52.1-54.5 % SL vs. 46.6-50.6 % SL).
The monotypic genus Virilia was described by Roberts (1967) based on an important thickening of the segments of the third unbranched anal-fin ray in males of the type species Phenacogrammus pabrensis. Paugy (1990b) however placed the species into Micralestes whereas Géry (1995) placed it into Rhabdalestes. According to Stiassny & Schaefer (2005) the placement of the species remains problematic and must await thorough phylogenetic analysis. Certainly other Rhabdalestes species, such as R. aeratis (see Stiassny & Schaefer, 2005), R. eburneensis (see Zanata & Vari, 2005) and R. septentrionalis (Paugy, 1990b) exhibit a similar modification and expansion of the male anal fin. Indeed, according to Zanata & Vari (2005) not only Rhabalestes (i.e. R. eburneensis, R. loennbergi, R. rhodesiensis and R. septentrionalis) and Virilia (i.e. V. pabrensis) but also the Hemigrammopetersius species examined (i.e. H. barnardi and H. intermedius) all are characterised by an anteroposterior thickened and distinctly curved third unbranched anal-fin ray (Zanata & Vari, 2005: characters 182 and 183). Rhabdalestes yokai is characterised by an elongation of the third unbranched anal-fin ray, i.e. compared to the first and the second one. However, whereas in P. pabrensis, and also for instance in R. aeratis, the first as well as the second unbranched anal-fin rays are small compared to the third one, in R. yokai the second one is of intermediate size between the small first one and the larger third one. Further, R. yokai lacks such an anteroposterior thickening (i.e. compared to the branched fin rays) and distinctly curving of this fin ray as found in P. pabrensis as well as R. aeratis. Regardless, in addition R. yokai can be readily distinguished from P. pabrensis by a higher number of outer premaxillary teeth (5-7 vs 4) and a complete lateral line with 25-26 tubes (vs. an incomplete lateral line with 6-10 tubes).
Bibliography
Rhabdalestes aeratis Stiassny & Schaefer, 2005
Type and type locality
Rhabdalestes aeratis Stiassny & Schaefer, 2005: 273-275, fig. 1-3. Type locality: “Democratiec Republic of Congo: main channel outlet from Lake Tumba near Irebu, 0°35.84’S 17°46.96’E”. Holotype: AMNH 235767; paratypes: AMNH 235768.
Common names
Estonian: Pronksjas tintsalmler
Description
Diagnosis: body depth 3.7-4.3 and head length 3.88-4,20 in SL. Dental formula: [4/8 (upper jaw), 8/0 (lower jaw)]. Cuspids number: [3/3-5 (upper jaw), 3-5/0 (lower jaw). Dorsal fin: II,8. Anal fin: III,14-15. Gill rakers: 17-19. Scales: 27-28 (longitudinal line); 4½ (above lateral line). Lateral line complete with 27-28 tubes (see table below).
Rhabdalestes aeratis: morphometric and meristic data.
Maximum reported size: 50.8 mm SL.
Colour: base body coloration brown dorsalIy and laterally with highly reflective golden-bronze iridescence. Dorsum of head and body darkly pigmented, concentration of chromatophores along posterior scale margins. Chest and belly creamy brown. All fins dusky, with pigment concentrated along margins of fin rays and interspaces. Dorsal fin occasionally with pigment concentration at apical tip. Anal fin base with dark band along entire length of fin-ray insertion, becoming diffuse and lighter grey distally. Caudal fin dusky black, without pigment concentration along median fin rays.
Affinities: distinguished from all putative congeners by having 17-19 gill rakers on the lower limb of the first arch (vs 11-17). Further distinguished from all congeners by the combination of a slender body, its depth contained 3.7-4.2 times in standard length, 14-15 branched anal-fin rays, 26-28 lateral-lines scales, all of which bear lateral-line canals, flanks with golden-bronze reflective coloration overlain by dark brown chromatophores, and dark midlateral pigmentation stripe absent. Rhabdalestes aeratis differs from R. leleupi, R. rhodesiensis, and R. tangensis in having fewer scales in the lateral line (27-28 vs 35-39). It differs from all other Rhabdalestes species, with the exception of R. maunensis, by an extremely slender body form (body depth 24-27% SL vs 28-33). Rhabdalestes aeratis is distinguished from R. maunensis by a greater number of gill rakers (17-19 vs 12) and fewer branched anal fin rays (14-15 vs 17). It differs from R. brevidorsalis, included in Rhabdalestes by Paugy (1990b), in having a complete lateral line with 27-28 pored scales (vs 6-7 pored scales) and a higher number of gill rakers (17-1 9 vs 11-13).
Remarks: prior to the description of R. aeratis, the only Rhabdalestes species recorded from the Congo River basin was R. rhodesiensis from the Bangweulu-Luapula region of the upper Congo River.
Distribution
Currently known only from the type locality: Democratic Republic of Congo, main channel outlet from Lake Tumba near Irebu, 0°35.84'S 17°46.96'E. Collections were made during the rainy season (average October rainfall 200-220 mm) and rising water levels had already inundated surrounding swamp grasslands and lowland forest. Specimens were collected using cast nets from pirogues and were taken in the large, black water, main channel outlet of Lake Tumba close to the flooded shoreline near Irebu (see also Faunafri).
Rhabdalestes aeratis is only known from the type locality Lake Tumba at Irebu, Central Congo River basin. The species may be more widespread than is currently known. More information is needed on the species distribution before an assessment can be made.
Major threats: none known.
Bibliography
Rhabdalestes brevidorsalis (Pellegrin, 1921)
Type and type locality
Petersius brevidorsalis Pellegrin, 1921: 49-50. Type locality: “Fort-Crampel (Gribingui)”. Syntypes: MNHN 21-10.
Synonyms
Petersius brevidorsalis Pellegrin, 1921
Hemigrammopetersius brevidorsalis Poll, 1945
Rhabdalestes brevidorsalis Paugy, 1990
Common names
Estonian: Lühiuim-tintsalmler
Hausa: Kawara (Nigeria)
Description
Diagnosis: body depth 3-3.2 (2.8-3) and head length 3.3-3.6 (3.3-3.5) in SL. Dental formula: [4/8 (upper jaw), 8/0 (lower jaw)], [type: 4/8 (upper jaw), 8/0 (lower jaw)]. Cuspids number: not indicated. Dorsal fin: II,8 (II,8). Anal fin: III,13-14 (III, 13-14). Gill rakers: 11-13 (11-13). Scales 25-26 + 2 (25) (longitudinal line); 4½ (above lateral line)/3½ (below lateral line) (4½/3½); 10 around caudal peduncle. Lateral line scales: 6-7 (7) tubes.
Maximum reported size: 33 mm SL.
Colour: a thin dark longitudinal line more marked at the back. Dorsal-fin tip blackish.
Distribution
Gribingui at Kaga Bandoro (ex Fort Crampel, Central Africa Republic) and Mayo-Kebbi (Cameroon), Chad basin (see also Faunafri).
The estimated EOO is less than 5,000 km² and AOO is less than 500 km², and it is restricted to two locations. Current information suggests no decline in habitat or distribution. Although the species has a restricted distribution it has no known major widespread threats and is found in very remote areas so is assessed as Least Concern.
Major threats: remote area with no known major threats.
Bibliography
Rhabdalestes leleupi Poll, 1967
Type and type locality
Rhabdalestes leleupi Poll, 1967: 130-132, fig. 28. Type locality: “Kenya, lake Jipe, Teita district”.Holotype: MRAC 153759.
Synonyms
Rhabdalestes leleupi Poll, 1967
Hemigrammopetersius (Rhabdalestes) leleupi Géry, 1977
Common names
English: Pangani robber (Kenya)
Estonian: Leleupi tintsalmler/Tanga tintsalmler
Finnish: Tanganalesti
German: Tangasalmler
Swahili: Dagaa (Tanzania)
Description
Diagnosis: body depth 4 and head length 3.8 in SL. Dental formula: [4/8 (upper jaw), 11/0 (lower jaw)]. Cuspids number: [3/4-5 (upper jaw), 1-5/0 (lower jaw). Dorsal fin: II,8 located behind pelvic-fin insertion. Anal fin: III,17. Gill rakers: 16. Scales 37 + 2 (longitudinal line); 6½ (above lateral line)/3½-4½ (below lateral line); 12-13 around caudal peduncle. Lateral line scales: 33 tubes.
Maximum reported size: 56 mm SL.
Colour: an indistinct mid-lateral blackish band, silvery, a bit clearer at the back. Fins are greyish, the anal fin delicately edged with black.
Affinities: this species is close to Rhabdalestes tangensis from Eastern Africa (Tanga River) of which it clearly differs for the sharpness of the caudal peduncle which is 1.8 times longer than depth ( versus 1.5), the high number of longitudinal line scales 37 + 2 (vs 35 + 2) and the low number of tubes: 33 (instead of a complete lateral line), the number of teeth of the lower jaw: 11 (vs 8) and the different sizes of the eye and the interorbital width.
|
Holotype description
Body depth 4, head length is 3.8 of the standard length. Head width is 2.15 of the head length. Short sub-rounded snout is, 4.15 of the head length, 1.6 of the eye diameter, 1.5 of the postorbital. Eye is 2.6 of the head length. Interorbital is 3.6 of the head length and 1.4 of the eye diameter. Sub-terminal mouth, with slightly prominent lower jaw. Four upper external teeth alternating with 8 upper internal teeth. A row of 11 lower teeth (no median internal teeth). A little number of cuspids, 3 for upper external teeth, from 4 to 5 for upper internal teeth, from 1 to 5 for lower teeth. The longest tooth of the upper jaw is the third internal one, in the lower jaw it is the second one. Dorsal fin II,8, non-filamentous, behind pelvic-fin insertion. Head length is 1.25 of the longest rays. Anal fin III,17, with anterior rays longer and stronger in mature male. Pectoral fin is 1.2 of the head length. Caudal fin is forked with sharp lobes. Caudal peduncle is 1.8 times longer than deep. Longitudinal line scales 37+2; transversal line scales 6½/3½-4½; scales around caudal peduncle 12-13. Lateral line shortened at the back, with 33 tubes. 6 gill rakers on the lower limb of the first gill arch. Colour : an indistinct mid-lateral blackish band, silvery, a bit clearer at the back. Fins are greyish, anal fin delicately edged with black. |
Distribution
Pangani River and Tanga region in East Africa (see also Faunafri).
The species has an estimated extent of occurrence <100 km² is restricted to a single location, the Nyumba ya Mungu lake and its outlet, and has suffered a significant population decline due to overfishing and deterioration of habitat. The causes of population decline are still ongoing.
Major threats: over-fishing accompanied by use of illegal gears and methods. Increased siltation due to deforestation and agricultural practice. Land-based pollution especially from domestic and agricultural activities.
Bibliography
Rhabdalestes maunensis (Fowler, 1935)
Type and type locality
Petersius maunensis Fowler, 1935:259-260, fig. 5. Type locality: “Thamalakane River at Maun”. Holotype: ANSP 15276.
Synonyms
Petersius maunensis Fowler, 1935
Alestes lateralis (non Boulenger, 1900) Jubb, 1963
Rhabdalestes maunensis Poll, 1967
Hemigrammopetersius (Rhabdalestes) maunensis Géry, 1977
Common names
Afrikaans: Mbala/Okavango Robber (Namibia), Slanke rower (South Africa)
English: Okavango robber/Slender robber (global)
Estonian: Okavango tintsalmler
Description
Diagnosis: body depth (5) and head length (3.4-3.65) in SL. Dental formula: [type: 8/0 (upper jaw), 8/0 (lower jaw)] (?). Cuspids number not indicated. Dorsal fin: (III,8) behind pelvic-fin insertion. Anal fin: (III,17). Gill rakers: (12). Scales: (28-29 + 2-3) (longitudinal line); 4½ (above lateral line)/3½ (below lateral line); (10) around caudal peduncle. Lateral line scales: 28-29 tubes.
Maximum reported size: 49 mm SL.
Colour: a mid-lateral black band, more visible at the back. Anal fin edged with black.
Habitat and Ecology
R. maunensis is a shoaling species that lives amongst vegetation in shallow water in rivers and flood plains. This species is rarely found in the main channel of the upper Zambezi river, patchily distributed on the floodplain but more common in small streams (Tweddle et al. 2004). It feeds on small aquatic insects and other invertebrates. A partial spawner breeding at high water (Skelton, 2001; Marshall, 2011).
Distribution
Cunene, Okavango, Upper Zambezi and Kafue River systems. A similar, possibly identical, species (R. rhodesiensis) occurs in the Zambian Congo system (Lakes Bangweulu and Mweru, and Luapula River) (see also Faunafri).
This species has a wide distribution, with no known major widespread threats. It is therefore listed as Least Concern.
Major threats: none known.
Bibliography
Rhabdalestes rhodesiensis (Ricardo-Bertram, 1943)
Type and type locality
Petersius rhodesiensis Ricardo-Bertram, 1943: 201. Type locality: “Chambezi River, lake Bangwelo”. Syntypes: BMNH 143.7.27:142-145.
Synonyms
Petersius rhodesiensis Ricardo-Bertram, 1943
Micralestes (Rhabdalestes) tangensis rhodesiensis Hoedeman, 1951
Rhabdalestes rhodesiensis Poll, 1967
Hemigrammopetersius (Rhabdalestes) rhodesiensis Géry, 1977
Common names
English: Slender Robber (USA)
Estonian: Sale tintsalmler
Lwena: Mungumba (Angola)
Description
Diagnosis: body depth 3.9-4.6 (4-4.5) and head length 3.8-4.25 (4-4.25) in SL. Dental formula: [4-6/8-10 (upper jaw), 8-10/0 (lower jaw)], [type: 4-6/8 (upper jaw), 6-8/0 (lower jaw)]. Cuspids number: [3/3-5 (upper jaw), 1-5/0 (lower jaw)]. Dorsal fin: II,8 (II,8) behind pelvic-fin insertion. Anal fin: III,17-19 (III,16-17). Gill rakers: 14-15 (16-17). Scales 35-37 + 2 (longitudinal line) (33-36); 5½-6½ (above lateral line)/3½-4½ (below lateral line) (5½/3½); 13-14 around caudal peduncle. Lateral line scales: 35-38 tubes.
Maximum reported size: 74 mm SL.
Colour: a mid-lateral black band, more visible at the back. Anal fin bottom edged with black.
Remark: possibly a synonym of R. maunensis (Skelton, 2001)
Distribution
Bangweulu-Luapula (Democratic Republic of the Congo and Zambia). Possibly present in the Kafue River system. Presence in southern Africa (upper Zambezi, Lake Kariba and the Kalomo River in Botswana) needs confirmation (see also Faunafri).
Although there are threats known in the region, the species is listed as Least Concern because of its relatively wide distribution and protection by the controlled fishing in the Luapula-Mweru system.
Major threats: in the Katanga region, mining for cobalt, copper, tin, uranium, dams and the use of toxic plants for fishing and overfishing form threats in this region.
Bibliography
Rhabdalestes septentrionalis (Boulenger, 1911)
Types and type localities
Petersius septentrionalis Boulenger, 1911: 373. Type locality: “Geba River at Bafata”. Syntypes: BMNH 1912.4.1:144-149.
Petersius loennbergi Svenson, 1933: 57-59. Type locality: “Gambia River”. Syntypes: NRMS 10229.
Petersius intermedius Blache & Miton, 1960: 102. Type locality: “Lac Tchad”. Syntypes: MNHN 59228.
Synonyms
Petersius septentrionalis Boulenger, 1911
Hemigrammopetersius septentrionalis Myers, 1929
Micralestes septentrionalis Hoedeman, 1951
Micralestes (Micralestes) septentrionalis Hoedeman, 1959
Rhabdalestes septentrionalis Poll, 1967
Hemigrammopetersius intermedius Poll, 1967
Rhabdalestes loennbergi Poll, 1967
Hemigrammopetersius (Rhabdalestes) septentrionalis Géry, 1977
Hemigrammopetersius (Rhabdalestes) loennbergi Géry, 1977
Petersius loennbergi Paugy, 1990
Petersius intermedius Paugy, 1990
Common names
Estonian: Kuldjoon-tintsalmler
Finnish: Kultajuova-alesti
German: Tschadsalmler
Description
Diagnosis: body depth 3.5-4.1 (3.5-3.75) and head length 3.3-3.8 (3.5-3.75) in SL. Dental formula: [4-6/8-10 (upper jaw), 8/0 (lower jaw)], [type: 4/8 (upper jaw), 8/0 (lower jaw)]. Cuspids number: [3-5/3-6 (upper jaw), 3-5/0 (lower jaw)]. Dorsal fin: II,8 (II,7) located at vertical through pelvic-fin insertion. Anal fin: III,15-17 (III,13-14). Gill rakers: 14-17 (12). Scales 24-27 + 2 (25-26) (lateral line); 4½ (above lateral line)/3½ (below lateral line) (4½/3½); 10 around caudal peduncle. Lateral line scales: 23-27 tubes.
Maximum reported size: 54 mm SL.
Colour: a mid-lateral black band, more visible at the back. Anal fin bottom edged with black.
Distribution
Occurs throughout most of Wertern African River basins: Chad, Niger, Benue, Mono, Volta, Pra, Comoe, Agnebi, Bandama, Konkoure, Kolente, Kaba, Sewa, Moa, Mano, Senegal, Gambia, Tomine, Geba, and Wouri (see also Faunafri).
This species has a wide distribution, with no known major widespread threats. It is therefore listed as Least Concern. It has also been assessed regionally as Least Concern for western Africa. It is estimated that less than 5 % of the species is found in the central Africa region, and has therefore been categorised as Not Applicable for this region.
Major threats: oil extraction in Nigeria threatens local populations.
Bibliography
Rhabdalestes tangensis (Lönnberg, 1907)
Type and type locality
Petersius tangensis Lönnberg, 1907: 2. Type locality: “Tanga”. Syntypes: NRMS 944.
Synonyms
Petersius tangensis Lönnberg, 1907
Hemigrammopetersius tangensis Myers, 1929
Micralestes (Rhabdalestes) tangensis tangensis Hoedeman, 1951
Rhabdalestes tangensis Poll, 1967
Hemigrammopetersius (Rhabdalestes) tangensis Géry, 1977
Common names
English: Pangani robber (Kenya)
Estonian: Leleupi tintsalmler/Tanga tintsalmler
Finnish: Tanganalesti
German: Tangasalmler
Swahili: Dagaa (Tanzania)
Description
Diagnosis: body depth 3.7 (3.75-4) and head length 4.1 (4-4.5) in SL. Dental formula: [5/8 (upper jaw), 8/0 (lower jaw)], [type: 4/8 (upper jaw), 8/0 (lower jaw)]. Cuspids number: [3/4-6 (upper jaw), 3-5/0 (lower jaw)]. Dorsal fin: II,8 (II,8) behind pelvic-fin insertion. Anal fin: III, 18 (III,16-17). Gill rakers: 14 (16-17). Scales: 35 + 2 (35-36) (longitudinal line); 6½ (above lateral line)/4½ (below lateral line) (6½/); 14 around caudal peduncle. Lateral line: 36 tubes.
Maximum reported size: 80 mm SL.
Colour: yellowish-silvery, a vague mid-lateral black band, more visible at the back.
Distribution
Pangani River basin and Lake Jipe (Tanzania) (see also Faunafri).
Relatively widespread with no major widespread threats identified.
Major threats: no information available.
Bibliography
Rhabdalestes yokai Ibala Zamba & Vreven, 2008
Type and type locality
Rhabdalestes yokai Ibala Zamba & Vreven, 2008: 378-381, fig. 1-4. Type locality: Republic of Congo: Léfini River, acces canal to Lake Itsitso, left bank of Louna River, Lésio-Louna Natural Reserve, 3°03’S 15°49’E. Holotype: MRAC: 2004.046.P.0258; paratypes: AMNH 239654 (former MRAC 2004.046.P.0270-0272), MRAC 2004.046.P.0259-0269.
Common names
Estonian: Yoka tintsalmler
Description
Diagnosis: body depth 3.23-3.80 and head length 3.49-3,66 in SL. Dental formula: [5-7/8 (upper jaw), 8/0 (lower jaw)]. Cuspids number: [3-5/5-7 (upper jaw), 3-7/0 (lower jaw). Dorsal fin: II,8. Anal fin: III,17-19. Gill rakers: 13-14. Scales: 25-26 (longitudinal line); 4½ (above lateral line)/3½ (below lateral line); 10 around caudal peduncle. Lateral line complete with 25-26 tubes.
Rhabdalestes yokai: morphometric and meristic data.
Maximum reported size: 52.2 mm SL.
Colour: coloration of preserved specimens. Body pale brown, darker on dorsal midline and lighter, yellowish, ventrally. A dark brown band along lateral side of body, from posterior border of opercle to caudal-fin base. Snout and upper surface of head blackish. Head yellowish-white below eye. Opercule generally with numerous small, blackish, spots. Anal fin translucent, whitish, with a thin dark band at its base. In addition, another thin blackish band, broader anteriorly and gradually narrowing posteriorly, parallel to anal-fin base is present. Pectoral fins translucent, whitish, with numerous blackish points on upper fin rays giving a blackish appearance to upper part of these fins. Pelvic fin translucent, whitish. Dorsal and caudal fins with a light blackish hue due to a fine blackish pigmentation.
Affinities: Rhabdalestes yokai can be distinguished from all other Rhabdalestes by the following combination of characters: 25-26 lateral line scales (vs 27-39 in R. aeratis, R. leleupi, R. maunensis, R. rhodesiensis and R. tangensis); a complete lateral line with 25-26 pored scales (vs incomplete with 6-7 pored scales in R. brevidorsalis); 5-7 outer premaxillary teeth with 5 cusps in the upper jaw, iii unbranched and 18-19 [exceptionally 17 (1 specimen)] branched anal-fin rays, and the lack of a black spot on the dorsal-fin tip [vs. 4 (exceptionally 6) outer premaxillary teeth with 3-5 cusps; iii unbranched and 13-17 branched anal-fin rays, and a black spot on the dorsal-fin tip in R. septentrionalis].
Rhabdalestes yokai is morphologically closest to R. septentrionalis. Poll (1967) mentioned 4-6 outer premaxillary teeth for the species. According to Paugy (1990b), Paugy (2003) and Paugy & Schaefer (2007), R. septentrionalis has 4 outer premaxillary teeth with 3-5 cusps, iii unbranched and 13-17 branched anal-fin rays and a characteristic black spot at the tip of the dorsal fin. Our study confirms the observations of Paugy (1990b), Paugy (2003) and Paugy & Schaefer (2007) except for the outer premaxillary teeth of single specimen originating from Sierra Leone (MRAC 73-10-P-2105) with has 6 instead of the usual 4 outer premaxillary teeth.
Distribution
Rhabdalestes yokai is known from the type locality, the canal connecting Lake Itsotso with the Louna River, left bank of the Louna River, right bank affluent of the Léfini River, and sub-affluent of the right bank of the Congo River basin (Republic of Congo). In addition, a single sample confirms its presence in the Sangha River basin (Central African Republic). Based on these records, the species seems to be endemic to the Congo River basin (see also Faunafri).
IUCN assessment
Not evaluated
Bibliography
