Bryconaethiops
Bryconaethiops Günther, 1873
The species of this genus are characterised by the presence of three rows of premaxillary teeth, a feature that readily distinguishes them from all other African Alestids. Eye covered with a very well developed adipose eyelid. All species exhibit pronounced sexual dimorphism affecting the shape of the anal fin. Adult males also have the first dorsal fin rays filamentous.
Synonyms
Brachyaletes Günther, 1874 (partim)
Type species:
Bryconaethiops microstoma Günther, 1873 by monotypy.
Currently, five species are assigned to the genus Bryconaethios.
Key to species.
1 5½ scales in transverse row between lateral line and dorsal fin origin.............................B. quinquesquamae
6½-7½ scales in transverse row between lateral line and dorsal fin origin....................................................2
2 10 scales around the caudal peduncle.....................................................................................B. macrops
12 scales around the caudal peduncle.....................................................................................................3
3 A large black spot below dorsal fin origin and a black stripe along posterior part of the flanks....B. boulengeri
A slight black lateral stripe extending from gill cover to the caudal fin.........................................................4
4 20-25 total gill rakers on first arch (11-13/1/8-12)..........................................................................B. yseuxi
28-40 total gill rakers on first arch (15-21/1/12-18)...............................................................B. microstoma
Bryconaethiops: morphological characters
Bryconaethiops: meristic characters.
Bibliography
Bryconaethiops boulengeri Pellegrin, 1900
Type and type locality
Bryconaethiops boulengeri Pellegrin, 1900: 101. Type locality: “Adouma (Ogôoué)”, type MNHN n° 85.356.
Synonyms
Bryconaethiops boulengeri Pellegrin, 1900
Bryconaethiops microstoma var. boulengeri Pellegrin, 1906
Common names
Finnish: Huutomerkkitetra (Finland)
German: Rufzeichensalmler (Germany)
Kele: Itotombe/Lotombe (Democratic Republic of Congo)
Lombo: Lotombe (Democratic Republic of Congo)
So: Lotombe (Democratic Republic of Congo)
Description
Diagnosis: the body is more or less elongated. The eyes are large and have a strong adipose eyelid covering their major part in front and at the back. Dorsal fin is filamentous in male; located well in front of pelvic-fin insertion. The forked caudal fin has two equal sharp lobes. The small mouth has three rows of teeth located on equal jaws. Males' fins show a sexual dimorphism. The scales are similar all over the body.
Maximum reported size: 140 mm TL and 250 mm TL.
Colour: dorsum often darker than the body, sometimes greenish or brownish. The belly is paler with a whitish or yellowish coloration. A few scattered stripes and blotches are found on body surface. There is an oval-shaped blotch on the antero-posterior axis of the body, above pectoral fins, as a pedunculary blotch getting thinner at the back. In males, pelvic fins, caudal fin as anterior rays of the dorsal fin and anal fin base are brown or red.
Diet
In the Djiri River, Congo River basin (Mikia et al., 2018), food items found in the stomachs of fish one spread over animal and plant fractions. Animal fraction contains 17 items divided into six classes: insects, arachnids, shellfish, nematodes, fish, birds feathers. The fraction consists in plant leaf, fruit and stems of dicotyledonous. The classification of preys by calculating the preponderance index (Ip) has classified insects (90.19%) in the category of main prey and macrophytes (8.17%) as accidental prey.
Bryconaethiops boulengeri: composition of diet in Djiri River Oc = % occurrence; % P = weight percentage; Ip = preponderance index.
The study of diet depending on the hydrological season shows no significant difference between the dry season and the rainy season, as welle as there is no significant variation in diet among the three sampling stations. Furthermore, no significant difference was observed between individuals of different size.
Habitat
B. boulengeri is a pelagic species. It inhabits riverine biotopes.
Distribution
B. boulengeri occurs all over the Congolese basin including Lake Tanganyika basins. The type locality is from the Ogowe River, however it is probable that this type locality is not correct (see also Faunafri).
The species is widespread or without major threats throughout central Africa and is assessed as Least Concern.
Major threats: none known.
Bibliography
Bryconaethiops macrops Boulenger, 1920
Type and type locality
Bryconaethiops macrops Boulenger, 1920: 5. Type locality: “Bafwasende, Avakubi, Basabangi and Fungi”, holotype BMNH n° 1919.9.10:100
Common names
Estonian: Suursilm-vimpelsalmler
Finnish: Maskitetra
German: Masken-Großaugensalmler
Kele: Itotombe/Lotombe (Democratic Republic of Congo)
Lombo: Lotombe (Democratic Republic of Congo)
So: Lotombe (Democratic Republic of Congo)
Description
Diagnosis: body more or less slender. Adult males have dorsal fin rays filamentous; dorsal fin origin distinctly in front of pelvic fin insertion. The forked caudal fin has two rounded lobes. Scales are similar all over the body. The small mouth has three rows of premaxillary teeth on the upper jaw. Jaws are equivalent in size. Anal fin branched rays 16-19. Gill rakers on lower limb of first arch 17-19. Scale counts, 6½-7½ between lateral line and dorsal-fin origin, 10 around caudal peduncle, and 33-36 in lateral line. Eye diameter/head length 35.6-50%.
Maximum reported size: 120 mm SL.
Colour: back is generally dark green, belly is lighter and whitish.
Distribution
B. macrops occurs in Congo basin, included Ubangi and Sangha, but records from the Lower Congo River need confirmation. It is found I the Lower Guinea region in the Ntem, Como and Ogowe River basins (see also Faunafri).
The species is widespread or without major threats throughout central Africa and is assessed as Least Concern.
Major threats: no information available.
Bibliography
Bryconaethiops microstoma Günther, 1873
Types and type localities
Bryconaethiops microstoma Günther, 1873: 143-144. Type locality: “Boma, Lower Congo”, syntypes BMNN n° 1873.7.28:25-26.
Brachyalestes mocquardianus Thominot, 1886: 167. Type locality: “San Benito”, holotype MNHN n° 85-428.
Synonyms
Bryconaethiops microstoma Günther, 1873
Bryconoethiops microstoma Sauvage, 1884
Brachyalestes mocquardianus Thominot, 1886
Bryconoethiops mocquardianus Pellegrin, 1900
Bryconaethiops microstoma var. mocquardiana Pellegrin, 1909
Bryconaethiops microstoma var. habereri Steindachner, 1914
Common names
Chokwe: Lutemba/Muka/Sese (Angola)
Estonian: Niituim/Niituim-vimpelsalmler
Finnish: Rihmatetra
German: Fadensalmler
Kele: Itotombe/Lotombe (Democratic Republic of Congo)
Lombo: Lotombe (Democratic Republic of Congo)
Luba-Kasai: Kusu (Angola)
Not specified: Akita/Ekira (Gabon)
So: Lotombe (Democratic Republic of Congo)
Description
Diagnosis: body is rather robust. Dorsal fin origin placed distinctly in front of pelvic fin insertion. The large caudal fin has two elongated and sharp lobes of which size is equivalent. The mouth has three rows of teeth at the upper jaw. Gill rakers on lower limb of first arch 11-19 and 14-15 on upper limb. Scale counts, 6½-7½ between lateral line and dorsal-fin origin, 12 around caudal peduncle, and 35-40 in lateral line.
Maximum reported size: 173 mm SL.
Colour: ground colour silvery. Back is dark green, belly is lighter and whitish. Fins whitish unpigmented.
Affinities: this species is closed to B. macrops. Nevertheless, the number of scales around the caudal peduncle is higher in B. microstoma (12 vs 10 in B. macrops) and the eye smaller (see table below).
Bryconaethiops species. Number of scales around the caudal peduncle (SPC); number of scales in transverse row between lateral line and dorsal fin origin (SS); number of lateral line scales (SLLt); eye diameter /head length (ED/HL); number of anal fin branched rays (AR).>
Distribution
B. microstoma occurres in lower and middle Congo basin and in Lake Kivu. In Lower Guinea it is found in the Nyong, Lobé (Lobi, Lobo), Ntem, Ogowe and Kouilou River basins and in the Nkomi lagoon (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 central and eastern Africa.
Major threats: water turbidity and siltation as a consequence of erosion and farming extension is a threat in east Africa.
Bibliography
Bryconaethiops quinquesquamae Teugels & Thys ven den Audenaerde, 1990
Type and type locality
Bryconaethiops quinquesquamae Teugels & Thys van den Audenaerde, 1990: 208. Type locality: “Cross River near Mamfe town, 5°46'N, 9°17'E, Cameroon”, holotype MRAC n° 73.040.P.28, paratypes MRAC n° 73.029.P.934, 73.029.P.935 to 938, 73.040.P.30, 88.035.P.185 to 186.
Common names
Estonian: Nigeeria vimpelsalmler
Description
Diagnosis: body, more or less slender. Fins are non-filamentous: the first dorsal fin, righted, is widely spread. It is located very in front of pelvic-fin insertion. The second dorsal fin is vestigial. It is located at vertical through posterior base of the anal fin. The forked caudal fin is slightly marked and has two sub-equals lobes, generally rounded. The mouth is small and has three rows of premaxillary teeth arranged on equal jaws. Eyes are large-sized. Scale counts, 5½ between lateral line and dorsal fin origin, 3½ between lateral line and pelvic fin origin, 10 around caudal peduncle, and 33-36 in lateral line. Total gill rakers of first arch 15-20.
Maximum observed size: 110 mm SL.
Colour: live specimens are rather pale with a silvery lateral stripe (black in preserved specimens) extending from gill cover to base of caudal fin.
Distribution
B. quinquesquamae is found in Cross, Kienké (Kribi) and Lobé (Lobi, Lobo) River basins and in the Niger delta (see also Faunafri).
Although B. quinquesquamae has a limited distribution and is known from fewer than 10 localities, there are currently no major widespread threats, and therefore it has been listed as Least Concern. It has also been assessed as Least Concern for central Africa. In western Africa it has been assessed as Endangered as it is only known from three localities, and is subject to ongoing decline in quality of habitat due to oil exploration activities.
Major threats: potential threats might arise if the proposal for dredging the river Cross to improve navigation is successful. It is also threatened by oil exploration.
Bibliography
Bryconaethiops yseuxi Boulenger, 1899
Type and type locality
Bryconaethiops yseuxi Boulenger, 1899: 82-83. Type locality: “Upper Congo”, syntypes BMNN n° 1899.6.27:38.
Common names
Estonian: Kongo vimpelsalmler
B. yseuxi was synonymized, successively with B. microstoma and B. macrops, subsequently rehabilitated, and then again considered as a junior synonym of B. microstoma. B. yseuxi is now considered as a valid species (Ibala Zamba et al., 2007), easily distinguished from all other Bryconaethiops species by its small size (maximum: 72.2mm SL), 7½ rows of scales between the dorsal fin origin and the lateral line; 11–13/1/8–12 gill rakers on the first gill arch and long dorsal fin and anal fin bases, respectively, 15.7-17.6% of SL and 22.7-25.9% of SL.
Description
Diagnosis: B. yseuxi can be distinguished from all known Bryconaethiops species based on the following unique combination of characters: a high number of scale rows between anterior origin of dorsal finnand lateral line [7½ vs 6½ or less (exceptionnaly 7½) in other species]; a low number of gill rakers on the first gill arch [11-13/1/8-12 (total: 20-25) vs 13-21/1/12-18 (total: 26-40) in other species]; and long dorsal-fin and anal-fin bases (respectively 15.7-17.6% and 22.7-25.9% SL vs shorter, respectively 13.4-15.5% and 16.8-22.8% in other species).
Meristics and morphometrics of B. yseuxi are given in tables below.
Bryconaethiops yseuxi: main morphometric characters.
Bryconaethiops yseuxi: main meristic characters.
B. yseuxi is a small-sized species (maximum size 72.2 mm SL). A cleared specimen of 50.8 mm SL (MRAC 55237) had its skeleton already entirely ossified. Roberts & Stewart (1976) found a gravid female of only 47 mm SL. Body deep and somewhat laterally compressed. Morphologically B. yseuxi is closest to small-sized B. microstoma specimens in overall shape of the body and the fins. Nevertheless, B. yseuxi specimens are always deeper bodied than B. microstoma specimens of the same size. Mouth terminal; upper jaw with three rows of premaxillary teeth: external row composed of two small median teeth with a small lateral cusp at their outer side (exceptionally also an even smaller one at their inner side) (vs. monoscuspid teeth in other Bryconaethiops species); a median row with six or seven (mono-, bi- or tricuspid) teeth; and an inner row of eight pluricuspid teeth [three (median teeth) to seven cusps] with their cusp on a median row and without an anterior cusp or row of cusps as generally found in the other Bryconaethiops species. Lower jaw with an external series of six large pluricuspid teeth and an inner row of two median caniniform teeth. A bilateral asymmetric growth favouring the left side of the jaws was observed by Roberts & Stewart (1976). However, based on our observations we can not confirm this statement. There is a well-marked sexual dimorphism in the dorsal and anal fins. In males, all dorsal fin rays, except the first and the last two, are filamentously elongated and can attain up to 70.7 % SL. The distal border of the anal fin is straight in females, juveniles and immature specimens, but slightly convex anteriorly in males.
Maximum reported size: 72 mm SL.
Colour: head and body of live mature male specimens silvery with a pinkish hue on sides of body. Upper side of head green-olive. Humeral spot present but not well marked. Adipose fin whitish transparent, blackish at base. Anterior two-thirds of distal part of anal fin blackish; posterior third of distal part of anal fin transparent; distal part bordered by a whitish submarginal band; basal part of anal fin greyish-black, transparent. Pelvic fins greyish-black with a black distal border bordered by poorly delimited whitish submarginal band. Dorsal fin greyish-white, transparent with blackish filaments. Pectoral and caudal fins whitish transparent. Distal margin of caudal fin black; base of upper and lower caudal fin lobe blackish resulting in a bilobed spot at base. Live colour pattern of females not observed. After preservation, body yellowish-white; darker above lateral line with scales above lateral line faintly dark brown on their basal part. Contrast between body parts above and below lateral line seem to fade away after time. Fins whitish, transparent in overall appearance; humeral spot not well distinguishable, or even regularly absent. In most preserved males, anterior part of distal border of anal fin blackish and bordered submarginally by a whitish band. Pelvic fins dark with poorly delimited blackish distal border. Dorsal fin filaments blackish. Posterior margin of caudal fin black. In preserved female and juvenile specimens, all fins pale to transparent and without whitish band on anal fin. Sometimes anal-fin base partially bordered by a fine dark brown band.
Distribution
B. yseuxi is known only from the Lower Congo River basin, from Boma to Pool Malebo (formerly Stanley Pool) (Kinsuka, Kinshasa). The species is reported here for the first time from the Djoue´ River, a right bank affluent from the Lower Congo River.
B. yseuxi has been reported from the Dja River basin, Cameroon, by Boulenger (1916). However, these specimens (BMNH 1920-5-17:5–6) are B. microstoma. As already reported by Banister & Bailey (1979), the Bryconaethiops specimens from the Ituri Bridge (BMNH 1975.6.20:172–174), still catalogued as B. yseuxi, also belong to B. microstoma (see also Faunafri).
IUCN assessment
Not evaluated
Bibliography
