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476
Accepted by E. Hilton: 29 Jan. 2016; published: 2 Jun. 2016
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN
1175-5334
(online edition)
Copyright © 2016 Magnolia Press
Zootaxa 4117 (4): 476
–
490
http://www.mapress.com/j/zt/
Article
http://doi.org/10.11646/zootaxa.4117.4.2
http://zoobank.org/urn:lsid:zoobank.org:pub:6943CE4D-B56A-487D-AFC5-23537D265E9D
Description of two new Bathyaethiops species (Teleostei: Alestidae)
from the Congo basin
TIMO MORITZ
1,2
& ULRICH K. SCHLIEWEN
3
1
Deutsches Meeresmuseum, Katharinenberg 14-20, 18437 Stralsund, Germany
2
Institute of Systematic Zoology and Evolutionary Biology, Friedrich-Schiller-University Jena, Erbertstr. 1, 07743 Jena, Germany.
E-mail: timo.moritz@meeresmuseum.de
3
SNSB-Bavarian State Collection of Zoology (ZSM), Münchhausenstr. 21, 81247 München, Germany. E-mail: schliewen@zsm.mwn.de
Abstract
Two new species of Bathyaethiops (Teleostei: Characiformes: Alestidae) are described. Bathyaethiops baka n. sp. is a
dwarf species with the largest known specimen being only 24.4 mm SL. The species is characterized by an incomplete
squamation and a large humeral spot. Bathyaethiops baka n. sp. is known so far only from the Ngoko River of Southeast-
ern Cameroon, a tributary of the Sangha River in the northern Congo basin. The second species, Bathyaethiops flammeus
n. sp., shows a diagnostic spot in front of the dorsal-fin base, which is devoid of melanophores and bright red in life. The
species is described from the Bakéré River at Yambula-Bakéré, a locality north-west of Kisangani in the Central Congo
basin. Other records of Bathyaethiops flammeus n. sp. from the Tshuapa respectively Ruki River at Boende and Eala, Cen-
tral Congo basin, suggests a wider geographic distribution. A key to all species of Bathyaethiops is provided.
Key words: Characiformes, new species, Petersiini, Bathyaethiops baka, Bathyaethiops flammeus
Introduction
Within the African endemic family Alestidae 114 species are presently recognized (Eschmeyer & Fong, 2016).
Morphological (Vari, 1979; Zanata & Vari, 2005) and molecular studies (Calcagnotto et al., 2005; Hubert et al.,
2005a,b) have provided evidence affirming their monophyly within the Characiformes. The interrelationships
within the family Alestidae remain, however, vaguely identified. A first subdivision of Alestidae into
Hydrocyninae and Alestidae (Roberts, 1969; Géry, 1977) had to be abandoned after the studies of Vari (1979) and
Brewster (1986) placing Hydrocynus close to Alestes. Also the presently used divisions sensu Poll (1967) of
Alestini, i.e. the medium sized to large species, and Petersiini, i.e. the smaller about 60 species (Schaefer, 2007),
have to be regarded as preliminary. Neither morphological (Zanata & Vari, 2005), nor molecular studies
(Calcagnotto et al., 2005; Hubert et al., 2005a) support this view, but also do not provide any stable alternative.
Several alestid genera lack clear delimitations. In particular, the genera of the Petersiini sensu Poll (1967) are
often poorly defined and their current taxonomy is in a state of permanent flux (Géry 1995, 1996; Stiassny &
Schaefer, 2005; Schaefer, 2007). Bathyaethiops caudomaculatus (Pellegrin, 1925), for example, has been variously
assigned to Micralestes, Hemigrammalestes, Alestopetersius (Microlepidalestes), Phenacogrammus
(Microlepidalestes), Phenacogrammus and Bathyaethiops. Other species currently placed in Brachypetersius, such
as B. altus (Boulenger, 1899) and B. cadwaladeri (Fowler, 1930), have also occasionally been included in the
genus Bathyaethiops (see Paugy, 1984). However, despite the original description of Bathyaethiops (Fowler, 1949)
and the generic revision of small alestids by Poll (1967) an operational diagnosis for Bathyaethiops is currently
unavailable. Poll´s (1967) differentiation of Bathyaethiops from Brachypetersius is not operational, because
according to his key Bathyaethiops can be distinguished from Brachypetersius by its incomplete lateral line, but he
stated in the generic diagnosis that the lateral line may be complete or not. In all other characteristics the two
genera greatly overlap. Géry (1995, 1996) consequently synonymized Bathyaethiops, together with
MORITZ & SCHL IEWEN
477
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Zootaxa 4117 (4) © 2016 Magnolia Press
Brachypetersius and Nannopetersius, with Phenacogrammus (s.l.). Even within Bathyaethiops (s.s.) genus level
differentiation remains questionable as, e.g., B. atercrinis Mamonekene & Stiassny, 2012, appears to be strongly
differentiated from all other Bathyaethiops species based on scale counts and color pattern. On the other hand,
Brachypetersius altus could be discussed as a member of Bathyaethiops based on molecular data (Arroyave &
Stiassny, 2011). Being aware of all these shortcomings, we will stick to Poll’s (1967) genera of ‘Petersiini’ for
practical purposes, as recently done by Stiassny & Schaefer (2005) for Micralestes, when describing a new alestid
species below. Following Poll (1967), summarized in an overview table by Paugy (1970), only three genera of
Petersiini may show a humeral spot and at the same time a caudal peduncle spot: Alestopetersius, Brachypetersius
and Bathyaethiops. Referring to the type species of these genera the herein described species resemble most closely
Bathyaethiops greeni Fowler, 1949, and are therefore described within this genus. Nevertheless, nomenclatural
changes may occur in the near future as phylogenetic studies may hopefully propose well founded hypotheses of
relationships and genus delimitations of Petersiini taxa.
Material and methods
Collections of small fishes were made mainly using a small seine (2 x 1.2 m; 4 mm mesh size) or fine-meshed (1
mm) hoopnets. To record live coloration photographs were made in aquaria shortly after capture. Specimens were
anaesthetized with benzocaine before fixing in 4 % formalin. Measurements were taken with a digital caliper (CD-
20DCX Absolute Digimatic, Mitutoyo) to the nearest 0.1 mm. Head length (HL), standard length (SL) and total
length (TL) were taken as measurements parallel to the body axis, corresponding to the measurements of a larger
fish specimen placed on a ruler or fish measuring board. Body depth was taken at origin of dorsal fin and head
depth at the level of mid-eye. All other distances were measured point to point, i.e. the tips of the caliper touch each
respective point. Pre-fin lengths are all from the tip of snout to the respective fin origin; the distance from dorsal fin
to adipose fin from the caudal insertion of the dorsal fin to the anterior insertion of the adipose fin. The longest fin
ray of the investigated species is the last unbranched in the dorsal fin and the first branched of the anal fin.
Fin rays were counted under a stereo-miscroscope LEICA Mz75. The two last rays in the anal-fin articulating
together on the last pterygiophore were counted as a single ray. Caudal-fin ray counts report upper procurrent +
upper principal + lower principal + lower procurrent rays; the first unbranched ray of the dorsal and ventral lobe is
counted as a principal ray. Vertebral counts were taken from radiographs, included the four vertebrae of the
Weberian apparatus and treat the ural complex as a single element. When the lateral line is incomplete, the scale
count continues along the respective row resulting in scales in ‘supposed lateral line’, which does not necessarily
equal the longitudinal series, because in Bathyaethiops the lateral line is not running straight from the gill opening
to the tail base. Along incomplete lateral lines sometimes additional pored scales are present in the posterior part of
the body; these were not added to the count.
Selected specimens were cleared and double stained following the protocol of Dingerkus & Uhler (1977) and
Taylor & van Dyke (1985). Drawings of dentition were made from dissected jaws of cleared and stained
specimens. The following abbreviations are used in the text: c&s—cleared and double stained; AMNH—American
Museum of Natural History, New York; ANSP—Academy of Natural Sciences, Philadelphia; DMM—Deutsches
Meeresmuseum, Stralsund; MRAC—Africamuseum, Tervuren; ZSM—Bavarian State Collection of Zoology,
Munich.
Bathyaethiops baka, new species
Dwarf Moon Tetra
(Figs. 1
–
2; Tables 1
–
2)
Type material. Holotype: ZSM 43939, 24.1 mm SL, male; Cameroon, Moloundou province: Ngoko River
between Chûte de Cholet and Chûte de Nki (N 02°19’10’’, E 14°28’15’’); coll: J. Schwarzer & T. Moritz,
10.02.2008.
Paratypes (n=15): DMM IE/9789, 2 specimens, 20.5
–
23.2 mm SL, same data as holotype; ZSM 38450, 1
specimen, 23.0 mm SL, same data as holotype; AMNH 265019, 3 specimens, 19.8
–
21.2 mm SL, Cameroon,
Zootaxa 4117 (4) © 2016 Magnolia Press
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478
DESCRIPTION OF TWO NEW BATHYAE THIOPS
Moloundou province: Ngoko River below Chûte de Nki; coll. J. Schwarzer & T. Moritz, 09.02.2008; ZSM 43940,
3 specimens, 20.3
–
21.6 mm SL, Cameroon, Moloundou province: Ngoko River below Chûte de Nki; coll. J.
Schwarzer & T. Moritz, 09.02.2008; ZSM 38454, 1 specimen, 22.1 mm SL, Cameroon, Moloundou province:
Ngoko River at Ndongo (N 02°06’40’’, E 14°52’42’’); coll. J. Schwarzer & T. Moritz, 04.02.2008; MRAC B5-023-
P-0004-0006, 3 specimens, 21.5
–
23.7 mm SL Cameroon, Moloundou province: Ngoko River at Ndongo (N
02°06’40’’, E 14°52’42’’); coll. J. Schwarzer & T. Moritz, 05.02.2008; ZSM 43941, 2 specimens, 23.3
–
24.4 mm
SL, Cameroon, Moloundou province: Ngoko River at Ndongo (N 02°06’40’’, E 14°52’42’’); coll. J. Schwarzer &
T. Moritz, 05.02.2008.
Additional material. ZSM 38453, 6 specimens, same data as holotype; ZSM 38456, 3 specimens, Cameroon,
Moloundou province: Ngoko River at Ndongo; coll. J. Schwarzer & T. Moritz, 03.02.2008 ZSM 43942, 6
specimens, Cameroon, Moloundou province: Ngoko River at Ndongo; coll. J. Schwarzer & T. Moritz, 05.02.2008;
ZSM 43943, 15 specimens, Cameroon, Moloundou province: Ngoko River at Ndongo; coll. J. Schwarzer & T.
Moritz, 08.02.2008; ZSM 43944, 8 specimens, Cameroon, Moloundou province: Ngoko River below Chûte de
Nki; coll. J. Schwarzer & T. Moritz, 09.02.2008; DMM IE/9792, 1 c&s, Cameroon, Moloundou province: Ngoko
River below Chûte de Nki; coll. J. Schwarzer & T. Moritz, 09.02.2008;
Differential diagnosis. Distinguished from all congeners by an incomplete squamation with the scale cover
variably reduced to no pre-dorsal scales, usually no scales on caudal peduncle, and usually a scale-free patch on
middle flank at about level of pelvic-fin origin. Furthermore distinguished by a unique color pattern, i.e., a
combination of a humeral spot of about pupil-size and the absence of dark vertical bars along midlateral flanks.
Difficult to distinguish from juvenile B. caudomaculatus, from which the new species differs by the (usually)
absence of unicuspid teeth in the second row of lower jaws (vs. presence), and (usually) the absent or rudimentary
supraneural between two neural spines directly in front of the first dorsal fin pterygiophore (vs. well developed).
Description. Based on holotype and 15 paratypes. For general appearance refer to Figs. 1 and 2.
Measurements and meristics summarized in Tables 1 and 2. A comparatively small species, maximum size 24.4
mm SL. Body laterally compressed, slightly elevated. Dorsal fin originating midway along body; pelvic fins
originating slightly in front of dorsal fin; anal fin originating approximately at level of end of dorsal-fin base;
adipose fin originating at level of caudal end of anal-fin base, positioned closer to caudal than to dorsal fin. Scale
cover variably reduced: no pre-dorsal scales; usually no scales on caudal peduncle; usually a scale free patch on
middle of flank at level of pelvic-fin origin. Number of pored scales in lateral line variable (0
–
9); lateral line never
complete.
FIGURE 1. Bathyaethiops baka sp. nov., holotype, ZSM 43939; 24.1 mm SL; Ngoko River below Nki falls; Cameroon.
Premaxilla with two teeth in outer row, each with three major and two minor cusps and four teeth in inner row
with four cusps in the first, six cusps in the second and third, and seven cusps in the last tooth (Fig. 3). Dentary with
four teeth in outer row, each with six cusps, except the last with only five cusps (Fig. 3); an inner single
monocuspid tooth usually absent (where it was possible to check this character without damaging the specimen
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only 2 out of 12 had inner monocuspid teeth). Anal fin convex in males (Figs 1, 2), but almost straight in females
and juveniles. Pectoral fin with 12 rays with dorsalmost and ventralmost rays unbranched. Pelvic fin with 8 rays,
with first and last rays unbranched. 2 hypurals in lower lobe and 4 hypurals in upper lobe; 3 epurals; small cartilage
present in front of anterior-most haemal spine. Other fin and vertebrae counts presented in Table 2. Supraneural
directly in front of first pterygiophore of dorsal fin reduced in size or absent.
This species seems to be a dwarf species within the genus Bathyaethiops. Juveniles of this species and juvenile
sympatric B. caudomaculatus are difficult to differentiate.
FIGURE 2. Bathyaethiops baka sp. nov., live male directly after capture (08. February 2008) at Ngoko River below Nki falls;
Cameroon.
FIGURE 3. Dentition of Bathyaethiops baka sp. nov., non-type material, DMM IE/9792, 21.1 mm SL. A—single teeth in
distal view. B—jaws in occlusal view.
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DESCRIPTION OF TWO NEW BATHYAE THIOPS
TABLE 1. Morphometric characters for Bathyaethiops baka n. sp. from Ngoko River. Range, mean and SD (= standard
deviation) include paratypes (N=15) and holotype.
Coloration. In life (Fig. 2) body pale translucent; dorsal, adipose and caudal fin bright red; pelvic and anal fin
light orange to yellow; pectoral fin yellowish; upper quarter of iris orange; caudal peduncle on its dorsal and
ventral margin slightly red. A prominent humeral spot the size of the pupil or larger, and a slightly larger dark spot
on the caudal peduncle; the latter is bisected by a dark line along the midlateral line starting slightly in front of
dorsal-fin origin and terminating just distal to the caudal peduncle spot; never any vertical stripes or barring along
the midlateral line. Few melanophores in mid-dorsal line along the back starting on lower jaw and reaching caudal
peduncle; thin line of melanophores along anal-fin base; often an elevated line of melanophores proximal to the
anal-fin base; a dark bar at the end of the caudal peduncle. Melanophores densely set on posterior dorsal half of
head. In general, contrast and coloration more pronounced in mature males.
In preservative (Fig. 1) pale whitish to light brown; red, orange and yellow coloration absent. Melanophore
pattern as in preserved specimens, but spot on the caudal peduncle less pronounced and smaller, i.e. not reaching
the anal fin base; humeral spot more intensively colored but of same size.
Etymology. Named after the Baka people, the native hunter-gatherer tribe in Southeastern Cameroon, where
the species was found. A noun in aposition.
Distribution and habitat. The species is so far known from several localities along the Ngoko River, from
below the Nki falls to the village of Ndongo (Fig. 4
–
5). The Ngoko, called Dja River above the Nki falls, is a
tributary to the Sangha River, a major northern tributary of the Congo River. All specimens were caught in the main
river channel, usually in or close to riparian vegetation over a substrate of fine particles and organic material. Water
Morphometric characters Holotype Range Mean SD
Standard length (SL) in mm 24.1 19.8–24.4 24.4 -
in %SL
Body depth in front of dorsal fin 32.8 29.0–33.5 33.5 1.34
Head length (HL) 27.4 24.6–31.5 26.9 1.49
Pre-dorsal length 53.2 50.9–56.2 54.4 1.44
Pre-anal length 65.3 63.9–69.6 66.0 1.39
Pre-pectoral length 26.7 23.3–34.3 26.3 2.37
Pre-ventral length 47.9 43.3–50.7 47.6 2.14
Pre-adipose length 87.9 85.9–91.3 87.6 1.14
Distance dorsal fin to adipose fin 22.3 19.6–23.0 21.6 0.87
Dorsal fin base 13.5 11.4–13.6 12.4 0.53
Longest dorsal fin ray 29.2 24.2–32.0 29.4 1.92
Anal fin base 28.5 22.8–28.5 25.9 1.44
Longest anal fin ray 12.2 7.6–14.3 11.5 2.08
Caudal peduncle length (CPL) 9.9 6.4–10.2 8.6 1.09
Caudal peduncle depth (CPD) 9.2 7.6–11.1 9.25 0.95
in %HL
Snout length 19.1 15.0–24.7 19.0 2.18
Eye diameter 45.7 38.6–48.1 44.5 2.55
Postorbital length 29.5 28.6–36.0 31.8 2.20
Interorbital distance 31.8 27.7–38.7 32.1 2.78
Head width 48.7 41.2–53.7 48.4 3.13
Head height at eye 72.5 57.5–72.5 67.7 3.33
CPD in %CPD 107.2 58.2–126.1 94.4 17.45
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parameters from the Ngoko River at Ndongo taken on 04.02.2008 were: pH 7.08; conductivity 23 µS; temperature
27.5°C.
TABLE 2. Meristic characters of Bathyaethiops baka n. sp. -) one specimen showed an abnormal anal fin which was not
counted for branched rays in the respective fin.
FIGURE 4. Records of Bathyaethiops species; filled symbols—localities where specimens where checked by Mamoneke &
Stiassny (2012) or in the present study; symbol outlines—other records from MRAC database; T—type localities; star—B.
atercrinis, cross—B. baka, circle—B. caudomaculatus, inverse triangle—B. flammeus, triangle—B. greeni, , square—B.
breuseghemi.
Meristic character Holotype Paratypes (N=15)
Simple dorsal fin rays 3 2 (15)
Branched dorsal fin rays 8 8 (15)
Simple anal fin rays 3 3 (15)
Branched anal fin rays 21 18 (1); 19 (5); 20 (7); 21 (1); - (1)
Upper procurrent caudal fin rays 9 5 (1); 6 (5); 7 (5); 8 (4)
Upper principal caudal fin rays 10 10 (13); 11 (2)
Lower principal caudal fin rays 9 9 (14); 10 (1)
Lower procurrent caudal fin rays 7 5 (4); 6 (10); 7 (1)
Vertebrae 37 35 (1); 36 (11); 37 (3)
Abdominal vertebrae 16 16 (4); 17 (10); 18 (1)
Caudal vertebrae 21 19 (10); 20 (5)
Dorsal fin inserting after vertebra 10 10 (10); 11 (5)
Anal fin inserting after vertebra 17 17 (10); 18 (5)
Supraneurals 6 6 (7); 7 (7); 8 (1);
Pored scales in LL* 5 0 (1); 5 (6); 6 (5); 7 (2); 9 (1)
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DESCRIPTION OF TWO NEW BATHYAE THIOPS
FIGURE 5. Ngoko River between Nki falls and Ndongo (approx. N 02°04’23’’, E 14°49’52’’); Cameroon.
Bathyaethiops flammeus, new species
Red-back Moon Tetra
(Figs. 6
–
8, Tables 3
–
4)
Type material. Holotype: ZSM 43945, 39.1 mm SL, female; Democratic Republic of Congo, Province Orientale:
Bakéré river at Yambula-Bakere (N 01°42’41’’, E 23°43’24’’); coll: U. Schliewen, J. Schwarzer & P.B. Mongindo,
19.07.2009.
Paratypes (n=22): ZSM 39295, 13 specimens, 24.5
–
39.9 mm SL, same data as holotype; AMNH 265018, 3
specimens, 29.4
–
32.3 mm SL, same data as holotype; DMM IE/9790, 2 specimens, 29.9
–
31.8 mm SL, same data as
holotype; DMM IE/9791, 1 c&s, 34.1 mm SL, same data as holotype; MRAC B5-023-P-0001-0003, 3 specimens,
30.5
–
36.3 mm SL, same data as holotype.
Additional material. MRAC 177882
–
889, 8 specimens, 26.7-42.3 mm SL; Democratic Republic of Congo,
Boende (S 0°14’, E 20°50’); coll. P. Brichard, 1969; ZSM A-0649, 3 specimens, 25.2–27.8 mm SL; Democratic
Republic of Congo, Ruki River (= lower Tshuapa River), Eala (close to Mbandaka); coll. Dr. Kiss, 17.11.1981.
Differential diagnosis. Distinguished from all congeners by the presence of a spot lacking melanophores (red
in life, white in preservation), located in front of the dorsal fin.
Description. Based on holotype and 22 paratypes augmented with data from 11 non-type specimens. For
general appearance refer to Figs. 5
–
7. Measurements are summarized in Tables 3
–
4 for type and non-type
specimens. Body laterally compressed, moderately elevated, maximum size 42 mm SL. Dorsal fin originating at
midbody; pelvic fins originating slightly in front of dorsal fin; anal fin originating at level of, or slightly caudal to,
end of dorsal-fin base. Scale cover complete; lateral line usually incomplete, but complete in a few specimens;
when incomplete, number of pored scales in anterior section variable, 5
–
16 (5
–
14 on type locality); sometimes
pored scales also present posteriorly after an interruption of varying extent. 7
–
10 pre-dorsal scales, but without
scales immediately in front of dorsal-fin origin.
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FIGURE 6. Bathyaethiops flammeus sp. nov., holotype, ZSM 43945; 39.1 mm SL.
FIGURE 7. Bathyaethiops flammeus sp. nov., live female directly after capture (05. August 2009) at Yambula-Bakéré,
Democratic Republic of Congo.
Premaxilla with two teeth in outer row, first with tree and second with five cusps, and four teeth in inner row
with four to five cusps on first, seven cusps on second and third and five cusps on last tooth (Fig. 9). Dentary with
four teeth in outer row with seven cusps on second, six cusps on first and third, and four cusps on last tooth; an
inner single monocuspid tooth close to symphysis present (Fig. 9). Anal fin enlarged and convex in mature males,
more or less straight in females and juveniles. Pectoral fin with 11
–
12 rays; pelvic fin with 9 rays. 2 hypurals in
lower lobe and 4 hypurals in upper lobe; 3 epurals; small cartilage present in front of anterior-most haemal spine.
Other fin and vertebrae counts presented in Table 4. Supraneural directly in front of the first dorsal pterygiophore
well developed or sometimes completely absent (well developed in all specimens from Boende and Eala).
Coloration. In life (Fig. 7) body silvery, slightly translucent; anterior half of dorsal fin and the melanophore-
free area in front of dorsal fin bright red; rest of dorsal fin, adipose fin and caudal fin grey; pectoral, pelvic and anal
fin transparent; anterior distal part of anal fin black marked in males; upper half of adipose fin black in most
specimens. A prominent dark humeral spot smaller than pupil and an extensive black blotch on the caudal
peduncle; the latter is bisected by a dark line along the horizontal septum starting slightly behind humeral spot and
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484
DESCRIPTION OF TWO NEW BATHYAE THIOPS
continuing to the end of the caudal peduncle (this line is faint on the caudal peduncle of specimens from Boende);
about 9 (7
–
9 in Boende, 10 in Eala) more or less regular vertical bars along the horizontal line with most bars
located dorsally from the level of midbody. A dark line from the lower jaw over along the mid-dorsal line on the
back to the end of caudal peduncle dark, with a prominent spot free of any melanophores in front of dorsal-fin base;
base of anal fin darkly pigmented, more prominent anteriorly; a prominent dark bar on the end of the caudal
peduncle broadened medially (less expressed in specimens from Boende and Eala); distal edge of adipose fin often
black or dark grey, rest of fin slightly grey or colourless (black edge in all specimens from Boende; colourless in all
specimens from Eala). Melanophores densely set on upper half of skull. Data on life coloration of specimens from
Boende and Eala unavailable.
FIGURE 8. Bathyaethiops flammeus MRAC 177882-889, specimen number 3; 36.9 mm SL, from Boende, Democratic
Republic of Congo.
FIGURE 9. Dentition of Bathyaethiops flammeus sp. nov., paratype, DMM IE/9791, 34.1 mm SL. A—single teeth in distal
view. B—jaws in occlusal view.
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Zootaxa 4117 (4) © 2016 Magnolia Press
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486
DESCRIPTION OF TWO NEW BATHYAE THIOPS
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MORITZ & SCHL IEWEN
487
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In preservative (Fig. 6, 8) pale yellow to brownish, all prominent red coloration vanished; the melanophore
free spot in front of the dorsal fin appears clear white; upper half of flank darker. Melanophore pattern less
pronounced, but better visible as in life specimens; black mid-dorsal line less prominent; black mark along anal-fin
base well visible in anterior part as in posterior part, where it is sometimes missing; this line (in contrast to life) not
confluent with blotch on caudal peduncle.
Etymology. From the Latin flammeus for bright red or burning, referring to the bright red spot on nape in front
of dorsal fin. An adjective.
Distribution and habitat. Type locality: Bakéré River at Yambula-Bakéré, Province Orientale, Democratic
Republic of Congo (Fig. 4), a large blackwater rainforest stream with no aquatic vegetation and sandy soil
northwest of Kisangani directly entering the Congo River. Additional specimens were collected in 1969 in the
Tshuapa River at Boende, and 1981 from the Ruki River (the name of the lower Tshuapa River after it has united
with the Momboyo River) at Eala, both in the Democratic Republic of Congo. For these collections no additional
data is available.
Remark. The specimens collected at Boende are clearly distinguishable from the type series, e.g., by scale
counts. However, because the three specimens from Eala appear somewhat intermediate, e.g. in having 33
–
34
scales in supposed lateral line (vs. 33
–
36 in Yambula-Bakéré and 36
–
41 in Boende) 7.5 scales between lateral line
and dorsal fin (vs. 6.5 in Yambula-Bakéré and 7.5
–
8.5 in Boende) and 14
–
16 scales around caudal peduncle (vs. 12
in Yambula-Bakéré and 13
–
18 in Bakéré), we conservatively interpret these differences as geographical variation
and consider these geographically disparate populations as conspecifics rather than being separate species.
Discussion
Bathyaethiops baka appears to be a dwarf species within the genus. Based on the present data the species fits the
definition of Weitzman & Vari (1988) for miniaturized fishes, i.e. sexually maturity is attained below 20 mm SL or
SL not exceeding 26 mm. Furthermore, it shows some reductive characters which may be interpreted as results of
miniaturization, especially the reduction in squamation, the lack or reduction of the last supraneural, and the lack of
monocuspid teeth as a second row in the lower jaw. The miniaturization process, however, has not led to major
reductions or special characters. It is possible that if larger specimens of B. baka may exclude the species from
being considered a miniature species in the future, but presently is has to be added to list of African miniature fish
species presented by Conway & Moritz (2006) as the second alestid species.
One of the best characters to distinguish most Bathyaethiops species from each other appears to be their
melanophore patterning (Fig. 10), which is clearly visible in most preserved specimens. Vertical bars along a
horizontal line characterize B. greeni Fowler, 1949, B. flammeus and may be present in B. caudomaculatus,
although specimens without bars are also known for this taxon. Within this barred species complex only B.
flammeus has a melanophore free spot in front of the dorsal fin base. In B. greeni the humeral spot is much more
pronounced than in B. caudomaculatus, if in the latter a spot is present at all. B. caudomaculatus appears to be the
most variable species with regard to the degree of color patterns like bars and spots: from present to faint or even
absent, except for the caudal peduncle spot, which is always present. The holotype of this species exhibits clearly
visible bars, as well as a humeral and caudal peduncle spot. Species without bars are B. breuseghemi Poll, 1945, B.
baka, B. atercrinis and, in part, B. caudomaculatus. Bathyaethiops baka is the only one having a humeral spot
larger than its pupil. Bathyaethiops atercrinis has no well-defined humeral spot, but rather a faint humeral stripe. In
the latter species the blotch on the caudal peduncle is large and extends on the anal fin. In B. breuseghemi the
blotch on the caudal peduncle is almost rectangular and hardly extending above the midlateral level; its humeral
spot is very small and, following Poll (1967), it may be even absent. Several of these coloration patterns have been
used to prepare a key for the species of Bathyaethiops below.
Géry (1996) noted that B. caudomaculatus and B. breuseghemi share the same meristics and might represent
‘geographical forms’ (Géry, 1996, p. 9) of the same species, as they are distinguished only by color pattern.
Presently, however, until more materials from more localities are available, it appears premature to synonymize
them. On the other hand we found meristic differences, i.e. in scale counts, which clearly allow distinguishing two
lots of B. flammeus. As their color pattern equals each other and the three specimens from Eala show intermediate
meristic counts, we refrain from describing them as a separate species, but conclude that this species exhibits
substantial geographic variation in meristic data.
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DESCRIPTION OF TWO NEW BATHYAE THIOPS
FIGURE 10. Pigmentation pattern (only melanophores) of species presently recognized in the genus Bathyaethiops. A—B.
flammeus (type locality); B—B. flammeus (Boende); C—B. caudomaculatus (strong pigmentation); D—B. greeni;E—B.
caudomaculatus (weak pigmentation); F—B. breusenghemi; G—B. baka; H—B. atercrinis.
Key to the species presently recognized in the genus Bathyaethiops
1 4.5 scale rows between lateral line and dorsal fin; 2.5 scale rows between lateral line and ventral fins; squamation always
complete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. atercrinis
- 6.5 or more scales between lateral line and dorsal fin; 3.5 scale rows or more between lateral line and ventral fins; or
squamation incomplete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 A spot free of any melanophores (red in life, white in preserved specimens) directly in front of dorsal fin.. . . . . . .B. flammeus
- No such spot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 Humeral spot only slightly smaller as the dark spot on the caudal peduncle; squamation on flanks incomplete; lateral line
MORITZ & SCHL IEWEN
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incomplete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B. baka
- Humeral spot significantly smaller than the dark spot on the caudal peduncle; squamation on flanks complete; lateral line
complete or incomplete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4 Dark spot on the caudal peduncle more or less rectangular and horizontally elongated hardly extending above midlateral level.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B. breuseghemi
- Dark spot on the caudal peduncle round or irregular with one third or more positioned above midlateral level. . . . . . . . . . . . . 5
5 6.5 scales between lateral line and dorsal fin; humeral spot smaller than ½ of the pupil (or even absent); caudal peduncle spot
horizontally elongated with a more or less irregular outline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B. caudomaculatus
- (7.5) 8.5 scales between lateral line and dorsal fin; humeral spot ¾ of the pupil or more; caudal peduncle spot about as high as
wide and more or less rounded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B. greeni
Common names. As common names for the new described species are proposed herein, suggestions of common
names of the other Bathyaethiops species are given: B. caudomaculatus—African Moon Tetra; B. breuseghemi—
Rectangle Spot Moon Tetra; B. greeni—Green’s Moon Tetra and B. atercrinis—Black Fin Moon Tetra.
Comparative material studied
Bathyaethiops breuseghemi: MRAC 59191, holotype, affluent of Luembe River west of Kakonge (Kasai); MRAC
59192.204 part, 5 paratypes (Nr. 9, 10, 15, 16, 17), same data as holotype; MNHN 2009-0152, 44 specimens,
Nome river about 35 km West of Bangassou;
Bathyaethiops caudomaculatus: MNHN-1925-0128, holotype, Sangha River at Ouesso, Democratic Republic of
Congo; MRAC 102196-102209, 14 specimens, Lilanda river, Yangola; MRAC 119014-053, part of 13
specimens, Stanley Pool, Democratic Republic of Congo; MRAC 87-42-P-145-149, 4 specimens, Lusa river,
affluent of Zaire, on route km 92 between Kisangani and Ubundu; MRAC 87-42-P-171-211, 41 specimens,
Uluko river, affluent of Zaire, on route km 73 between Kisangani and Ubundu; MRAC 88-25-P-1043, 1
spceimen, Aketi at Kagola river, affluent of Itimbiri river; ZSM 36772, 15 specimens, Ngoko River below
Chûte de Nki, Cameroon; ZSM 36825, 2 specimens, Ngoko River below Chûte de Nki, Cameroon; ZSM
36890, 1 specimen, Ngoko River below Chûte de Nki, Cameroon; ZSM 37026, 3 specimens, Ngoko River
between Chûte de Nki and Chûte de Cholet, Cameroon; ZSM 37850, 4 specimens, Congo river at Yalala rapid,
Province Bas Congo; DMM IE/9794 , 5 specimens, Cameroon, Moloundou province: Ngoko River between
Chûte de Cholet and Chûte de Nki [10.02.2008].
Bathyaethiops greeni (photographs and x-rays): ANSP 71877, holotype, Oka, north of Eovo, Lembesse river,
French Equatorial Africa; ANSP 94719, 4 paratypes, same data as holotype: ZSM 29644, 2 specimens, Lokoro
River close to Lui Kotale, Bandundu Province, Democratic Republic of Congo.
Brachypetersius altus: ZSM 29640, 2 specimens, Lokoro River close to Lui Kotale, Bandundu Province, DRC;
Acknowledgements
We would like to thank for facilitation of fieldwork in Cameroon during fish inventory work for the Djengi Project
(WWF, gtz), in particular L. Usongo and Solospierre Mbakwa (Bamenda); in DRC, U. Ali-Patho, P. B. Mongindo
& Kadange Theophile (UniKis). Further thanks go to J. Schwarzer for help in field work, to Mark Sabaj Pérez for
providing images and x-rays of B. greeni type material and to Miguël Parrent for preparing loan of specimens from
MRAC, Patrice Pruvost and Romaine Causse for preparing the loan of specimens from MNHN, and Dirk Neumann
for collection management at ZSM. Two anonymous reviewers made important and constructive suggestions to
improve the first version of the manuscript.
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