A review of the Distichodus antonii assemblage (Characiformes: Distichodontidae) from the Congo basin
Moelants, Tuur
Zebe, Victorine Mbadu
Snoeks, Jos
Vreven, Emmanuel
Journal of Natural History
2014
2014-03-03
48
27 - 28
1707
1735
36XLG
Nichols and Griscom, 1917
Nichols and Griscom
1917
[367,880,1630,1654]
Actinopterygii
Distichodontidae
Distichodus
Animalia
Characiformes
20
1726
Chordata
species
langi
Type material Holotype. AMNH 5915, Faradje, Dungu region( DRC) (± 3°44′ N, 29°43′ E) ( 364 mmSL). Note on the original description. Distichodus langihas been described by Nichols and Griscom in 1917 based on one typefrom Faradje and one other specimen with the same data. The current holotypehas a size of 364 mmSL ( 472 mmTL), which does not correspond to the 510 mmSL mentioned by Nichols and Griscom (1917). This latter SL should be considered a lapsus because after verification of the Lang and Chapin collection, no D. langispecimen of this size has been found. The other specimen mentioned in the original description is reported to measure 325 mmSL, but this also does not correspond to the size of the other specimen ( AMNH7010), which measures 250.7 mmSL, 299.0 mm TL. This specimen has been wrongfully assigned paratypestatus ( Eschmeyer 2013) (see ICZN 1999: article 72.4.6). It has been re-identified as D. fasciolatusin this review (see above). In the original description, the size of the illustrated specimen ( Nichols and Griscom 1917: plate LXIX) is mentioned as 560 mmTL, which corresponds to a recalculated standard length of 466 mmSL. This does not correspond to either of the two specimensmentioned by Nichols and Griscom (1917). In addition, the drawing does not resemble either of the two specimens. Based on the following counts and observations made on the illustration: 22 circumpeduncular scales; 13 scales between the LL and the dorsal fin, 24 dorsal fin rays and clearly black ventral fins, we assume this illustration represents a specimen from the D. atroventraliscomplex. Figure 8. Distichodus langi(MRAC 2878)from Avakubi (DRC), 300.0 mm SL. (A) Lateral view; (B) Detail of the colour pattern on the adipose fin. Other material examined MRAC 2878, Avakubi( DRC) ( 1°19′ N, 27°33′ E) ( 300 mmSL).
Differential diagnosis Within the Congobasin, D. langican be distinguished from D. affinis, D. altus, D. decemmaculatus, D. noboli, D. notospilusand D. teugelsiby its higher total number of LL scales, i.e. 68–70 (versus <46); from D.maculatusby the absence of large, dark spots all over the body and a higher number of dorsal fin rays, i.e. 26–28 (versus 19– 21); from D. antoniiby its inferior (versus terminal) mouth, its higher number of scales between the LL and the dorsal fin, i.e. 15–16 (versus 10–12) and its higher number of LL scales in front of HJ, i.e. 68–70 (versus 52–64); from D. fasciolatusby its higher number of dorsal fin rays, i.e. 26–28 (versus 24–26); its higher number of pelvic fin rays, i.e. 11 (versus generally 10) and its deeper head, 67.4–69.4 %HL (versus 35.9–62.9 %HL); from D.lusossoby its inferior (versus terminal) mouth and feebly compressed snout (versus distinctive prolonged); from D. sexfasciatusby its feebly compressed snout (versus strongly compressed), its higher number of dark vertical bars along the body, i.e. 13 (versus 6–7) and its higher number of teeth on the outer row on both jaws (> 20 versus 12–14) and from the D. atroventraliscomplex by a higher number of scales between the LL and pelvic fin, i.e. 12 (versus 9–11), its higher number of pectoral fin rays, i.e. 21 (versus 17–20); its higher number of circumpeduncular scales, i.e. 24–25 (versus 20–24) and its deeper head, 67.4–69.4 % HL (versus 35.1–55.7 %HL) ( Table 4).
Description Morphometric and meristic data are given in Table 5. Body relatively deep (within D. antoniiassemblage). Dorsal head profile and dorsal body outline concave to end of dorsal fin, straight from end of dorsal to adipose fin, and convex from adipose to caudal fin. Ventral head profile straight, concave from posterior to head to end of anal fin, and convex from end of anal to caudal fin. Head compressed with nasal openings relatively closely set (14.4 %HL and 15.9 %HL), but deep (67.4 %HL and 69.4 %HL). Mouth inferior. Posterior edge of maxillary not passing the nostrils. Two rows of bicuspid teeth in each jaw. Origin of dorsal fin well in front of pelvic fin origin along vertical axis. Distal margin dorsal fin straight or slightly concave, distal margin of anal fin straight to slightly convex. Base and distal end of pelvic fin relatively close to vent, i.e. 23.4 %SL and 25.9 %SL, and 1.6 %SL and 7.8 %SL, respectively. Pectoral and pelvic fin rays decreasing in length from outer to inner fin margin. Adipose fin little further removed from dorsal fin than from caudal fin. Caudal peduncle deeper then long. Caudal fin forked with two rounded lobes covered with numerous small scales except for translucent area distally. As only two specimensare currently known from D. langi, allometry could not be assessed. Maximum recorded length: 364 mmSL, 472 mmTL. Colouration Lang provided information on the presumable life colour pattern based on five specimens( Nichols and Griscom 1917). It is however unsure whether these specimens are conspecific (see above), and therefore this information is not presented here. The body of the two preserved specimens is uniformly brown-yellowish, with a slightly lighter belly. Dorsal fin scattered with many small, dark spots. Caudal fin brownish, with slightly darker median rays. Adipose fin with translucent distal margin ( Figures 3Cand 8). Pectoral fins pale to yellow-orange. Pelvic fins generally pale, while in the additional specimen the distal edges are darker coloured. Thirteen vague dark vertical bars have been observed on the flanks of the additional specimen, whereas the holotypehas none.
Ecology Notmuch is known about the ecology of D. langi. In the original description of Nichols and Griscom (1917), Lang is cited mentioning the following: “Evidently swimming in schools, as five of them have been killed by one explosion”. However, since this original description is based upon three different species (see above), the relevance of this information is difficult to assess.
Distribution This species is only known from two specimensfrom two different locations, Faradjein the Dungu region, Uele Riverbasin ( DRC) and Avakubi, Aruwimi Riverbasin ( DRC) ( Figure 5).
Etymology The species name “ langi” refers to the collector Herbert Lang (1879–1957), who collected fish in the Congobasin from 1909 to 1915 for the AMNH, in collaboration with James Chapin ( Slack 2003). List of specimens examined of the D. atroventralis complex (all lengths are SL)( Figure 3D). Democratic Republic of the Congo(DRC): Syntypes: MRAC 30. Boma( DRC) (± 5°50′ S, 13°03′ E), coll. Wilverth1896 ( 70.9 mm)– BMNH 1891.12.29.13. Congo River, Lower Congo( DRC), received from Utrecht University Museum1891 ( 63.5 mm); Specimens: AMNH I-243645. Lulua River, Katende2, Dipumu(± 6° 00′27.0″ S, 22°23′43″ E), coll. Mbimbi 01/12/2007( 64.2 mm; 90.2 mm)– AMNH I-243646. Lulua River, Nsanga Nyembo(± 5°56′53.41″ S, 22°20′29.40″ E), coll. Mbimbi 03/12/2007( 76.7 mm; 123.3 mm)– AMNH I-247823. Lulua, Bunkonde( 6°14′49.2″ S, 22°28′48.0″ E), coll. Mbimbi 30/06/2008( 34.4 mm)– AMNH I-247825. Lulua, Katende1, Nkombua( 6°00′16.2″ S, 22°23′25.8″ E), coll. Mbimbi 21/05/2008(37.0 mm)– MRAC 158797. Dundo, affl. Luachimo(± 7°21′ S, 20°50′ E), coll. De Barros Machado 02/06/1949( 225.5 mm)– MCZ50439. Zaire Rivernear Inga, a few km upstream and on the opposite side of river from Ingahydroelectric dam ( 5°27′30″ S, 13°36′??″ E), coll. Robertsand Stewart1973 ( 53.2 mm; 62.8 mm)– MRAC 738. Banana( 6°00′ S, 12°24′ E), coll. Delhez1899 ( 53.5 mm)– MRAC 739. Matadi( 5°49′ S, 13°27′ E), coll. Delhez, 1899 ( 246.6 mm)– MRAC 740. Matadi( 5°49′ S, 13°27′ E), coll. Delhez1899 (66.0 mm)– MRAC 741. Dolo( 4°19′ S, 15°19′ E), coll. Delhez1899 (357.0 mm)– MRAC 742. Kutu, (± 2°44′ S, 18°08′ E), coll. Delhez1899 ( 158.3 mm)– MRAC 67444. Léopoldville(± 4°18′ S, 15°18′ E), coll. Henri van Moorsel7/1944 ( 127.7 mm)– MRAC 117366. Stanley Pool, Yankauchannel, N’ Dukaindigenous dam (± 4°20′ S, 15°24′ E), coll. MissionBrien-Poll-Bouillon 23/ 9/1957( 199.5 mm)– MRAC 73-22-P-1195-1197. Stanley Pool, Nsele river(± 4°15′ S, 15°33′ E), coll. Mandeville 29/10/1957( 23.8–41.2 mm)– MRAC 73-22-P-1201-1202. Stanley Pool, Ndjili river(± 4°20′ S, 15°22′ E), coll. Mandeville 30/10/1957( 67.8 mm; 76.8 mm)– MRAC 73-22-P-1223. Stanley Pool, Mbamu island(± 4°14′ S, 15°22′ Eto ± 4°18′ S, 15°30′ E), coll. Mandeville J., 28/10/1957( 33.1 mm)– MRAC A7-014-P- 0025. Pool Maleboat Kinkole, Mipongi island(± 4°16′26.9″ S, 15°30′29.6″ E), coll. Mbadu Zebe 26/1/2006(128.0 mm)– MRAC A7-033-P-267. Congo Riverclose to the Kinsangachannel, Inga(± 5°39′ S, 13°39′ E), coll. Hanssens2007 ( 142.6 mm)– MRACB0-017-P-0020. Lomami River, affluent Congo River, village Lieki, coll. Congo2010 2/06/2010(343.0 mm)– MRACB0-017-P-0021-0022. Isangi, rive gauche fleuve Congo, coll. Congo2010 5/06/2010( 261.9 mmSL; 325.0 mm SL)– MRACB0-017-P-0093. Lomami River, left bank, just downstream of village Lieki(± 0°40′55″ N, 24°11′08″ E), coll Exp. Congo2010 27/05/2010( 31.5 mm)– MRACB0-017-P-0094. Littlemarsh on Lomami River, left bank, upstream of village Yandjambi(± 0°41′57.44″ N, 24°13′36.0114″ E), coll Exp. Congo2010 28/05/2010( 31.4 mm)– MRACB0-017-P-0095. Lomami River, left bank, upstreamof village Lieki(rive gauche riv. Lomami, en amont du village Lieki(± 0°40′55″ N, 24°11′08″ E), coll Exp. Congo2010 01/06/2010( 61.6 mm)– MRACB0-017-0096-0097. Lomami River, right bank, downstream of village Lieki(± 0°40′ 55″ N, 24°11′08″ E), coll. Exp. Congo2010 30/05/2010( 21.7 mm; 25.9 mm)– MRACB0-017-P-0098. Lomami River, downstream of village Lieki(± 0°40′55″ N, 24°11′ 08″ E), coll Exp. Congo2010 27/05/2010(32.0 mm)– MRACB0-017-0099-0100. Lomami River, downstream of village Lieki(± 0°40′55″ N, 24°11′08″ E), coll. Exp. Congo2010 03/06/2010( 27.6 mmSL; 36.2 mm)– MRACB0-017-P-0101. Lomami Riverat confluence with Koli River, right bank, downstream of village Lieki(± 0°40′ 55″ N, 24°11′08″ E), coll. Exp. Congo2010 01/06/2010( 25.6 mm)– MRAC B1-009- P-0022. Lobaye River, left bank, Site2 (± 0°28′28.8″ N, 24°11′57.9″ E), village Bambondji II, coll. Danaduand Moelants 08/05/2011(93.0 mm). Republic of the Congo( Brazzaville): MRAC A8-020-P-0386-0390 (2/4). Léfini River, “Massala ma soso” rapids, right bank ( 2°55.93′ S, 16°07.42′ E), coll. Vrevenand Ibala Zamba 23/8/2008( 46.5 mm; 68.5 mm).
AMNH
Democratic Republic of the Congo
3.7333333
Faradje
1307
29.716667
Dungu region
21
1727
AMNH 5915
1
holotype
[144,881,1139,1163]
MRAC
Democratic Republic of the Congo
1.3166666
Avakubi
1308
27.55
22
1728
MRAC 2878
1
Democratic Republic of the Congo
Aruwimi River
Faradje
Avakubi
23
1729
1
DRC
Wilverth
Democratic Republic of the Congo
-5.8333335
Boma
1305
13.05
24
1730
MRAC 30
1
syntype
DRC
Utrecht University Museum & Specimens
Democratic Republic of the Congo
Congo River
Lower Congo
24
1730
BMNH 1891.12
1
syntype
2007-12-01
AMNH
Mbimbi
Democratic Republic of the Congo
Dipumu
-6.0075
Lulua River
15
22.395277
Katende
24
1730
I-243645
1
syntype
2007-12-03
AMNH
Mbimbi
Democratic Republic of the Congo
-5.9481697
Lulua River
1
22.341501
Nsanga Nyembo
24
1730
I-243646
1
syntype
2008-06-30
AMNH
Mbimbi
Democratic Republic of the Congo
-6.2469997
Lulua
1
22.480001
Bunkonde
24
1730
I-247823
1
syntype
2008-05-21
AMNH
Mbimbi
Democratic Republic of the Congo
Nkombua
-6.0045
Lulua
1
22.3905
Katende
24
1730
I-247825
1
syntype
1949-06-02
MRAC
De Barros Machado
Democratic Republic of the Congo
-7.35
Dundo
1303
20.833334
Luachimo
24
1730
MRAC 158797
1
syntype
MCZ 50439
MCZ
Roberts & Stewart
Democratic Republic of the Congo
Inga
-5.458333
Zaire River
Inga
24
1730
1
syntype
MRAC
Delhez
Democratic Republic of the Congo
-6.0
Banana
1305
12.4
24
1730
MRAC 738
1
syntype
MRAC
Delhez
Democratic Republic of the Congo
-5.8166666
Matadi
1305
13.45
24
1730
MRAC 739
1
syntype
MRAC
Delhez
Democratic Republic of the Congo
-5.8166666
Matadi
1305
13.45
24
1730
MRAC 740
1
syntype
MRAC
Delhez
Democratic Republic of the Congo
-4.3166666
Dolo
1306
15.316667
24
1730
MRAC 741
1
syntype
MRAC
Delhez
Democratic Republic of the Congo
-2.7333333
Kutu
1307
18.133333
24
1730
MRAC 742
1
syntype
MRAC
Henri van Moorsel
Democratic Republic of the Congo
-4.3
Leopoldville
1306
15.3
24
1730
MRAC 67444
1
syntype
1957-09-23
MRAC
Mission
Democratic Republic of the Congo
Duka
-4.3333335
Stanley Pool
1306
15.4
Yankau
24
1730
MRAC 117366
1
syntype
1957-10-29
MRAC
Mandeville
Democratic Republic of the Congo
-4.25
Stanley Pool
1306
15.55
Nsele river
24
1730
MRAC 73-22
1
syntype
1957-10-30
MRAC
Mandeville
Democratic Republic of the Congo
-4.3333335
Stanley Pool
1306
15.366667
Ndjili river
24
1730
MRAC 73-22
1
syntype
1957-10-28
MRAC
Mandeville J.
Democratic Republic of the Congo
-4.3
Stanley Pool
1306
15.5
Mbamu island
24
1730
MRAC 73-22
1
syntype
2006-01-26
MRAC
Mbadu Zebe
Democratic Republic of the Congo
Mipongi island
-4.274139
Pool Malebo
1
15.508223
Kinkole
24
1730
A7-014
1
syntype
MRAC
Hanssens
Democratic Republic of the Congo
Inga
-5.65
Congo River
1305
13.65
Kinsanga
24
1730
A7-033
1
syntype
2010-06-02
MRAC
Lieki & Congo
Democratic Republic of the Congo
Lomami River
Congo River
24
1730
1
syntype
2010-06-05
MRAC
Congo
Democratic Republic of the Congo
Isangi
Congo
24
1730
1
syntype
2010-05-27
MRAC
Exp. Congo
Democratic Republic of the Congo
0.6819445
Lomami River
21
24.185555
Lieki
24
1730
1
syntype
2010-05-28
MRAC
Exp. Congo
Democratic Republic of the Congo
Yandjambi
0.6992889
Little
1
24.226671
Lomami River
24
1730
1
syntype
2010-06-01
MRAC
Exp. Congo
Democratic Republic of the Congo
Lieki
0.6819445
Lomami River
21
24.185555
Lomami
24
1730
1
syntype
2010-05-30
MRAC
Exp. Congo
Democratic Republic of the Congo
0.6819445
Lomami River
21
24.185555
Lieki
24
1730
1
syntype
2010-05-27
MRAC
Exp. Congo
Democratic Republic of the Congo
25
1731
0.6819445
Lomami River
21
24.185555
Lieki
24
1730
1
syntype
2010-06-03
MRAC
Exp. Congo
Democratic Republic of the Congo
0.6819445
Lomami River
21
24.185555
Lieki
25
1731
1
syntype
2010-06-01
MRAC
Exp. Congo
Democratic Republic of the Congo
Lieki
0.6819445
Lomami River
21
24.185555
Koli River
25
1731
1
syntype
2011-05-08
MRAC
Bambondji II & Danadu & Moelants
Democratic Republic of the Congo
0.47466666
Lobaye River
1
24.199415
Site
25
1731
B1-009
1
syntype
2008-08-23
MRAC
Vreven & Ibala Zamba
Republic of the Congo
-2.9321666
Lefini River
13
16.123667
25
1731
A8-020
1
Brazzaville