APHYOSEMION ZYGAIMA

 

Ichthyology

 

A New But Well-known Aphyosemion Species From the Southern Congolese Plateau, Aphyosemion zygaima n. sp.

 

by J.H. Huber*

 

* Laboratoire d'Ichtyologie, Museum national d'Histoire naturelle, 43 rue Cuvier, 75231 Paris Cedex 05, France.

 

Our experience with the genus Aphyosemion has taught us to be cautious regarding the identification of killifishes imported by the commercial trade under a name described prior to the 1950's. A classic case of confusion was the early importation of Nigerian A. gardneri under the incorrect name A. calliurum. First, the type localities of the two taxa are separated by about 300 kilometers, although the actual distribution of each is not fully known. Second, A. gardneri inhabits the inland plateau, while A. calliurum is restricted to the coastal plain, a difference now considered as a key in the separation of superspecies in Aphyosemion. Third, the supposed origins of commercial imports were situated far from both type localities. These factors resulted in confusion for many years. Several other similar cases could be mentioned.

This paper is concerned with confusion surrounding a fish from Mindouli referred to as A. louessense. Scheel (1968, Rivulins of the Old World: 277-278) reported "In 1964 Brichard and Roberts collected live specimens of various cyprinodont species in the Congo… Among them there was a strain of Aphyosemion collected near Mindouli on the upper reaches of the Niari River, an affluent of the Kouilou River".

Scheel studied and identified these fish as A. louessense (Pellegrin, 1931), though he admitted that other strains collected by J. Lambert closer to the type locality of A. louessense (i.e., more northerly) were different. Scheel's identification has been followed until now.

In 1978, two expeditions in the southern Republic of the Congo provided more information and live specimens of this fish and others. During the first, north of the Niari River and within the Du Chaillu Massif, Wachters and Buytaert, and then two weeks later the author, too, found many populations of the A. ogoense (Pellegrin) superspecies. All of them were characterized by an asymmetrical color pattern in the caudal fin and by a high haploid number of chromosomes. During the second expedition, this one south of the Niari River, near Mindouli, the author rediscovered Brichard's fish which was characterized by a symmetrical color pattern in the caudal fin and, according to Scheel (op. cit.), a very low number of haploid chromosomes (n=10), relating it to A. labarrei from Zaïre.

The problem was then to redefine Pellegrin's real A. louessense according to three criteria :

1. Geography: holotype from the Louessé River, which flows north of the Niari River.

2. Caudal pattern: asymmetrical.

3. Karyotype: unknown, butindividuals collected in the Mapati-Sibiti area, 30 km east of the Louessé River show a high number of chromosomes (n=20). [The identity of louessense is still uncertain, as it appears that the holotype is a female from a little more northern locality in the Louessé Basin and that the color pattern (one red longitudinal band) is based on individuals (paratypes) from the Lali River near Sibiti (for further discussion, a subsequent article reviewing the ogoense group will be published in Germany)].

Therefore, A. louessense is a member of the ogoense group, north of the Niari River, and Brichard's Aphyosemion from South of the Niari River should be considered as distinct.

It is described below under the name A. zygaima.

 

APHYOSEMION ZYGAIMA, New Species

 

Holotype. -73-39 P 1635-645, male, 46.9 mm in TL, 36.8 mm in SL, collected at Mindouli, southern Republic of the Congo, some 100 km west of Brazzaville. Brichard leg. 1964, Musée Royal de l'Afrique Centrale, Tervuren, Belgium.

Paratypes(1).-73-39 P 1635-645, 1 male, 1 female and 9 other specimens from the same sample. Tervuren.

Paratypes (2).-78-19 P 3994, 1 male and 5 other specimens from another sample, probably from a nearby locality. Brichard leg. 1964, Tervuren.

Additional Material. -One collected by the author at Mindouli, near the train station, Loc. 175, brook named Voma, 9 VIII 1978 (J .H. Huber collection).

Color Pattern.-Males show some red spots and blotches placed irregularly on the rnetallic blue-green sides. The number of spots varies but is never large. The unpaired fins present a symmetrical flamed pattern. The caudal pattern is as follows: blue-green margin, red sub-margin, red flames on a green background, red sub- margin, blue-green margin. Females show the same red pattern legs intensively; their basic color is light brown. The name evokes the often-linked flames of a blood-red color. The red pattern remains after preservation.

 

Morphology (see Table 1).
-The fin counts are typical of the average Aphyosemion: D.13; A.16; D/A=+6. As a comparison, the same figures for A. louessense in the present sense are given. It seems that A. zygaima is a little less elongate and that its dorsal is placed nearer to the anal, but these differences, based only on a few specimens from two populations, should be checked on a larger collection. A. zygaima shows a G frontal scalation (no H scales) and open neuromasts.

Discussion.
-By the karyotype, the color pattern and the locality, A. zygaima should be approached in the Zaire fauna by A. labarrei Poli, 1952, A. ferranti (Boulenger, 1910) and possibly some other forms to be discovered. All three known forms show a symmetrical caudal pattern. A. zygaima and A. labarrei both have a low haploid number of chromosomes, but their karyotypes are different according to Scheel. Though their type localities are separated by only 120 km, the Zaire River rails between them and may be a barrier. A. labarrei and A. ferranti show a similar red longitudinal band on the body, but their type localities are separated by 900 km.

By the karyotype, A. zygaima is distinct from ail the medium- sized Aphyosemion of this region that show a high chromosome number, including :

1. The ogoense plateau group with three branches and many recently described species :

a. A. ogoense and its allies: A. louessense (in the present sense) , A. pyrophore (Huber and Radda, 1979), A. caudafasciatum (Huber and Radda, 1979), A. sp. RPC 200-207 (coll. Buytaert, 1979), A. sp.-Malinga (loc. 212, Huber collection, 1979). All of them show an asymmetrical caudal pattern.

b. A. thysi and its yellow counterpart, A. schluppi (Radda and Huber, 1978), with an asymmetrical pattern.

c. A. wachtersi and A. buytaerti (Radda and Huber, 1978), tentatively placed here according to their karyotypes, though they show a different body pattern and blue dots in the caudal.

 

2. The coeleste superspecies that inhabits mainly the Gabon part of the Du Chaillu Massif: A. coeleste (Huber and Radda, 1977), with a symmetrical pattern.

 

3. The striatum coastal group : A. microphtalmum (Lambert & Géry, 1967) and perhaps, in the Nyanga, A. primigenium Radda & Huber, 1977, with a symmetrical pattern.

 

Morphologically, A. zygaima is distinct from the more slender species A. australe from the coastal plain from Lake Tchimba to Pointe Noire and the elegans superspecies whose elements inhabit the Batéké Plateau to the east and the Kinkala area, where it may be sympatric with A. zygaima.

 

TABLE I. Data on meristics and morphology

(all percentages are based on SL)

 

April 1981

 

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