ADAMAS FORMOSUS

Cyprinodonts of the Congo Basin Adamas formosus new genus, new species) and new description of Aphyosemion splendidum).

 

By J.H. Huber*

 

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

 

 

Abstract

From the results of his 1978 trip to Congo, the author studies here the systematics, biology and ethology of some Cyprinodonts from the western part of the Congo Basin.

A new genus is created for an original new species, Adamas formosus. The author discusses the systematic position of Aphyoplatys duboisi, Epiplatys chevalieri and Aphyosemion (Raddaella) splendidum. Two taxa are put in synonymy: Ep. nigricans is a junior synonym of Ep. chevalieri and A. kunzi is a junior synonym of A. splendidum.

 

 

Introduction

My attempt in the regrouping of the species of the genus Aphyosemion has made me aware of the importance of their biology, the study of which was the principle objective of a trip in solo to the Congo from July 3, 1978 to Aug. 15, 1978.

Eighty new localities (n°101 to 180) inhabited by Cyprinodonts are reported, among which sixteen (n°104, 106, 107, 110 to 114, 124 to 126, 128, 129, 133, 140, 157), are located within the Congo basin. Many problems surrounding the population genetics of this region are now closer to being solved. They will be the object of a series of articles, this one includes only specimens collected from the Congo basin. I wish to express my sincere thanks to Mr. and Mrs. Dédel and to Mr. and Mrs. Kong, originating from Guyane, for their invaluable help in the course of my stay in Congo.

 

The Congo Basin

The People's Republic of the Congo extends above and below the equator over 342,000 km², to the east and to the south of Gabon. The northern area encompasses the interior plateau, consisting of savannahs to the west and forests in the north; the Congo basin is in the eastern part of this area. This basin consists of a vast plain (low decline of altitude, maintained between 200 m and 400 m above sea level) and of the large Congo river, with its many tributaries; from the north to the south: the Oubangui, the Likouala-aux-Herbes, the Sangha, the Likouala-Mossaka (Kouyou, Mambili), the Alima, the Nkéni and the Léfini.

 

The Congo basin covers one third of the total land mass of this country. Its length extends 800 km to the north and south and is 250 km wide to the east and west, but the area of this basin actually located in the Congo is of little importance, when compared to that located in the country of Zaire, to the left bank of the Congo river. In total, the basin encompasses 4 million km², and the river is 12-20 km wide in the area of Mossaka. The Congo basin is delimited by plateaus and hills: The Oubanguians plateaus to the north, and the Batéké plateaus to the south, plus the highlands of the Sangha to the west. The soils are sedimentary. The climate is of a subequatorial type, with the seasons being only slightly differentiated. The strong rains overwhelm the land mass and are absorbed only slowly, which explains the presence of the forest.

 

The vast forest of the North covering 13 million hectares is flooded over 55% of its area. Roads are non-existent and in order to get to the center of the basin, Ntokou (loc. 133), it was necessary to use a motor boat steadily for 7 hours. The 15 other localities are situated at the border of the basin or, more to the west, in the marshy galleries of the tributaries of the Congo river.

 

STUDY OF THE COLLECTED FORMS.

 

1) Adamas formosus new genus, new species

 

Holotype (MNHN 1979-199) male, 17.3 mm S.L. (standard length), 22.1 mm T.L. (total length) from locality n°133, in front of the village Ntokou, near the banks of the Likouala-Mossaka, People's Republic of the Congo. Ntokou is situated seven hours by boat downstream from Makoua slightly beyond the meeting of the Likouala and the Mambili, and that of the Likouala and the Bokiba which forms the Likouala-Mossaka. Note that Ntokou is erroneously situated on the Mambili, to the north-east of Makoua, on the IGN map. This specimen was collected July 17, 1978 at 9:00 am.

 

Paratypes (MNHN 1979- 200): 4 specimens from locality n°133.

 

Paratypes (MNHN1979-201): 6 specimens from locality n°125, of which one was studied (table 1).

 

Paratypes (MNHN 1979- 202): 6 specimens from locality n°111 of which 3 were studied (table 1).

 

Locality n°125 is situated 50 km to the north of Obouya near the bridge over the Vouma. Locality n°111, the southern most, facing TchicaPika, about 30 km to the east of Olombo. The fish were collected on the 13th and the 9th of July (respectively).

 

Color Pattern in life

The male's color pattern resembles, to a great degree, that of Aphyosemion: blue fins bordered with red, the body is a pale blue with many red spots, sometimes forming irregular lines. At a glance, the fish has a striking resemblance to a young male of certain populations of A. christyi.

The female is dull in coloration, being a light tan with a few red spots on the body ­bearing a strong similarity to a female Aphyosemion.

 

However three characteristics distinguish this species clearly from an Aphyosemion species.

1) The most important is the existence, in the two sexes, of a frontal spot which is a brilliant white, tinged with blue and unique in this species - it is found in no other Cyprinodont known. This spot does not resemble that of the Epiplatys species which is yellow and of an imprecise shape. The spot found in Adamas is clearly limited to only the four scales on the top of the head.

2) The second is the presence of a temporary black band (or gray) all over the body of the female. This band does not extend to the ventral areas of the fish. This band appears following certain stimuli and is, at first, narrow and gray - it then becomes wider and darker.

3) The third, minor, is the presence of a red line on the dorsal and anal, along the lower line of insertion.

 

Color Pattern in the preserved state

 

The holotype shows nearly no pigmentation in the fins any more. The red "shield" remains, as do the rows of red spots which have become yellowish (from back to belly: 7 spots in the first series, 22 in the second one, 24 in the third, 19 in the fourth and 8 in the fifth). The frontal spot has become black. Finally, melanophores are numerous all over the body with the exception of the ventral area.

The females are darker, overall grayish. There is an abundance of melanophores, except in the ventral regions. A few red spots may still be seen on the dark background. The frontal spot is equally apparent and is black in color.

 

Morphology

 

This is one of the smallest fishes of the family, elongated in shape, presenting a combination of the following characteristics:

1) Large and brilliant eyes, head elongated.

2) Short dorsal (D= 8-9), anal fin of average length, possessing certain elongated rays (A= 15), the displacement value D/A is very high; D/A= 12-14.

3) Frontal scalation is poorly defined - probably of G-type. The 6 largest frontal scales seems not to overlap, but appear nearly independent.

4) Neuromasts and sensitive pores of the front are characterized by an imprecise configuration and exhibit extreme variability, within a popula­tion; usually, the postorbital neuromasts are visible: the 6

orbital neuromasts are sometimes visible, but are frequently replaced by sensitive pores; finally the two pre-orbital neuromasts can both be present or both absent, or one present and one absent (either one, or both, can then be replaced by sensitive pores. These neuromasts may be reduced to miniscule "buttons" that are hardly visible even at a magnification of 40X.

The sensitive organs, are only rarely protected by channels and are, rather, almost completely exposed.

Moreover, the fish possesses 1­ to 4 sensitive organs in the proximity of the eye, frontward or backwards, and/or 2 neuromasts, vertically oriented at about one third of the distance eye-opercle. The lateral line is almost totally absent.

5) Teeth, small, monocuspid, recurved innerly, and numerous on both maxillaries.

 

Discussion

In keeping with the unique characteristics enumerated above, l propose to create the new genus, Adamas, for this new fish.

 

Etymology

From Latin, Adamas, antis, substantive (noun) masculine. steel or diamond, in reference to the spot which is unique to the family of Cyprinodontidae.

 

Besides, the new genus shows specific characters either to Rivulins or to Procatopodins.

 

It is similar to certain Rivulins, notably the components of Aphyosemion, on the basis of its general external morphology, its color pattern, its sexual dimorphism; it is, however, distinguished by the unusually high D/A value, the structure of the frontal sensitive organs, and its ethology and biology.

It is similar to the Procatopodins by the 4 last mentioned features, as well as by the abundance of the black pigmentation (and the larger eye). Adamas is differentiated from Procatopodins on the basis of the frontal scale which is probably of type G, and the pattern of coloration, notably the presence of the red "shield".

 

As a result, it is difficult to place Adamas in one sub-family rather than the other. Following the Clausen's proposals (1967), it should belong to the Procatopodins on the basis of the vestigial and variable structure of its frontal sensitive organs. However, Adamas seems to me closer to the Rivulins, on the basis of certain characteristics shared with Aphyosemion.

 

Our knowledge being too fragmentary, it maybe prefer­able to consider Adamas as an intermediate between Procatopodins and Rivulins, while waiting that a revision better defines the limits of these two subfamilies.

 

Observations in Aquarium

 

These preliminary observations are due to M. Chauche (personal communication, February 24. 1979). "The fish, 7 in number, were received in a very weakened state on the 15th of August 1978. After a few weeks of live food, two pairs were still alive and had grown in size to about 3 cm. The first fry (about 3 mm in length) appeared toward the end of January. Since then, the adults were moved to a new aquarium and some two weeks later 3 newborn fish appeared in the old tank, so that the incubation period can be estimated to be about two weeks (as a minimum). The eggs are probably very small and have not yet been found. The behavior is quiet, between the 2 males and between sexes".

 

2) Aphyoplatys duboisi (PolI, 1953)

 

This species was described on the basis of 11 individuals collected in the region of the Stanley Pool near Kinshasa in Zaire. Several importations have confirmed its presence in this region, and l have caught it myself near Brazzaville, in the island of Mbamou (location n°179). The presence of this fish in the Congo basin is however reported here for the first time.

Although the two regions are 400 km apart, I have not yet found significant differences between the two groups of populations. The color pattern of the fish that l collected is characterized by an iridescent light green color, decorated with rows of red spots with a brilliant lemon-yellow head (as in Epiplatys dageti ), by a black lower lip and by the unpaired fins adorned with a red sub-marginal band.

The structure of the sensitive organs from the front presents some analogies with those of Adamas formosus: strong variability, presence of pores in place of neuromasts, exposed organs. The frontal scalation is of the standard G-type, with sometimes F-scales.

 

Clausen (loc. cit.) has separated duboisi from the other Epiplatys to place it in a monotypic genus Aphyoplatys, "intermediate between" Aphyosemion and Epiplatys.

 

According to Scheel (1968), in the contrary, duboisi must be linked with Epiplatys, because of the high number of chromosome (n= 24) and of the hemoglobin type.

 

However, the ethology and the biology seem to distinguish this species from Epiplatys (see further). Besides, Scheel (loc. cit.) reports that the pre-nuptial behavior looks more like Procatopodins. As for Adamas, it is difficult to decide, and for all these reasons, I prefer to separate duboisi from Epiplatys and consider Aphyoplatys as valid.

 

 3) Epiplatys chevalieri (PelIegrin, 1904)

 

This species has been described after 3 specimens from Brazzaville; later, it has been collected several tiles in the same region in Congo and Zaire.

 

On the other hand, the taxon Epiplatys nigricans has been established by Boulenger (1913) after 3 specimens from Dungu, in the central Congo basin. Many authors have collected this species in the entire Congolese cuvette: Sangha basin, lake Tumba.

 

The two species are isomorphic and Lambert (1961: 29-30) considers E. nigricans as a sub-species of E. chevalieri, the nomino-typical form being stockier.

My specimens from the same region, show a variable morphology and it is possible, on a case basis, to assign them to either the former sub-species or the latter; I propose therefore that nigricans be considered as a junior synonym of E. chevalierî

 

4) Aphyosemion (Raddaella) splendidum (PelIegrin, 1930)

 

New Description

The species has been described from material collected in 2 localities.

Those from Sangha are considered as typical, although no holotype has been designated; the other have been caught near the road between Souanké and Garabinzam, in far northwestern Congo. I have visited the 2 regions (location 157 and 154 respectively) and I found the fish.

 

On the other hand, Radda (1975) described A. kunzi on the basis of specimens from the Makokou region in north-east Gabon. I have collected the fish several times in the Mékambo region. The comparison of the fishes in vivo, leaves little to doubt as to the identity of A. kunzi and A. splendidum. These fish show also the same morphology (see table 1).

 

To check this last point, I have reviewed Pellegrin's material. I feel justified in designating a lectotype, and proposing a new description as the older one does not correspond with the information now at hand.

 

Lectotype : MNHN 1929-247, male, 62.6 mm (SL), 78.2 mm (TL).

 

Paralectotypes : 51 specimens from the locality of the lectotype (Sangha), of which one was also studied: 41.8 mm (SL) and 51.9 mm (TL).

 

Paralectotypes : 23 specimens from the road between Souanké and Garabinzam, northwestern Congo (kunzi s.s.).

 

Complimentary Material (MNHN): 4 males, 1 female, from the locality n°157 in the region of Ouesso, about 40 km to the south, on right bank of the Sangha, near a forested camp before Mboko. J.H. Huber, leg.

 

Morphology .

Large fish, reaching 8 to 12 cm in length, presenting the following combination of characteristics.

- the number of rays in the dorsal are many (D= A= 16-19) with the deviation of the dorsal and the anal fins being small (D/A= +4) and the presence of filaments being variable.

- frontal neuromasts are "open"; frontal scale is of G-type, knowing that F scales may or may not be present,

- ctenoid spines are frequently present, especially on older males (Huber 1978: 12).

 

Color Pattern .

Variable in the male. All specimens have a post-opercular red spot and a white inferior marginal band on the caudal fin in common. The color of the body and the anal vary widely from one fish to another. The female shows only a few red spots on the body, that shows a light brown background.

 

Geographic Distribution .

The synonymy of this fish with A. kunzi, and the discovery of this species in localities n°111 arid n°133 significantly extend the range of this fish, which extends from Gabon to Congo. In the north A. (R.) splendidum is replaced by A. (R.) batesii and it is not yet known, what its southern most distribution is.

 

Systematic Position .

The subgenus Raddaella occupies a unique position among Aphyosemion. Recent studies on their life cycle, their behavior, and their characterization as a "pseudo-annual" [Note: the development requires 4 months of incubation in dry peat in captivity, but actually, the eggs do not completely dry in the course of the dry season in the wild (based on repeated observations in the field, by Congolese inhabitants], all support the creation of a new subgenus (Huber,1977)

 

 

BIOLOGY, ETHOLOGY

 

The biotopes visited are different from the "marigots" and the small slowly flowing forest streams on sandy beds that are often inhabited by Aphyosemion. In the contrary, biotopes of the basin ("cuvette") are very calm and slightly stagnant bodies of water, with bottom covering of clay or peat.

 

Schematically, one differentiate between two types of biotopes.

1) The very calm banks of big or small rivers and streams. Vegetation is abundant, consisting of water hyacinths and water lilies. The water is clear. This description is typical of location n°133 which is located in the center of the basin. On July 17. 1978, at 9:00, the temperature of the air was 21.5°C, and that of the water was 22.3°C. The water was 50 cm deep and had a pH of 5.8 and a total hardness of 1.5. Fish were very abundant and were quickly caught among the roots of the water hyacinths. E. chevalieri (young) and Adamas formosus were. both extremely common, while Apyoplatys duboisi and Kribia nana appeared less frequent. Also, three females of A. splendidum were caught by chance.

In general, this type of biotope (loc. 104, 112, 125) is favorable to Ep. chevalieri and to Adamas formosus.

 

Epiplatys lives at the surface, with the juveniles swimming in open places, whereas adults tend to remain in hiding and do not move much. Adamas formosus is very peaceful and appears gregarious, often they were found in groups of 15 to 30 with males and females being represented. The fish swim quietly in mid waters. The schools a remarkable cohesion: in a defensive action (in case of a danger), the fish aggregate into a tight circle, swimming concentrically.

In this type of biotope, Aphyosemion are very rare, if they are even present at all.

 

2) The stagnant "marigots" and pools, bordering the streams and rivers. Superficies is highly variable. The diameter of these bodies of water varies from a few meters to 50 m in length. Aquatic vegetation is non-existent because sunlight is not able to penetrate the dense forests. The soil is marshy and consists of a yellow clay covered over by a thick layer of leaves. For example, location n°111 displayed the following characteristics: small pools and trenches of flooded forest, isolated from one another at the end of the dry season. At 16:00 on July 30, 1978 the temperature of the air was 24°C. and that of the water was 24.2°C. The water was relatively shallow with an average depth of 20 cm, pH 4.4, total hardness 0.5.

Adamas formosus was found in abundance in the company of Ep. multifasciatus and Ctenopoma sp. The behavior of Adamas formosus was the same as noted above, but the schools were localized rather close to the shores. That of Ep. multifasciatus was similar to Ep. chevalieri. The behavior of Aphyoplatys duboisi is poorly known; it does not form schools, and it prefers the deeper areas of the pools in which it lives. This is in contrast to Epiplatys.

Generally, this type of biotope seems to be more suitable to Ep. multifasciatus, Aphyosemion of the elegans group, and to A. splendidum, which are nevertheless quite rare. Note that A. splendidum was never collected in abundance with the exception of only one case (location 157), this is probably because it prefers the more remote reaches of the creek or the pool. They are found in greater abundance in isolated pools and ditches where they can hide at the bottom among the leaves. The females are more numerous that the males, each corner dwelt by one male and several females of variable size. This fish' s reaction to fright is unique - once it has been discovered (often a male is concerned) it leaves its hiding place in a savage fashion and darts quickly in a perpendicular direction to the shore of the pool.

 

Table II presents a synopsis of the way in which the various 16 localities visited were populated (occurrence and density for each species).

It is difficult to try to draw any definitive conclusions because the data is too limited; therefore, I shall limit comments to the following remarks:

 

1) Ep. chevalieri prefers the clear banks of rivers, whereas multifasciatus prefers the more stagnant waters of the basin. It was shown that Ep. multifasciatus is very abundant in the basin belts, neighboring the plateau.

2) The same dichotomy could exist between Adamas formosus and Aphyoplatys duboisi but this point needs to be elaborated perhaps.

3) The Aphyosemion of the elegans group and A. splendidum are very rare in the flooded areas of the basin. The representatives of the elegans group are, in contrast, very abundant in the regions of the plateau where they live, often in the company of Ep. multifasciatus; the highly marshy areas of the Congo basin are probably not very favorable to them. Finally, as it was shown for the related species A. batesii, A. splendidum is caught in variable numbers, depending on time of collection, for unknown reasons. For example, at locality n° 140, only 40 km north of locality n° 157, A. splendidum was totally missing, although the biotope was favorable.

 

CONCLUSION

 

The Cyprinodonts which inhabit the Congo basin are different from those of the plateau.

A new species, very unique, has been discovered for which the creation of a new genus was seen justified. Three other species are also interesting:

Aphyoplatys duboisi, Epiplatys chevalieri and Aphyosemion splendidum.

It has been established that nigricans is a junior synonym of Ep. chevalieri, while A. kunzi is a junior synonym of A. splendidum.

Finally, Adamas formosus and Aphyoplatys duboisi are perhaps very primitive and relict and probably represent two parallel evolutionary lines. It would be useful to learn more about these fishes in order to understand better the evolution of the African Rivulins and the African Procatopodins.

 

 

BIBLIOGRAPHY

 

Clausen (H.S.), 1967. Tropical old world Cyprinodonts. Akademisk Forlag Copenhagen.

Huber (J .H.), 1977. Liste nominale annotée de Aphyosemion Myers avec description de Raddaella et Kathetys. Supplément à Killi Revue, 4 (4).

Huber (J.H.), 1978. Caractères taxinomiques et tentative de regroupement des espèces du genre Aphyosemion. Rev. fr. Aquariol., 5 (1).

Lambert (J.), 1961. Ann. Mus. Afr. Centr. (8) 93.

Pellegrin (J.), 1904. Bull. Mus. Hist. Nat., 10.

Pellegrin (J.), 1930. Bull. Soc. Zool. De France, 50.

 

Table I : proportions (as a % of standard length) and meristic data. 

Species	Localities	Sex	LS (mm)	LT (mm)	LT (%SL)	PD (%SL)	PA (%SL)	PV (%SL)	Hd (%SL)	Ht (%SL)	D	A	D/A	L.L.
Adamas formosus	n°133 (Holotype)	male	17.3	22.1	128	68	55	42	29	18	9	15	+14	29+2
	n°125	male	14	17.6	126	72	60	46	31	21	9	15	+14	27+1
	n°111	male	18.6	23.6	127	73	56	47	28	19	8	15	+13	27+2
	n°111	male	15.4	19.6	127	70	56	44	28	21	9	15	+12	27
	n°111	male	14.1	17.8	126	72	58	43	29	20	9	15	+13	27
Aphyoplatys duboisi	124	male	15.6	21	135	71	60	51	28	20	11	18	+ 9	26
	124	female	14.2	17.7	125	72	63	51	29	20	10	16	+ 8	27+1
	124	female	13	16.8	129	69	60	51	28	19	10	17	+ 8	26
	124	female	12.1	16	132	70	62	52	29	21	11	16	+ 8	26
	125	male	17.5	22.5	129	69	59	49	27	19	11	15	+ 7	26+1
Epiplatys chevaleri	n°129	male	31.6	37.6	119	76	58	49	28	20	8	14	+13	29
	n°129	female	20.9	24.4	117	78	58	49	29	18	8	13	+12	28+2
	n°129	juvenile	16.7	20.5	123	78	60	51	30	19	7	14	+13	27
	n°133	male	33.7	40.6	120	77	60	48	28	20	9	16	+12	27+2
	n°133	female	27	36	133	79	61	51	28	17	9	15	+12	27+2
	n°133	female	25.1	33.2	132	78	63	49	28	17	9	15	+11	28+2
Aphyosemion splendidum	lectotype	male	62.6	78.2	125	59	56	48	27	19	16	17	+ 3
	paralectotype	male	41.8	51.9	124	57	56	47	27	19	17	18	+ 4
	n°157	male	49.9	59.5	119	60	55	44	26	17	17	18	+ 3	36+1
	n°157	male	44.6	55.0	123	61	56	46	25	18	18	19	+ 4	37
	n°157	male	45.3	57.1	126	59	54	46	25	18	17	18	+ 4	38
	n°157	male	43.4	52.6	122	59	54	45	24	18	17	18	+ 4	36+2
	n°157	female	35.7	43.2	121	58	58	47	25	17	18	19	+4	35+3
A. kunzi s.s.	Makokou	male	42.4	52.5	124	58	55	48	25	17	17	17	+ 3
(coll. Brosset)	Makokou	male	39.2	46.7	119	59	56	43	24	17	16	17	+ 3
	Makokou	male	30.9	37	120	58	56	46	28	19	17	17	+ 4

  

Translation by George Davis for J.A.K.A. (revised J. Huber. November 2001)

First published in Rev. fr. Aquariol. 6 (1979). March 26. 1979. 5-10.

 

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