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Aphyosem ion mengilai, a new killifish species from the northern Massif du Chaillu, central Gabon (Cyprinodontiformes: Nothobranchiidae).

Abstract

Aphyosemion mengilai, new species, is described from small streams belonging to the hydrographic system of the Ikoy River basin on the northern part of the Massif du Chaillu, central Gabon. It is similar to A. grelli and distinguished from all other congeners in having grey to black margins in the unpaired fins in males and females. It can be distinguished from A. grelli by having more dorsal and anal fin rays in males and females, by the more anterior insertion of dorsal fin relative to anal-fin origin, by having more scales on transverse series, more scales around caudal peduncle, and by the presence of light blue submarginal stripes in dorsal, anal, and caudal fin in females. Aphyo-semion mengilai belongs to a clade, herein named A. grelli species group, which is diagnosed by the unique distinctive colour pattern of males and females consisting of grey to black margins on dorsal and anal fins.

Zusammenfassung

Aphyosemion mengilai, n. sp., aus kleinen Bachen des hy-drographischen Systems des Ikoy-Beckens im nordlichen Teil des Massif du Chaillu in Zentralgabun wird beschri-eben. Es ahnelt A. grelli und unterscheidet sich von alien an-deren Gattungsangehorigen durch den Besitz grauer bis schwarzer Rander der unpaarigen Flossen der Mannchen und Weibchen. Es kann von A. grelli durch den Besitz von mehr Flossenstrahlen in der Dorsale und Anale bei Mann-chen und Weibchen, den weiter vorne befindlichen Ansatz der Dorsale im Verhaltnis zum Ansatz der Anale, den Besitz von mehr Schuppen in Langsreihe, mehr Schuppen urn den Schwanzstiel herum und das Vorhandensein hellblauer sub-marginaler Streifen in der Dorsale, Anale und Caudale der Weibchen unterschieden werden. Aphyosemion mengilai gehort zu einer Gruppe, die hier A. grelli-Artengruppe genannt wird, welche durch das einzigartige charakteristische Farbungsmuster von Mannchen und Weibchen diagno-stiziert werden kann, bestehend aus grauen bis schwarzen Randern der Dorsale und Anale.

Resume

Aphyosemion mengilai, nouvelle espece, est decrit venant de petits cours d'eau du systeme hydrographique du bassin de la riviere Ikoy, situe sur la partie nord du Massif du Chaillu, Gabon central. Elle se rapproche d'A. grelli et se distingue de tous ses autres congeneres par des liseres noirs sur les nageoires impaires des males comme des femelles. Elle se distingue d'A. grelli par un nombre plus leve de rayons dorsaux et a l'anale des males et des femelles, par l'insertion plus anterieure de la dorsale par rapport a la naissance de l'anale, par un nombre plus eleve d'ecailles en series transversales, plus d'ecailles autour du pedoncule caudal et par la presence de lignes submarginales bleu clair sur les nageoires dorsales, anale et caudale des femelles. Aphyosemion mengilai fait partie d'un clade, designe ici comme groupe d'especes A. grelli, qui se base sur le patron de coloration unique et distinctif des males et des femelles, consistant en liseres gris a noirs sur les dorsales et l'anale.

Sommario

Aphyosemion mengilai, nuova specie, e descritta da piccoli corsi d'acqua appartenenti al sistema idrografico del bacino del flume Ikoy nella parte settentrionale del massiccio del Chaillu, Gabon centrale. E simile ad A. grelli e si distingue da tutti gli altri congeneri per avere margini grigi o neri delle pinne impari sia nei maschi sia nelle femmine. Essa puo essere distinto da A. grelli per avere in entrambi i sessi un maggior numero di raggi dorsali e anali, per l'inserimen-to piit anteriore della pinna dorsale rispetto alrorigine della anale, per un maggior numero di scaglie su serie trasversali, piii scale intorno al peduncolo caudale e per la presenza di strisce submarginali blu chiaro nella dorsale, anale e caudale delle femmine. Aphyosemion mengllai appartiene a un clade, ivi denominato gruppo di specie A. grelli, che viene diagno-sticato per la peculiare livrea di maschi e femmine, caratte-rizzata di margini grigio-neri sulle pinne dorsale ed anale.

INTRODUCTION

The Massif du Chaillu is a mountain range starting in central Gabon and extending into the Republic of Congo with an average elevation of 400 to 700 metres a.s.1.; systematic collections along the few roads in this mountain range have shown a remarkable present day diversity of the nothobranchiid fauna, in particular for the species belonging to the genus Aphyosemion Myers 1924 (Valde-salici & Eberl 2013). This genus is a speciose clade of West African killifishes, with over 80 species inhabiting small streams from Togo to Angola along the coastal plain, on the inland plateau, and the lowlands of the Congo River basin (Huber 2000).

In the Gabonese part of the Massif du Chaillu, ten Aphyosemion species are currently known, apart from A. grelli Valdesalici & Eberl 2013, A. hofman-ni Radda 1980, A. hanneloreae Radda & Piirzl 1985, and A. wuendschi Radda & Piirzl 1985 not belonging to any defined group and A. joergen-scheeli Huber & Radda 1977, which seems genetically close to A. escherichi (Ahl 1924), all remaining species belong to the A. coeleste Huber & Radda 1977 species group (Valdesalici & Eberl 2013).

In January 2006, the second author discovered an Aphyosemion from a stream on the northern part of the Massif du Chaillu. At first supposed to be A. grelli, it became apparent that these specimens represent a species unknown to science, which is herein formally described.

MATERIAL AND METHODS

Measurements and counts follow Amiet (1987), with modifications as per Valdesalici (2010). Measurements were made with a digital caliper, under a dissecting microscope, to the nearest 0.1 mm. Measurements are presented as percentage of standard length (SL), except for those related to head morphology, which are expressed as percentage of head length (HL). The number of all visible rays of the dorsal, anal, caudal, pelvic, and pectoral fins were counted; the abbreviation D/A means the relative position of the first dorsal-fin ray in regard to the opposite anal-fin ray. Scale count on the mid-longitudinal series is the number of scales between the upper attachment of the opercular membrane and the caudal fin base. Excluded are the scales posterior to the hypural junction, which were counted separately. Nomenclature for the neuromast system on the head follows Scheel (1968) and Huber (2000) and that for the frontal squamation follows Hoedeman (1958). Morphological data from Huber (1994), Huber & Radda (1977), Rad-da (1980), van der Zee & Sonnenberg (2010), and Valdesalici & Eberl (2013) were used here for comparisons. Osteological preparations (cleared and stained, C&S) were made according to Taylor & Van Dyke (1985), but not stained for cartilages.

The examined material is deposited in: Staatliches Museum far Naturkunde (SMNS), Stuttgart; Museum National d'Histoire Naturelle (MNHN), Paris; Stefano Valdesalici Private Collection (CSV), Viano (RE), Italy.

Aphyosemion mengilai, n. sp.

(Figs 1-3, Table I)

Table I. Morphometric data of Aphyosemion mengilai n. sp.

             Holotype  All males  Mean   SD    females  Mean   SD
                           (n=8)                 (n=8)

Standard         39.2  27.0-39.2  34.3  3.9  27.4-41.6  35.2  5.9
length (mm)

Percentage
of standard
length

Depth at         22.9  21.4-22.9  21.9  0.6  21.5-22.9  22.0  0.5
pelvic fin

Predorsal        63.5  60.5-66.5  64.0  1.9  64.1-68.5  65.9  1.4
length

Length of        15-6  15.6-19.8  17.9  1.2  14.1-19.6  15.9  1.6
dorsal fin
base

Preanal          58.6  57.0-61.3  59.4  1.4  59.1-62.4  60.8  1.1
length

Length of        20.4  18.8-22.6  20.1  1.3  16.7-19.6  17.9  1.0
anal fin
base

Prepelvic        48.4  47.2-51.6  49.5  1.8  45.1-52.6  49.3  2.4
length

Length of        20.9  17.1-23.9  21.4  2.1  21.2-23.4  22.9  1.1
caudal
peduncle

Depth of         13.7  11.4-13.7  12.4  0.8  11.7-13.1  12.4  0.5
caudal
peduncle

Head length      27.5  25.5-27.5  26.7  0.7  24.2-29.3  26.8  1.4

Percentage
of head
length

Snout              25  24.4-33.3  28.6  3.1  24.5-28.8  25.7  1.5
length

Eye              25.9  23.2-37.6  27.9  4.7  23.4-31.5  27.6  2.2
diameter

Interobital      15.6  38.6-45.4  34.3  3.9  38.6-45.2  41.4  3.2
width


Holotype: SMNS 27069, male, 39.2 mm SL; Gabon, Province de la Ngounie, Departement de Tsamba-Magotsi, 42 km east of Ikobey (Ikobe), small stream named [degrees]bele in the village Evouta, 01[degrees]03'75"S, 11[degrees]11'34"E, Wolfgang Eberl & Francois Mengila 20 January 2006.

Paratypes: SMNS 27070, 3 males 36.2-38.2 mm SL and 4 females 39.2-41.6 mm SL, same data as holotype. MNHN 2013-0645: 2 males 32.2-33.2 mm SL & 2 females 29.0-30.1 mm SL, same data as above, Wolfgang Eberl & Guido Passaro, 15 January 2012. MNHN 2013-0646: 1 male 33.0 SL & 1 female 33.3 mm SL: Gabon, stream without a name in the village Omboue, 01[degrees]01'06,3" S 11[degrees]14'35,2" E, Wolfgang Eberl & Guido Passaro, 16 January 2012.

MNHN 2013-0647: 1 male 27.0 SL & 1 female 27.4 mm SL: Gabon, stream Mongadi in the village Divinde, 01[degrees]02'17,0"S 11[degrees]09'21,2"E, Wolfgang Eberl & Guido Passaro, 16 January 2012.

Additional material, non type: CSV 1012, 1 male 34.0 mm SL C&S, same data as holotype.

Diagnosis: Aphyosemion mengilai can be distinguished from all other congeners apart from A. grelli by having grey to black margins in the unpaired fins in males and females. Distinguished from A. grelli by having more dorsal and anal fin rays in males and females (13-14 vs. 10-12 and 15-16 vs. 13-14), by greater dorsal fin base length (14.1-19.6 vs. 12.513.9% SL), and shorter preanal length in females (59.1-62.4 vs. 62.8-63.9% SL), relatively greater anal fin base length in males (18.8-22.6 vs. 17.219.8 % SL), by the more anterior insertion of dorsal fin relative to anal fin origin (D/A 4-6 vs. D/A 6-7), by having more scales on transverse series (11-12 vs. 9-10), more scales around caudal peduncle (15-18 vs. 12), and by presence of light blue submarginal stripes in dorsal, anal, and caudal fin in females (vs. absence).

Description: Morphometric data presented in Table I. Aphyosemion mengilai shows sexual dimorphism: males are more colourful; dorsal and anal fin positioned more anteriorly compared to females. Body slightly laterally compressed; dorsal profile slightly convex, maximum body depth at pelvic-fin origin. Ventral profile slightly convex; profile of the caudal peduncle slightly concave to nearly straight. Snout slightly rounded, mouth directed upwards, lower jaw longer than upper jaw. Caudal fin sub-truncated. Dorsal and anal fins located posterior to mid-body, tips rounded.

Frontal neuromast series 'open' type. Anterior supraorbital series with three neuromasts. Preoper-cular canal with six pores. One neuromast on each scale of median longitudinal series.

Scales cycloid, body entirely scaled; frontal squamation G-type; scales on mid-longitudinal series 3032+4; scales on transverse series 11-12, scales around caudal peduncle 15-16. Dorsal-fin rays 13-14, first dorsal-fin ray on vertical between 4th to 6th anal-fin ray; anal-fin rays 15-16; caudal-fin rays 26-29; pectoral-fin rays 17-18; pelvic-fin rays 6.

Premaxilla and dentary with unicuspid, slightly curved teeth. Vomerine teeth absent, anterior border of vomer thickened. Post-temporal lateral process absent. Anterodorsal process of the urohyal bifid.

Coloration in life : Males (Fig. 2). Body and head metallic light blue, darker dorsally, four interrupted horizontal series of red dots on flank, dots in close proximity from each other. Two narrow oblique red bars on opercle. Dorsal, anal, and caudal fin light blue, with narrow black distal margin, horizontal series of dots on the proximal parts of dorsal and anal fin. Pelvic fin light blue. Pectoral fin hyaline with ventral light blue margin.

Females (Fig. 3). Body and head brownish-grey, two interrupted horizontal series of small red dots on flank. Pectoral fin hyaline, dark yellow at base. Pelvic fin dark yellow with light blue margin. Dorsal and anal fins dark yellow with narrow grey distal margins and light blue submarginal stripe. Caudal fin hyaline, dark yellow at base, marginal region grey, submarginal portion light blue.

Distribution (Fig. 4): Aphyosemion mengilai is known from four localities belonging to the hydrographic system of the Ikoy River basin on the northern part of the Massif du Chaillu, central Gabon.

Etymology: The new species is dedicated to Francois Mengila, born in Lambarene, living in Libreville, in appreciation of his continued help as driver and guide during all collecting trips of the second author in Gabon since 2002.

DISCUSSION

Both A. mengilai and A. grelli are distributed in the same geographical area and in the same hydrographic basin, on the northern part of the Massif of Chaillu, but A. grelli is present on the western slope and is known only from one locality in the drainage of the lower Ikoy River, whereas A. mengilai is known further east in the central Ikoy and mainly from some localities in the drainage of its tributary Oumba River, where so far it has not been found together with another killifish species.

At a location only a few kilometers away from two collecting places of A. mengilai and in a left-margin affluent of the Ikoy River, A. joergenscheeli and A. citrinezpinnis Huber 8c Radda 1977 were found by the second author, so that their known distribution area has to be widened considerably to the north. A. mengilai is clearly separated by A. joergenscheeli by having horizontal stripes on flank (vs. vertical bars on caudal peduncle), by having light blue dorsal, anal, and caudal fin, with narrow black distal margin (vs. light blue margin and red subdistal stripe), by the more posterior insertion of dorsal fin relative to anal-fin origin (D/A 4-6 vs. D/A 1-4), and by having more scales on mid-longitudinal series (30-32 vs. 28-29). A. mengilai is clearly separated from A. citrinezpinnis (see below comments on A. coeleste species group) by having stripes on flank (vs. absence), by having light blue dorsal, anal, and caudal fin (vs. lemon yellow), by having more dorsal fin rays in males and females (13-14 vs. 11-12), and by the more anterior insertion of dorsal fin relative to anal-fin origin (D/A 4-6 vs. D/A 7-8).

In geographical terms, A. mengilai occurs in closest proximity also to A. escherichi, which is known from a locality situated 40 km west of the type locality of the former. It is separated from A. escherichi by having light blue dorsal, anal, and caudal fin, with narrow black distal margin (vs. light blue to yellowish broad margin, sometimes with red rim and red sub-distal stripe), and by having more dorsal and anal fin rays in males and females (13-14 vs. 11-12 and 1516 vs. 13-15). Aphyosemion mengilai and A. grelli are clearly separated from the other known species presenting black margins on unpaired fins in males, Aphyosemion congicum (Ahl 1924) because those species do not present less than 10 dorsal fin-rays, the females do not show a strong reticulation due to dark scale borders, and the edges of the caudal fin in males are not pointed or extended as in the species of the subgenus Aphyosemion (Huber 2005; van der Zee & Sonnenberg 2011). Both species can be distinguished from A. labarrei (Poll 1951) by having stripes on flank (vs. a dense pattern of large red blotches, forming fused irregular bands on caudal peduncle), by the shape of the caudal fin (subtrun-cated vs. pointed dorsally and ventrally), and by presenting more circumpeduncular scales (15-16 vs. 13-14). Aphyosemion mengilai and A. grelli can be distinguished from members of the Aphyosemion coeleste species group (Huber & Radda 1977), A. ocellatum Huber & Radda 1977, and A. passaroi Huber 1994, by possessing males with dotted pattern on the flank from humeral to caudal-fin base (vs. absence or if present, limited to humeral area or few, smaller and irregularly distributed dots), and from A. teugelsi van der Zee & Sonnenberg 2010 by different colour of the pectoral-fin margin (light blue vs. dark brown), by the different shape of the dorsal and anal fins margins (rounded vs. pointed), by more pectoral- and caudal-fin rays (17-18 vs. 1415 and 26-29 vs. 23-25, respectively), and by more scales on transverse series (11-12 vs. 7-8) as reported in Valdesalici & Eberl (2013).

Apart from differences reported in Diagnosis, there is also an apparent difference in maximum SL, with A. mengilai attaining 40 mm versus less than 30 mm SL for A. grelli. Aphyosemion mengilai is hypothesized to be a member of a clade, herein termed A. grelli species group, including these two species, defined by an apomorphic colour pattern of males and females, consisting of grey to black margins on dorsal and anal fins. This combination does not occur in other Aphyosemion, in which, if present, the black margin on fins is present only in males (Valdesalici & Eberl 2013; Van der Zee & Sonnenberg 2010).

ACKNOWLEDGEMENTS

We want to thank the following persons for their contribution and support both in the field and during the preparation of this manuscript: Guido Passaro, Francois Mengila, Winfried Grell, Chiara Valdesalici, and Francesca Fontana. We are grateful to Ronald Fricke and Andreas Schluter (both from SMNS), and Romain Causse and Patrice Pruvost (both from MNHN) for allowing the examination of material under their care.

REFERENCES

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HOEDEMAN, J. 1958. The frontal scalation pattern in some groups of toothcarps (Pisces: Cyprinodontiformes). Bulletin of Aquatic Biology, 1 (3): 23-28.

HUBER, J. H. 1994. Aphyosemion passaroi, espece inedite du Gabon sud-oriental, au patron de coloration unique et description complementaire de Aphyosemion deco rsei (Pellegrin). Cyprinodontiformes, Aplocheilidae. Revue francaise d'Aquariologie flerpetologie, 20 (3): 77-79.

HUBER, J. H. 2000. Mi-Data 2000. Updated checklist of taxonomic names, collecting localities and bibliographic references of oviparous Cyprinodont fishes (Cyprinodontiformes). Societe Francaise d'Ichtyologie, Paris. 538 pp.

HUBER, J. H. 2005. Identifikation einer kleinen Sammlung von Aphyosemion aus Zaire im Miinchener Museum (ZS.M), mit weiteren Kommentaren iiber die Validitiit der bekannten Komponenten der elegans-Superspezies. 1. Teil Deutsche Killifisch Gemeinschaft Journal, 37: 8-21.

HUBER, J. H. & RADDA, A. C. 1977. Cyprinodontiden-Stu-dien in Gabun. IV. Das Du Chaillu-Massiy. Aquaria: Viva-ri stische Fachzeitschrifi fir die Schweiz und Osterreich, 24: 99-110.

RADDA, A. C. 1980. Beschreibung zweier neuer Aphyosemion-Arten aus Stid-Gabun. Aquaria 27 (11): 201-205.

SCHEEL, J. J. 1968. Rivulins of the Old Word Tropical Fish Hobbyist Publication, Neptune City, 480 pp.

TAYLOR, W. R. & VAN DYKE G.C. 1985. Revised procedures for staining and clearing small fishes and other vertebrates for bone and cartilage study. Cybium, 9 (2): 107-109.

VALDESALICI S. 2010. Nothobranchius boklundi (Cyprin-odontiformes: Nothobranchiidae): a new annual killifish with two male colour morphs from the Luangwa River basin, Zambia. aqua, International Journal of Ichthyology 16 (2): 51-60.

VALDESALICI S. & EBERL W. 2013. Aphyosemion grelli (Cyprinodontiformes: Nothobranchiidae), a new species from the Massif du Chaillu, southern Gabon. Vertebrate Zoology, 63 (2): 155-160.

VAN DER ZEE, J. R. & SONNENBERG, R. 2010. Aphyosemion teugelsi (Cyprinodontiformes: Nothobranchiidae), a new species from a remote locality in the southern Democratic Republic of the Congo. Zootaxa, 2724: 58-68.

VAN DER ZEE, J. R. & SONNENBERG, R. 2011. Aphyosemion musafirii (Cyprinodontiformes: Nothobranchiidae), a new species from the Tshopo Province in the Democratic Republic of Congo, with some notes on the Aphyosemion of the Congo Basin. Bonn zoological Bulletin 60: 73-87.

Stefano Valdesalici (1) and Wolfgang Eberl (2)

1) Via Ca Bertacchi 5, 42030 Viano (RE), Italy. E-mail: valdekil@tinit or valdesalici.stefano@gmail.com

2) Haldenstr. 27, D-73614 Schorndorf, Germany. E-mail: wolfgang.eberl@yahoo.de

Received: 28 September 2013-Accepted: 24 February 2014
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