Petrocephalus balayi

Petrocephalus balayi Sauvage, 1883

Original Published Description:

Sauvage, H. E. (1883).  Descriptions de quelques poissons de la collection du Muséum d'Histoire Naturelle. Bulletin de la Société Philomatique de Paris. 7, 156-161.
 
Languages: English

Overview

General Description

Petrocephalus balayi, described by Sauvage (1883), is a large, robust species within the genus Petrocephalus (maximum standard length = 95.6 mm SL). Body ovoid, body 2.5–2.8 longer than high and laterally compressed. Head length between 3.3 and 3.4 times (holotype = 3.3) in standard length. Head width 1.9 times (holotype = 2.2) in head length. Snout short, wide and square–shaped. Mouth wide (2.7 ≤ Head length/Mouth width ≤ 3.1, holotype = 3.4), sub–terminal, opening under the anterior half of the eye. Teeth small and bicuspid, 30 in a single row in the lower jaw and 20–21 in the upper jaw. Eye small (4.5 ≤ Head length/Eye diameter ≤ 4.8, holotype = 4.6). Dorsal and anal fins originate in the posterior half of the body (standard length/pre–dorsal distance = 1.6 and standard length/pre–anal distance = 1.6), with pre–dorsal distance equal to pre–anal distance. Pre–dorsal distance slightly exceeds pre–anal distance in the holotype. Dorsal fin with 22 branched rays (holotype = 21). Anal fin with 27 branched rays (holotype = 26). Scales cover the entire body, except for the head. Lateral line visible and complete with 36 pored scales. Caudal peduncle relatively thick (1.7 ≤ CPL/CPD ≤ 1.8, holotype = 2.3). Twelve circumpeduncular scales. Skin on head thick, becoming opaque with formalin fixation. Knollenorgans organized into the three rosettes.

Body gray/silver, slightly darker dorsally. The head is also slightly darker than the rest of the body. Iridescent pigment along side of body sometimes visible with correct orientation of light. Pigmentation pattern with three black patches: (1) a distinct round black mark on each side of the body below the dorsal fin origin; (2) an ovoid black mark on each side at the base of the caudal peduncle that does not extend onto the upper and lower parts of the caudal fin; (3) a black mark, sometimes diffuse in larger individuals but always present, at the base of the pectoral fins. The fins themselves are translucent.

Author(s): Lavoué, Sébastien
Rights holder(s): Lavoué, Sébastien

Description

Diagnostic Description

Petrocephalus balayi is distinguished from all other Petrocephalus species in Central Africa by the following combination of characteristics. Dorsal fin with 20–22 branched rays. Anal fin with 26–27 branched rays. Eye small (4.5 ≤ Head length/eye diameter, range = 4.5–4.9). Mouth very wide (Head length/mouth width ≤ 3.9, range = 2.7–3.9) associated with a very characteristic head shape when viewed from below. Fourteen teeth or more in the upper jaw (range = 14–21). Twenty–eight teeth or more in the lower jaw (range = 28–38). Melanin pattern consisting of the following: (1) a distinct black round mark on each side of the body below dorsal fin origin; (2) an ovoid mark on each side at the base of the caudal peduncle, not extending onto the upper and lower parts of the caudal fin; (3) a black mark, sometimes diffuse but always present, at the base of the pectoral fins. The EOD is of normal polarity.

Author(s): Lavoué, Sébastien
Rights holder(s): Lavoué, Sébastien

Electric Organ Discharge

EOD recordings are only available for a small number of individuals: one specimen from the coastal river Doumvou at Doumvou, Gabon (Lavoué, et al., 2004); and two specimens from Odzala National Park, Republic of Congo (Lavoué, et al., 2008). Among these few recordings, the overall waveform of EODs produced by P. balayi seems to be typical for the genus, similar to those produced by several other Petrocephalus species (mainly biphasic). EOD duration = 0.324 – 0.340 msec.

Electrocytes in P. balayi are of type NPp.

Author(s): Lavoué, Sébastien
Rights holder(s): Lavoué, Sébastien

Size

to 95.6mm SL

Author(s): Lavoué, Sébastien
Rights holder(s): Lavoué, Sébastien

Ecology and Distribution

Distribution

Petrocephalus balayi occurs in the southern part of the Lower Guinea province (from the Ogooué River) and in the Congo River basin, including Odzala National Park and the Lower Congo River

Author(s): Lavoué, Sébastien
Rights holder(s): Lavoué, Sébastien

Ecology

In Odzala, Petrocephalus balayi seems to prefer the small tributary creeks flowing through forest. In Gabon (Lower Guinea province), Petrocephalus balayi occurs in the lower courses of the Ogooué River and numerous associated lakes (and their tributary streams), as well as in small coastal creeks from south of the Ogooué to the border with the Congo.

Author(s): Lavoué, Sébastien
Rights holder(s): Lavoué, Sébastien

Evolution and Systematics

Phylogenetic Relationships

Petrocephalus balayi forms a monophyletic group with Petrocephalus odzalaensis and Petrocephalus binotatus.

Author(s): Lavoué, Sébastien
Rights holder(s): Lavoué, Sébastien

Taxonomic Notes

often spelled "ballayi" but original spelling is "balayi"

References

Banister, K. E., & Bailey R. G. (1979).  Fishes collected by the Zaïre River Expedition, 1974-75. Zoological Journal of the Linnean Society. 66,
 
Bigorne, R. (1990).  Mormyridae. (LévêqueC., PaugyD., TeugelsG G., Ed.).Faune des poissons d'eaux douces et saumâtres de l'Afrique de l'Ouest = The fresh and brackish water fishes of West Africa. 122-184. Paris, Tervuren (Belgium): ORSTOM, MRAC.
 
Boulenger, G. A. (1899).  A revision of the genera and species of fishes of the family Mormyridae. Proceedings of the General Meetings for Scientific Business of the Zoological Society of London. 1898, 775-821.
Boulenger, G. A. (1909).  Catalogue of the Fresh-Water Fishes of Africa in the British Museum (Natural History). I, 373. London: British Museum (Natural History).
 
David, L., & Poll M. (1937).  Contribution à la faune ichthyologique du Congo Belge: Collections du Dr. H. Schouteden (1924-1926) et d'autres récolteurs. Annales du Musée du Congo Belge (Série 1). 3 (fasc. 5), 189–294.
 
Harder, W. (2000).  The Mormyridae and other Osteoglossomorpha (CD-ROM). World Biodiversity Database, CD-ROM Series. 2000, New York: Springer Verlag, ETI-UNESCO.
Hopkins, C. D., Lavoué S., & Sullivan J. P. (2007).  12. Mormyridae. (StiassnyM L J., TeugelsG G., HopkinsC D., Ed.).The Fresh and Brackish Water Fishes of Lower Guinea, West-Central Africa. 1, 220–334.
 
Lavoué, S., Arnegard M. E., Sullivan J. P., & Hopkins C. D. (2008).  Petrocephalus of Odzala offer insights into evolutionary patterns of signal diversification in the Mormyridae, a family of weakly electrogenic fishes from Africa. Journal of Physiology-Paris. 102, 322-339. Abstract
 
Lavoué, S., Sullivan J. P., & Arnegard M. E. (2010).  African weakly electric fishes of the genus Petrocephalus (Osteoglossomorpha: Mormyridae) of Odzala National Park, Republic of Congo (Lékoli River, Congo River basin) with description of five new species. Zootaxa. 2600, 1-52.
 
Pellegrin, J. (1908).  Sur une seconde collection de poissons recueillis par M. E. Haug à Ngomo. Bulletin de la Société Philomatique de Paris. 11, 184-190.
 
Poll, M. (1939).  Les Poissons du Stanley-Pool. Annales du Musée du Congo belge. C.–Zoologie Série I.. 4, 1-60.
 
Sauvage, H. E. (1883).  Descriptions de quelques poissons de la collection du Muséum d'Histoire Naturelle. Bulletin de la Société Philomatique de Paris. 7, 156-161.
 
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