Petrocephalus grandoculis

Petrocephalus grandoculis Boulenger, 1920

Original Published Description:

Boulenger, G. A. (1920).  Poissons recueillis au Congo Belge par l'expédition de Dr C. Christy. Annales du Musée du Congo belge. Zoologie. Série I, Matériaux pour la faune du Congo. 2, 38.
 
Languages: English

Overview

General Description

Petrocephalus grandoculis is a medium–sized species within the genus Petrocephalus (maximum standard length observed = 97.8 mm). Body ovoid, body 2.5-3.1 longer than high (syntypes = 3.0–3.1) and laterally compressed. Head length 3.8–4.2 times in standard length (syntypes = 3.9–4.1). Eye quite large (2.8 ≤ head length/eye diameter ≤ 3.1, syntypes = 3.1–3.2). Snout short and round. Mouth very small (5.2 ≤ head length/head width ≤ 6.1, syntypes = 5.7–6.1), sub–terminal, opening under the anterior half of the eye. Teeth small and bicuspid, only 8–11 (syntypes = 10–11) in a single row in the upper jaw, 18–22 (syntypes = 19–20) in a single row in the lower jaw. 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 = 1.7]. Pre–dorsal distance slightly greater than pre–anal distance. Dorsal fin with 25–26 branched rays (syntypes = 24–26). Anal fin with 30–33 branched rays (syntypes = 30–31). Scales cover the body, except for the head. Lateral line visible and complete with 37–39 (syntypes = 38) pored scales along its length. Caudal peduncle relatively thin (2.2 ≤ caudal peduncle length/caudal peduncle diameter ≤ 3.0, syntypes = 3.0). Twelve scales around the caudal peduncle. Skin on head thick, becoming opaque with formalin fixation. The numerous Knollenorgan electroreceptors on the head are organized into two visible rosettes (Augenrosette and Nackenrosette). The third rosette, the Kehlrosette, is present but this structure is not as discernable as it is in other species (e.g., P. binotatus).

Body mostly white–silver. Dorsum slightly darker than the rest of the body. Pigmentation pattern consists of two melanin markings: (1) a distinct, but weak, round black mark below the anterior base of the dorsal fin (first to fifth rays); (2) a crescent–shaped mark at the base of the caudal fin, which does not extend onto the rayed portions of the upper and lower caudal fin lobes. No black mark is present at the base of pectoral fin. The fins themselves are translucent.

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

Description

Diagnostic Description

Petrocephalus grandoculis is distinguished from all other Petrocephalus species in Central Africa by the following combination of characteristics. Very small mouth (5.2 ≤ head length /head width ≤ 6.1). Eight to 11 teeth in the lower jaw. Upper jaw with 18–22 teeth. Eye large (2.8 ≤ head length/eye diameter ≤ 3.2). Snout short. Dorsal fin with 24–26 branched rays. Anal fin with 30–33 branched rays. Pigmentation pattern consists of two melanin markings (black patches): (1) a distinct, although generally weak, round black mark on each side of the body below the anterior base of the dorsal fin (first to fifth rays); (2) a crescent–like mark at the base of the caudal fin on each side, not extending onto the rayed portions of the upper and lower caudal fin lobes. EOD of normal polarity.

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

Electric Organ Discharge

EODs have only been recorded from one individual of Petrocephalus grandoculis, which was collected in Odzala National Park. The EOD duration for this individual (0.380 msec, based on 1.5% deviations from baseline) and the general appearance of the waveform are typical for Petrocephalus.

Electrocyte anatomy is unknown, although it is expected to be type "NPp" as deduced from the EOD waveform.

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

Size

To 97.8 mm SL

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

Ecology and Distribution

Distribution

Endemic to the central Congo basin. The type locality is situated on the Lower Congo River at Kinshasa/Brazzaville. Specimens known from several localities.

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

Evolution and Systematics

Phylogenetic Relationships

Petrocephalus grandoculis belongs to a large clade of Central Africa endemic species of Petrocephalus.

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

References

Boulenger, G. A. (1920).  Poissons recueillis au Congo Belge par l'expédition de Dr C. Christy. Annales du Musée du Congo belge. Zoologie. Série I, Matériaux pour la faune du Congo. 2, 38.
 
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.
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.
 
Poll, M. (1939).  Les Poissons du Stanley-Pool. Annales du Musée du Congo belge. C.–Zoologie Série I.. 4, 1-60.
 
Roberts, T. R., & Stewart D. J. (1976).  An ecological and systematics survey of fishes in the rapids of the Lower Zaïre or Congo River. Bulletin of the Museum of Comparative Zoology. 147, 239–317.
 
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Boulenger1920_Poissons recuellis au Congo Belge.pdf4057.52010-11-10T20:23:13Z
Lavoué et al 2010.pdf4462.32010-11-19T21:53:21Z
Poll_1939.pdf3843.62010-11-23T20:58:48Z
Roberts & Stewart 1976.pdf2731.92010-12-07T20:24:40Z
david_poll_1937.pdf857.12014-03-18T20:15:15Z
lavoue_et_al_2008d.pdf2492.52011-02-28T05:43:08Z