Petrocephalus grandoculis Boulenger 1920
Creators: name: Lavoué, Sébastien
name: Sullivan, John P.
name: Arnegard, Matthew E.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Osteoglossiformes
Mormyridae
Petrocephalus
Petrocephalus grandoculis

description: Petrocephalus grandoculis Boulenger, 1920
Petrocephalus grandoculis Boulenger (1920): 10.
[Odzala field identification: Petrocephalus sp. 10, OTU 10]
Images. Fig. 12 A, photo of a live specimen from Odzala, Fig.12 B, photo of a preserved specimen from Odzala and Fig. 14, drawing of one syntype from Boulenger (1920), p. 10. Photo of two syntypes in Harder (2000).
Type material. Syntypes, BMNH 1919.9.10.16–17 [examined] and MRAC 7158, 7167 [not examined]. Leopoldville (Kinshasa), Zaire (Democratic Republic of the Congo)[estimated 4.25 ° S, 15.33 ° E].
Other specimens. We also examined two specimens from Odzala National Park (specimen list provided in the section “additional material examined”).
Diagnosis. The following diagnosis is based on all examined specimens of P. grandoculis, regardless their geographic origins. Petrocephalus grandoculis is distinguished from all other Petrocephalus species in Central Africa by the following combination of characteristics. Very small mouth (5.2 ≤ HL/MW ≤ 6.1). Eight to 11 teeth in the lower jaw. Upper jaw with 18–22 teeth. Eye large (2.8 ≤ HL/ED ≤ 3.2). Snout short (6.5 ≤ HL/SNL ≤ 10.7). 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); and (2) a crescentlike 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.
Min–Max Min–Max
Meristic counts:
Number of scale rows between the anterior base of 15– 15 13–15 11 the anal fin and the lateral line (SDL)
Number of teeth in the upper jaw (TUJ) 10–11 8–8 12 Number of teeth in the lower jaw (TLJ) 19–20 18–22 14 Description. Table 10 provides morphometric ratios and meristic data for the two Kinshasa syntypes and, separately, for the two non-type specimens from Odzala National Park. The following description applies to the two Odzala specimens, with separate reference to the two syntypes. Petrocephalus grandoculis is a medium-sized species within the genus Petrocephalus (maximum SL observed = 97.8 mm). Body ovoid, longer than high (2.5 ≤ SL/H ≤ 2.7, 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 ≤ HL/ED ≤ 3.1, syntypes = 3.1–3.2). Snout short (6.5 ≤ HL/SNL ≤ 10.7, syntypes = 6.5–6.7) and round. Mouth very small (5.2 ≤ HL/MW ≤ 5.9, syntypes = 5.7–6.1), sub-terminal, opening under the anterior half of the eye. Teeth small and bicuspid, only eight (syntypes = 10 or 11) in a single row in the upper jaw, 18–22 (syntypes = 19 or 20) in a single row in the lower jaw. Dorsal and anal fins originate in the posterior half of the body [SL/PDD = 1.6 and SL/PAD = 1.7 (syntypes = 1.7–1.8), respectively]. Pre-dorsal distance slightly greater than pre-anal distance (1.0 ≤ PDD/ PAD ≤ 1.1). Dorsal fin with 25–26 branched rays (syntypes = 24–26). Anal fin with 32 or 33 branched rays (syntypes = 30 or 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 ≤ CPL/CPD ≤ 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 clearly organized into two visible rosettes (Augenrosette and Nackenrosette). In our examination of specimens, we were uncertain about the definitive presence of the third rosette, the Kehlrosette, as this structure did not appear to us to be as distinct as it is in other species (e.g., P. binotatus). However, more definitive recent analysis using toluidine blue staining of the skin now suggests that the Kehlrosette is present, but smaller and harder to discern than in other Petrocephalus (M. Hollmann and B. A. Carlson, unpub. obs.).
Live coloration (Fig. 12 A). 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); and (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 fins. The fins themselves are translucent.
Distribution (Fig. 1). Endemic to the Congo basin. The type locality is situated on the Lower Congo River at Kinshasa. In Odzala, we collected only two specimens of P. grandoculis from the main channel of the Lékoli River.
Electric organ discharge (Fig. 12 C). EODs have only been recorded from one individual of P. 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. Statistics for waveform landmarks and other EOD measurements are provided by Lavoué et al. (2008). Electrocyte anatomy is unknown, although it is expected to be type "NPp" as deduced from the EOD waveform.
description: Published as part of Lavoué, Sébastien, Sullivan, John P. & Arnegard, Matthew E., 2010, African weakly electric fishes of the genus Petrocephalus (Osteoglossomorpha: Mormyridae) of Odzala National Park, Republic of the Congo (Lékoli River, Congo River basin) with description of five new species, pp. 1-52 in Zootaxa 2600 on pages 35-38, DOI: 10.5281/zenodo.197589