Petrocephalus sullivani, Lavoué & Hopkins & Toham, 2004

Lavoué, Sébastien, Hopkins, Carl D. & Toham, André Kamdem, 2004, The Petrocephalus (Pisces, Osteoglossomorpha, Mormyridae) of Gabon, Central Africa, with the description of a new species, Zoosystema 26 (3), pp. 511-535 : 523-526

Petrocephalus sullivani n. sp.

( Figs 4D; 5D ; 6B )

TYPE MATERIAL. — Holotype: Gabon, Ogooué River near the park of La Lopé, 00°06’S, 11°35’N, 20.VIII.2001, M. E. Arnegard, C. D. Hopkins, S. Lavoué and T. Uschold coll., Ƌ 93.1 mm SL ( MNHN 2003-619 ) . Paratypes: same locality, collectors, and date as the holotype, 32 specimens in total ( MNHN 2002-266 , 10 specimens; CU88992, 6 specimens and CU83120, 2 specimens; MRAC A3-06 -P- 1-7, 7 specimens; AMNH 233602 , 7 specimens) .

OTHER MATERIAL EXAMINED. — Gabon. Ogooué basin, tributary Ivindo at the rapids of Loa Loa , downstream of Makokou , 00°34’N, 12°52’E, 1964, J. Géry coll., 2 specimens ( MNHN 1987-899 ). — Ogooué basin, tributary Ivindo at the rapids of Loa Loa , downstream of Makokou , 00°34’N, 12°52’E, 28.IX.1964, J. Géry coll., 1 specimen ( MNHN 1987-898 ). — Nyanga basin, River Moukalaba nearby of the ferry at Mougambou, 02°47’S, 10°44’E, 22.VII.2001, S. Lavoué and V. Mamonekene coll., 4 specimens ( MNHN 2002-263 ). — Ogooué basin River Ikoy at Ikobey, 01°03’S, 10°59’E, 30.VI.2001, S. Lavoué, V. Mamonekene and J. H. Mvé Beh coll., 1 specimen ( MNHN 2002-264 ). — Ogooué basin, River Onoy , 01°50’S, 11°15’E, 18.VII.2001, S. Lavoué and V. Mamonekene coll., 2 specimens ( MNHN 2002- 265 ). — Ogooué basin, Louétsi River , at the falls of Bongolo, 37 km northeast of Ndendé , 02°31’S, 11°20’E, 3.X.1986, T. Roberts coll., 4 specimens ( MRAC 91-79 -P-89-92). — Ogooué basin, tributary Ivindo at the rapids of Loa Loa , downstream of Makokou , 00°34’N, 12°52’E, 28.IX.1964, J. Géry coll., 1 specimen ( MRAC 80-15 -P-59). — Ogooué basin, tributary Ivindo , Balé creek , upstream of the bridge, 00°31’N, 12°48’E, 13.IX.2001, S. Lavoué coll., 1 specimen (CU88993). — Nyanga basin, River Moukalaba , in the vicinity of the ferry at Mougambou , 02°47’S, 10°43’E, VIII.2001, S. Lavoué and D. Paugy coll., 1 specimen (CU88994). — Ogooué basin, tributary Ivindo at the confluence with the Nounah River , 01°11’N, 13°08’E, 27.I.1998, C. D. Hopkins, S. Lavoué and J. P. Sullivan coll., 3 specimens (CU). — Okoloville Creek crossing road, 01°29’S, 13°31’E, 11.VIII.1999, C. D. Hopkins, J. P. Sullivan, M. E. Arnegard, A. Ngankale, M. Nganjobi and J.-F. Liwouwou coll., 2 specimens (CU80359). — Ntem River just in front of auberge d’Ayengbe , 02°18’N, 11°33’E, 3.IX.1999, J. P. Friel, S. Lavoué and J. P. Sullivan coll., 2 specimens (CU81093) ; 2 specimens (CU80714) ; 5 specimens of which 2 examined in this study ( AMNH 233600 ) ; 2 specimens ( AMNH 233594 ). — Louétsi River, below dam in rocks, 02°14’S, 11°27’E, 23.VII.1999, J. P. Sullivan and J. Beck coll., 1 specimen ( AMNH 233592 ). — Louétsi River just below Bongolo Dam, 02°14’S, 11°27’E, 7.IX.1998, J. P. Sullivan and J. Beck coll., 1 specimen ( AMNH 233597 ). — Louetsi River just below Bongolo dam, 02°14’S, 11°27’E, 10.IX.1998, J. P. Sullivan and J. Beck coll., 1 specimen ( AMNH 233598 ). — Louetsi River at Bongolo dam below bridge, 02°14’S, 11°27’E, 14.IX.1998, J. P. Sullivan and J. Beck coll., 1 specimen ( AMNH 233601 ) .

Cameroon. Ntem basin at Nyabessan, 02°24’N, 10°24’E, 1979, D. Depierre coll., 3 specimens ( MNHN 1979-575). — Ntem basin at Nyabessan, 02°24’N, 10°24’E, 1979, D. Depierre coll., 1 specimen ( MNHN 1979-635).

ETYMOLOGY. — We dedicate this species to our colleague and friend, John P. Sullivan, in recognition of his contributions to the systematics of the Mormyridae . DIAGNOSIS. — Petrocephalus sullivani n. sp. is distinguished from all other Petrocephalus species from Gabon by the following characters: 20 to 25 branched rays in the dorsal fin and 24 to 30 in the anal fin; 14 to 20 scales (average 17.5) between the anterior base of the anal fin and the lateral line; mouth clearly inferior (distance between anterior extremity of the snout and corner of the mouth between 2.7 and 4.4 times in head length; mouth opens under the posterior half of the eye, whereas in P. simus and P. balayi it opens under the anterior half of the eye); large eye (diameter of the eye between 3.0 and 4.1 times in head length, average 3.6); and no sub-dorsal black spot. The EOD is short (216 ms mean duration) with a peak FFT frequency of 9597 Hz. The EOD presents a prominent third phase (P3) with an amplitude of 12.8% of peakto-peak height.

DESCRIPTION

Counts and measurements are shown in Table 4. This is a species of Petrocephalus of medium size (maximal standard length observed = 104.7 mm). Body ovoid, longer than high (2.8 <SL/H <3.7), and compressed. Snout short and very round. Mouth inferior, below the eye. Teeth small and bicuspid, with 10 to 13 in the upper jaw and 12 to 15 in the lower jaw. Eye relatively large. Eye diameter between 3.0 and 4.1 times in head length (average 3.5). Dorsal fin originates in the posterior half of the body (1.5 <SL/PDD <1.7). Pre-dorsal distance equal to, or slightly greater than, pre-anal distance (1.0 <PDD/PAD <1.1). Scales cover the entire body, except for the head. Lateral line visible and complete, with 35 to 42 pored scales along its length. Ratio of caudal peduncle length to height between 2.1 and 3.2 (average 2.5). Specimens from the Ivindo basin possess a somewhat thinner caudal peduncle (average 2.9), and specimens from the Nyanga River basin have somewhat thicker caudal peduncles (average 2.2), as noted for P. simus above. Twelve circumpeduncular scales present. Thick skin, with numerous electroreceptors, covers the head and part of the body. Skin turns opaque with formalin fixation. Three rosettes of Knollenorgan electroreceptors present on the head: the “Nakenrosette”, the “Kehlrosette”, and the “Augenrosette”.

EOD CHARACTERISTICS

Among the Petrocephalus species reported here, the EODs of P. sullivani n. sp. are the shortest in duration ( Fig. 2D ; Table 5) with the highest peak

power spectrum frequency ( Fig. 3 ). The third phase (P3) is also quite prominent in this species (12.8 ± 3.6% of peak-to-peak height).

LIFE COLORATION

The body is silver to slightly gold. The back is darker than the abdomen. With differing angles of illumination, the golden metallic reflections are more prominent. The fins are unpigmented, with the exception of the first rays of the dorsal fin, which are black.

DISTRIBUTION ( Fig. 7 )

Petrocephalus sullivani n. sp. has a widespread distribution in Gabon. It has been collected from the Ogooué basin (excepting its most upper and lower reaches), the Ntem and Ivindo basins, and the Nyanga basin. On numerous occasions, we collected this species together with P. simus .

REMARKS

Petrocephalus sullivani n. sp. most closely resembles P. christyi Boulenger, 1920 , described from the Congo basin. The two species are distinguished one from the other by the larger number of scales between the origin of the anal fin and the lateral line in P. sullivani n. sp. (14-20, average 17.5) than in P. christyi (12-14, average 13); and P. christyi has a very distinct sub-dorsal black spot on each side of the body, which is lacking in P. sullivani n. sp.

Figures

FIG. 5. — Drawing of specimens of Petrocephalus; A, P. simus Sauvage, 1879 (syntype, MNHN A 0892) (from Boulenger 1909-1916); B, P. balayi Sauvage, 1883 (holotype of Mormyrus amblystoma Günther, 1896, BMNH 1896.5.5) (from Boulenger 1909-1916); C, non type specimen of P. microphthalmus Pellegrin, 1908 from Angola (from Poll 1967); D, P. sullivani n. sp. (holotype, MNHN 2003-619, 93.1 mm SL). Scale bars: 1 cm.

FIG. 6. — Photos of live specimens of Petrocephalus; A, P. simus Sauvage, 1879 (from the Ivindo River, near Loa Loa, CU75445, 56 mm SL); B, P. sullivani n. sp. (from the Ogooué River, near La Lopé, CU83120, 109 mm SL); C, P. microphthalmus Pellegrin, 1908 (Ogooué River, near Franceville, CU80479, 64 mm SL). Photographs by Carl D. Hopkins.

FIG. 2. — Representative electric organ discharge (EOD) waveforms (left) and power spectra of EODs (right) superimposed for 31 individuals representing four species of Petrocephalus from Gabon. Individual field numbers are listed to the left. All EOD recordings are made with head-positivity upward. EODs have been normalized to the same peak-to-peak height and centered around the midpoint between peaks P1 and P2.

FIG. 3. — Scatterplot of the peak frequency of the Fourier Transform of an electric organ discharge (EOD) vs the relative amplitude of peak P3 for four species of Petrocephalus from Gabon. The inset shows examples of the two measures from a specimen of P. sullivani n. sp.

FIG. 7. — Geographical distribution in Gabon of Petrocephalus simus Sauvage, 1879 (●), P. balayi Sauvage, 1883 (■), P. microphthalmus Pellegrin, 1908 (◆) and P. sullivani n. sp. (O).