Petrocephalus valentini, Lavoué, Sébastien, Sullivan, John P. & Arnegard, Matthew E., 2010

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, Zootaxa 2600, pp. 1-52 : 13-16

Petrocephalus valentini n. sp.

[Odzala field identification and in Lavoué et al. (2008): Petrocephalus sp. 3, OTU 3]

Images. Fig. 5 A, photo of a live specimen from Odzala and Fig. 5 B, photo of the preserved holotype (CU 88117).

Type material. Holotype, CU 88117 (morpho, EOD), male, 77.2 mm SL. Republic of the Congo, Cuvette-Ouest, Lékoli River ( Congo basin), Odzala National Park (0.62 ° N, 14.93 ° E), J.P. Friel, S. Lavoué & J.P. Sullivan, 24 August 2002.

Paratypes. CU 87828 (morpho, EOD), sex undet., 73.6 mm SL; AMNH 251420 (ex CU 87827) (morpho, EOD), male, 70.9 mm SL; AMNH 251423 (ex CU 88116) (morpho, EOD), sex undet., 64.5 mm SL; CU 88120 (morpho, EOD), sex undet., 66.7 mm SL; CU 88118 (morpho, EOD, DNA), sex undet., 58.1 mm SL. Republic of the Congo, Cuvette-Ouest, Lékoli River ( Congo basin), Odzala National Park (0.62 ° N, 14.93 ° E), J.P. Friel, S. Lavoué & J.P. Sullivan coll., 24 August 2002. CU 87834 (morpho, EOD), male, 70.6 mm SL; AMNH 251422 (ex CU 88073) (morpho, EOD), sex undet., 65.9 mm SL; AMNH 251421 (ex CU 88072) (morpho, EOD), male, 72.9 mm SL. Republic of the Congo, Cuvette-Ouest, Lékénie River at Mboko débarcadère, Odzala National Park (0.62 ° N, 14.91 ° E), J.P. Friel, S. Lavoué & J.P. Sullivan coll., August 2002.

Other specimens. We examined three other specimens from Odzala National Park (specimen list provided in the section "additional material examined").

Diagnosis. Petrocephalus valentini n. sp. is distinguished from all other Petrocephalus species in Central Africa (i.e., Lower Guinea and Congo provinces) by the following combination of characteristics. Dorsal fin with 19–24 branched rays. Anal fin with 24–26 branched rays. Eye large (HL/ED ≤ 3.2, range = 2.9–3.2). Mouth very small (HL/MW ≤ 5.8, range = 4.7–5.8). Twelve teeth or fewer in the upper jaw (range = 7–12), 17 teeth or fewer in the lower jaw (range = 15–17). Pigmentation pattern subtle, including two components: (1) a pale dorsal black mark on each side of the body below the anterior base of the dorsal fin (under the second to sixth dorsal rays); (2) an ovoid mark, sometimes scarcely visible, at the base of the caudal fin, extending weakly onto the upper and lower lobes of the fin. EOD of normal polarity.

Description. Morphometric ratios and meristic data are given in Table 3 for the holotype and paratypes separately. Petrocephalus valentini n. sp. is a small sized species within the genus (maximum SL = 77.2 mm, holotype). Body ovoid, longer than high (2.8 ≤ SL/H ≤ 3.0, paratype average = 2.9, holotype = 2.8) and laterally compressed. Head length between 3.4 and 3.7 times in standard length (paratype average = 3.6, holotype = 3.4). Snout short (6.5 ≤ HL/SNL ≤ 8.2, paratype average = 7.4, holotype = 6.5) and round. Mouth small (4.7 ≤ HL/MW ≤ 5.8, paratype average = 5.2, holotype = 5.1) and sub-terminal, positioned under the anterior half of the eye. Eye large (2.9 ≤ HL/ED ≤ 3.2, paratype average = 3.0, holotype = 3.1). Teeth small and bicuspid, 7–12 (paratype median = 9, holotype = 9) in a single row in the upper jaw, 15–17 (paratype median = 16, holotype = 17) in the lower jaw. Dorsal and anal fins originate in the posterior half of the body (1.6 ≤ SL/PDD ≤ 1.7 and SL/PAD = 1.6). Pre-dorsal distance approximately equal to the pre-anal distance. Dorsal fin with 19–24 branched rays (paratype median = 22, holotype = 22). Anal fin with 24–26 branched rays (paratype median = 25, holotype = 25). Scales cover the body, except for the head. Lateral line visible and complete with 35–36 pored scales along its length (paratype median = 36, holotype = 35). Nine to 12 scales (paratype median = 11, holotype = 11) between the anterior base of the anal fin and the lateral line. Caudal peduncle relatively thin (2.2 ≤ CPL/CPD ≤ 2.5, paratype average = 2.3, holotype = 2.3). Twelve scales around the caudal peduncle. Skin on head thick, turning opaque with formalin fixation. Knollenorgans clearly organized into two visible rosettes (the Augenrosette and the Nackenrosette). During 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 some other species (e.g., P. binotatus ). Recently, however, more definitive analysis using toluidine blue staining of the skin suggests that the Kehlrosette is in fact present, but it is indeed smaller and harder to discern than in other Petrocephalus (M. Hollmann and B. A. Carlson, unpub. obs.).

Holotype (m) Paratypes (n=8)

Min–Max Mean Std–Dev Min–Max Median

Meristic counts:

Number of scale rows between the anterior base of the 11 9–12 11 anal fin and the lateral line (SDL)

Number of teeth in the upper jaw (TUJ) 9 7–12 9 Number of teeth in the lower jaw (TLJ) 17 15–17 16 Live coloration ( Fig. 5 A). Body uniformly white-silver, with two faint black patches, sometimes hardly distinguishable: (1) a dorsal mark on each side of the body, below the anterior base of the dorsal fin under the second to the sixth rays; (2) an ovoid/crescent-shaped mark centered at the base of the caudal fin (sometimes the center of this second mark is less distinguishable than the two arms of the crescent), with each arm slightly extending onto the upper and lower parts of the caudal fin. There is no melanin marking at the base of the pectoral fins. Fins translucent.

Distribution ( Fig. 1 ). Apparently endemic to the Congo basin. Common in Odzala National Park. At night, we collected single specimens cruising in the main channel of the Lékoli River. At the times we surveyed Odzala, P. valentini seemed absent from the small tributary creeks flowing through the park’s forest or savannah. Elsewhere in the Congo basin, P. valentini n. sp. has been collected from the Lower Congo River in the vicinity of the Pool Malebo (museum specimen records, pers. obs.).

Electric organ discharge ( Fig. 5 C). The EOD waveform produced by P. valentini n. sp. is similar in its characteristics to those produced by many other Petrocephalus species. EOD duration = 0.520 – 1.022 msec.

Statistics for waveform landmarks and other EOD measurements are provided by Lavoué et al. (2008). Electrocytes are assumed to be of type NPp based on the EOD waveform, although this has not been confirmed histologically.

Remarks. Without careful inspection, it is possible that specimens of Petrocephalus valentini n. sp. could be misidentified as Petrocephalus catostoma or Petrocephalus simus because of the absence or near absence of pigmentation patterns in all three species. However, these three species differ from each other in several morphometric measurements and meristic counts, and their geographical distributions, as currently known, are non-overlapping.

Etymology. Named in honor of Mr. Valentin Mbossi, pinassier extraordinaire at Odzala National Park. Fieldwork is as important as laboratory bench work and analysis when it comes to investigations of electric fish taxonomy, behavior and evolution. Valentin assisted us during both of our expeditions to Odzala. We use his first name for this species to reflect our appreciation of him as both colleague and friend and to avoid confusion with a similarly named species, below.

Figures

FIGURE 1. Map of Africa (right) showing the entire Congo River and its main tributaries together with the neighboring Lower Guinea province (first inset at center). The boundary between the Congo and Lower Guinea provinces is shown by a dashed line. Filled black circles indicate type localities for all Petrocephalus species that were described from either province and were considered valid just prior to the present study. Exact type localities are unknown for P. b a l a y i and P. sauvagii. Based on our understanding of the chronology of Central African exploration at the time of the descriptions, we estimate these type localities to be the following: the vicinity of Pool Malebo on the Lower Congo River near the modern cities of Brazzaville and Kinshasa [4.25 ° S, 15.29 ° E] for P. sauvagii; and the vicinity of the present-day city Lambaréné on the Lower Ogooué River [0.7 ° S, 10.22 ° E] for P. b a l a y i. Second inset at the far left: detailed map of Odzala National Park, located in the Congo River basin. Within the boundaries of the park, forest is shown in green and savannah in yellow. The red oval indicates our collection area (a segment of the Lékoli drainage system, including the lower parts of two of its tributaries, the Pandaka and Lékénie Rivers).

FIGURE 5. Petrocephalus valentini n. sp. of the Lékoli River system of Odzala National Park, Republic of the Congo. A. Photograph of a live specimen (no scale). B. Photograph of the preserved holotype (CU 88117; scale bar = 1.0 cm). C. EOD waveforms. One EOD was arbitrarily selected from each recorded individual and superimposed with the other recordings (N = number of individuals). All EODs are scaled to the same peak-to-peak voltage, and they are plotted (head-positive up) on the same time scale as overlays centered on the largest positive peak of each waveform (scale bar = 0.2 msec).

Tables

TABLE 3. Principal morphometric ratios and meristic counts for the holotype (CU 88117) and eight paratypes (CU 87828, CU 87834, CU 88120, CU 88118, AMNH 250924, AMNH 250925, AMNH 250926, AMNH 250927) of Petrocephalus valentini n. sp. (Abbreviations: m = male; Std – Dev = standard deviation; Min – Max = minimum – maximum).

Standard length (mm)	77.2	58.1–73.6	67.9	5.2
Head length (mm)	22.4	16.0–20.2	18.8	1.4
Ratio of standard length (SL):
SL/body height (H)	2.8	2.8–3.0	2.9	0.1
SL/head length (HL)	3.4	3.6–3.7	3.6	0.0
SL/pre-dorsal distance (PDD)	1.7	1.6–1.7	1.7	0.0
SL/pre-anal distance (PAD)	1.6	1.6–1.6	1.6	0.0
SL/dorsal fin length (DFL)	4.2	4.3–4.9	4.4	0.2
SL/anal fin length (AFL)	4.1	3.9–4.3	4.1	0.1
SL/caudal peduncle length (CPL)	5.1	5.1–5.8	5.3	0.3
SL/mouth width (MW)	17.5	17.2–20.6	18.9	1.2
Ratio of head length (HL):
HL/snout length (SNL)	6.5	6.8–8.2	7.4	0.5
HL/mouth width (MW)	5.1	4.7–5.8	5.2	0.4
HL/eye diameter (ED)	3.1	2.9–3.2	3.0	0.1
HL/interorbital width (IOW)	3.2	2.8–3.2	3.0	0.1
HL/head width (HW)	2.1	1.8–1.9	1.9	0.0
HL/mouth position (MP)	4.7	3.6–4.3	3.9	0.3
Ratio of caudal peduncle length (CPL):
CPL/caudal peduncle depth (CPD)	2.3	2.2–2.5	2.3	0.1