Petrocephalus leo, Lavoué, Sébastien, 2016

Lavoué, Sébastien, 2016, Petrocephalus leo, a new species of African electric fish (Osteoglossomorpha: Mormyridae) from the Oubangui River basin (Congo basin), Zootaxa 4121 (3), pp. 319-330 : 322-325

Petrocephalus leo sp. nov.

( Table 1, Figures 2 and 3 )

http://zoobank.org/ 008688C1-B0E9-48E6-B4C5-8AABAF0D829F

Holotype. CUMV 95314 (male, 76.1 mm SL). Field no. JPF 06-012, Central African Republic, Basse-Kotto, Kotto River at Mingala, Kotto-Oubangui province (5.10N, 21.82E), collectors: R. Bills, J. P. Friel & D. Reid, 2 March 2006.

Paratypes (34). CUMV 91853 17 specimens, same locality, collector and date as the holotype ( DNA tissues 590 and 595). MRAC 2016-012-P-00001-00003 three specimens, same locality, collector and date as the holotype. AMNH 264802 three specimens, same locality, collector and date as the holotype. CUMV 91854 11 specimens. Field no. JPF 06-014, Central African Republic, Basse-Kotto, Rapids on Kotto River north of Mingala, Kotto/Oubangui (5.27N, 21.89E), R. Bills, J. P. Friel & D. Reid, 3 March 2006.

Diagnosis. Petrocephalus leo sp. nov. is distinguished from all other Petrocephalus species of Central Africa (i.e., Lower Guinea and Congo ichthyofaunal provinces) by the following combination of characteristics: absence of electoreceptive rosettes on head, body coloration brownish with distinct black mark at the base of pectoral fin, but no subdorsal ovoid black mark; 21 to 24 branched dorsal-fin rays (mean = 22) and 26 to 29 branched anal-fin rays (mean = 27).

Description. Morphometric ratios and meristic data for holotype and paratypes are presented in Table 1. Petrocephalus leo sp. nov. is a small-sized species within the genus (maximum SL observed = 78.9 mm; holotype = 76.1 mm). Body ovoid, 2.9–3.4 times longer than high (paratype average = 3.2, holotype = 3.3) and laterally compressed. Head length between 3.1 and 3.7 times in standard length (paratype average = 3.5, holotype = 3.6). Snout short (5.2 ≤ HL/SNL ≤ 7.4, paratype average = 5.9, holotype = 6.0) and round. Mouth small (3.8 ≤ HL/MW ≤ 4.9, paratype average = 4.2, holotype = 3.8), sub-terminal, opening under posterior half of eye. Teeth small and bicuspid, 7–9 in a single row in the upper jaw (paratype median = 8, holotype = 8), 15–23 in a single row in lower jaw (paratype median = 18, holotype = 18). Dorsal and anal fins originate in posterior half of body (1.5 ≤ SL/PDD ≤ 1.6 and 1.6 ≤ SL/PAD ≤ 1.7, respectively). Pre-dorsal distance slightly greater than pre-anal distance (1.0 ≤ PDD/ PAD ≤ 1.1). Dorsal fin with 21–24 branched rays (paratype median = 22, holotype = 22). Anal fin with 26–29 branched rays (paratype median = 27, holotype = 27). Body scaled except for head. Lateral line visible and complete with 34–38 (paratype median = 36, holotype = 37) pored scales along its length. Twelve scales around caudal peduncle. Nine to 12 scales (paratype average = 10, holotype = 9) between anterior base of anal fin and lateral line. Caudal peduncle thin (1.9 ≤ CPL/CPD ≤ 2.5, paratype average = 2.2, holotype = 2.2). Twelve scales around caudal peduncle. Skin on head thick, turning opaque with formalin fixation. Knollenorgans visible, but not clustered into the three distinct rosettes as described in Harder (1968).

Holotype (m) Paratypes (n=34)

Min–Max Mean Std-Dev Standard length (SL, in mm) 76.1 50.5–78.9 67.9 6.6 Head length (HL, in mm) 23.0 14.8–22.9 19.5 1.7 Ratio of head length (HL):

HL/snout length (SNL) 6.0 5.2–7.4 5.9 0.5 HL/mouth width (MW) 3.8 3.8–4.9 4.2 0.3 HL/eye diameter (ED) 3.7 3.7–4.4 4.0 0.2 HL/interorbital width (IOW) 3.2 2.7–3.6 3.2 0.2 HL/head width (HW) 1.9 1.8–2.0 1.9 0.0 HL/mouth position (MP) 3.4 3.2–4.2 3.5 0.2 Ratio of caudal peduncle length (CPL):

CPL/caudal peduncle depth (CPD) 2.2 1.9–2.5 2.2 0.1 Min–Max Median

Meristic counts:

Dorsal fin branched rays (DR) 22 21–24 22 Anal fin branched rays (AR) 27 26–29 27 Number of scales in the lateral line (SLL) 37 34–38 36 Number of scale rows between the anterior 9 9–1 2 1 0 base of the anal fin and the lateral line (SDL)

Number of teeth in the upper jaw (TUJ) 8 7–9 8 Number of teeth in the lower jaw (TLJ) 18 15–23 18 Absence of the three typical Petrocephalus electroreceptive rosettes on the head distinguish P. l e o sp. nov. from most of its congeners. Only four other species of Petrocephalus lack all three electoreceptive rosettes: Petrocephalus microphthalmus , Petrocephalus haullevillii , Petrocephalus schoutedeni Poll 1954 , and Petrocephalus zakoni . Petrocephalus leo sp. nov. can be easily distinguished from these species (and all other species of Petrocephalus ) by its unique pattern of melanin markings: a distinct black spot at the origin of the pectoral fins but no subdorsal pigmentation mark. Petrocephalus microphthalmus , P. haullevillii , and P. schoutedeni lack a black mark at the origin of the pectoral fins and P. z a k on i possesses a distinct subdorsal pigmentation mark below the anterior base of the dorsal fin which often extends onto the first dorsal rays and makes contact over the dorsum with the contralateral mark ( Figure 2 ; Lavoué et al. 2010). Petrocephalus leo sp. nov. can be further distinguished from Petrocephalus zakoni by its slender body (SL/H= 2.9-3.4, mean= 3.2; holotype =3.3 versus 2.5-2.7 [mean = 2.6] in P. zakoni ); its relatively shorter dorsal fin (SL/DFL= 4.4-5.0, mean= 4.6; holotype =4.6 versus 4.0-4.3 [mean = 4.1] in P. zakoni ) and its smaller eye (HL/ED= 3.7-4.4, mean= 4.0; holotype =3.7 versus 3.1-3.3 [mean = 3.2] in P. z a k on i). Petrocephalus leo sp. nov. can be further distinguished from P. microphthalmus , P. haullevillii , and P. schoutedeni , by a higher dorsal-fin ray count (range= 21-24, mean and holotype = 22 versus <20 in P. microphthalmus , P. haullevillii , and P. schoutedeni ).

Live coloration ( Figure 2 ). Body background brown/copper with metallic reflection on flanks, darker dorsally with belly whitish/silver with many dense melanophores visible. Caudal peduncle darker and lower margin of dorsal and anal fins blackish. A distinct black mark at base of the pectoral fins and a crescent-shaped mark at base of the caudal fin extending onto upper and lower lobes of caudal fin. All fins mostly whitish-brownish and translucent, anterior of dorsal fin darker. Eye black.

Distribution ( Figure 1 ). Petrocephalus leo sp. nov. is only known from two adjacent localities along the course of the Kotto River (Oubangui River basin).

Electric organ discharge. Unknown. Electrocyte anatomy not studied; all Petrocephalus species examined have electric organ of type "NPp" ( Lavoué et al. 2008).

Etymology. This species is named after my son Léo (Latin name leo ).

Figures

FIGURE 1. Map of the hydrographic system of the central part of the Oubangui River basin showing the Petrocephalus localities surveyed (top-left inset showing the location of the Congo basin in Africa). Filled black and open stars indicate the type locality and the second locality on the Kotto River, respectively, of Petrocephalus leo sp. nov.

FIGURE 2. Petrocephalus leo sp. nov. and Petrocephalus zakoni from the Oubangui River basin, Central African Republic. Top, photograph of a live specimen of Petrocephalus leo sp. nov. of about 70 mm standard length showing the live coloration (untagged specimen; photo by Roger Bills, SAIAB). Center, photograph of the preserved holotype of Petrocephalus leo sp. nov. (CU 95314, scale bar = 1.0 cm; photo by John P. Sullivan, CUMV). Bottom, photograph of a preserved specimen of Petrocephalus zakoni of about 70 mm standard length from the Oubangui River (Field station JPF 06 - 009, CU 91852; photo by John P. Sullivan, CUMV).

FIGURE 3. Schematic drawing of Petrocephalus leo sp. nov., holotype, 76.1 mm standard length. Drawn by Yi-Hsuan Lin.