Sternarchorhynchus jaimei, Santana & Vari, 2010

Santana, Carlos David De & Vari, Richard P., 2010, Electric fishes of the genus Sternarchorhynchus (Teleostei, Ostariophysi, Gymnotiformes); phylogenetic and revisionary studies, Zoological Journal of the Linnean Society 159 (1), pp. 223-371 : 312-314

STERNARCHORHYNCHUS JAIMEI SP. NOV.

( FIGS 49 , 50 ; TABLE 8)

Diagnosis: Sternarchorhynchus jaimei is distinguished from congeners by the following combination of characters: a short gape that terminates posteriorly at, or slightly short of, the vertical through the anterior nares, the absence of scales along the mid-dorsal region of the body as far posteriorly as the vertical through the posterior limit of the pectoral fin, the presence of a narrow, more lightly coloured band of mid-dorsal pigmentation on the head and mid-dorsal region of the body extending posteriorly to the origin of the electroreceptive filament and sometimes beyond that point, the lateral line that extends to the base of the caudal fin, the presence of four to seven premaxillary teeth, 23–26 anterior unbranched anal-fin rays, and 180– 195 total anal-fin rays, the distance from the anus to the anal-fin insertion (4.8–12.3% of HL), the distance from the posterior naris to the snout (8.1– 12.9% of HL), the head width (22.7–28.9% of HL), the head depth at the nape (41.8–43.2% of HL), the interocular distance (6.6–10.7% of HL), the postocular distance (41.5–49.1% of HL), the height of the branchial opening (11.4–17.9% of HL), the postocular distance (41.5–58.7% of HL), the pectoral-fin length (35.7–58.4% of HL), the caudal depth (10.1– 19.2% of caudal length), and the caudal-fin length (17.3–46.0% of caudal length).

Description: Morphometric data for examined specimens in Table 8.

Lateral line extending posteriorly to base of caudal fin, but absent on fin. Snout elongate, compressed and slightly curved ventrally along anterior portion; curvature more pronounced in larger individuals. Mouth terminal. Dentary with distinct fleshy pad anteriorly. Rictus located anterior to vertical through anterior naris. Anus and urogenital papilla located ventral to head, with position apparently ontogenetically variable. Anus and urogenital papilla located along vertical about two orbital diameters posterior of eye in juveniles and along vertical through eye in larger specimens. Combined opening for anus and urogenital papilla ranging from circular to longitudinally ovoid.

Premaxilla with four to seven teeth (N = 5) apparent in whole specimens. Dentary with two tooth rows; outer row with eight to nine teeth and inner row with two to three teeth (N = 5).

Branchiostegal rays five; with first to third rays narrow and elongate and fourth and fifth rays large and broad. Precaudal vertebrae 16 (12–13 anterior; three to four transitional; N = 12).

Pectoral-fin rays ii + 11–14 [ii + 11] (N = 12). Analfin origin located anterior to opercle. Anterior unbranched anal-fin rays 23–36 [25] (N = 12). Total anal-fin rays 180–195 [184] (N = 7). Scales above lateral line at midbody nine to 12 [12] (N = 12). Scales along mid-dorsal midline of body absent or sparse to midlength of body in smaller specimens, and absent in larger specimen as far posteriorly as vertical through posterior limit of pectoral fin, then sparse to midlength of body and followed by regular series of scales as far posteriorly as origin of midsaggital electroreceptive filament. Origin of midsaggital electroreceptive filament located on posterior half of body, at point approximately 65% of TL. Filament extending posteriorly four to six scales anterior of vertical through posterior terminus of base of anal fin. Tail compressed and short, ending in small, somewhat rounded caudal fin in juveniles and in small, somewhat lanceolate fin in large individuals. Caudal-fin rays 11–18 [14] (N = 7).

Coloration in alcohol: Overall coloration of head and body brown. Head with variably intense band of dark pigmentation extending along dorsolateral surface of snout nearly to tip of snout. Ventrolateral portion of snout dark. Two dark bands on snout border intermediate more lightly coloured region on anterior half of snout. Dorsal band of dark coloration forms lateral margin of narrow, lightly coloured stripe extending from tip to snout to varying degrees beyond vertical through eye and onto mid-dorsal postocular portion of head. Stripe on head variably obscurely continuous with narrow, lightly coloured mid-dorsal stripe on body. Mid-dorsal stripe on body extending posteriorly to origin of electroreceptive filament. Pectoral fin dusky with rays somewhat darker than membranes. Anal fin dusky with rays darker than membranes. Caudal fin dark with distal regions somewhat lighter.

Distribution: Sternarchorhynchus jaimei is only known from the Rio Uatumã , Amazonas, Brazil ( Fig. 50 ).

Secondary sexual dimorphism: No sexual dimorphism was apparent in the examined samples of S. jaimei .

Etymology: The species name, jaimei , is in honour of Jaime Ribeiro Carvalho Júnior, of the Centro do Jovem Aquarista, in recognition of his invaluable assistance to the first author during the early phases of his studies of gymnotiforms.

Remarks: One of the examined specimens, a female of 115 mm TL, had clearly developing eggs and it seems likely that the species matures at relatively small body sizes. Sternarchorhynchus jaimei was collected at the same type locality as S. higuchii . The species differ in various details of pigmentation, meristics, and morphometrics detailed in Remarks under S. higuchii .

Material examined

Holotype: – BRAZIL. Amazonas : Rio Uatumã, Cachoeira do Miriti, Presidente Figueredo (approximately 2°01′S, 59°28′W), collected by E. Ferreira, R. Leite, and S. Kullander, 4.x.1987; INPA 28359 (200, maturing female).

Paratypes: – BRAZIL. Amazonas: Rio Uatumã, Cachoeira do Miriti, Presidente Figueredo (approximately 2°01′S, 59°28′W), collected with holotype by E. Ferreira, R. Leite, and S. Kullander, 4.x.1987; INPA 22902, 2 (72.2–75.6). Rio Uatumã, Cachoeira Morena, Presidente Figueredo , collected by E. Ferreira, R. Leite, and S. Kullander, 7.x.1987; INPA 26122, 10 (one cleared and stained, 88–123); USNM 391716, 1 (127).

Figures

Figure 49. Sternarchorhynchus jaimei sp. nov., holotype, female, 200 mm total length, INPA 28359; Brazil, Amazonas, Cachoeira do Miriti, Rio Uatumã.

Figure 50. Map of central and northern South America showing geographical distribution of Sternarchorhynchus jaimei (1 = holotype locality), Sternarchorhynchus kokraimoro sp. nov. (2 = holotype locality), Sternarchorhynchus mareikeae sp. nov. (3 = holotype locality), Sternarchorhynchus marreroi sp. nov. (4 = holotype locality), and Sternarchorhynchus mendesi sp. nov. (5 = holotype locality) (some symbols represent more than one locality and/or lot of specimens).