Brachyhypopomus provenzanoi, Crampton & de Santana & Waddell & Lovejoy, 2016

Crampton, William G. R., Santana, Carlos D. de, Waddell, Joseph C. & Lovejoy, Nathan R., 2016, A taxonomic revision of the Neotropical electric fish genus Brachyhypopomus (Ostariophysi: Gymnotiformes: Hypopomidae), with descriptions of 15 new species, Neotropical Ichthyology (e 150146) 14 (4), pp. 639-790 : 760-762

Brachyhypopomus provenzanoi , new species urn:lsid:zoobank.org:act:E64D737C-8334-47FA-9598-79B4F76C89CF

( Fig. 40 ; Tables 2-5, 17)

Brachyhypopomus sp. “pro”. -Crampton, 2011: 176, table 10.2, species list; 179, figs. 10.2-10.3, phylogeny, geographical and ecological distributions (gymnotiform biology).

Brachyhypopomus sp. “provenzanoi ”. - Crampton et al., 2016: 1-66, table 1, 3-4, figs. 1-7, 18-20 (phylogeny, biogeography and ecology of Brachyhypopomus ).

Holotype. MBUCV-V 35650 , immature, 87 mm TL, 71 mm LEA, Venezuela, Amazonas, mun. San Fernando de Atabapo, caño “CVG” (Corporacion Venezuelana Guyana), km 10.5 km on San Fernando de Atabapo-Santa Barbara rd. , affl. río Orinoco , Orinoco dr., 03º58′59″N, 067º38′29″W, 11 Mar 2004, W. Crampton, N. Lovejoy, S. Willis & C. Montaña .

Paratypes. 59 specimens, all from Orinoco dr. Venezuela . Amazonas. MBUCV-V 12991 , 2 , 71-72 mm, MBUCV-V 12993 , 4 (2 measured), 79-108 mm, Pozo de Lucas , ca. 7 km S San Fernando de Atabapo, affl. río Orinoco , ca. 04°15′N, 067°39′W, 8 Apr 1982, R. Royero & G. Pereira. MBUCV-V 35651 , 16 (14 immature [1 CS], 73-93 mm, 2 male, 92-94 mm), caño Viejita, on rd. from San Fernando de Atabapo to Santa Barbara, affl. río Atabapo, 03°55′59″N, 067°36′34″W, 13-15 Mar 2004, W. Crampton, N. Lovejoy, S. Willis & C. Montaña . UF 177347 33 (19 immature [3 CS], 67-87 mm, 10 female, 69-110 mm, 4 male, 83-94 mm), collected with holotype .

Non-types. 10 specimens. Venezuela . Amazonas. MBUCV-V 11221 , 1, 107 mm, caño Chola , rd. to Solano , at km 17.7 from San Carlos de rio Negro , río Negro , upper rio Negro, Amazonas dr., ca. 01°57′N, 066°59′W. UF 185344 , 9 , immature, collected with holotype .

Diagnosis. Brachyhypopomus provenzanoi is diagnosed from congeners by the following combination of characters: scales absent in middorsal region of anterior third of body (vs. present in all congeners except B. benjamini ); dorsal surface of body with irregular pattern of distinct dark blotches on depigmented tan-colored background, vs. speckled with small brown chromatophores on light brown background in B. benjamini .

Description. Head and body shape, and pigmentation illustrated in Fig. 40 . Meristic and morphometric data for examined specimens presented in Tables 2-5 and 17. Body shallow in depth. Head short to moderate in length and shallow in depth. Dorsal profile of head approximately straight from occiput to snout, ventral profile of head gently convex between operculum and snout, snout rounded. Eye moderate in size. Upper jaw with slight sigmoidal angle between premaxillary and maxillary portions in lateral view. No accessory electric organ over operculum. Gill filaments on first gill arch 26-32 (median 29, n = 9). Pectoral fin narrow, pectoral-fin rays 12-15 (mode 13). Precaudal vertebrae 15-17 (mode 16), with 1-2 (mode 1) transitional vertebrae. Anal-fin origin slightly (<0.25 HL distance) to substantially (0.33-0.5 HL distance) posterior to tip of pectoral fin. Anal-fin rays 162-195 (median 184). Dorsal rami of recurrent branch of anterior lateral line nerve visible. Middorsal region of body without scales in anterior third of body. Middorsal region with small scales completely occluded by skin in posterior two thirds of body. Rows of scales above lateral line 4-5 (mode 4); at measuring point in mid-anal fin, scale rows do not reach dorsal midline – instead middorsal region is scaleless, as is condition anterior. Scale rows reach dorsal midline just posterior to this point. Lateral line continuous. Sparse depigmented epidermal canals present as short parallel scratch like marks dorsal to and near lateral line; mostly restricted to posterior third of body. Three bilateral horizontal columns of electrocytes at anal-fin terminus, and at a mid-point between anal-fin terminus and tip of caudal filament in immature, mature female, and mature male specimens. Caudal filament short to moderate in length.

Coloration. ( Fig. 40 ). Pale straw to tan background. Dorsal region comprising irregular brown patches and a pale straw or tan background, with no pale stripe along dorsal midline from occipital region to base of caudal filament. Distinct stripes or saddles on flank absent. Region over anal-fin pterygiophores straw colored with very faint irregular markings. Caudal filament darker than body, with indistinct, disrupted vertical bars. Head with evenly scattered dark chromatophores, darker dorsally. Eye without prominent suborbital patch, or stripe, of chromatophores/subcutaneous pigmentation. Pectoral-fin and anal-fin membranes hyaline. Pectoral-fin rays hyaline and unpigmented. Anal-fin rays with light scattering of dark chromatophores, in posterior half of fin only. Color in live individuals similar to preserved specimens, with opercular region usually rosy due to underlying gills.

Size. Small adult size, largest specimen examined 110 mm TL, 91 mm LEA (n = 70). Largest male specimen examined 94 mm TL, 83 mm LEA (n = 6). Largest female specimen examined 110 mm TL, 91 mm LEA (n = 10).

Sexual dimorphism. No known secondary sexual dimorphism.

Geographic distribution. Venezuela ( Fig. 31 ). Known from the upper Orinoco and upper Negro (Amazonas dr.).

Ecological notes. Ecology known only for the type series. Brachyhypopomus provenzanoi was collected in small, gently flowing, low-conductivity clearwater terra firme forest and savanna streams, and from static leaf-litter choked blackwater streams and swamps in Mauritia palm swamps. Most specimens in streams were found sheltering in submerged and marginal aquatic vegetation growing in sandy beds, and those in Mauritia palm swamps were collected from dense leaf litter banks and root mats. The following water parameters were recorded at the sampling sites: conductivity 9-10 μScm-1, dissolved oxygen 1.6-3.8 mgl-1, temperature 25.8-28.2°C, pH 3.1-4.0. Reproductive biology is unknown. Stomach contents comprise aquatic insect larvae and other small aquatic invertebrates (WGRC unpublished data).

Co-occurring congeners: In the region of the type locality, Brachyhypopomus provenzanoi was found in sympatry and in ecological syntopy with B. bullocki , B. brevirostris , and B. sullivani . Its geographical range also overlaps with that of B. beebei and B. regani .

Etymology. The specific name is a patronym (noun in the genitive case) in honor of Francisco Provenzano Rizzi, Venezuelan ichthyologist, for his contributions to Neotropical ichthyology.

Local names. Venezuela: cuchillo.

Figures

Fig. 40. Brachyhypopomus provenzanoi. MBUCV-V 35650, holotype, immature, 87 mm TL (head in lateral view, and body in lateral and dorsal view, specimen fixed in formalin and preserved in EtOH); Venezuela, río Orinoco, Orinoco dr. Scale bars = 5 mm.

Fig. 31. Collection records for Brachyhypopomus hendersoni (circles) and B. provenzanoi (squares). Holotype locations are marked with open symbols. Elevation data refers to altitude above mean sea level (see Fig. 2 for legend).