Brachyhypopomus benjamini, 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 : 679-681

Brachyhypopomus benjamini , new species u r n: l s i d: z o o b a n k. o rg: a c t: E 9 3 B C B F 9 - 4 7 2 A - 4 2 E F - B4B6-D60937293835

( Fig. 12 ; Tables 2-5, 7)

Brachyhypopomus sp. I . - Crampton & Albert, 2006: 672, fig. 23.8, color photograph of head of live individual with EOD, position in phylogenetic tree; 681, notes on EOD (gymnotiform species and EOD diversity).

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

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

Holotype. MUSM 39915 , male, 126 mm TL, 103 mm LEA, Peru, Loreto, mun. Requena, nr. Jenaro Herrera, quebrada Caño Fierro , affl. río Ucayali, Amazonas dr., 04°51′59″S, 073°38′48″W, 16 Jan 2004, B. Crampton, W. Crampton, H. Ortega, R. Reis, F. Lima & J. Oliveira.

Paratypes. 68 specimens, localities from Amazonas dr., collected by W. Crampton, E Correa Roldán, M. Guevara, J. Waddell, unless otherwise stated. Peru. Loreto (localities listed from nr. Jenaro Herrera are from the río Ucayali dr., mun. Requena ). MUSM 44676 , 1 , female, 115 mm, stream nr. Jenaro Herrera , 04°53′59″S, 073°38′51″W, 28 Jul 2009 . MUSM 44689 , 2 , immature, 109-131 mm, stream nr. Jenaro Herrera, 04°51′51″S, 073°38′45″W, 13 Jul 2009 . MUSM 44694 , 56 (48 immature, 79-135 mm, 8 female, 95-119 mm), stream nr. Jenaro Herrera , 04º52′09″S, 073º38′44″W, 15 Jul- 5 Aug 2009 . UF 148511 , 1 , male, 110 mm, stream nr. Jenaro Herrera, 04º53′S, 073º39′W . UF 148512 , 2 , 97-98 mm (1 immature 97 mm, 1 male, 98 mm), collected with holotype, 16 Jan 2004 , W. Crampton, H. Ortega, R. Reis, F. Lima, B. Crampton, J. Oliveira. UF 184015 , 4 , immature, 89-117 mm, stream nr. Jenaro Herrera, 04°54′26″S, 073°36′44″W, 17 Jul 2009 . USNM 405574 , 2 , immature (96- 96 mm), stream nr. Jenaro Herrera, 04°54′26″S, 073°36′44″W, 25 Jul 2009 .

Non-types. 8 specimens. Peru . Loreto. UF 183771 , 8 , 81- 112 mm (5 immature, 1 CS, 81-100 mm, 2 female, 90-100 mm, 1 male, 112 mm), río Nanay , 50 km Iquitos, Amazonas dr., 03°53′50″S, 073°40′01″W .

Diagnosis. Brachyhypopomus benjamini 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. provenzanoi ; dorsal surface of body speckled with small brown chromatophores on light brown background, vs. irregular pattern of distinct dark blotches on depigmented tan-colored background in B. provenzanoi .

Description. Head and body shape, and pigmentation illustrated in Fig. 12 . Meristic and morphometric data for examined specimens presented in Tables 2-5 and 7. Body shallow to moderate in depth. Head short to moderate in length and shallow to moderate in depth. Dorsal profile of head straight from occiput to snout, ventral profile of head straight anteriorly, gently convex under operculum, snout truncated to rounded. Eye of moderate to large 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 30-36 (median 34, n = 5). Pectoral fin narrow to moderate in width, pectoral-fin rays 10-13 (mode 12). Precaudal vertebrae 16- 17 (mode 17), including 1-2 (mode 2) transitional vertebrae. Anal-fin origin slightly (<0.25 HL) to moderately (reaching 0.33 HL) posterior to tip of pectoral fin, never anterior to tip of pectoral fin. Anal-fin rays 174-197 (median 186). Dorsal rami of recurrent branch of anterior lateral line nerve usually clearly visible. Middorsal region of body without scales in anterior third of body, scales in posterior two thirds of body small and completely occluded by skin. Rows of scales above lateral line 5-7 (mode 6). Lateral line continuous. Sparse groove-like depigmented or dark-pigmented epidermal canals found mainly in posterior half of body – parallel to and close to lateral line, mostly dorsal to lateral line. Three bilateral horizontal columns of electrocytes at anal-fin terminus, and at 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. 12 ). Background light tan to dark brown. Dorsal region speckled with small brown chromatophores on light brown background. No pale stripe in middorsal region. Dorsal areas of flank mottled with dark patches. Distinct stripes or saddles on flank absent. Ventral areas of flank with only sparse, irregular dark blotches. 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. Color in live individuals similar to preserved specimens, with opercular region usually rosy due to underlying gills.

Size. Small adult size, largest specimen examined 135 mm TL, 107 mm LEA (n = 77). Largest male specimen examined 126 mm TL, 103 mm LEA (n = 4). Largest female specimen examined 119 mm TL, 109 mm LEA (n = 11).

Sexualdimorphism. Noknownsecondarysexualdimorphism.

Geographic distribution. Peru ( Fig. 5 ). Known only from the type series near the town of Jenaro Herrera, Loreto – in forest stream tributaries of the lower río Ucayali, and in forest stream tributaries of the río Nanay, near Iquitos , Loreto .

Ecological notes. Occurs in small low-conductivity blackwater terra firme rainforest streams. In the region of the type locality B. benjamini is locally common in streams within undisturbed closed-canopy forest, and absent from streams in open cattle pastures or clearings. Brachyhypopomus benjamini occurs in and around submerged debris and leaf litter, and in root mats and holes along the stream banks. The following water parameters were recorded at the sample sites: conductivity 5-15 µScm-1, dissolved oxygen 1.8-6.0 mgl-1, temperature 25-27.5°C, and pH 4.5-6.5. Breeding occurs during the rainy season in the area of the type locality (approximately December to April) (JCW unpublished data). Stomach contents of specimens from the type locality comprise small aquatic invertebrates (JCW unpublished data).

Co-occurring congeners: Brachyhypopomus benjamini is known to co-occur in geographical sympatry and ecological syntopy with B. beebei , B. brevirostris , B. sullivani , B. verdii , and B. walteri . It also exhibits an allotopic distribution with B. bennetti , B. flavipomus , B. hamiltoni , and B. regani .

Etymology. The specific name is a patronym (noun in the genitive case) in honor of Benjamin T. D. Crampton, British diplomat and amateur ornithologist, collector of the holotype.

Local names. Peru: macana.

Figures

Fig. 12. Brachyhypopomus benjamini. MUSM 39915 (WC10.160104), holotype, male, 126 mm TL (head, and body in lateral and dorsal view, specimen fixed in formalin and preserved in EtOH); Peru, río Ucayali, Amazonas dr. Scale bars = 5 mm.

Fig. 5. Collection records for Brachyhypopomus alberti (circles), B. batesi (squares), and B. benjamini (triangles). Holotype locations are marked with open symbols. Elevation data refers to altitude above mean sea level (see Fig. 2 for legend).