Brachyhypopomus batesi, 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 : 667-669

Brachyhypopomus batesi , new species urn:lsid:zoobank.org:act:728CA0A5-F5C5-465F-8793-D1176B3E7F57

( Figs. 1a , 8 ; Tables 2-6)

Brachyhypopomus sp. 1 . - de Oliveira et al., 2009: fig. 41, color photograph ( Brazil, Amazonas , Catuá-Ipixuna Reserve, ca. 03°48′S, 063°59′W).

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

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

Holotype. MCP 47020 , female, 104 mm TL, 82 mm LEA, Brazil, Amazonas , mun. Tefé , igarapé Xidarini , affl. lago Tefé (mouthbay of rio Tefé), Amazonas dr., 03°23′52″S, 064°41′17″W, 31 Dec 1996, W. Crampton.

Paratypes. 4 specimens, localities from Amazonas dr., collected by W. Crampton. Brazil. Amazonas. MCP 45308 , 1 , male, 78 mm, mun. Maraã , igarapé São Sebastião , affl. rio Baré , affl. lago Amanã , affl. rio Japurá, 02°17′05″S, 064°41′25″W, 17 Feb 1993, W. Crampton. MCP 45341 , 2 , (1 female, 99 mm, 1 male, 100 mm), collected with holotype. MCP 45357 , immature, 75 mm, mun. Tefé, igarapé Xidarini, affl. lago Tefé, rio Tefé, 03°23′52″S, 064°41′17″W, 13 Aug 2001, W. Crampton .

Non-types. (24 specimens). Brazil. Amazonas (localities from Amazonas dr.) . MCP 45312 , 16 (11 immature, 76- 115 mm, 4 female, 83-121 mm, 1 male, 120 mm), mun. Tefé, igarapé Xidarini, affl. lago Tefé , rio Tefé , 03°22′46″S, 064°41′17″W . MCP 45356 , 2 (1 immature, 80 mm, 1 female [CS], 85 mm), mun. Tefé, igarapé Xidarini, affl. lago Tefé , rio Tefé , Amazonas dr., 03°23′52″S, 064°41′17″W . MZUSP 85041 , 1, 104 mm, blackwater affl. rio Tiquié, Comunidade Fronteira, affl. rio Uaupés , affl. rio Negro , 00°15′35″N, 070°02′43″W . MZUSP 92234 , 2 , 53-73 mm, mun. São Gabriel da Cachoeira, ca. 500 m downstream São José II, igarapé Cunuri, affl. rio Tiquié , affl. rio Uaupés , affl. rio Negro , 00°13′N, 069°36′W . MZUSP 93067 , 1 , 60 , mun. São Gabriel da Cachoeira, igarapé Castanha, nr. Sítio São Pedro , affl. rio Tiquié , affl. rio Uaupés , affl. rio Negro , 00°11′N, 069°35′W . Colombia. Vuapés: SINCHI-CIACOL. 1054, 2 (1 immature, 40 mm, 1 female, 101 mm), stream affl. río Cuduyarí, affl. río Vuapés, affl. rio Negro , 01°17′36″N, 070°16′53″W .

Diagnosis. Brachyhypopomus batesi is diagnosed from congeners by the following combination of characters: anal-fin rays 165-179, vs. 180-293 in B. alberti , B. beebei , B. belindae , B. bennetti , B. brevirostris , B. bullocki , B. diazi , B. gauderio , B. hendersoni , B. janeiroensis , B. jureiae , B. occidentalis , B. palenque , B. verdii , and B. walteri ; scales present in entire middorsal region (although sparse and hard to see in some specimens), vs. absent in middorsal region of anterior third of body in B. benjamini and B. provenzanoi ; accessory electric organ over the opercular region absent, vs. present in B. bombilla , B. menezesi , and B. regani ; head depth at occiput 61.0-67.9% HL, vs. 71.4-94.6% in B. cunia , B. draco , B. flavipomus , B. hamiltoni , and B. pinnicaudatus ; absence of scattered conspicuous black or charcoal flecks on flanks, vs. presence in B. sullivani .

Description. Head and body shape, and pigmentation illustrated in Figs. 1a and 8 . Meristic and morphometric data for examined specimens presented in Tables 2-6. 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 approximately straight with convex and concave portions, snout truncated. 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 61 (n = 1). Pectoral fin narrow to moderate in width, pectoral-fin rays 12-13 (mode 13). Precaudal vertebrae 16-18 (mode 18) including 1-2 (mode 2) transitional vertebrae. Anal-fin origin substantially posterior (between 0.25 and 0.75 HL distance) to tip of pectoral fin. Anal-fin rays 159-173 (median 168). Dorsal rami of recurrent branch of anterior lateral line nerve visible. Entire middorsal region of body scaled, although scales in anterior third of body sparse and mostly occluded by skin. Rows of scales above lateral line 5-6 (mode 5). Lateral line complete. Sparse groove-like depigmented epidermal canals found mainly in posterior half of body (mainly in posterior third of body), forming parallel or crisscrossing wavy lines either side of lateral line, as single wavy lines on flank midway from lateral line to dorsal midline, and as a pair of long irregular lines either side of dorsal surface in dorsal portion of flank. 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. ( Figs. 1a , 8 ). Pale straw to tan background. Several distinct, truncated, brown vertical bands extending from across upper portion of flank, fading towards lateral line and absent from below lateral line, most prominent for approximately one head length posterior to occiput. 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. Region over anal-fin pterygiophores straw colored with very faint irregular markings, mostly posteriorly. Head with evenly scattered dark chromatophores, darker dorsally. Eye usually with an indistinct or prominent suborbital patch or stripe of chromatophores and subcutaneous pigmentation extending from anteroventral portion of eye to chin. Pectoral and anal fins with hyaline membranes. Pectoral-fin rays hyaline. Anal-fin rays hyaline in anterior half of body, with light scattering of brown chromatophores in posterior half. Color in live individuals similar to preserved specimens, with opercular region usually rosy due to underlying gills. Size. Small adult size, largest specimen examined 121 mm TL, 98 mm LEA (n = 28). Largest male specimen examined 120 mm TL, 100 mm LEA (n = 3). Largest female specimen examined 121 mm, 98 mm LEA (n = 8).

Sexual dimorphism. No known secondary sexual dimorphism.

Geographic distribution. Brazil and Colombia ( Fig. 5 ). Known from the central Amazon, near the main stem of the rio Solimões (Amazon), and from the upper rio Negro.

Ecological notes. The type series was collected from the lower, seasonally flooded reaches of low-conductivity blackwater rainforest streams that flow into lago Tefé, and lago Amanã (large blackwater ria lakes of similar conductivity to the streams). Most specimens were encountered in marginal root mats or submerged leaf-litter along stream edges. The following water parameters were recorded at the time of sampling: conductivity 10-30 µScm-1, dissolved oxygen 2.0-5.2 mgl-1, temperature 24.3- 27.0°C, and pH 4.5-6.0. During the high water period this species disappears from the flood-swollen lower stream reaches, probably due to declining dissolved oxygen levels, and apparently moves upstream to terra firme stream reaches above the seasonal river-floodplain flood influence. Breeding occurs during the early rising-water period, which in the Tefé region corresponds to the rainy season (WGRC unpublished data). Records of B. batesi outside the area of the type series are all from low-conductivity blackwater rainforest streams. Stomach contents of specimens from the type locality comprise aquatic insect larvae (primarily Chironomidae ), and other small aquatic invertebrates (WGRC unpublished data).

Co-occurring congeners: In the region of the type locality Brachyhypopomus batesi co-occurs in geographical sympatry and ecological syntopy with the terra firme stream-occurring species: B. beebei , B. brevirostris , B. sullivani , and B. walteri . It also exhibits an allotopic distribution with B. belindae , B. bennetti , B. flavipomus , B. hamiltoni , B. hendersoni , B. pinnicaudatus , and B. regani . In the rio Negro, B. batesi occurs in geographical sympatry with B. beebei , B. brevirostris , B. bullocki , B. hendersoni , B. regani , B. sullivani , and B. walteri .

Etymology. The specific name is a patronym (noun in the genitive case) in honor of Henry Walter Bates (1825-1892), British naturalist and explorer, for his contributions to the natural history of the Tefé region, where the type series was collected.

Local names. Brazil: sarapó (widespread).

Figures

Fig. 1. Live individuals of 12 sympatric species of Brachyhypopomus and one species of Microsternarchus from the vicinity of Tefé, Amazonas, Brazil (Amazonas dr.). a. Brachyhypopomus batesi MCP 45312 (WC01.191293b), immature, 102 mm TL. b. Brachyhypopomus beebei head – uncat., immature, 75 mm TL; body – MCP 45450 (WC04.090600), female, 178 mm TL. c. Brachyhypopomus belindae MCP 45430, paratype, immature, 104 mm TL (photographed out of water, close up of head not available). d. Brachyhypopomus bennetti MCP 45451, male, 196 mm TL. e. Brachyhypopomus brevirostris uncat., immature, 224 mm TL. f. Brachyhypopomus flavipomus MCP 45453 (WC09.090600), female, 98 mm TL. g. Brachyhypopomus hamiltoni MCP 45482 (WC05.080301), holotype, female, 97 mm TL. h. Brachyhypopomus hendersoni MCP 45489, female, 164 mm TL. i. Brachyhypopomus pinnicaudatus MCP 45455, female, 135 mm TL. j. Brachyhypopomus regani, MCP 45285 (WC02.100301), male, 119 mm TL. k. Brachyhypopomus sullivani MCP 45464 (WC04.210201), immature, 79 mm TL. l. Brachyhypopomus walteri MCP 45458 (WC 03.090600), male, 161 mm TL. m. Microsternarchus bilineatus uncat., 85 mm TL.

Fig. 8. Brachyhypopomus batesi. MCP 47020 (WC07.291297b), holotype, female, 104 mm TL (head in lateral view, body in lateral and dorsal views, specimen fixed in formalin and preserved in EtOH); Brazil, rio Tefé,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).