Brachyhypopomus hendersoni, 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 : 731-735

Brachyhypopomus hendersoni , new species urn:lsid:zoobank.org:act:A0D96996-8B4E-4001-A700-64F9093BFA4F

( Figs. 1h , 30 ; Tables 2-5, 13)

Brachyhypopomus beebei (‘H2’). -Heiligenberg & Bastian, 1980: 197, fig. 1, black and white photograph ( Brazil, Amazonas, rio Negro, gymnotiform species and EOD diversity).

Brachyhypopomus sp. 8 . - Crampton, 1996a: 77, table 6.1.a, species list; 79, fig. 6.1 inset 30-31, color photographs; 85, fig. 6.2; 88: fig. 6.3; 92-94, figs. 6.4a, 6.5; 191, fig. 11.2; 193, fig. 11.3, EOD data; 110, table 7.5, 113, table 7.7, 115, fig. 7.1, habitats ( Brazil, central Amazon, ecology and signal diversity).

Brachyhypopomus sp. 4 . - Crampton, 1998a: 821, list of Brachyhypopomus ( Brazil, Amazonas, species and EOD diversity). - Crampton, 1998b: 314, table 2, list of Brachyhypopomus ( Brazil, Amazonas, hypoxia tolerance).

Brachyhypopomus sp. D . - Crampton, 1999: 17 ( Brazil, Amazonas, Mamirauá Reserve, listing of species). - Crampton & Albert, 2006: 672, fig. 23.8, position in phylogenetic tree; 681, notes on EODs (gymnotiform species and EOD diversity). -Crampton et al., 2008: 231, fig. 6, black and white photograph of head of live individual ( Brazil, Amazonas, adaptations to hypoxia).

Brachyhypopomus sp. ‘basepreta’. - Ferreira et al., 2007: 164, bottom left photograph, live individual ( Brazil, Roraima, rio Branco, photographic album of fishes).

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

Brachyhypopomus sp. “hendersoni ”. - Crampton et al., 2016: 1-66, table 1, 3-4, figs. 1-7, 12, 13, 15, 18-20 (phylogeny, biogeography and ecology of Brachyhypopomus ).

Holotype. MCP 45305 , male, 146 mm TL, 98 mm LEA, Brazil, Amazonas , mun. Maraã , lago Amanã , Igarapé Juá Grande , rio Japurá, Amazonas dr., 02°28′50″S, 064°48′50″W, 3 Dec 1998, W. Crampton & J. Oliveira.

Paratypes. 47 specimens, localities from Amazonas dr., collected by W. Crampton & J. Oliveira unless otherwise stated. Brazil. Amazonas. BMNH 1998.3.12.22-24, 3, immature, 122-140 mm, 7-10 Jan 1997, MCP 45483 , 3 , 142- 142 mm, 1997, mun. Tefé, Ressaca do Socorro , lago Tefé, rio Tefé , 03°18′45″S, 64°41′50″W. BMNH 1998.3.12.175, 1, female, 159 mm, 27 May 1994, BMNH 1998.3.12.176-177, 2 (1 immature, 132 mm, 1 male, 171 mm), 27 Jan 1995, mun. Tefé, Ressaca do Cachorro , lago Tefé, rio Tefé , 03°19′50″S, 64°42′15″W. INPA 9950 , 10 , 125-154 mm, mun. Tefé, Cabeceira do lago Tefé, rio Tefé , ca. 03°34′S, 064°58′W, 11 Jan 1995. MCP 45272 , 1 , female, 174 mm, mun. Tefé, Ilha do Martelo , rio Tefé , 03°46′56″S, 064°59′39″W, 22 Jan 1999. MCP 45273 , 1 , male, 121 mm, mun. Tefé, Cabeceira do lago Tefé, rio Tefé , 03°38′01″S, 064°57′59″W, 22 Jun 1999. MCP 45274 , 1 , female, 143 mm, mun. Tefé, rio Tefé , 03°41′23″S, 064°59′08″W, 16 Feb 2001. MCP 45309 , 1 , immature, 69 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. MCP 45369 , 3 (2 immature, 144-147 mm, 1 female, 175 mm), mun. Tefé, mouth of igarapé Açu, Lago Tefé, rio Tefé , 03°25′00″S, 064°48′23″W, 26-28 Jun 1998. MCP 45397 , 13 (3 immature, 158-183 mm, 6 female, 140- 203 mm, 4 male, 125-190 mm), mun. Tefé, lago Caiambé, rio Caiambé , 03º35′40″S, 064º26′54″W, 28 Dec 1998. MCP 45408 , 1 , female, 162 mm, mun. Tefé, Ressaca do Socorro , lago Tefé, rio Tefé , 03°18′45″S, 064°41′50″W, 11 Aug 1998. MPEG 973 , 2 , 109-110 mm, MPEG 974, 1, 127 mm, mun. Tefé, lago Jurupari, rio Tefé , ca. 03°48′S, 065°00′W, 1 Jul 1979, M. Goulding. MPEG 976 , 1, 102 mm, mun. Tefé, Arana-tuba, rio Tefé, ca. 04°02′S, 065°01′W, 8 Jul 1979, M. Goulding. MZUSP 99170 , 2 , 96-130 mm, canal do lago Amanã, affl. rio Japurá, ca. 02°44′S, 064°39′W, 30 Sep 1979, R. Barthem .

Non-types. 103 specimens. Brazil. Amazonas (localities from Amazonas dr.). BMNH 1998.3.12.08-10, 3 (2 immature, 153-167 mm, 1 female, 167 mm), BMNH 1998.3.12.13-14, 2, female, 155-167 mm, MCP 45271 , 26 (10 immature [1CS], 120-170 mm, 8 female, 145-172 mm, 8 male, 148-180 mm), mun. Tefé, lago Tefé, rio Tefé, 03°18′45″S, 064°41′50″W. BMNH 1998.3.12.159-174, 16 unsexed, 108-193 mm, BMNH 1998.3.12.178-182, 5, immature, 102-135 mm, MCP 45270 , 3 (2 immature, 130- 142 mm, 1 male, 195 mm), mun. Tefé, Ressaca do Cachorro, lago Tefé, rio Tefé , 03°19′50″S, 064°42′15″W. IDSM 456, 1, immature, 130 mm, mun. Tefé, Cabeceira do lago Tefé, rio Tefé , 03°35′41″S, 064°58′05″W. INPA 9781 , 2 , 79- 140 mm, rio Jaú , affl. rio Negro , ca. 01°57′S, 061°28′W. MCP 45304 , 1 , immature ( CS), 100 mm, mun. Maraã, lago Amanã, mouth of igarapé Uxi, affl. rio Japurá , 02°32′41″S, 064°40′12″W. MCP 45454 , 4 (3 female [1CS], 127-153mm, 1 male [CS], 175 mm), mun. Tefé, Cabeceira do lago Tefé, rio Tefé , 03°38′01″S, 064°57′59″W. MCP 45426 , 1 , female ( CS), 166 mm, mun. Tefé, Cabeceira do lago Tefé, rio Tefé , 03°38′01″S, 064°57′59″W. MCP 45432 , 6 (3 immature [1CS], 134-146 mm, 2 female, 143-163 mm, 1 male [CS], 161 mm), mun. Tefé, rio Tefé , 03º37′43″S, 064°59′03″W. MCP 45489 , 2 , female, 164-166 mm, mun. Tefé, Ilha do Martelo , rio Tefé , 03°46′56″S, 064°59′39″W. MCP 45491 , 5 (4 immature, 128-148 mm, 1 female, 120 mm), mun. Tefé, rio Tefé , 03°41′23″S, 064°59′08″W. MCP 45682 , 4 , 123-152 mm, mun. Tefé, Ressaca do Socorro , lago Tefé, rio Tefé , 03°18′45″S, 64°41′50″W. MPEG 979, 5 (part), 65-147 mm, mun. Tefé, Ipanema da Baixa , rio Tefé , ca. 03°53′S, 065°00′W. MPEG 1125, 1, 81 mm, mun. Novo Airão, Anavilhanas archipelago, rio Negro , ca. 02°40′S, 060°44′W. MZUSP 30044 (part), 1, 127 mm, mun. Tefé, lago Jurupari, rio Tefé , ca. 03°48′S, 065°00′W. MZUSP 30050 , 1, 106 mm, mun. Tefé, Mastro, rio Tefé , no coordinates. MZUSP 78032 (part), 1, 110 mm, mun. Maraã, Paraná do Castanho, lago Amanã, affl. rio Japurá , ca. 02°44′S, 064°39′W . Guyana. Upper Demerara-Berbice. INHS 49276, 1, 112 mm, 1.54 mi. SW Rockstone, Essequibo River (Long Lake), Essequibo River dr., ca. 05°58′N, 058°32′W. Upper Tukutu-Upper Essequibo. ANSP 179500, 2, 70-113 mm, AUM 35818, 2, 84-118 mm, stream at crossing on Massara-Karanambo rd. , 10.3 km NW Karanambo, affl. Rupununi River , Essequibo River dr., 03°48′27″N, 059°23′06″W. AUM 48815, 1, 80 mm, Rupununi River at Massara landing, Essequibo River dr., 03°53′42″N, 059°17′37″W. BMNH 1972.7.519-525, 7, 34-109 mm, Rupununi River , Essequibo River dr., no coordinates .

Diagnosis. Brachyhypopomus hendersoni is diagnosed from congeners by the following combination of characters: caudal filament length 32.3-64.5% LEA, vs. 7.4-31.6% in B. alberti , B. arrayae , B. batesi , B. belindae , B. benjamini , B. bennetti , B. bombilla , B. hamiltoni , B. occidentalis , B. palenque , B. provenzanoi , B. regani , B. sullivani , and B. verdii ; precaudal vertebrae 15-17, vs. 18-25 in B. beebei , B. brevirostris , B. draco , B. flavipomus , B. gauderio , B. janeiroensis , B. jureiae , and B. pinnicaudatus ; head width at occiput 39.2-47.8% HL, vs. 49.5-70.4% in B. bullocki , B. diazi , and B. menezesi ; dorsal rami of the recurrent branch of the anterior lateral line nerve not visible, vs. visible in B. cunia and B. walteri .

Description. Head and body shape, and pigmentation illustrated in Figs. 1h and 30 . Meristic and morphometric data for examined specimens presented in Tables 2-5 and 13. Body shallow to moderate in depth. Head short and shallow to moderate in depth. Dorsal profile of head convex from occiput to snout, ventral profile of head with areas of convexity near mouth and areas of concavity under eye, snout truncate to rounded. Eye moderate to large in size. No accessory electric organ over operculum. Gill filaments on first gill arch 32-34 (median 33, n = 4). Pectoral fin moderate in width, pectoral-fin rays 12-16 (mode 13). Precaudal vertebrae 15-17 (mode 16), with 1-2 (mode 1) transitional vertebrae. Anal-fin origin slightly (<0.25 HL distance) anterior to, or near, tip of pectoral fin. Anal-fin rays 192-210 (median 200). Dorsal rami of recurrent branch of anterior lateral line nerve not visible. Middorsal region of body scaled. Rows of scales above lateral line 5-7 (mode 6). Lateral line continuous. Sparse depigmented epidermal canals in posterior two thirds of body, present in three series: as an irregular, interrupted, single groove either side of dorsal midline along most of posterior two thirds of body, as a meandering sometimes bifurcating single groove on each dorsal flank approximately midway from lateral line to dorsal midline, and in posterior third of body as sparse scratch like marks dorsal to and near lateral line. 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 moderate in length to long.

Coloration. ( Figs. 1h , 30 ). Background color tan or light grey to dark brown. Dorsal region with uniform speckling of dark chromatophores, and often with a thin pale line extending along midline from occipital region to deep into caudal filament, but without a prominent depigmented stripe. Flank with narrow diffuse, vague vertical stripes dorsal to lateral line, extending to but not crossing lateral line. Flank in region of body cavity ventral to lateral line with irregular dark flecks and patches, not forming vertical stripes. Prominent horizontal dark band extends from anal-fin margin to near dorsal margin of anal-fin pterygiophores along entire length of anal fin, darkening ventrally and posteriorly. This dark band along anal-fin base is more conspicuous in some specimens than others. Dark spots and diffuse vertically elongated stripes also present over anal-fin pterygiophores, extending dorsally towards lateral line. Caudal filament very dark, with irregular lighter markings, often with black tip; darkened tip resembles root tips of water hyacinths when viewed underwater. Head with evenly scattered dark chromatophores, darker dorsally. Eye with suborbital patch or stripe of chromatophores and subcutaneous pigmentation (more conspicuous in some specimens than others). Pectoral and anal-fin membranes hyaline. Pectoral-fin rays hyaline with light scattering of melanophores. Anal-fin rays with scattered or dark chromatophores, mostly concentrated near anal-fin margin. Color in live individuals similar to preserved specimens, with opercular region usually rosy due to underlying gills and flank over body cavity whitish.

Size. Moderate adult size, largest specimen examined 203 mm TL, 130 mm LEA (n = 150). Largest male specimen examined 195 mm TL, 123 mm LEA (n = 18). Largest female specimen examined 203 mm TL, 130 mm LEA (n = 31).

Sexual dimorphism. Breeding males exhibit slightly enlarged electrocytes relative to immature specimens and females. No other secondary sexually dimorphic characters known.

Geographic distribution. Brazil and Guyana ( Fig. 31 ). Known from the central Amazon from blackwater ria lakes near Tefé, from the lower Negro, and from the Essequibo drainage.

Ecological notes. In the region of the type locality B. hendersoni is common in marginal emergent plants (mainly wild rices, Oryza spp. ), rafts of floating macrophytes (including grasses, e.g., Paspalum , and water hyacinths, Eichhornia spp. ), and decaying plant matter along the edges of low-conductivity blackwater floodplain ria lakes (e.g., lago Tefé, lago Amanã, and lago Caiambé), and along river and oxbow lake margins (e.g., in the rio Tefé floodplain). The following water parameters were recorded in the rio Tefé floodplain: conductivity 7-18 µScm-1, dissolved oxygen 3.0-6.7 mgl-1, temperature 29.0-33.3°C, and pH 5.3- 6.7. Brachyhypopomus hendersoni occurs in habitats that are not typically exposed to protracted and severe seasonal hypoxia. Crampton et al. (2008) documented the relatively small gill sizes of B. hendersoni relative to congeners that occur in seasonally hypoxic whitewater floodplain systems. Breeding occurs in floating macrophytes during the rising and high water period (WGRC unpublished data). 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 hendersoni commonly co-occurs in geographical sympatry and ecological syntopy with B. brevirostris , and B. walteri , and sometimes with B. beebei . It exhibits an allotopic distribution with B. batesi , B. belindae , B. bennetti , B. flavipomus , B. hamiltoni , B. pinnicaudatus , B. regani , and B. sullivani . In the middle rio Negro B. hendersoni co-occurs in geographical sympatry with B. batesi , B. bullocki , B. beebei , B. brevirostris , B. hamiltoni , B. regani , B. sullivani , and B. walteri . In the Essequibo River B. hendersoni co-occurs in geographical sympatry with B. bullocki , B. beebei , B. brevirostris , B. regani , B. sullivani , and B. walteri .

Etymology. The specific name is a patronym (noun in the genitive case) in honor of Peter A. Henderson, British fish biologist, and doctoral co-advisor of WGRC; for his contributions to Amazonian aquatic ecology.

Local names. Brazil: sarapó; Guyana: knifefish.

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. 30. Brachyhypopomus hendersoni. a. MCP 45408 (WC07.110898b), paratype, female, 162 mm TL, (head, and body in lateral and dorsal view, specimen fixed in formalin); Brazil, rio Tefé, Amazonas dr. b. MCP 45305 (WC13.031298), holotype, male, 146 mm TL (head in lateral view, body in lateral and dorsal view, specimen fixed in formalin and preserved in EtOH); Brazil, rio Japurá, Amazonas 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).