Brachyhypopomus janeiroensis (Costa & Campos-da-Paz, 1992)

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 : 735-737

Brachyhypopomus janeiroensis (Costa & Campos-da-Paz, 1992)

( Fig. 32 ; Tables 2-5, 15)

Hypopomus janeiroensis Costa & Campos-da-Paz, 1992: 118, fig. 2, black and white photograph of holotype, fig. 3, color photograph of live paratype (original description, type locality – Brazil, Rio de Janeiro, rio São João dr.) .

Brachyhypopomus janeiroensis . -Mago-Leccia, 1994: 48 (listing of Brachyhypopomus ). - Sullivan, 1997, 118 (redescription). -Albert & Crampton, 2003: 495 ( Brazil, catalog of hypopomids). - Crampton &Albert, 2006: 672 fig. 23.8, position in phylogenetic tree; 681, notes on EODs (gymnotiform species and EOD diversity). -Crampton, 2011: 176, table 10.2, species list; 179, figs. 10.2-10.3, phylogeny, geographical and ecological distributions (gymnotiform biology). - Crampton et al., 2016: 1-66, table 1, 3-4, figs. 1-7, 18-20 (phylogeny, biogeography and ecology of Brachyhypopomus ).

Diagnosis. Brachyhypopomus janeiroensis is diagnosed from congeners by the following combination of characters: bilateral columns of electrocytes at the anal-fin terminus 4, vs. 6 in B. bennetti and vs. 3 in all other congeners except B. belindae , B. diazi , B. jureiae , B. occidentalis (except some populations in Colombia and Venezuela, see redescription of B. occidentalis ), and B. palenque ; caudal filament length 31.3-59.1% LEA, vs. 7.4-30.7% in B. belindae , B. occidentalis , and B. palenque ; dorsal rami of the recurrent branch of the anterior lateral line nerve visible, vs. not visible in B. diazi ; snout to pectoral-fin base 10.7-12.3% LEA, vs. 12.3-15.7% in B. jureiae .

Description. Head and body shape, and pigmentation illustrated in Fig. 32 . Meristic and morphometric data for examined specimens presented in Tables 2-5 and 15. Body shallow to moderate in depth. Head short and shallow to moderate in depth. Dorsal profile of head straight to slightly convex from occiput to snout, ventral profile of head straight between operculum and snout, snout truncate to rounded. Eye moderate in size. Upper jaw with moderate to acute sigmoidal angle between premaxillary and maxillary portions in lateral view. No accessory electric organ over operculum. Gill filaments on first gill arch 44-51 (median 48, n = 4). Pectoral fin narrow to moderate in width, pectoral-fin rays 13-16 (mode 15). Precaudal vertebrae 19-20 (mode 20), with 1-2 (mode 1) transitional vertebrae. Anal-fin origin slightly (<0.25 HL distance) anterior to, posterior to, or near, tip of pectoral fin.Anal-fin rays 181-223 (median 203). Dorsal rami of recurrent branch of anterior lateral line nerve visible. Middorsal region of body scaled. Rows of scales above lateral line 4-6 (mode 5). Lateral line continuous. Very sparse and irregular presence of depigmented epidermal canal; restricted mostly to posterior half of body, as parallel striations flanking lateral line, and as single irregular meandering lines around midway from lateral line to dorsal midline, or near edges of dorsal surface. Four bilateral 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 moderate in length to long.

Coloration. ( Fig. 32 ). Background pale tan to brown. Dorsal region with irregular dark markings, without prominent depigmented pale stripe extending along midline from occipital region to base of caudal filament. Diffuse, narrow vertical bands extend from dorsal region to lateral line in some specimens, mainly in anterior third of body. Irregular series of dark spots often present along lateral line. Ventral flank without vertical bands, with irregular dark spots in region of body cavity and over anal-fin pterygiophores. Caudal filament slightly darker than body, usually relatively free of dark markings. Head with evenly scattered dark chromatophores, darker dorsally. Eye without prominent suborbital patch, or stripe, of chromatophores/subcutaneous pigmentation. Pectoral and anal-fin membranes hyaline. Pectoral-fin rays with light, even scattering of dark chromatophores. Anal-fin rays with light scattering of dark chromatophores, which fuse in proximal part of rays. Color in live individuals similar to preserved specimens, with opercular region usually rosy due to underlying gills.

Size. Moderate adult size. Largest specimen examined 230 mm TL, 148 mm LEA (n = 227). Largest male specimen examined 199 mm TL, 135 mm LEA (n = 15). Largest female specimen examined 230 mm TL, 148 mm LEA (n = 13).

Sexual dimorphism. Breeding male specimens develop somewhat elongated caudal filaments in comparison to immature individuals and breeding females, but do not exhibit an elevated number of horizontal bilateral columns or vertical rows of electrocytes. Instead breeding males exhibit clearly enlarged electrocytes relative to immature specimens and females. Males not known to reach greater average lengths than females, despite elongated caudal filaments. Tip of caudal filament in large males does not exhibit a paddle-like lateral compression. No sexual differences in pigmentation.

Geographic distribution. Brazil ( Fig. 23 ). Known from the rio São João, rio Paraíba do Sul, and small intervening coastal drainages (e.g., rio Ururaí-Lago Feia dr.), in the state of Rio de Janeiro. Brachyhypopomus janeiroensis was also collected from the area now comprising urban Rio de Janeiro during the 1865-1866 Thayer Expedition, in the presence of the Emperor of Brazil Dom Pedro II ( MCZ 9457 and 165863) .

Ecological notes. Throughout its range B. janeiroensis occurs in the aquatic vegetation of normoxic, slow-flowing streams, and also lentic, swampy, and periodically hypoxic habitats (pers. comm., R. Campos-da-Paz, UFRJ). The type locality of B. janeiroensis is a narrow slow-flowing stream with a sandy bottom and heavily vegetated banks, which traverses forest fragments and pastureland (Costa & Campos-da-Paz, 1992). In April 2006 the following water parameters were recorded at this site: conductivity 38 μScm-1, dissolved oxygen 5.0 mgl-1, temperature 23.9 C, transparency slightly silted (WGRC & R. Campos-da-Paz, unpublished data). Reproductive biology is unknown. Stomach contents of specimens from the type locality comprise aquatic insect larvae and other small aquatic invertebrates (WGRC unpublished data).

Co-occurring congeners: None.

Local names. Brazil: tuvira.

Material examined. 227 specimens. Brazil. Rio de Janeiro. FMNH 15201, 6, 125-165 mm, FMNH 54545, 27, 83-210 mm (11 sexed, 3 immature, 148-156 mm, 3 female, 122-157 mm, 5 male, 126-199 mm), Campos, rio Paraíba do Sul dr., ca. 21°45′S, 041°18′W. FMNH 54547, 4, 131-184 mm (2 sexed: 1 female, 150 mm, 1 male, 184 mm), Lagoa Feia , Tocas [Caxia de Tocos?], rio Ururaí-Lagoa Feia dr., ca. 22°00′S, 041°20′W. MCZ 9457, 25, 105-216 mm, MCZ 165863, 72 (30 examined), 104-202 mm, mun. Rio de Janeiro, Santa Cruz , rio Grande (arroio Fundo ), in urban Rio de Janeiro, coastal drainage of urban Rio de Janeiro, ca. 22°56′S, 043°12′W. MNRJ 12127 , 1 (paratype), 166 mm, mun. Silva Jardim , affl. rio Maratuan , rio São João dr., ca. 22°39′S, 042°24′W. MNRJ 13503 , 1, 195 mm, MNRJ 14634 , 2 , 34-176 mm, mun. São Fidelis , Fazenda Poço d’Antas , rio Dois Rios , aff (R bank), rio Piraíba do Sul dr., ca. 21°38′S, 041°51′W. MNRJ 15593 , 1, 134 mm, mun. Campos dos Goytacazes , Lagoa Feia at Ponta Grossa dos Fidalgos, rio Ururaí-Lago Feia dr., ca. 21°57′S, 041°20′W. MNRJ 17509 , 1 , 64 mm, mun. Macaé , Lagoa Preta (restinga de Quissamã), boundary of Macaé with Campos , Lagoa Preta dr., ca. 22°08′S, 041°25′W. MNRJ 38510 , 12 (10 immature, 99-162 mm, 1 female, 153 mm, 1 male, 111 mm), mun. Silva Jardim , ca. 5 km NNW Silva Jardim, bridge over small creek, affl. rio São João dr., 22°35′46″S, 042°24′52″W. MZUSP 22702 , 5 (3 immature, 72-85 mm, 1 female, 121 mm, 1 male, 149 mm), MZUSP 22703 , 1 , female, 114 mm, São João da Barra , rio Paraíba do Sul dr., ca. 21°39′S, 041°03′W. MZUSP 23013 , 1 , São Fidelis , rio Paraíba do Sul dr., ca. 21°38′S, 041°44′W. MZUSP 43130 , 1 (holotype), 124 mm, MZUSP 43131 , 7 (paratypes), 75-129 mm LEA, UFRJ 598 , 4 (paratypes), 76-131 mm LEA, UFRJ 599 , 2 (paratypes), 80- 80 mm LEA, collected with holotype. UFRJ 529 , 3 , 79-91 mm LEA, córrego Salto d’Água 6 km N Silva Jardim (rd. from Gaviões ), rio São João dr., ca. 22°39′S, 042°23′W. MZUSP 45880 , 20 , mun. Silva Jardim , riacho Fazenda Nova , 5 km road to Bananeiras , rio São João dr., ca. 22°40′S, 042°22′W. MZUSP 80122 , 2 , male (1 CS), 174-176 mm, mun. Silva Jardim , 28 km N by Boqueirão-Japuiba rd. , at Gaviões , rio São João dr., ca. 22°34′S, 042°34′W. NRM 22480, 2, 123-151 mm, mun. Silva Jardim , Japuiba , Gaviões , rio São João dr., ca. 22°33′S, 042°31′W. SU 36964 , 1 , 98 mm, USNM 129915 , 6 , 85-230 mm (3 sexed: 1 immature, 148 mm, 2 female, 138-230 mm), Rio de Janeiro and its vicinity, ca. 22°55′S, 043°09′W. SU 62742 , 4 , 44-87 mm, Rio de Janeiro, old Petrópolis rd. , no coordinates. UF 183780 , 2 (1 CS), 120-130 mm, mun. Casimiro de Abreu , rio São João dr., ca. 22°29′S, 042°12′W. ZMH 11627, 18 (14 measured and sexed: 5 immature, 112-129 mm, 4 female, 120-159 mm, 5 male, 152-185 mm), prov. Rio de Janeiro, no coordinates .

Figures

Fig. 32. Brachyhypopomus janeiroensis. MZUSP 80122; male, 174 mm TL (head in lateral view, and body in lateral and dorsal view, specimen fixed in formalin and preserved in EtOH). Brazil, rio São João dr. Scale bars = 5mm.

Fig. 23. Collection records for Brachyhypopomus draco (circles), B. janeiroensis (squares), and B. jureiae (triangles). Holotype locations are marked with open symbols. Elevation data refers to altitude above mean sea level (see Fig. 2 for legend).