Electrophorus varii, de Santana & Crampton & Dillman & Frederico & Sabaj & Covain & Ready & Zuanon & de Oliveira & Mendes-Júnior & Bastos & Teixeira & Mol & Ohara & Castro & Peixoto & Nagamachi & Sousa & Montag & Ribeiro & Waddell & Piorsky & Vari & Wosiacki, 2019

de Santana, C. David, Crampton, William G. R., Dillman, Casey B., Frederico, Renata G., Sabaj, Mark H., Covain, Raphaël, Ready, Jonathan, Zuanon, Jansen, de Oliveira, Renildo R., Mendes-Júnior, Raimundo N., Bastos, Douglas A., Teixeira, Tulio F., Mol, Jan, Ohara, Willian, Castro, Natália Castro e, Peixoto, Luiz A., Nagamachi, Cleusa, Sousa, Leandro, Montag, Luciano F. A., Ribeiro, Frank, Waddell, Joseph C., Piorsky, Nivaldo M., Vari, Richard P. & Wosiacki, Wolmar B., 2019, Unexpected species diversity in electric eels with a description of the strongest living bioelectricity generator, Nature Communications 10 (4000), pp. 1-10 : 6

Electrophorus varii , sp. nov. de Santana, Wosiacki, Crampton, Sabaj, Dillman, Mendes-Júnior and Castro e Castro

Holotype: MPEG 25422 , 1000 mm TL; Goiapi River , Marajó Island, Pará, Brazil.

Paratypes: INPA 46378 , INPA 46379 (3) ; MHNG 2748.083 ; MPEG 30480 (3).

Etymology: In honor of Richard Peter Vari (1949–2016) for his contributions to ichthyology.

Diagnosis: Eleven nucleotides in COI: A(64), A(80), G(146), G (164), T(190), A(251), A(467), C(512), T(517), A(536), and C (569). Pectoral-fin rays 20–28 and lateral-line pores 124–186 (versus 32–38, and 88–101, respectively, in E. electricus ). Distinguished by head narrow, Fig. 2a (versus wide, Fig. 2b , in E. voltai ; distance between medial margins of contralateral dentaries at transverse through last two ventral pores 2–3 times shorter in E. varii than E. voltai , Fig. 2a, b ), skull deep, cleithrum lies between vertebrae 1 and 2, Fig. 2b (versus skull depressed, cleithrum lies between vertebrae 5 and 6, in both E. electricus and E. voltai Fig. 2a, c ).

Description: As for E. electricus , except as noted in Diagnosis and except clear band along body always absent. Species illustrated in Figs. 2 , 3 , and 6. Maximum size examined specimens 1485 mm TL. Morphometric and meristic data in Supplementary Data 2. Low-voltage EOD duration 1.24–1.78 ms ( Fig. 4d ), highvoltage EOD 151 V (200 mm TL) to 572 V (609 mm TL) ( Fig. 4d ), n = 4. For distribution see Fig. 1a ; Supplementary Data 1.

Figures

Fig. 2 Key morphological features to recognize the three species of Electrophorus. Top, radiographs of lateral view of the anterior portion of body (skull and pectoral girdle highlighted red). The cleithrum lies between the fifth and sixth vertebrae (v) in Electrophorus electricus (a) and E. voltai (b) versus first and second vertebrae in E. varii (c). Bottom, illustrations of ventral view of the head, showing key features listed in Diagnoses. a top: National Museum of Natural History, NMNH 403765, 300 mm TL, Cuyuni River, Guyana; bottom: NMNH 225576, 1000 mm TL, Corantijn River, Suriname. b top: Instituto Nacional de Pesquisas de Amazônia, INPA 39009, 450 mm TL, Teles Pires River, Brazil; bottom: Academy of Natural Sciences of Drexel University, ANSP 197583 (t3539), 1280 mm TL, Xingu River, Brazil. c top: NMNH 306677, 450 mm TL, Lago Janauari, Amazon River, Brazil; bottom: NMNH 196634, 1220 mm TL, Amazon River, Brazil

Fig. 3 Electrophorus tree of life and time of species diversification. Time-calibrated genealogy of Electrophorus based on a maximum clade credibility (MCC) species tree derived from *BEAST2.4 analyses of 10 genes (colored lines) and 94 specimens of Electrophorus (relaxed molecular clock and uncorrelated lognormal model implemented). Purple bars represent 95% highest posterior density distributions for the estimated divergence time of each major node. Voltage measurements made by us are reported below E. electricus (National Museum of Natural History, NMNH 225670, 520 mm TL, Corantijn River, Suriname), E. voltai (Museu Paraense Emílio Goeldi, MPEG 15529; holotype, 1290 mm TL), and E. varii (MPEG 25422; holotype, 1000 mm TL)

Fig. 4 Ecological Niche Model and electric organ discharges for species of Electrophorus. Species niche models generated by MaxEnt for Greater Amazonia: a Electrophorus electricus (red); b E. varii (yellow); and c E. voltai (blue). d Measurements of voltage of high-voltage EODs, low-voltage EODs waveforms from Sach’s organ, and posterior one-third of Hunter's organ (grey lines = individually recorded fish, black lines = averaged waveform for each species). e Nearest-neighbor hierarchical clustering of prominent time-frequency features of the low-voltage Sach’s organ EOD from seven individuals of Electrophorus

Fig. 1 Sampling localities and gene trees for the three species of Electrophorus. a Map of northern South America showing distributions of sampled records and type localities (indicated by numbers) for three electric eel species: Electrophorus electricus (red dots, 1 = Suriname River, Suriname); E. voltai (blue dots, 2 = Rio Ipitinga, Brazil); and E. varii (yellow dots, 3 = Rio Goiapi, Brazil). Bicolor dots (blue/yellow) indicate sympatric co-occurrence of E. voltai and E. varii. The map was created in ArcGIS (https://www.arcgis.com) with images available at Shuttle Radar Topography Mission, Global Multi-resolution Terrain Elevation Data, and HydroSHEDS database. b *BEAST2.4 species tree (top cladogram; 94 specimens:15 E. electricus, 41 E. voltai, 38 E. varii) based on 5 mitochondrial (trees 1–5; 107 specimens: 19 E. electricus, 43 E. voltai, 45 E. varii) and 5 nuclear genes (6–10; 94 specimens). Higher shading densities represent areas where the majority of trees agree in topology and branch lengths (posterior probabilities>0.99), while lower densities represent areas of uncertainty (Supplementary Data 1)