Eigenmannia bumba Dutra & Ramos & Menezes 2022, new species

Eigenmannia bumba, new species

urn:lsid:zoobank.org:act: 3F3C0B90-6FB3-43E8-9B03-A158FD487271

(Figs. 2, 3A, B; Tab. 1)

Eigenmannia virescens (non Valenciennes, 1836). —Guimarães et al., 2020:7 (listed, ichthyofauna of the Pindaré River).

Holotype. MZUSP 125870, 117.5 mm LEA, rio Santana, tributary of rio Grajaú, rio Mearim basin, Grajaú, Maranhão, Brazil, 05°35’39.48”S 46°14’30.88”W, O. Oyakawa, F. Dagosta, M. Marinho & P. Camelier, 16 Out 2014.

Paratypes. MZUSP 123709, 22 +3 CS, 77.5–123.5 mm LEA; MZUSP 123714, 21, 53.6–107.1 mm LEA, collected with holotype.

Non-types. MZUSP 5065, 1, 89.7 mm LEA, Rio Grajaú, Grajaú, Maranhão, 5°49”S 46°09’W, Expedição do Departamento de Zoologia, 15 Jun 1966. MZUSP 125873, 1, 83.9 mm LEA, Rio Pindaré, Bom Jesus das Selvas, Maranhão, 4°36’32.6”S 46°56’09.2”W, O. Oyakawa, F. Dagosta, M. Marinho, P. Camelier, 21 Out 2014.

Diagnosis. Eigenmannia bumba, a member of the E. trilineata species-group, differs from the E. humboldtii species-group by the anal-fin hyaline (vs. anal-fin margin distinctly darkened), and from E. macrops (Boulenger, 1897) by the absence of enlarged eye (21.3–25.4% HL vs. 26.4–29.7% HL), and the presence of a short caudal filament (19.2–30.8% LEA vs. 67.5–79.3% LEA). Within the E. trilineata species-group, the new species differs from all other species, except E. besouro Peixoto & Wosiacki, 2016, E. correntes Campos-da-Paz & Queiroz, 2017, E. dutrai Peixoto, Pastana & Ballen, 2021, E. guchereauae (Meunier, Jegu & Keith, 2014), E. meeki Dutra, de Santana & Wosiacki, 2017, E. oradens Dutra, Peixoto, de Santana & Wosiacki, 2018, E. robsoni, E. sirius Peixoto & Ohara, 2019, E. vicentespeleaea Triques, 1996, E. virescens, and E. waiwai Peixoto, Dutra & Wosiacki, 2015 by having a subterminal mouth (vs. terminal). Eigenmannia bumba differs from the aforementioned species by the following combination of characters: (1) lateral line stripe restricted to last two thirds of body (vs. complete in E. besouro, E. correntes, E. dutrai, E. guchereauae, E. meeki, E. oradens, E. sirius, E. vicentespelaea, and E. waiwai); (2) superior midlateral stripe present (vs. absent in E. guchereauae E meeki, E. oradens, E. robsoni, and E. virescens); (3) 176–205 anal-fin rays (vs. 143–154 in E. correntes, 211– 204 in E. meeki); (4) 10–15 scales rows above lateral line (vs. 7–8 in E. vicentespelaea); (5) 109–125 scales on lateral line (vs. 140–168 in E. meeki), (6) 19–23 premaxillary teeth (vs. 75 in E. guchereauae, 30–55 in E. meeki, 38–42 in E. oradens, 32–34 in E. robsoni, 25–26 in E. vicentespeleaea, and 35–40 in E. waiwai); (7) 20–29 dentary teeth (vs. 16–18 in E. correntes, 35–36 in E. dutrai, 88 in E. guchereauae, 31–38 in E. oradens, 35–44 in E. robsoni, 38–41 in E. vicentespelaea, 39 in E. virescens, and 37–38 in E. waiwai); (8) 6–10 endopterygoid teeth (vs. 13–15 in E. meeki, 14–17 in E. waiwai); (9) depth of posterodorsal expansion on infraorbitals 1+2 half as long as infraorbitals 1+2 length (vs. as long as infraorbitals 1+2 length in E. dutrai, E. guchereauae, E. oradens, E. sirius); (10) basibranchial 1 unossified (vs. ossified in E. virescens); (11) 13–14 precaudal vertebrae (vs. 15 in E. meeki and E. sirius); (12) length of coronomeckelian bone corresponding to 20% of Meckel’s cartilage length (vs. 45% in E. oradens and E. waiwai). A summary of diagnostic characters among species of the E. trilineata species-group is provided on Tabs. 2–3.

Description. Body shape and pigmentation shown in Fig. 2, morphometric data in Tab. 1. Largest examined specimen 123.5 mm LEA. Body elongate and distinctly compressed. Greatest body depth at vertical crossing distal tip of pectoral fin. Dorsal profile of body slightly convex from snout tip to vertical through anal-fin terminus. Ventral profile of body convex from tip of lower jaw to anal-fin terminus. Caudal filament short.

Head laterally compressed; greatest width at opercular region, greatest depth at nape. Dorsal profile of head convex from snout tip to nape. Ventral profile of head convex from tip of lower jaw to isthmus. Snout pointed in lateral view. Mouth subterminal. Mouth rictus at vertical through a point between anterior and posterior nares or vertical through posterior nostril. Anterior nostril tube-like; closer to snout tip than to anterior margin of eye. Posterior nostril round, not tubular, closer to anterior margin of eye than to snout tip, at horizontal line between middle and dorsal margin of eye. Eye small, circular, completely covered by skin, on anterior one-half of HL, laterally oriented. Anus adjacent to urogenital papilla, shifting ontogenetically from vertical through middle of opercle to vertical through posterior margin of eye. Urogenital papilla usually not developed in specimens under 95.5 mm LEA. Branchial membranes joined at isthmus. Gill rakers on first branchial arch 11(3).

Scales cycloid, small, extending from posterior most part of head to vertical through tip of caudal-filament, present on mid-dorsal region of body. Scales above lateral line at vertical through end of pectoral fin 12(1), 13(6), 14*(4), or 15(4). Anterior most perforated lateral-line scale along vertical through pectoral-fin origin. Lateral-line

scales to vertical through base of last anal-fin ray 109–125(N = 15), 119 in holotype.

Pectoral-fin rays ii,13*(2), ii,14(10), or ii,15(3). Distal pectoral-fin margin straight. Total anal-fin rays 176–205(N = 15), 202 in holotype. Anal-fin origin along vertical through pectoral-fin insertion or slightly posterior. Distal margin of anal fin slightly convex. First unbranched rays tiny, subsequent rays progressively increasing in size toward first branched rays. Branched rays of nearly equal length except for posterior most rays that progressively decrease in length.

Relevant osteological features. Premaxillary teeth 19(1) or 23(2) in four(3) rows (Fig. 3A). Dentary teeth 20(1), 26(1), or 29(1) in two(2) or three(1) rows (Fig. 3B). Dentary teeth not increasing in size along dentigerous surface. Coronomeckelian bone

length near 20% Meckel’s cartilage length. Endopterygoid teeth six (1), seven (1), or 10 (1) in one (2) or two (1) rows. Antorbital and infraorbitals 1 to 4 enlarged, partially cylindrical with slender osseous arches. Fifth and sixth infraorbitals slender and tubular. Depth of posterodorsal expansion on infraorbitals 1+2 half as long as infraorbitals 1+2 length. Branchiostegals five(3). Upper pharyngeal teeth six(1), seven(1), or eight(1). Lower pharyngeal teeth nine(1), 10(1) or 13(1). Precaudal vertebrae 13(2), or 14(1). Transitional vertebrae four(3). Pleural ribs six(2) or seven(1). Displaced hemal spines three(3).

Coloration in alcohol. Body ground coloration cream. Body with two layers of chromatophores. Outer layer covered by dark chromatophores gradually more spaced ventrally, more concentrated between lateral line and anal pterygiophores forming a superior midlateral stripe. Lateral line stripe faint and restricted to last two thirds of body. Superior medial stripe thick, covering the space equivalent to one to three scales vertically, tapering from vertical through end of body cavity to vertical through to posterior one-third of LEA. Inner layer of pigmentation formed by multiple, small bars of dark chromatophores situated between the musculature associated with anal-fin pterygiophores. Dark individual bars in combination forming a stripe-like pattern on anal-fin base. Anal-fin base stripe approximately half as wide as orbital diameter. Head covered by dark chromatophores, more concentrated on opercular region. Pectoral and anal fins hyaline with scattered dark chromatophores overlying fin rays.

Geographical distribution. Eigenmannia bumba is known from rio Grajaú and rio Pindaré, both tributaries of the rio Mearim, Northeastern Brazil (Fig. 4).

Ecological notes. Specimens of Eigenmannia bumba were collected in clear and slow flowing waters with substrates comprising sand and organic matter. Sampled sites were 5 to 15m in width and 1.7m deep, with riparian vegetation dominated by grassy and herbaceous vegetation.

Etymology. The epithet “ bumba ” is in reference to “ bumba meu boi ” or “ boi-bumbá ”, a folklore character in Northern Brazil. A noun in apposition.

Conservation status. Eigenmannia bumba apparently does not match any of the extinction risk categories giving by International Union for Conservation of Nature (IUCN). Therefore, according with the currently available data, and using the criteria of the IUCN Standards and Petitions Subcommittee (IUCN, 2019), we propose that the species should be classified as Least Concern (LC). Despite being described from only three localities, E. bumba likely possesses a wider distribution in the Mearim basin than reported here.