Protocheirodon, Vari & Melo & Oliveira, 2016

Vari, Richard P., Melo, Bruno F. & Oliveira, Claudio, 2016, Protocheirodon, a new genus of Characidae (Teleostei: Characiformes) with the redescription of the poorly known Protocheirodon pi, Neotropical Ichthyology 14 (2), No. e 150154, pp. 1-7 : 3-5

Protocheirodon pi (Vari, 1978)

Leptagoniates pi Vari, 1978: 185, figs. 1-2 (original description; río Mamoré, Bolivia). - Malabarba, 1998: 229 (in phylogeny of Cheirodontinae ). Lima et al., 2003: 144 (in list of incertae sedis species in Characidae ). -Bogotá- Gregory & Maldonado-Ocampo, 2006: 66 (in list of fishes in Colombian Amazon). -Maldonado-Ocampo et al., 2008: 170 ( Colombia, Amazon; in checklist of freshwater fishes of Colombia). -Duarte et al., 2010: 323 (in list of fishes from lower rio Purus, Brazil). Ortega et al., 2010: 36 (in list of freshwater fishes of Peru). - Lima et al., 2013: 299 (in list of fishes from rio Madeira, Brazil). -Tagliacollo et al., 2012: 305 (in molecular phylogeny of Aphyocharacinae ). -Mariguela et al., 2013: 29 (in molecular phylogeny of Cheirodontinae ).

Diagnosis. As for Protocheirodon above.

Description. Summary morphometrics in Table 1. Body distinctly compressed and moderately elongate with greatest depth immediately anterior to dorsal-fin origin. Dorsal profile of head convex from margin of upper lip to vertical through anterior margin of orbit and then very slightly concave to rear of head. Predorsal profile of body straight to very slightly sigmoid. Dorsal profile strongly posteroventrally angled along dorsal-fin base and then straight and less posteroventrally angled to caudal peduncle. Ventral profile of head and body gently convex from tip of lower jaw to anal-fin origin, straight and posterodorsally angled along anal-fin base to caudal peduncle.

Mouth small. Maxilla distinctly posteroventrally slanted and reaching horizontal through ventral margin of orbit. Margin of non-tooth bearing portion of maxilla gently convex. Teeth in single series in each jaw with functional dentition of premaxilla and dentary followed internally by replacement tooth series. All teeth pedunculate and tricuspidate with median cusp distinctly larger. Premaxilla with seven or eight teeth. Maxilla with four or five teeth. Dentary with nine to 11 teeth. Third infraorbital falling short of horizontal arm of preopercle; fourth and fifth infraorbitals reduced to tubular ossifications at rear of orbit.

Dorsal fin long and pointed; tip of adpressed fin reaching one-half distance to adipose-fin insertion. Dorsalfin rays ii,7(18) or ii,8(1). Pectoral fin pointed with tip of fin typically extending well beyond vertical through pelvicfin insertion. Pectoral-fin rays i,11(20) or i,12(5). Pelvic fin short, reaching only one-half distance to anal-fin origin. Pelvic-fin rays i,4(3) or i,5(22). Anal fin elongate; first three rays originate from single basal pterygiophore. Third through sixth to eighth anal-fin rays longer than remaining rays and forming distinct lobe; remainder of fin margin straight. Anterior rays form distinct lobe. Anal-fin rays iii,44(4), iii,45(13), iii,46 (16), iii,47(3), or iii,48(1). Adipose fin small. Caudal fin emarginate with 11 to 13 dorsal and 7 to 9 ventral procurrent rays.

Scales thin and cycloid. Lateral line completely pored. Lateral line scales 32(1), 33(3), 34(10), 35(8), 36(9), 37(4), 38(2), or 39(1). Scales above lateral line to middorsal line 7 (9) or 8(13). Scales below lateral line to pelvic-fin insertion 4(21).

Coloration in alcohol. Ground coloration pale yellow ( Fig. 2a ). Concentration of dark chromatophores variably present on middle of posterior region of caudal peduncle and base of middle caudal-fin rays. Scattered dark pigmentation present on dorsal most region of body in some specimens. Fins hyaline overall, but some individuals with series of small, dark chromatophores along fin-ray margins. Region of pseudotympanum over anterior chamber of swimbladder and area overlying ventral portions of sub-chambers of posterior chamber of swimbladder slightly darker; coloration function of reduction in body wall thickness rather than dark pigmentation.

Coloration in life. Head and abdominal region silvery with guanine most prominent on dorsolateral and lateral surfaces of head and over intestinal tract ( Fig. 2b ). Vertical sub-chambers of posterior portion of swimbladder obvious through translucent body wall and covered by guanine; region with very slight greenish tint in some specimens. Body translucent with vertebral column and myomeres margins obvious. Some individuals with narrow dark line apparent above vertebral column and with myomeres outlined with variably intense dark chromatophores. Patch of dark chromatophores variably present on middle of posterior of caudal peduncle and base of middle caudalfin rays. Median fins most often hyaline, but overall darker specimens with fin ray margins outlined by series of dark chromatophores. Distal portion of lobe at anterior of anal fin white. Pectoral and pelvic fins hyaline or with few dark chromatophores along fin-ray margins. Ventral margin of caudal fin with elongate, very narrow white stripe in some individuals.

Ecology. Samples of Protocheirodon pi originated in marginal areas of rivers and streams, often over sandy substrates and in still backwaters. Sexual dimorphism was not observed.

Distribution. Protocheirodon pi is widely distributed in the major river systems of the central and western portions of the Amazon basin ( Fig. 3 ) including the Amazonas- Solimões, Purus, Madeira and Ucayali rivers (see also Remarks below).

Remarks. One examined lot (USNM 191640) reputedly originated in the rio Araguaia, near Aruanã, Goiás, Brazil (14º58’S 51º24’W). This location is distant from the known limits of the range of Protocheirodon and would represent the only record of the genus from the rio Tocantins basin, let alone in its upper reaches. This sample was collected during wide ranging sampling efforts focused on aquarium fishes and some portions of material have questionable locality data (S. H. Weitzman, pers. comm.).

Conservation status. Given the broad distribution throughout central and western Amazon ( Fig. 3 ) and the absence of significant threats over many sampled localities, Protocheirodon pi should be categorized as Least Concern (LC) under the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014).

Material examined. Holotype. AMNH 35952 , 29.2 mm SL, Bolivia, Departamento Beni, río Mamoré , 10 km W of San Pedro, lagoons communicating with river, approximately 14º21’01.7”S 64º59’40”W, 17 Sep 1965, S. Anderson . Paratypes. AMNH 35953 , 3, 27.2-31.0 mm SL ; BMNH 1977.6.9.138 , 1, 28.0 mm SL, collected with holotype . Non-types. Brazil: LBP 10565 , 10, 29.3-32.2 mm SL, Acre, Rio Branco, rio Acre-Purus , 10º03’28.6”S 67º51’25.6”W . LBP 15095 , 1, 30.0 mm SL, Acre, Rio Branco, rio Acre-Purus , 09º56’16.6”S 67º52’43.6”W . LBP 18603 , 4, 27.2-34.2 mm SL, Acre, Porto Acre, rio Acre-Purus , 09º35’24.6”S 67º31’53.4”W . MZUSP 49643 , 2, 27.7-30.8 mm SL, Acre, Seringal do Acre, rio Purus . MZUSP 12400 , 5, 20.7-27.6 mm SL, Amazonas, Boca do Paraná do Catito, rio Solimões, below mouth of rio Juruá , 02°38’S 64°45’W . MZUSP 17427 , 2, 20.6-27.0 mm SL, rio Solimões, at Jacaré, near Fonte Boa , 02º30’59.9”S 66º06’0.2”W . MZUSP 9604 , 2, 18.9-23.3 mm SL, Amazonas, Boca do Lago Pereira, rio Solimões, in front of Codajás , 03º50’60”S 62º3’60”W . MZUSP 12399 , 2, 22.2-23.6 mm SL, Amazonas, Fonte Boa, 02º30’59.9”S 66º06’0.2”W . MZUSP 57224 , 1, 19.3 mm SL, Amazonas, rio Solimões, below rio Purus , 03º33’23.7” 61º9’52.1”W . MZUSP 56150 , 4, 21.9-24.1 mm SL, Amazonas, rio Solimões , 34.3 km below Juruá, 03º34’52.2”S 66º25’37.7”W . MZUSP 56142 , 2, 23.9-25.2 mm SL, Amazonas, rio Solimões , 31.5 km below Juruá, 02º39’50”S 65º36’32.3”W . MZUSP 35619 , 2, 27.5-29.4 mm SL, Amazonas, rio Madeira, Ilha do Puruzinho , 07°23’S 63°45’W . MZUSP 55923 , 5, 24.8- 27.4 mm SL, Amazonas, rio Madeira , 1.9 km below Paraná do Urucurituba, 03º33’31.1”S 58º55’45.4”W . MZUSP 35606 , 2, 25.2-26.1 mm SL ; MZUSP 98292 , 1, 32,1 mm SL, Rondônia, rio Madeira, cachoeira de Santo Antônio , 08°50’S 64°01’W . MZUSP 76856 , 4, 19.6-21.4 mm SL, Rondônia, rio Madeira, Calama, lago do Caraparu , 08º02’12.1”S 62º52’33.4”W . Colombia: CAS 41749 , 2, 25.7-29.5 mm SL, Amazonas, Isla de Santa Sofia II , ca. 20 mi (= 32 km) NW of Leticia, large lake near shoreline . Peru: ANSP 149428 , 2, 26.2-27.4 mm SL ; ANSP 149430 , 1, 26.2 mm SL, Loreto, vicinity of Iquitos , S of Isla Iquitos. ANSP 149429 , 2, 25.8-29.8 mm SL, Ucayali, Inahuaya District . ANSP 150120 , 4, 28.4-35.6 mm SL, río Ambiyacu . ANSP 178120 , 1, 31.7 mm SL, Loreto, Maynas, río Napo, upstream of río Maza, town of Mazan . CAS 41748 , 1, 26.2 mm SL, Loreto, Caño del Chancho, near Pebas . CAS 70650 , 5, 18.8-25.2 mm SL, Ucayali, sandbars of río Bajo Ucayali, at Inhehuaya . FMNH 84201 , 4, 23.6-28.7 mm SL, Ucayali, sand beach across from Pucallpa . MZUSP 26387 , 4, 28.9-30.0 mm SL, Ucayali, Pucallpa , río Ucayali . SU 58309 , 1, 24.3 mm SL, Ucayali, río Ucayali, sandbanks near Orellana, small town on right bank below Contamana . USNM 280399 , 14, 19.4-22.9 mm SL, Ucayali, Distrito Coronel Portillo, side caño off Caño Yarinacocha . Questionable locality : USNM 191640 , 2, 29.1-31.2 mm SL, Brazil, Goiás, rio Araguaia, near Aruanã , 14º58’S 51º24’W .

Figures

Fig. 2. Protocheirodon pi, (A) CAS 41749, 29.5 mm SL; Colombia, Amazonas, Isla de Santa Sofia II, ca. 20 mi (= 32 km) NW of Leticia; (B) live specimen from aquarium without locality information. Scale bar = 5 mm. Photo credits: (A) Sandra Raredon (USNM) and (B) Martin and Peter Hoffmann.

Fig. 3. Central and western Amazon basin showing the distribution of Protocheirodon pi. Star indicates the type locality. Black lines represent country boundaries.