Poecilia (Pamphorichthys) akroa, Figueiredo & Moreira, 2018

Figueiredo, Carlos Augusto & Moreira, Cristiano R., 2018, Poecilia (Pamphorichthys) akroa, a new poeciliid species (Cyprinodontiformes: Poeciliidae) from the Rio Tocantins basin, Brazil, Zootaxa 4461 (3), pp. 438-444 : 439-443

Poecilia (Pamphorichthys) akroa , sp. n.

Figs 1–3 ; Table 1

Holotype. MZUSP 121698 (male, 16.9 mm SL), Brazil, Tocantins, Dianópolis, rio Palmeiras on the road Dianópolis—Formosa do Rio Preto, at Fazenda Nova Iguaçu, 11°37'52"S, 46°25'58"W, 16 November 2002, C. Moreira and J. C. Nolasco.

Paratype. MZUSP 83547, 50 alc. 4 cs, (5 males, 15.4–18.1 mm SL, 45 females, 10.9–24.6 mm SL, MNRJ 50508, 5 alc., (2 males, 17.6–18.8 mm SL; 3 females, 21.2–22.5 mm SL), UMMZ 250318, 5 alc. (2 males, 16.2– 17.9 mm SL; 3 females, 19.5–21.0 mm SL), collected with holotype ; MZUSP 83549 , 19 alc. (2 males, 14.7–16.8 mm SL; 17 females, 10.9–23.8 mm SL) same locality and collectors of holotype, 4 August 2002 ; MZUSP 83548 , 1 alc. (female, 11.8 mm SL) Brazil, Tocantins, Novo Jardim, Lagoa Bonita, marginal lake of rio Palmeiras, rio Tocantins basin, 11°40'24"S, 46°39'24"W, 16 November 2002, C. Moreira and J.C. Nolasco ; MZUSP 83550 , 3 alc. (all males, 13.8–16.9 mm SL), same locality as MZUSP 83548 , 28 June 2002, C. Moreira, J.C. Nolasco, and M. Avila.

Diagnosis. Poecilia (Pamphorichthys) akroa can be distinguished from all other species of the genus, except members of the subgenus Pamphorichthys by possessing 10 or 11 pectoral-fin rays (vs. 12 or more). It can be distinguished from all other species of the subgenus by the following exclusive characters: neuromast of the preopercular ramus and the posterior portion of the supraorbital ramus (posterior remnant of infraorbital system sensu Rosen & Mendelson, 1960) of the cephalic sensory system enclosed in canals (vs. only superficial neuromasts on the preopercular and supraorbital rami of the cephalic sensory); the presence of a faint longitudinal band along the body (vs. longitudinal band absent); one gonapophysis (vs. two). The new species can be additionally distinguished from all P. araguaiensis , P. hollandi , P. minor and P. scalpridens by an homogeneous reticulate color pattern on sides of body composed by chromatophores more concentrated at border of scales (vs. general reticulate color pattern on sides of body with a longitudinal band more pigmented forming a longitudinal zigzag band). It is distinguished from all species of the subgenus, except P. pertapeh , by urogenital region of females heavily pigmented (vs. urogenital region pale); distalmost segments of the anterior branch (4a) of the fourth gonopodial ray fused into an elongated segment turned anteriorly (vs. on the same axis of anterior segments); and general osteological structure of second branched pelvic-fin ray of males, similar to the other pelvic-fin rays (vs. second branched pelvic-fin ray of males with lateral digitiform projection). Poecilia (Pamphorichthys) akroa is distinguished from P. hasemani by subdistal segments of anterior branch (5a) of fifth gonopodial ray simple, without anterior (ventral) projections; and distal portion of dorsal fin with a basal black blotch (vs. dorsal fin hyaline). It is distinguished from P. pertapeh by the presence of chromatophores more concentrated on the posterior margin of the mid-ventral scale series of the caudal peduncle and ventrolateral margin of the adjacent scales, forming a series of rhombi posterior to anal fin (vs. chromatophores with similar pattern on all ventral and ventrolateral scales).

Description. Morphometric and meristic data given in Table 1. Females larger than males. Dorsal profile of males gently convex from snout to dorsal-fin origin, more convex in females. Dorsal-fin base posteroventrally slanted. Dorsal profile of caudal peduncle nearly straight. Ventral profile of lower jaw convex, from anguloarticular to isthmus nearly straight. In females, from isthmus to anal-fin origin slightly convex, to pronouncedly convex, anal-fin slightly posterodorsally slanted. Caudal peduncle ventral profile straight in females. Ventral profile of males from isthmus to pelvic-fin insertion straight and projected from body. Notch between pelvic-fin insertion and urogenital papillae. Anal-fin base projected ventrally. Caudal peduncle ventral profile slightly convex. Distal margin of dorsal fin in males and females gently curved. Distal margin of caudal fin in males and females rounded. Distal margin of anal fin in females nearly straight. Pectoral fins rounded and symmetrical. Pelvic fins in mature males with second ray elongated and third ray curved at its subdistal end. Gonopodium with a gonopodium palp enveloping its tip and extending beyond the tips of the gonopodium rays.

Mouth superior. Premaxillary teeth on the outer row, males: 7(1) or 8(1), females: 7(1), 8(1) or 9(1). Dentary teeth on the outer row, 7(1) or 8(1) in males, and 7(1) or 8(2) in females. Dorsal-fin rays i, 6*(25), i,7(4) or ii,6(1). Anal-fin rays in females iii, 5 (2) or iii, 6 (17). Pelvic-fin rays i,4(5). Caudal-fin branched rays 11(5), unbranched superior caudal-fin rays 6(4) or 7(1) and unbranched inferior caudal-fin rays 5(1) or 6(4). Pectoral-fin rays ii, 8(1) or ii, 9(4). Scales in longitudinal series 26(4), 27*(17) or 28(4), scales in transversal series 7*(21) or 8(6), scales around caudal peduncle 14(1), 15(3) or 16*(24). Predorsal scales 12(3), 13*(16) or 14(5). Precaudal vertebra 14(5), caudal vertebra 14(5); First proximal radial of dorsal fin between 10th and 11th vertebrae (5); branchiostegal rays 4(2) or 5(3). One gonapophysis (2) originating at 13th vertebra (2), with narrow Hollister foramen ( Rodriguez, 1997) restricted to tip. Seven gonactinosts (2), gonactinostal complex (gonactinosts 2-5) elongated with central laminar flange anteriorly expanded at dorsal tip, and less pronounced lateral flanges. Tip of gonactinosts 6 and 7 inserted at Hollister foramen. Gonopodial ray 3 with anterior lepidotrichia wider than deep, abruptly narrowing at distal half; no ornamentation on subdistal segments. Tip of gonopodial ray 3 slightly dorsally directed. No dorsal processes on gonopodial ray 4a segments. Distal segment of gonopodial ray 4a elongated, approximately size of three anterior segments, and ventrally curved. Subdistal portion of ray 4p with approximately 14 serrated segments (sensu Rosen & Bailey, 1963). Serrae base taking almost all dorsal portion of segment. Distal portion of gonopodial ray 4p set apart from ray 4a, reunited, and curved ventrally at tip of both rays. Ray 5a simple, ventral border of subdistal portion of gonopodial ray 5 without keel or serrae, slightly curved dorsally on distal portion. Ray 5 shortest of three elongated rays, its tip parallel to ray 4p and slightly curved dorsally ( Fig 2 ).

Color in alcohol. Color pattern not sexually dimorphic, except for pigmentation on anal fin. Cream to pale yellow body background color. Snout more pigmented than remaining of head and body. Dark chromatophores concentrated on dorsal half of head. Few chromatophores on the posteroventral infraorbital region. Base of pectoral fin more densely pigmented. Middorsal dark line from supraoccipital to dorsal-fin origin. Scales with dark chromatophores on posterior margin producing a reticulate pattern, except those from the abdomen which are not pigmented. Chromatophore density fainter on ventrolateral portion of caudal peduncle. Faint longitudinal band along body, composed of uniformly distributed chromatophores superposed to reticulate pattern, mainly on central portion of scales of longitudinal series. Horizontal septum with thin darker line, more conspicuous at caudal peduncle. Chromatophores concentrated on posterior margin of mid-ventral scale series of caudal peduncle and ventrolateral margin of adjacent scales, forming series of rhombi posterior to anal fin. Adult females with urogenital region surrounded with conspicuous dark pigmentation ( Fig. 3 ). Proximal portion of dorsal fin with basal black blotch. In less pigmented specimens, interradial membranes at basal portion of middle dorsal-fin rays hyaline. Distal portion of dorsal fin with dark chromatophores concentrated on interradial membranes, leaving medial portion of fin hyaline or with few chromatophores. Pelvic fins hyaline. Pectoral fin with scattered chromatophores on border of rays. Anal fin of females with scattered chromatophores, more concentrated on anterior, and distal margins. Gonopodium faintly pigmented with scattered chromatophores, except for gonopodial palp, with more densely pigmentation. Males can be more intensely pigmented than females, but overall, no dimorphism was detected in color pattern in alcohol-preserved specimens.

Distribution. The new species is known only from two localities of Rio Palmeiras, Rio Tocantins basin, State of Tocantins, Brazil. Across most of the Rio Tocantins Basin, reports of the subgenus belong to Poecilia (Pamphorichthys) araguaiensis , indicating that P. (Pam.) akroa is endemic from a small portion of the basin.

Ecological notes. Specimens were collected in a lentic, 1–2m deep stretch of the Rio Palmeiras and a 1.5 m deep marginal lake connected to Rio Palmeiras through a channel. Both localities have clear waters and sandy bottom.

Etymology. In honor of the Akroá people, one of the indigenous populations who lived in the northeastern part of the Brazilian State of Tocantins, including the type locality. The city of Dianópolis was a settlement founded by the Portuguese Crown in the XVIII Century for the Akroá people. A noun in apposition.

Remarks. Figueiredo (2008) proposed 13 putative synapomorphies for the subgenus Pamphorichthys . However, with the description of Poecilia akroa herein, and the new phylogenetic hypotheses for the family ( Meredith et al. 2010; Meredith et al. 2011; Pollux et al. 2014), we restrict the definition of the subgenus to four exclusive character states in Poecilia : 10-11 pectoral-fin rays (vs. 12 or more in other species of Poecilia ); gonapophyses parallel to the vertebral column (vs. gonapophyses in acute angle in relation to vertebral column); small Hollister foramen restricted to the anterior tip of the first gonapophysis, surrounding tightly the gonactinostal complex (vs. larger Hollister foramen occupying at least most of distal portion of gonapophysis, not tightly surrounding gonactinostal complex); pelvic-fin insertion of males much anterior than in females, ventral or slightly posterior to pectoral-fin insertion (vs. pelvic-fin origin of males approximately at the same position as in females, or slightly anterior, but never as anterior as in Pamphorichthys ).

Figures

FIGURE 1. Poecilia (Pamphorichthys) akroa sp. n.: top, holotype, MZUSP 121698, 16.9 mm SL, male, Brazil, Tocantins, Dianópolis, rio Palmeiras; bottom, MZUSP 83547, 23.9 mm SL, female, same locality as holotype.

FIGURE 2. A. Osteology of the gonopodium of Poecilia (Pamphorichthys) akroa sp. n., scale bar: 1 mm; B. detail of gonopodium tip. Gonopodium palp represented by long, contiguous lines over osteological structures, scale bar: 0.25 mm.

FIGURE 3. Ventral view of pelvic fins, urogenital region and anterior portion of anal fin of Poecilia (Pamphorichthys) akroa, MZUSP 83547, 23.9 mm SL, female. Anterior to left. Scale bar: 1 mm.