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A new Poptella from the rio Xingu basin, Brazil (Characiformes: Characidae)

Abstract

A new species of Poptella is described from the rio Xingu basin, Pará and Mato Grosso states, Brazil. The new species is distinguished from all congeners by having a greater number of scales around the caudal peduncle (15–18 vs. 13–14). Furthermore, this species can be easily distinguished from P. brevispina, P. longipinnis, and P. fuscata by the lower number of branched rays in the dorsal fin (9 vs. 10–11). The description of new taxon represents the third species of the genus Poptella described in the last five years.

Keywords:
Amazon; Biodiversity; Stethaprioninae; Stethaprion clade; Taxonomy

Resumo

Uma nova espécie de Poptella é descrita da bacia do rio Xingu, estados do Pará e Mato Grosso, Brasil. A nova espécie é distinguida de todas as espécies congêneres por apresentar maior número de escamas ao redor do pedúnculo caudal (15–18 vs. 13–14). Além disso, esta espécie pode ser facilmente distinguida de P. brevispina P. longipinnis e P. fuscata pelo menor número de raios ramificados na nadadeira dorsal (9 vs.10-11). A descrição do novo táxon representa a terceira espécie do gênero Poptella descrita nos últimos cinco anos.

Palavras-chave:
Amazônia; Biodiversidade; Clado Stethaprion; Stethaprioninae; Taxonomia

INTRODUCTION

Garcia-Ayala, Benine (2020)Garcia-Ayala JR, Benine RC. A new Amazonian species of Brachychalcinus (Characiformes: Characidae) from the Trombetas River basin, Brazil. J Fish Biol. 2020; 96(4):950–55. https://doi.org/10.1111/jfb.14284
https://doi.org/10.1111/jfb.14284...
referred to as “Stethaprion Clade” the clade formed by the genera Stethaprion Cope, 1870, Brachychalcinus Boulenger, 1892, Poptella Eigenmann, 1908, and OrthospinusReis, 1989Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86., as hypothesized by Mirande, (2019)Mirande JM. Morphology, molecules and the phylogeny of Characidae (Teleostei, Characiformes). Cladistics. 2019; 35(3):282–300. https://doi.org/10.1111/cla.12345
https://doi.org/10.1111/cla.12345...
. These taxa are diagnosed by the presence of three unbranched dorsal-fin rays, of which the first one is modified into an anteriorly oriented spine-like element (Mirande, 2010Mirande JM. Phylogeny of the family Characidae (Teleostei: Characiformes): from characters to taxonomy. Neotrop Ichtyol. 2010; 8(3):385–568. https://doi.org/10.1590/S1679-62252010000300001
https://doi.org/10.1590/S1679-6225201000...
, 2019Mirande JM. Morphology, molecules and the phylogeny of Characidae (Teleostei, Characiformes). Cladistics. 2019; 35(3):282–300. https://doi.org/10.1111/cla.12345
https://doi.org/10.1111/cla.12345...
), traditionally called “predorsal spine” (Eigenmann, 1907Eigenmann CH. Fowler’s “heterognathous fishes” with a note on the Stethaprioninae. Am Nat. 1907; 41(492):767–72.; Géry, 1977Géry J. Characoids of the World. Neptune City: TFH. Publications; 1977.; Reis, 1989Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86.).

The genus Poptella currently consists of six valid species: P. compressa (Günther, 1864), P. longipinnis (Popta, 1901), P. paraguayensis (Eigenmann, 1907Eigenmann CH. Fowler’s “heterognathous fishes” with a note on the Stethaprioninae. Am Nat. 1907; 41(492):767–72.), P. brevispinaReis, 1989Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86., P. actenolepisGarcia-Ayala & Benine, 2019, and P. fuscataGarcia-Ayala & Benine, 2021. It is widely distributed in all major cis-Andean South American hydrographic basins (Reis, 1989Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86., 2003Reis RE. Subfamily Stethaprioninae (Silver dollar tetras). In: Reis RE, Kullander SO, Ferraris CJ, Jr., editors. Checklist of the freshwater fishes of South and Central America. Porto Alegre: Edipucrs; 2003. p.209–11.). Poptella is diagnosed by the saddle-shaped predorsal spine and the characin regular shape of the first anal-fin ray (Reis, 1989Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86.). Our comparative morphological analysis of Poptella specimens collected in various localities along the Amazon basin revealed a new species from the rio Xingu basin, which we formally describe herein.

MATERIAL AND METHODS

Counts and measurements follow Fink, Weitzman, (1974)Fink WL, Weitzman SH. The so-called cheirodontin fishes of Central America with descriptions of two new species (Pisces: Characidae). Smithson Contrib Zool. 1974; 192:1–46. http://doi.org/10.5479/si.00810282.172
http://doi.org/10.5479/si.00810282.172...
and Sidlauskas et al., (2011)Sidlauskas BL, Mol JH, Vari RP. Dealing with allometry in linear and geometric morphometrics: a taxonomic case study in the Leporinus cylindriformis group (Characiformes: Anostomidae) with description of a new species from Suriname. J Linn Soc London, Zool. 2011; 162(1):103–30. https://doi.org/10.1111/j.1096-3642.2010.00677.x
https://doi.org/10.1111/j.1096-3642.2010...
, and Garcia-Ayala, Benine, (2019)Garcia-Ayala JR, Benine RC. A new species of Poptella (Characiformes: Characidae: Stethaprioninae) from the rio Juma basin, rio Madeira basin, Brazil. Neotrop Ichthyol. 2019; 17(2):e180149. https://doi.org/10.1590/1982-0224-20180149
https://doi.org/10.1590/1982-0224-201801...
. Measurements were taken point to point with a digital caliper (precision of 0.1 mm) on the left side of the specimens. All measurements are presented as percent of standard length (SL), except those of the head, which are given as percent of the head length in the description, values in parentheses indicate the number of specimens with a particular count, and the asterisk indicates the values of the holotype. Measurements and counts of damaged and/or poorly preserved specimens were not included either in the text and/or in the Tab. 1. Counts of supraneurals, vertebrae, procurrent caudal-fin rays, branchiostegal rays, gill-rakers of the first branchial arch, tooth cusps, diminutive dentary teeth, and the position of pterygiophores were taken from four cleared and stained (c&s) paratypes prepared according Taylor, Van Dyke, (1985)Taylor WR, Van Dyke GC. Revised procedures for staining and clearing small fishes and other vertebrates for bone and cartilage study. Cybium. 1985; 9(2):107–19.. Radiographs were also used for eight paratypes taken using the X-ray system Faxitron LX60 DC12 at Laboratório de Ictiologia de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil. Vertebral counts included the four vertebrae of the Weberian apparatus, and the terminal centrum counted as one single element. Institutional acronyms are described in Sabaj, (2020)Sabaj MH.Codes for Natural History Collections in Ichthyology and Herpetology. Copeia. 2020; 108(3):593–669. https://doi.org/10.1643/ASIHCODONS2020
https://doi.org/10.1643/ASIHCODONS2020...
.

RESULTS

Poptella fortispina, new species

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(Figs. 14, Tab. 1)

Poptella compressa. —Reis, 1989Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86.:24 (specimens examined). —Garcia-Ayala, Benine, 2017:571 (comparative material examined, specimens from rio Xingu).

Poptella sp. —Garcia-Ayala, Benine, 2019Garcia-Ayala JR, Benine RC. A new species of Poptella (Characiformes: Characidae: Stethaprioninae) from the rio Juma basin, rio Madeira basin, Brazil. Neotrop Ichthyol. 2019; 17(2):e180149. https://doi.org/10.1590/1982-0224-20180149
https://doi.org/10.1590/1982-0224-201801...
:7 (comparative material examined, specimens from rio Xingu). —Garcia-Ayala, Benine, 2021Garcia-Ayala JR, Benine RC. Poptellafuscata, a new Stethaprionini from the upper Amazon basin, Peru (Characiformes: Characidae). J Fish Biol. 2021; 98(5):1281–88. https://doi.org/10.1111/jfb.14658
https://doi.org/10.1111/jfb.14658...
:7 (comparative material examined).

Holotype. INPA 59843, 53.3 mm SL, Brazil, state of Pará, municipality of Altamira, igarapé Cobal, rio Xingu basin, 03°23’88”S 51°75’19”W, 8 Apr 2013, D. Bastos.

Paratypes. All from Brazil, rio Xingu basin. State of Pará: INPA 52827, 39 (20, 38.3–60.8 mm SL), same data as holotype. ANSP 194605, 1, 31.7 mm SL, rio Bacajái, sand/gravel shoal and rocky outcrop ca. 2.2 and 3 river km, respectively, upstream from the confluence with rio Xingu, 03°35’30.4”S 51°45’156.3”W, 16 Sep 2013, M. H. Sabaj Pérez, L. M. Sousa, A. Gonçalves, N. K. Lujan, D. B. Fitzgerald, P. Madoka Ito, A. Oliveira, R. Robles & fishermen. ANSP 194636, 10, 31.0–39.4 mm SL, rio Itatá ca. 1.1 river km upstream from confluence with right bank of rio Xingu, 03°37’15.7”S 51°49’14.1”W, 17 Sep 2013, A. O. Sawakuchi, J. L. Antinao Rojas, M. H. Sabaj Pérez & fishermen. ANSP 197062, 1, 22.4 mm SL, rio Bacajái, a shallow channel through forest and flooded sedges, ca. 5 river km upstream from the confluence with rio Xingu, 03°36’13”S 51°46’03.5”W, 10 Mar 2013, A. O. Sawakuchi, J. L. Antinao Rojas, M. H. Sabaj Pérez & fishermen. INPA 59846, 4, 31.4–37.4 mm SL, Travessão, rio Xingu, 08°17’41”S 55°12’67”W, 5 Aug 2015, F. C. T. Lima, O. Oyakawa, W. Ohara & M. Pastana. LBP 16680, 4, 38.3–40.5 mm SL, rio Xingu, 03°37’14.3”S 52°02’19”W, 30 Sep 2012, C. Oliveira, R. Britzke, L. M. Souza & D. Bastos. LBP 16681, 38 (24, 32.0–40.2 mm SL), radiographed, 4 c&s, 32.6–38.9 mm SL, rio Xingu, unnamed creek, 03°30’14.3”S 52°02’19”W, 30 Sep 2012, C. Oliveira, R. Britzke, L. M. Souza & D. Bastos. LBP 17695, 2, 37.8–38.2 mm SL, rio Xingu, creek on road PA-279, 06°44’29.5”S 51°49’52”W, 18 May 2013, R. Britzke & M. Martins. MCP 54911, 5, 32.8–34.4 mm SL, rio Xingu, unnamed creek, 03°30’14.3”S 52°02’19”W, 30 Sep 2012, C. Oliveira, R. Britzke, L. M. Souza & D. Bastos. MZUSP 119361, 5, 26.4–46 mm SL, disctric of Castelo dos Sonhos, rio Xingu, creek on road BR-163, 08°17’41”S 55°12’67”W, 5 Aug 2015, F. C. T. Lima, O. Oyakawa, W. Ohara & M. Pastana. ROM 112950, 5, 31.3–33.8 mm SL, municipality of Altamira, rio Xingu, unnamed creek, 03°30’14.3”S 52°02’19”W, 30 Sep 2012, C. Oliveira, R. Britzke, L. M. Souza & D. Bastos. ZUEC 17550, 5, 30.8–33.4 mm SL, Altamira, unnamed creek, 03°30’14.3”S 52°02’19”W, 30 Sep 2012, C. Oliveira, R. Britzke, L. M. Souza & D. Bastos. State of Mato Grosso, municipality of Gaúcha do Norte: MZUSP 94333, 28, 15, 33.1–38.8 mm SL, marginal lagoon at the mouth of the ribeirão da Anta, just above the farm of the Mr. Zezé, rio Culuene, 13°30’51”S 53°05’49”W, 22 May 2007, F. C. T. Lima, F. A. Machado, C. A. Figueiredo & J. L. Birindelli. MZUSP 96886, 8, 38.1–54.9 mm SL, córrego do Lício tributary to rio Culuene, 13°50’22”S 53°14’59”W, 5 Oct 2007, F. C. T. Lima, F. A Machado, C. L Moreira, A. C. Ribeiro, O. Oyakawa, W. Ohara & M. Pastana.

FIGURE 1 |
Poptella fortispina, holotype, INPA 59843, 53.3 mm SL, Brazil, Pará, rio Xingu basin.

Diagnosis.Poptella fortispina can be distinguished from all congeners by having a higher number of scale rows around the caudal peduncle (15–18 vs. 13–14). It can be further distinguished from P. brevispina, P. longipinnis, and P. fuscata by having fewer branched dorsal-fin rays (9 vs. 10–11). The new species is distinguished from P. compressa, P. paraguayensis, and P. actenolepis by having a comparatively robust, thick, broad, and downward curved predorsal spine (vs. delicate, thin, and narrow straight predorsal spine) (Figs. 2, 4). Additionally, it can be distinguished from P. actenolepis by having more scale rows between the lateral line and dorsal-fin origin (8–10 vs. 7) and a comparatively elongated predorsal spine (4.3–5.5 vs. 2.8–4.2% mm SL).

Description. Morphometric data summarized in Tab. 1. Largest specimen examined 60.8 mm SL. Greatest body depth at dorsal-fin origin. Dorsal profile slightly convex between tip of snout and vertical through middle of orbit; slightly concave from this point to end of occipital process, and convex from tip of occipital process to dorsal-fin origin. Dorsal-fin base posteroventrally slanted. Profile straight or slightly convex from posterior terminus of dorsal-fin base to end of adipose fin. Caudal peduncle profile slightly concave both dorsally and ventrally. Ventral profile convex from tip of dentary to anal-fin origin. Body profile along anal-fin base straight and posterodorsally slanted. Prepelvic region compressed with median keel.

TABLE 1 |
Morphometric data of holotype (H) and paratypes of Poptella fortispina. Range includes values of the holotype. N = the total number of specimens examined. SD = Standard deviation.

FIGURE 2 |
Predorsal spine and dorsal-fin rays of Poptella fortispina, LBP 16681, paratype, 32.1 mm SL, lateral view, left side. Scale bar = 1 mm.

Mouth terminal. Distal tip of maxilla reaches vertical through anterior margin of pupil, not extending beyond third infraorbital. Premaxillary teeth in two rows; outer row with four*(110), rarely five (4) tricuspid teeth. Inner row with five*(113) or rarely six (1) pentacuspid teeth. Maxilla with one (37) or two*(75) conical or tricuspid teeth. Dentary with four teeth with five cusps, usually central cusp longest, and one small tricuspid tooth, followed by five to seven small conical teeth (Fig. 3).

FIGURE 3 |
Premaxilla, maxilla, and dentary of Poptella fortispina, LBP 16681, paratype, 33.7 mm SL, lateral view, right side. Scale bar = 1 mm.

FIGURE 4 |
Predorsal spines of Poptella species: A. P. fortispina, INPA 52827, paratype, 59.9 mm SL; B. P. paraguayensis, LBP 3826, 48.9 mm SL; C. P. compressa, ROM 97574, 48.4 mm SL; D. P. actenolepis, MZUSP 12282, paratype, 54.6 mm SL; lateral view, left side. Scale bars = 1 mm.

Dorsal-fin rays iii,9*(124). First dorsal-fin element modified into well-developed spine. Anterior end of predorsal spine rounded and ventrally concave, saddle-shaped (Figs. 24). Predorsal-spine origin anterior to vertical through middle of standard length. First unbranched dorsal-fin ray shorter than second one. Second unbranched and first branched dorsal-fin rays slightly longer than following ones. Adipose fin present. Anal-fin rays iv* (124) or v (1), 25 (1), 27 (7), 28 (33), 29 (44), 30 (26), 31 (13), 32 (1). Pectoral-fin rays i,10 (20), i,11* (98) or i,12 (7). Posteriormost unbranched and first branched anal-fin rays longer than branched rays. Tip of pectoral fin reaching middle of when depressed pelvic fin. Pelvic-fin rays i,7* (125). Tip of pelvic fin reaching first two small unbranched anal-fin rays when depressed. Caudal fin i,16,i (1) or i,17,i (8). Dorsal procurrent caudal-fin rays 10 (2) or 11 (2); ventral procurrent caudal-fin rays 8 (3) or 9 (1). Caudal fin forked, lobes somewhat pointed and of similar size.

Scales cycloid, with two to six parallel radii. Lateral-line series with 35 (34), 36* (72) or 37 (19) perforated scales. Lateral line slightly curved downward. Predorsal scale series 1 (19), 2 (9) or 3* (3), irregularly arranged. Scale rows between dorsal-fin origin and lateral line 8 (20), 9* (50), or 10 (55). Scale rows between lateral line and midventral scale series 8 (4), 9* (70), or 10 (51). Scale rows around the caudal penducle 15 (48), 16 (23), 17 (25) or 18* (29). Small scales at base of anal fin in two series at first fin rays and becoming a single series extending to middle of anal fin. Small scales covering proximal two-thirds of caudal-fin lobes.

Total vertebrae 30 (10) or 31 (2). Supraneurals 3 (12) with bony lamellae on upper portion. First gill-arch with 13* (76), 14 (24) or 15 (3) gill rakers on ceratobranchial, 1* (103) on cartilage between ceratobranchial and epibranchial, and 9 (23), 10 (70) or 11 (10) gill rakers on epibranchial.

Coloration in alcohol. General body color yellowish. Dorsal portion of head and body darkly pigmented. Chromatophores concentrated on snout, jaws, dorsal portion of neurocranium and along dorsal midline of body. Posterior portion of scales slightly dark and generally delineated by dark chromatophores. Two vertically elongated humeral blocthes, extending up to six horizontal scale rows above lateral line and one scale row below lateral line, and separated by two horizontal scale rows. First blotch more conspicuous, with concentration of dark chromatophores forming a darker round blotch just above lateral line. Second humeral blotch faint. Narrow longitudinal dark line with chevron-like marks running along horizontal septum, extending from humeral region to caudal peduncle. Caudal peduncle blotch absent. Pectoral fin hyaline, with chromatophores scattered throughout interradial membranes. Dorsal, pelvic, and anal fins with scattered dark chromatophores concentrated along first rays and interradial membrane. Adipose fin with scattered dark chromatophores. Caudal fin with scattered dark pigmentation on its distal margin (Fig. 1).

Sexual dimorphism. Mature males with small bony hooks on the unbranched and branched rays of the dorsal and anal fins. Dorsal fin with one to two hooklets on the distalmost segments of the posterior branch of the 2nd to the 4th branched rays. Anal-fin hooks unevenly distributed on the distalmost segments of the 1st unbranched ray to the 26th branched rays, being more numerous in the first twelve branched rays, with one to two hooks per segment.

Geographical distribution.Poptella fortispina is widely distributed in the rio Xingu basin, Pará and Mato Grosso states, Brazil (Fig. 5).

FIGURE 5 |
Map showing the known distribution of Poptella fortispina. Red star indicates the type-locality. Symbols may represent more than one locality.

Etymology. The name fortispina is from Latin “fortis” meaning strong and “spina” meaning spine, in reference to the robust predorsal spine.

Conservation status. Considering that no imminent threats to the species were detected in area of occurrence, we suggest that Poptella forstispina be classified as least concern (LC) according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2022International Union for Conservation of Nature (IUCN). Standards and Petitions Committee. Guidelines for Using the IUCN Red List Categories and Criteria. Version 15.1 [Internet]. 2022. Available from: https://www.iucnredlist.org/documents/RedListGuidelines.pdf
https://www.iucnredlist.org/documents/Re...
).

Remarks. As demonstrated by Garcia-Ayala, Benine, (2020)Garcia-Ayala JR, Benine RC. A new Amazonian species of Brachychalcinus (Characiformes: Characidae) from the Trombetas River basin, Brazil. J Fish Biol. 2020; 96(4):950–55. https://doi.org/10.1111/jfb.14284
https://doi.org/10.1111/jfb.14284...
, the number of branched dorsal-fin rays is helpful for the taxonomy of the Stethaprion Clade in properly separating the species of Poptella and Brachychalcinus. Poptella may be split into three groups according to the number of branched rays in the dorsal fin: nine, ten or eleven (Garcia-Ayala, Benine, 2020Garcia-Ayala JR, Benine RC. A new Amazonian species of Brachychalcinus (Characiformes: Characidae) from the Trombetas River basin, Brazil. J Fish Biol. 2020; 96(4):950–55. https://doi.org/10.1111/jfb.14284
https://doi.org/10.1111/jfb.14284...
). Poptella fortispina is the seventh species described for the genus and shares with P. compressa, P. paraguayensis, and P. actenolepis the condition of nine branched dorsal-fin rays. Poptella brevispina and P. longipinnis have ten branched dorsal-fin rays and P. fuscata has eleven branched dorsal-fin rays (Tab. 2).

TABLE 2 |
Species of Poptella grouped based on the number of branched dorsal-fin rays.

Along with the number of branched dorsal-fin rays, the length of the predorsal spine has been employed in the taxonomy of Poptella (Reis, 1989Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86.; Garcia-Ayala, Benine, 2019Garcia-Ayala JR, Benine RC. A new species of Poptella (Characiformes: Characidae: Stethaprioninae) from the rio Juma basin, rio Madeira basin, Brazil. Neotrop Ichthyol. 2019; 17(2):e180149. https://doi.org/10.1590/1982-0224-20180149
https://doi.org/10.1590/1982-0224-201801...
, 2020Garcia-Ayala JR, Benine RC. A new Amazonian species of Brachychalcinus (Characiformes: Characidae) from the Trombetas River basin, Brazil. J Fish Biol. 2020; 96(4):950–55. https://doi.org/10.1111/jfb.14284
https://doi.org/10.1111/jfb.14284...
). Reis, (1989)Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86. used the length of the predorsal spine as part of the diagnostic characters for the species of Poptella, indicating, however, overlapping ranges for P. compressa (3.1–6.9% mm of SL), P. longipinnis (2.5–3.4% mm of SL), P. paraguayensis (4.7–6.4% mm of SL), and P. brevispina (2.6–4.2% mm of SL). The population of Poptella from the rio Xingu basin was first identified by Reis, (1989)Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86. as P. compressa, due to the presence of nine branched dorsal-fin rays, adipose fin hyaline, and an elongated predorsal spine. Owing to the broad range and probably in an attempt to identify a putatively hidden diversity, Reis, (1989)Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86. subdivided P. compressa into four populations named Guyana, rio Madeira, NE Brazil, and rio Orinoco. This procedure substantially reduced the range in each subgroup, except for NE Brazil, which kept values between 4.0% and 6.9% mm of SL. Reis’ (1989)Reis RE. Systematic revision of the Neotropical characid subfamily Stethaprioninae (Pisces, Characiformes). Comum Mus Cienc Tecn PUCRS. 1989; 2(6):3–86. NE Brazil included 32 specimens from tributaries of the rio Tocantins, rio Araguaia, rio Corda (Maranhão state), rio Parnaíba, and rio Xingu. Our analyses also showed more discrete subdivisions when these drainages were analyzed separately. Predorsal spines in specimens from the rio Tocantins-Araguaia vary between 5.4–7.0% mm of SL; from the rio Parnaíba, 3.9–4.9% mm of SL; and in specimens from the rio Xingu is 4.3–5.5% mm of SL. Therefore, these values indicate that the length of the predorsal spine may help distinguish specimens from the rio Xingu (P. fortispina) from those from the Tocantins-Araguaia basin. These differences, along with other diagnostic features (e.g., the number of scale rows around the caudal peduncle), indicate a hidden diversity in northeastern Brazil yet to be described.

Comparative material examined.Brachychalcinusretrospina Boulenger, 1892: Brazil: NUP 879, 6, 39.7–58.7 mm SL. Orthospinus franciscensis (Eigenmann, 1914): Brazil: LBP 8105, 15, 42.5–53.9 mm SL. Poptella actenolepis: Brazil: MZUSP 117586, 15, 17.4–39.9 mm SL, paratypes. Poptella brevispina: Brazil: INPA 3493, 13, 50.5–63.1 mm SL; LBP 9332, 28, 54.3–88.2 mm SL; LBP 21127, 11, 29.4–44.3 mm SL. Poptella compressa: Guyana: ROM 87123, 10, 48.6–63.7 mm SL. Poptella longipinnis: Brazil: INPA 2220, 3, 43.5–50.3 mm SL; LBP 7792, 3, 33.6–37.7 mm SL. Suriname: MCP 11904, 2 59.4–64.1 mm SL. Venezuela: LBP 3060, 17, 34.8–42.3 mm SL. Poptella paraguayensis: Brazil: LBP 3826, 15, 39.9–57.9 mm SL; LBP 5114, 11 32.1–49.2 mm SL; LBP 9885, 10, 39–48.5 mm SL. Poptella sp.: Brazil: INPA 12329, 4, 34.8–36.4 mm SL; INPA 25677, 3, 31.6–46 mm SL; INPA 12329, 4, 34.8–36.4 mm SL; INPA 25677, 3, 31.6–46 mm SL; LBP 8777, 15, 26.7–46.5 mm SL; LBP 8881, 11, 31.2–38.9 mm SL; LBP 8882, 14, 33.1–38.3 mm SL; LBP 14115, 15, 56.7–70 mm SL; LBP 14204, 1, 52.5 mm SL; LBP 14241, 1, 44.2 mm SL; LBP 16213, 1, 39.1 mm SL; LBP 16222, 7, 38.5–68.2 mm SL; LBP 16228, 1, 36 mm SL; LBP 16268, 1, 50.5 mm SL; LBP 16408, 1, 54.4 mm SL; LBP 23782, 8, 38.2–57.1 mm SL; LBP 23782, 8, 37.4–46.4 mm SL; LBP 24486, 16, 31.8–38.3 mm SL; LBP 24495, 16, 41–50 mm SL; LBP 24496, 39, 40–45 mm SL; LBP 24498, 12, 36.1–42.1 mm SL; LBP 24497, 3 50.1–52.4 mm SL; MCP 22932, 15, 34.6–54 mm SL; MCP 38841, 5, 35.8–54.2 mm SL; MZUSP 89289, 39, 29.3–43 mm SL; MZUSP 89385, 20, 36.5–47 mm SL; MZUSP 92288, 10, 67.3–39 mm SL; MZUSP 97276, 14, 30.2–35.5 mm SL; MZUSP 115653, 11, 34.8–45.4 mm SL; NUP 12724, 10, 36.8–44.1 mm SL; ZUEC 15196, 7, 29.6–36.9 mm SL. Peru: MCP 22939, 8, 29.8–42.7 mm SL; MZUSP 90585, 5, 36.8–43.4 mm SL; MZUSP 98723, 10, 33.9–46.1 mm SL; UMSM 23642, 10, 23.2–57.1 mm SL; UMSM 44773, 15, 56.4–66.3 mm SL; UMSM 47327, 11, 41.5–71.2 mm SL. Stethaprion crenatum Eigenmann, 1916: Brazil: LBP 31261, 2, 67.8–68.1 mm SL.

ACKNOWLEDGEMENTS

We thank Lúcia R. Py-Daniel (INPA), Aléssio Datovo (MZUSP), Claudio Oliveira (LBP), and Mark Sabaj (ANSP) for curatorial assistance. We are grateful to Flávio A. Bockmann and André Esguícero (LIRP) for assistance with radiographs using the Faxitron LX60 DC12 (equipment acquired with support from FAPESP 09/54931–0). This work received support from the Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq Projects: “Revisão taxonômica da subfamília Stethaprioninae (Teleostei: Characiformes, Characidae)” (Proc. 140606/2015–7). RCB is financially supported by CNPq (Proc. 307975/2019–3).

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ADDITIONAL NOTES

  • HOW TO CITE THIS ARTICLE

    Garcia-Ayala JR, Benine RC. A new Poptella from the rio Xingu basin, Brazil (Characiformes: Characidae). Neotrop Ichthyol. 2023; 21(1):e220086. https://doi.org/10.1590/1982-0224-2022-0086

Edited-by

Priscila Camelier

Publication Dates

  • Publication in this collection
    28 Apr 2023
  • Date of issue
    2023

History

  • Received
    5 Sept 2022
  • Accepted
    15 Mar 2023
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