Rio Tocantins Basin Research Articles

A systematic assessment of Leporinus tigrinus (Characiformes: Anostomidae) using morphological and molecular data

Leporinus tigrinus was described based on specimens collected in the rio Tocantins basin, and was only recently recorded at the rio Xingu, rio Tapajós and upper rio Paraná basins. So far, no study has compared specimens of all these distinct drainages focusing on understanding whether all these populations truly belong to a single species or may consist instead in a species complex. Our study focused on investigating the intraspecific variation within Leporinus tigrinus using morphological and molecular data. Both morphology and molecular analyses support that all samples belong to a single species widespread in the rio Araguaia, rio Tocantins, rio Xingu and rio Tapajós. In addition, the population occurring at upper rio Paraná is considered to be allochthonous, originating from the rio Araguaia/Tocantins. A comprehensive morphological description of the species, including osteological illustrations and descriptions are provided, as well as a comparative diagnosis with similar-looking species.

A new tiny-spotted species of Hypostomus (Siluriformes: Loricariidae) from the upper Rio Tocantins basin, Gois State, Brazil.

Scientific visits to ichthyological collections revealed a potentially new species of Hypostomus from the Rio Tocantins basin. From there, subsequent ichthyological surveys led us to capture the taxon in the upper portion of this basin and address it to the H. punctatus group. Here, we present it as a new species to science. The new species is distinguished from its congeners, except those from the H. punctatus group, by having bicuspid teeth with elliptic medial cusps, moderate keels on the head and flanks, small spots on the body, and caudal peduncle that are long and low. From the H. punctatus group, except H. subcarinatus and H. commersoni, it differs by having extremely small dark spots; from H. subcarinatus, it differs by having a beige-brown dorsal-fin background color versus blue in live specimens; and from H. commersoni, it differs by having a short to moderate dorsal fin versus a long dorsal fin.

New species of Rhyacoglanis (Siluriformes: Pseudopimelodidae) from the upper rio Tocantins basin

Abstract A new species of Rhyacoglanis from the upper rio Tocantins basin is described based on morphological and molecular data. The new species differs from the congeners by its color pattern, caudal fin shape, hypural bones fusion pattern, pectoral-fin spine shape, and barcode sequence of cytochrome oxidase subunit I (COI). In this study, two putative monophyletic groups of Rhyacoglanis are proposed based on morphology, one consisting of species with a short post-cleithral process and caudal fin with rounded lobes, Rhyacoglanis epiblepsis and R. rapppydanielae, and the other with a longer post-cleithral process and caudal fin with pointed lobes, R. annulatus, R. paranensis, R. pulcher, R. seminiger, and the new species described herein.

Revision of the smaller-sized dorados (Salminus), with comments on the monophyly of the genus and its biogeography (Characiformes: Bryconidae)

A revision of the genus Salminus, excluding the large-sized species S. brasiliensis and S. franciscanus, is presented. In addition to the two large-sized species, four additional Salminus species are recognized: Salminus affinis Steindachner, from the río Magdalena, río Sinú, and río Rancheria basins, Colombia; Salminus hilarii Valenciennes, from the rio Paraná, rio São Francisco, and rio Jaguaribe basins, Brazil, Argentina, and Paraguay; Salminus iquitensis (Nakashima), new combination, from the western portion of the Amazon basin, rio Branco, and río Orinoco basins, Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela; and Salminus santosi new species, from the rio Tocantins basin, Brazil. These four species are described/redescribed and illustrated, and a key to the species belonging to the genus is presented. Comments on the diagnosis of the genus Salminus and its biogeography taking into account recent phylogenetic hypotheses published for the genus, are presented.

Museum specimens reveal a rare new characid fish genus, helping to refine the interrelationships of the Probolodini (Characidae: Stethaprioninae)

(Received 7 July 2021; accepted 23 September 2021) Two new characid fish species are described from the upper rio Tocantins basin, Chapada dos Veadeiros, Goiás State, Brazil. Both species were discovered among specimens in museum collections. Relationships of taxa were evaluated in a more comprehensive phylogenetic analysis utilizing the largest dataset available of molecular and morphological data for the family Characidae. The two species were recovered as sister species and described in a new genus, closely related to Erythrocharax and Phycocharax. Dinotopterygium gen. nov. is distinguished from all other characid genera by the unique combination of ten synapomorphies, including the unique anal-fin morphology with a small number of branched anal-fin rays (13-16). Dinotopterygium uniodon sp. nov. and D. diodon sp. nov. differ by the number of tooth series in the premaxillary bone (one or two) and number of tooth cusps (7 or 5). The additional phenotypic variation for a taxonomically informative character within the Characidae through the discovery of new forms has helped to refine the interrelationship of the tribe Probolodini (Characidae: Stethaprioninae). The discovery of these new and possibly critically endangered species emphasizes the importance of museum collections for understanding biodiversity past and present. http://zoobank.org/urn:lsid:zoobank.org:pub:E0FD8207-590B-4FF7-B9CA-FD481A7F8B0E

Reproduction, development, asymmetry and late eye regression in the Brazilian cave catfish Ituglanis passensis (Siluriformes, Trichomycteridae): evidence contributing to the neutral mutation theory

The troglobitic (exclusively subterranean source population) catfish Ituglanis passensis (Siluriformes, Trichomycteridae) is endemic to the Passa Três Cave, São Domingos karst area, Rio Tocantins basin, Central Brazil. This unique population presents variably reduced eyes and melanic pigmentation. We describe reproduction and early development in this species based on a spontaneous (non-induced) reproductive-event that occurred in the laboratory in January–February, 2009, while simultaneously comparing with data from the cave-habitat and a previous reproductive event. Egg laying was parceled. Egg-size and number were within variations observed in epigean congeners. Larvae behavior and growth is described. A single surviving specimen was monitored over two years. Eye-regression started late, one year after birth, and followed a pattern of stasis phases intercalated with slow growth and fluctuating asymmetric rates. Late eye regression, associated with asymmetry in eye development and intra-population variability of troglomorphic traits, as shown by several Brazilian subterranean fishes, provide support for the Neutral Mutation Theory.

A new species of Characidium (Characiformes: Crenuchidae) from the Chapada dos Veadeiros, Goiás, Brazil

Abstract A new species of Characidium is described from the tributaries of the rio Tocantinzinho, rio Tocantins basin, located in the southern portion of the Chapada dos Veadeiros, at about 1,200 meters of elevation, Goiás, Brazil. The new species can be diagnosed by an unusual combination of two apomorphic features present in distinct clades of Characidium, the presence of a scaleless isthmus in allied to with a single row of dentary teeth. Additionally, the new species has a unique color pattern of inconspicuous vertical bars disconnected from the dorsal midline, forming seven to nine square blotches along body sides, and the presence of a dark saddle-shaped mark at the dorsal-fin base. Osteologically, it can be diagnosed by having the first and second anal-fin proximal radials fused and contacting the third hemal spine, which is branched. The new species also has a peculiar, unusual variation of fin-ray counts among its congeners.

A new species of Satanoperca (Teleostei: Cichlidae) from the Rio Tocantins basin, Brazil

Abstract A new species of Satanoperca is described from the Rio Araguaia, Rio Tocantins basin, Brazil, and non-native records are available in the upper Rio Paraná basin. It differs from congeneric species by color pattern characters, such as head and flank marks. It is included in the Satanoperca jurupari species group, characterized by the absence of black rounded blotches on the flank, and low meristic values. A description of the ontogeny of melanophore marks of the S. jurupari species group revealed two different types of arrangement on the flank and numerous melanophore marks on the head. A discussion on morphologically diverse assemblages in the S. jurupari species group is also provided.

Two new species of Knodus (Characidae: Stevardiinae) from the upper rio Tocantins basin, with evidence of ontogenetic meristic changes

ABSTRACT Two new species from the upper rio Tocantins basin are described in Knodus based on the traditional definition of the genus. The new species are distinguished from other congeners by meristic and morphometric characters, such as the number of cusps in the premaxillary and dentary teeth, the number of scale series between dorsal-fin origin and lateral line, the orbital diameter and the body depth. With the two new species, the number of endemic species in the upper rio Tocantins basin upstream of the mouth of the rio Paranã, rises to 53 (89 to the confluence with rio Araguaia). The existence of a meristic character that changes through ontogeny (allomery), viz. the number of scale series between dorsal-fin origin and lateral line, was detected in some species of Knodus through a regression analysis. Additionally, this paper describes an unambiguous, more informative and precise new method for counting vertebrae, which will enhance the efficacy of this trait in species comparisons.

New species of the Corumbataia cuestae group (Siluriformes: Loricariidae) from the Rio Tocantins basin, with comments on its phylogenetic relationships

Abstract A new species of Corumbataia is described from Rio Maranhão, Rio Tocantins basin, central Brazil. The new species is distinguished from all congeners by the presence of a small, naked area on snout tip; by having the abdomen covered with small platelets forming a shield which reaches the lateral mid-ventral plates; by the anterior profile of the head rounded in dorsal view; by the lower lip not reaching the transversal line of the pectoral girdle; and by the presence of 28 or 29 vertebrae. High genetic divergence in mitochondrial cytochrome c oxidase subunit I (COI) further supports the validity of this new species. Our phylogenetic analysis shows a derived subclade in Corumbataia, herein named as the Corumbataia cuestae group, composed of the new species plus C. cuestae, C. tocantinensis, C. britskii, C. liliai, and C. lucianoi. This group is defined by having a conspicuous crest of hypertrophied odontodes on head; absence of the adipose fin or a single series of platelets at adipose-fin position; and anastomosis of the infraorbital and otic sensory canals over the pterotic-supracleithrum. Here we also restrict the distribution of C. tocantinensis to the Rio Araguaia basin.

A new species of Parotocinclus (Loricariidae: Hypoptopomatinae) from Rio Tocantins basin, Brazil.

A new species of Parotocinclus is described from the Rio Tocantins basin, Tocantins State, Brazil. The new species is distinguished from congeners by a combination of characters such as: (1) a unique pattern of body coloration with five transverse dark bars; (2) absence of an adipose fin or small platelet at typical adipose-fin region; (3) absence of conspicuous dark dots broadly distributed on the body; (4) absence of a triangular dark blotch at the anterior base of the dorsal fin; and (5) presence of a V-shaped spinelet.

A new Creagrutus from the upper rio Xingu basin, Brazil (Teleostei: Characiformes: Characidae)

A new species of Creagrutus is described from the upper rio Xingu basin, Mato Grosso state, Brazil. The new species can be distinguished from its congeners by a combination of characters that includes dorsal fin mostly black, a dark oblique blotch on middle and upper-inferior caudal-fin rays, and presence of only two rows of premaxillary teeth. Creagrutus mucipu, formerly known only from the upper rio Tocantins basin in Brazil, is recorded herein as occurring syntopically with the new species in the upper rio Xingu basin.

Moenkhausia goya (Characiformes: Characidae): a new species from the upper rio Tocantins basin, Central Brazil

A new species of Moenkhausia is described from the upper rio Tocantins basin, States of Goiás and Tocantins, Brazil. Moenkhausia goya, new species, can be distinguished from its congeners by the shape of the humeral blotch in combination with a uniform dark pigmentation covering the interradial membranes of the dorsal and anal fins. Among congeners, the new species is most similar to M. britskii Azevedo-Santos Benine, M. grandisquamis (Müller Troschel) and M. xinguensis Steindachner by presenting a deep body, a large, round humeral blotch and fins without discrete patches of dark pigmentation (i.e., without well-defined blotches or stripes). With the description of M. goya, the number of species endemic to the upper rio Tocantins basin (considered upstream from the mouth of the rio Paranã) is raised to 51. Of these, some are widespread in the upper rio Tocantins basin, while others seem to be restricted to one of its sub-basins.

Pseudacanthicus major: description of one of the largest known Loricariidae (Hypostominae: Ancistrini), a species from rio Tocantins basin, Brazil.

The genus Pseudacanthicus currently comprises the following six species distributed in the Amazon and Tocantins basins, and coastal drainages from Guyana to French Guyana: P. serratus, P. fordii, P. histrix, P. spinosus, P. leopardus, P. pitanga, and P. pirarara. Herein we describe P. major, from rio Tocantins basin, one of the largest loricariid species known. The new species is distinguished from its congeners by the following combination of characters: having body color pattern with dark brown background without spots or blotches and dorsal and caudal fins with transversal white bands; anterior process of compound pterotic with no contacting with the posterior margin of the orbit and by the absence of a conspicuous crest on the posterior edge of parieto-supraocciptal. Other osteological characteristics are further used to diagnose P. major from others congeners. A discussion on gigantism and miniaturization in freshwater fish, ornamental fisheries activities, threats and conservation of the new species are also provided.

Description of a new species of Gymnotocinclus from the rio Tocantins basin with phylogenetic analysis of the subfamily Hypoptopomatinae (Siluriformes: Loricariidae).

Gymnotocinclus canoeiro n. sp. of the Hypoptopomatinae is described from small tributaries of the upper rio Tocantins basin. It is distinguished from G. anosteos by having five characters: (1) the presence of body dermal plates, (2) the pectoral girdle not exposed in ventral view, (3) the pelvic spine longer than pectoral spine in males, (4) the pectoral fin with seven to eight branched rays, and (5) the presence of an adipose fin. Furthermore, maximum likelihood (ML) analysis was used to estimate a molecular phylogeny from previously published data of one nuclear (F-Reticulon 4) and three mitochondrial (16S RNA, COI and CytB) genes. The phylogenetic results revealed the new species as a sister taxon of Gymnotocinclus anosteos within the Otothyrini. We also included samples of Nannoplecostomus eleonorae that appeared sister group to all other Neoplecostomini species, and Plesioptopoma curvidens that appeared within the Neoplecostomini forming a sister clade to all species of Neoplecostomus, except N. ribeirensis and the species of Pareiorhina, except P. rudolphi.

Ecology of Mylesinus paucisquamatus Jégu & Santos, 1988, an endangered fish species from the rio Tocantins basin

ABSTRACT Mylesinus paucisquamatus is a threatened fish endemic to the rio Tocantins basin, with little information about its natural history. Using monitoring data obtained between 1998 and 2009, we investigated the spatial distribution, feeding and reproduction of this species in a long stretch of the middle-upper rio Tocantins. Eighty-one individuals were captured over a decade of intensive sampling. In addition, we recorded the species in only 13 out of 35 sites, particularly in the Tocantins and Paranã rivers. Most individuals were captured alone, while the remaining formed small groups. These results indicate that this fish is rheophilic and rare. We recorded seasonal variation in fish abundance, with higher values during the dry season, indicating seasonal movements. The species is herbivorous and specialized in the consumption of plants attached to substrates, particularly bryophytes. We also observed seasonality in reproduction, since reproductive activity increased during the early dry season. These ecological traits, e.g. , rarity, rheophilic and specialized feeding habits, indicates that M. paucisquamatus is vulnerable to environmental changes, particularly river damming. Considering that three large dams currently regulate and fragment this section of the rio Tocantins, the persistence of this species is jeopardized, demanding effective conservation actions.

Feeding and reproductive ecology of Cichla piquiti Kullander & Ferreira, 2006 within its native range, Lajeado reservoir, rio Tocantins basin

Cichla piquiti is endemic to the Tocantins-Araguaia river basin, but information about its biology is restricted to populations introduced in other basins. In order to fill this gap, we investigated the feeding ecology and reproductive dynamics of C. piquiti in Lajeado reservoir, rio Tocantins. A total of 270 fish were collected between November 2010 and October 2011. The diet is rich and composed of at least 23 resources, predominantly fish (at least 19 species). We observed no clear influence of sex, periods and ontogeny on diet, which was basically composed of Characidae and Cichlidae. Considering its reproductive dynamics, immature, reproductive and non-reproductive fish were recorded during the whole study, and reproductive effort did not differ among periods. Cichla piquiti also showed no pattern of energy allocation between reproductive and somatic activities. These results indicate that reproduction is occurring throughout the year and that this activity is not synchronized among individuals. In conclusion, this study presented valuable information on the ecology of C. piquiti within its natural range, which may subsidize management programs to conserve local stocks. This information may also provide theoretical insights to explain why C. piquiti , a voracious predator, is so harmful when introduced in non-Amazonian reservoirs.

Retroculus acherontos, a new species of cichlid fish (Teleostei) from the Rio Tocantins basin.

Retroculus acherontos is described from the Rio Tocantins basin, Brazil. It is distinguished from all congeners by the presence of a nuchal hump in large specimens, an irregular black blotch located on the middle of the anterior soft dorsal-fin rays, fewer pectoral-fin rays (15-16), a deeper body, a convex ventral profile, a more transversely convex ventral surface of the body, and by chest scales similar in size to the scales on the side. An expanded diagnosis for the genus Retroculus is provided.

Rhinolekoscapetinga: a new cascudinho species (Loricariidae, Otothyrinae) from the rio Tocantins basin and comments on its ancestral dispersal route.

The present study deals with the description of a new species of Rhinolekos. It can be distinguished from its congeners by having 31 vertebrae, the anterior portion of the compound supraneural-first dorsal-fin proximal radial contacting the neural spine of the 9th vertebra, the absence of transverse dark bands in the pectoral, pelvic and anal-fin rays, 24–28 plates in the dorsal series, the lack of odontodes on the ventral tip of the snout, the absence of accessory teeth, a greater prenasal length, a smaller head length, and by a greater snout length. Rhinolekos capetinga is restricted to the headwaters of the rio Tocantins and it is the first species of this genus in the Amazon basin. Additionally, we present a brief discussion of a biogeographic scenario that may explain the dispersal of the new species from the rio Paranaíba to the rio Tocantins basin. We suggest that the ancestral lineage of Rhinolekos capetinga reached the rio Tocantins from portions of the rio Paranaíba at the end of the Miocene, about 6.3 Mya (4.1–13.9 Mya 95% HPD), probably as a result of headwater capture processes among adjacent drainages.

A new species of Hyphessobrycon Durbin (Characiformes: Characidae) from the middle rio São Francisco and upper and middle rio Tocantins basins, Brazil, with comments on its biogeographic history

A new species of Hyphessobrycon Durbin is described from tributaries of the rio Grande (rio São Francisco basin) draining east to the Serra Geral de Goiás, of the rio São Domingos (upper rio Tocantins basin) and rio do Sono basins (middle rio Tocantins basin). Hyphessobrycondiastatos can be diagnosed from its congeners by the absence of humeral spot, 15-18 branched anal-fin rays, 1-3 maxillary conical to tricuspid teeth, a relatively well-defined dark caudal-peduncle spot, and elongation of dorsal- and anal-fin rays in mature males. The biogeographical significance of the distribution of the new species is evaluated and discussed.