Species Of Astyanax Research Articles

Chromosome evolution in fish: BrdU replication patterns demonstrate chromosome homeologies in two species of the genus Astyanax

A comparison of R-banding patterns obtained by 5-bromodeoxyuridine incorporation was made between the chromosomes of two fish species of the genus Astyanax (Characiformes: Tetragonopterinae), A. altiparanae with 2n = 50 chromosomes, and A. schubarti with 2n = 36 chromosomes. The two species present the highest and the lowest chromosome numbers found in this fish genus, respectively, for which the modal chromosome number is 50. R-band homeology was detected, involving eleven chromosomes of A. schubarti and seventeen chromosomes of A. altiparanae, indicating a close chromosomal relationship between the two species, in spite of their great difference in chromosome number. A chromosome fusion in the past history of the group was hypothesized as a possible cause of the discrepant chromosome numbers of the two species.

Astyanax tumbayaensis, a new species from northwestern Argentina highlands (Characiformes: Characidae) with a key to the Argentinean species of the genus and comments on their distribution

A new species of the characid genus Astyanax is described from a man-made small channel connected with the Rio Grande basin, in Jujuy Province, northwestern Argentina. This species can be distinguished from its congeners by the following combination of characters: body relatively high (39.2-45.3% SL); head short and heavy (24.0-26.7% SL); snout very short (16.1-20.8% HL); eye small (28.9-35.0% HL); interorbital very wide (38.8-44.1% HL); mouth sub-superior; maxilla short with 1-2 teeth; iii-v, 19-22 anal fin rays; 33-36 perforated scales on the lateral line, and a distinctive color pattern, consisting in a reticulated body, with dorsal, pelvic, anal, and caudal fins with dark margins. A very narrow lateral dark stripe ending in a caudal spot, and one large vertically elongated humeral spot. In addition the males of Astyanax tumbayaensis have bony hooks in the dorsal, pelvic, anal and caudal fins. A key for Argentinean species of Astyanax is provided. The primary traits of the distribution of species in the country are discussed, with reference to the main basins and some zoogeographically important localities.

Astyanax pampa (Characiformes, Characidae), a

Astyanax pampa sp. n., the new species of characid described herein, is known from arroyo Las Mostazas, an Atlantic Ocean drainage, and the lower no Colorado basin. Astyanax pampa sp. n. is distinguished from all other Astyanax species by the possession of 17-20 branched anal-fin rays, one maxillary tooth unicuspidate to tricuspidate, short anal-fin base (24.2-30.3% of SL), and long caudal peduncle (10.5-12.7% of SL).

A new species of Astyanax (Characiformes: Characidae) from the rapids of the lower rio Xingu, Brazil

Astyanax dnophos, new species, is described from the lower rio Xingu, Pará, Brazil. The new species is distinguished from its purported congeners by the presence of a broad longitudinal, midlateral dark stripe that extends from the snout to the caudal peduncle. Astyanax dnophos dwells on shadowed, rocky shelters on rapids, and it is apparently one of the few species of Characidae outside Serrasalminae reported to be rheophilic.

Epigean and subterranean ichthyofauna from the São Domingos karst area, Upper Tocantins River basin, Central Brazil

In a survey of epigean and cave streams in the São Domingos karst area, 38 species were present in the stream reaches, including 10 characiforms, 19 siluriforms, seven gymnotiforms and two perciforms. One species of Astyanax and the new armoured catfish species Parotocinclus were the most common epigean fishes in São Domingos. The most conspicuous non‐troglomorphic cave fishes were Hoplerythrinus unitaeniatus, Astyanax sp., Brycon sp. and two species of Imparfinis, with I. hollandi being the most common fish in most caves. São Domingos karst area has the most diverse and abundant Brazilian cavefish fauna, not only in terms of troglobitic species but also in general fish richness, with 22 non‐troglomorphic species recorded in caves in addition to five troglobitic ones. Most fishes examined for stomach contents had at least partially full stomachs. The studied fishes were carnivorous, feeding primarily on aquatic insects. Fishes with developed gonads recorded in caves were I. hollandi, Rhamdia quelen, Pseudocetopsis plumbeus, Hoplerythrinus unitaeniatus and Cichlasoma araguaiensis, indicating a potential for reproduction in the subterranean habitat.

Chromosome Characterization of <i>Astyanax</i> sp B (Characidae, Tetragonopterinae), an Endemic Species of the Iguaçu River, Paraná, Brazil

Cytogenetics studies on Astyanax sp B, an endemic species of the Iguaçu River (Paraná, Brazil) were carried out. The specimens showed a standard diploid number of 2n=50 chromosomes with a karyotype consisting of 6 metacentric, 24 submetacentric, 6 subtelocentric and 14 acrocentric chromosomes. In addition to the basic karyotype, all the specimens presented 1–2 supranumerary or B chromosomes in mitotic metaphases. Three morphological types of B chromosomes have been identified in population under analysis: an acrocentric-type microchromosome; a metacentric macrochromosome smaller than the first pair of the normal karyotype complement; a small submetacentric chromosome. C-band analysis shows discrete markings in the centromeric regions of various chromosomes which contrast with strongly heterochromatic blocks in the telomeric regions of the long arms of chromosome pairs 20, 21 and 22 (acrocentric). Heterochromatic block-sized heteromorphism has been among homologues of pair 20. The chromosome characterisitics of Astyanax sp B indicate similarity with other species of the genus Astyanax with regard to karyotypic macrostructure, distribution of constitutive heterochromatin (C-band pattern) and occurrence of B chromosomes. Some aspects related B chromosomes in this species are discussed.

Cytogenetic Characterization and NOR Polymorphism in <i>Astyanax</i> sp. C (Tetragonopterinae, Characidae) from the First Plateau of the Iguaçu River (Paraná State, Brazil)

The characids belong to the greater freshwater fish family of the world with around 700 recognized species. Whithin this group the genus Astyanax includes several species with unclear phylogenetic relationships, showing a wide karyotypic diversity. In the highly endemic Iguacu river basin these problems are also observed being distinguished 6 unnamed Astyanax species (A to F). In the present work were cytogenetically studied 2 populations of A. sp. C from the first plateau of the Iguacu river (Parana State, Brazil). Fishes of both populations are similar in chromosome number, having 2n=50, however were evidenced clear differences in C-banding and nucleolar organizing regions (NORs) patterns. With the use of the restriction enzyme Alu I were obtained the same results as C-bands. These results indicate the complexity of Astyanax and the importance of further taxonomic revisions joining morphological, cytogenetic and molecular approachings.

Diet of Astyanax species (Teleostei, Characidae) in an Atlantic Forest River in Southern Brazil

Feeding habits of six species of Astyanax from river Maquiné are described. Fishes were sampled bi-monthly from November/95 to September/96 in two zones of the river. Items were identified, counted and had their abundance estimated according to a semi-quantitative scale. Frequency of occurrence, alimentary importance index (IFI) values and a similarity analysis of diets for each species-river zone sample were examined. All the species were considered typically omnivorous, with insects and vegetal matter being the most important items in their diet. These species could act as seed dispersers, particularly for macrophytes. Intra-specific spatial differences were not observed in comparisons of samples from two diferent regions of the river, except for A. fasciatus. The presence of Podostemaceae macrophytes in the mid-course of the river seemed to be important both as an autochthonous food resource and as habitat for several organisms preyed by the Astyanax species.

Conservation of the 5S-bearing chromosome pair and co-localization with major rDNA clusters in five species of Astyanax (Pisces, Characidae)

Major and 5S ribosomal genes have been localized in chromosomes from five fish species, genus Astyanax, using in situ hybridization (FISH) with 28S and 5S rDNA probes. In situ signals for the major rDNA co-localized with the 5S rDNA clusters in the pericentromeric region of one marker chromosome in all five species analyzed. The conserved local- ization of these two rDNA clusters in the five related Astyanax species was considered as indicative of a close relationship among them. The use of these molecular markers for elucidating evolutionary relationships among closely related taxa is discussed.

Karyotypic Studies in the Characidae Fish, Genus Astyanax. An Endemic and Highly Isolated Population of Astyanax sp..

The chromosomes of Astyanax sp. is now described for the first time. Ten specimens of a highly isolated population from the Sinkhole 1 (Vila Velha State Park, Ponta Grossa, PR, Brazil) were analyzed, with the characterization of the karyotype, constitutive heterochromatin and nucleolar organizer regions. Males and females of this species present a similar karyotypic structure (2n=48, 6M+18SM+14ST+10A), without morphologically differentiated sex chromosomes. A great variability concerning the heterochromatin located on the subtelo-acrocentric chromosomes appears also in this species, accordingly to that occur in some other Astyanax species.

Two new species of the genus Astyanax (Characiformes, Characidae) from the Paraná river basin in Argentina

Astyanax leonidas and A. troya are described from the rio Parana basin in northeastern Argentina. Both species share similar number of anal-fin rays and perforated scales in the lateral line, one maxillary tooth, a deep dentary and the presence of small hooks on pectoral, pelvic, anal, and caudal fin of males. These characters are also present in A. ojiara and separate the three species from the remaining species of the genus. Astyanax leonidas is differenciated by the robust body, dorsal profile almost straight, a long and slender maxillary tooth, teeth of premaxillary inner row with notable long central cusp, dentary teeth of similar shape than those of premaxilla, and 4 large dentary teeth followed by one intermediate tooth, and 3 or 4 small teeth. Also this species does not have hooks on dorsal-fin rays and pelvic axillary scale. Astyanax troya has a dorsal profile with marked concavity on supraoccipital area, one broad and low pentacuspid maxillary teeth, teeth of inner premaxillary row gently expanded distally with cusps arising in the same line, central cusp of premaxillary teeth scarcely longer, 8-10 dentary teeth decreasing in size anteroposteriorly, and males with hooks in all fins and pelvic axillary scale.

Restriction fragment length polymorphisms of mitochondrial DNA among five freshwater fish species of the genus Astyanax (Pisces, Characidae)

Restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA) was employed to characterize species and populations of Astyanax, a Neotropical freshwater fish genus. Samples of five species, A. altiparanae, A. fasciatus, A. lacustris, A. scabripinnis paranae and A. schubarti, from the Upper Parana and Sao Francisco river basins were analyzed. Two out of the ten restriction enzymes employed generated species-specific mtDNA patterns for each of the five species. MtDNA exhibited considerable polymorphism within and among populations. All populations sampled showed relatively high values of haplotype diversity. Geographically localized haplotypes were detected for A. altiparanae and A. fasciatus from the Upper Parana and Sao Francisco basins. The relationships between populations are discussed.

Occurrence of a Metacentric Macrochromosome B in Different Species of the Genus Astyanax (Pisces, Characidae, Tetragonopterinae).

Several cases of B chromosomes have been described for neotropical fish species. In some fish groups, this occurrence is sporadic, whereas in others it is more frequent. A high frequency of a metacentric macrochromosome B has been reported for Astyanax scabripinnis populations from different locations. In the present study, this kind of chromosome is reported for the first time in 2 other species of the same genus, A. fasciatus and A. schubarti. This coincidence, as well as the differential B chromosome frequency among the 3 Astyanax species, permit some considerations about its probable common origin and further distribution in this fish group.

A new species of Astyanax (Characiformes, Characidae) from Uruguay river basin in Argentina, with remarks on hook presence in Characidae

A new species of Astyanax (Characiformes, Characidae) from Uruguay river basin in Argentina, with remarks on hook presence in Characidae

Feeding ecology of three Astyanax species (Characidae, Tetragonopterinae) from a floodplain lake of Mogi-Gua�� River, Paran� River Basin, Brazil

The feeding ecology of three characids (A. fasciatus, A. bimaculatus and A. schubarti) was studied monthly during 1988 in Lake Infernao, a major floodplain lake of the Mogi-Guacu River in the State of Sao Paulo. River flooding directly influenced the diet of the omnivorous A. bimaculatus and A. fasciatus which responded to maximum inundation (March) by consuming predominantly allochthonous insects. In contrast, A. schubarti was less influenced by the river flood cycle on qualitative changes in diet and relied basically on aquatic macrophytes and periphytic algae. The importance of zooplankton in the diet of the three species was low, and may be attributed to its low density in the water column (< 1 ind l−1). Ontogenetic diet changes were evident for the three species. For A. fasciatus and A. bimaculatus the importance of zooplankton was high at the early stages, decreasing with size. A. schubarti at younger stages consumed diversified items which gradually decreased quantitatively up to the size class of 65 mm; from this size onwards, the diet became restricted to the consumption of periphytic algae and macrophytes.

Description of a new species of the genus Astyanax (Characiformes: Characidae) from the rio Araguaia basin, Brazil

Description of a new species of the genus Astyanax (Characiformes: Characidae) from the rio Araguaia basin, Brazil

Differential cropping of the caudal fin lobes of prey fishes by the piranha, Serrasalmus spilopleura Kner

Regression analysis of log10 upper and lower caudal lobe area (whole ‘uncropped’ caudals) against log10 standard length for ten prey species of the piranha showed significant differences in both slope and intercept for only one species (Astyanax fasciatus) although intercepts alone were significantly different for two others (A. bimaculatus and Poecilia vivipara). Caudal lobe — standard length regression statistics were used to generate estimates of caudal lobe loss in cropped prey species and these clearly demonstrated highly significant differential cropping incidences in several species and size categories. Particularly in the Astyanax species, the upper caudal lobe was subject to low cropping loss and the lower caudal lobe to high cropping loss. Differential cropping of caudal fin lobes suggests that piranha initiate their attack from below and behind prey fishes.

Cytogenetic Considerations on the GenusAstyanax(Pisces, Characidae). I. Karyotypic Variability

SUMMARYA study was carried out on mitotic and meiotic chromosomes of four species of the genus Astyanax (Pisces, Characidae) from three different water basins in the State of Sao Paulo, Brazil. The following karyotypic characteristics were observed: A. bimaculatus, 2n = 50 (n = 25, FN = 86–88); A. fasciatus, 2n = 46 (n = 23, FN = 90); « A. fasciatus » from the Juquia river, 2n = 48 (n = 24, FN = 94); A. schubarti, 2n = 36 (n = 18, FN = 70) and A. scabripinnis paranae, 2n = 50 (n = 25, FN = 90–92). The diversity in the number and morphology of the chromosomes suggests a model of non-conservative karyotypic evolution in this genus, with chromosome rearrangements of the centric fusion/fission type and/or inversion playing an important role in these alterations. On the basis of its characteristics, A. schubarti has the most differentiated karyotype and, in view of the low diploid number and small number of subtelocentric-acrocentric chromosomes, is probably of most recent origin. The two karyotypes encountere...

Possible case of aggressive mimicry in a neotropical scale-eating fish

Probolodus heterostomus, one of the scale-eating characoid fishes, is found in the coastal rivers of southeastern Brazil from Espirito Santo to Sao Paulo1–3. The species is usually placed in the subfamily Cheirodontinae2–4 although a taxonomic affinity with the Tetragonopterinae has been suggested1. The latter view was apparently based largely on the morphological similarity of Probolodus with some species of Astyanax and especially A. fasciatus, a member of the Tetragonopterinae. The external similarity between the two species, which are sympatric over the Rio Paraiba drainage, is indeed striking (Fig. 1). But data accumulated from population samples, stomach contents and the behaviour of individuals maintained in aquaria suggest that Astyanax is the principal prey of Probolodus, at least in certain areas of its range. I suggest here that the similarity between these two genera is a form of aggressive mimicry5,6 irrespective of taxonomic affinities.