The reproductive strategy of Leporinus friderici (Characiformes, Anostomidae) in the Paraná River basin: the effect of reservoirs

The reproductive strategy of a species depends upon the interaction between intrinsic and extrinsic factors. Examining the population of Leporinus friderici in two reservoirs of the Upper Paraná River basin in reference to first gonadal maturation and breeding season and sites, the present investigation tested whether the environment formed by damming promoted spatial and temporal changes in the reproductive strategy of this species. Analyses of sex ratios showed that females significantly predominated in Itaipu, while in Corumbá the sexes were about equal with a slight predominance of males. Size-associated sexual dimorphism was observed, that is females dominated the longer length categories, and males the shorter. The minimum size at which L. friderici initiated reproduction varied from year to year, and was larger in the periods soon after formation of both reservoirs. In Itaipu, stabilization between the maximum and minimum lengths at first maturation was also noted after year 6 following closure and continuing until year 15. In general, the breeding season lasted from October through April, although cyclic changes in the duration and intensity of this season were evident. Young individuals predominated during the entire study period in Corumbá. The formation of Itaipu Reservoir had a greater effect on the reproduction of L. friderici, where a gradual adaptation of the reproductive strategy of this species may possibly have been occurring. It is also possible that some of the characteristics of the Itaipu population will in the future be shown by the Corumbá population. It was concluded that reproductive strategies constitute ecological adaptations that are temporally and spatially altered and are fitted to resource availability and environmental pressure.     

Reproductive success of nuclear nonhybrid males of Squalius alburnoides hybridogenetic complex (Teleostei, Cyprinidae): an example of interplay between female choice and ecological pressures?

The hybridogenetic fish complex Squalius alburnoides comprises diploid males with non-hybrid nuclear genomes and several hybrid forms varying in ploidy and relative proportions of the parental genomes. In this paper, we present evidence that in captivity females prefer to mate with non-hybrid males. We suggest that female choice combined with different ecological requirements of hybrid and non-hybrid males may explain the extreme variation in the relative abundance of male types among drainages.Electronic Supplementary Materials Supplementary material is available for this article at     

Allozyme relationships in hypostomines (Teleostei: Loricariidae) from the Itaipu Reservoir,Upper Rio Paraná basin,Brazil

In an allozyme electrophoresis survey of 15 hypostomine species from the Itaipu Hydroelectric Reservoir, 25 loci from 14 enzyme systems were scored. Allozyme data allowed recording diagnostic genetic markers for all species analyzed and for some species groups within Hypostomus, a taxon which is taxonomically still unresolved in the Upper Rio Paraná basin. The mean expected heterozygosity of the species was considerably variable and hypotheses to tentatively explain this variation are discussed. A cladogram based upon the allelic frequencies of the species analyzed was produced by the continuous maximum likelihood method: Rhinelepis aspera and M. parananus were separated from the species of Hypostominae by a long branch length. Pterygoplichthys anisitsi was the sister of all the representatives of the genus Hypostomus. Within Hypostomus, two main clades were produced: in the first, H. cochliodon was the sister of the species comprising the H. plecostomus group, and in the second, the tree showed the following relationships: (H. albopunctatus (H. regani + Hypostomus sp. 3) + (H. margaritifer (H. microstomus (Hypostomus sp. 1 (H. ternetzi + Hypostomus sp. 2))))). Hypostomus ternetzi and Hypostomus sp. 2 are referred to here as representatives of the H. ternetzi group.     

Karyotypic variability in Iheringichthys labrosus (Teleostei, Pimelodidae) from the Tibagi River basin (Paraná State, Brazil)

Cytogenetic analyses were carried out in a populational sample of Iheringichthys labrosus from the Guaraúna River (Upper Tibagi River; Paraná State, Brazil) in order to provide a karyotypic comparison with another previously studied population from the Lower Tibagi River, characterized by the presence of 32m + 8sm + 6st + 10a (2n = 56, FN = 102) and occurrence of supernumerary chromosomes (80% of individuals). The 17 specimens of I. labrosus (6 females, 10 males and 1 of unknown sex) from the Upper Tibagi River showed 2n = 56 chromosomes, a karyotype formula of 14m + 32sm + 4st + 6a (FN = 106), without evidence of sex chromosome heteromorphism or supernumerary chromosomes. The heterochromatin was detected at telomeric and centromeric positions in several chromosomal pairs. The Ag-nucleolar organizer regions were heteromorphic and located at terminal position on short arms of the 16th chromosomal pair, suggesting a positive association with heterochromatic regions. The inter-populational karyotypic differentiation reported indicates distinct evolutionary pathways within I. labrosus in the Tibagi River basin.     

Species diversity in Gymnogeophagus (Teleostei: Cichlidae) and comparative biogeography of cichlids in the Middle Paraná basin,an emerging hotspot of fish endemism

Hydrobiologia - We address the diversity of two species groups of the cichlid genus Gymnogeophagus in the Middle Paraná basin using molecular phylogeography and traditional morphological...     

The fish zonation of the Itanhaém river basin in the Atlantic Forest of southeast Brazil

The distribution range of fishes along an upstream–downstream gradient within a river basin is determined by the ecological requirements of each fish species. This differential pattern of distribution may suggest the occurrence of fish zones, where different functional guilds would prevail. The earliest concept of fish zonation highlighted the preferential position of several species in European rivers. Nowadays, there is a consensus that for a broad application of this concept, it is necessary to consider the division in functional groups along the downstream profile as related to reproductive, feed and population dynamics traits. However, for a number of tropical systems, such information does not exist. In this case, it is possible to use the fish family as a surrogate metric, by assuming that it fully covers common aspects of morphology, feeding, and behavior. Using this surrogate metric, we analyzed the distribution range of fish species along an elevation gradient in a typical Atlantic Forest basin in southeast Brazil. Our objective was to delimit fish zones based on the representativeness of some dominant fish families. Between 2006 and 2008, we sampled 42 sites from the estuary to the headwater creeks in elevations that varied from 3 to 783 m. The data were explored using the species (or family) occurrence, relative numerical abundance (N′), relative biomass (B′), and the importance index (IP). We applied the non-metric multidimensional scaling (NMDS) to ordinate the sampling sites using the Jaccard distance calculated on the species occurrence matrix. Data on family importance were superimposed to the NMDS to check how the distribution and the abundance of the families were correlated to the ordination. We caught 64 species distributed among 25 fish families. Based on the dominance of some families, we propose that the fish assemblage in the Itanhaém river basin can be organized in four fish zones (FZ) and three transitory zones (TZ), which replace each other along the longitudinal gradient. The marine/estuarine fishes dominated in FZ1 and TZ1. The freshwater fishes were dominated by Characidae (FZ2), Heptapteridae (FZ3), and Gymnotidae (FZ4). TZ2 was equally dominated by Characidae, Loricariidae, and Heptapteridae. The distinct assemblage composition along the FZ’s may relate to complex interactions involving seasonal patterns of variation in salinity levels (next to estuary), slope, presence of downstream barriers, and availability of food resources. We expect that the patterns observed in our study will also be presented in other coastal Atlantic Forest basins in Southeast Brazil.     

A new species of Parspina Pearse, 1920 (Digenea: Cryptogonimidae) from Pimelodella gracilis (Valenciennes) (Siluriformes: Heptapteridae) in the Paraná River basin, Argentina, and a key to the genus

A new species of cryptogonimid belonging to the genus Parspina Pearse, 1920 is described from the intestine of Pimelodella gracilis (Valenciennes) in the Paraná River basin, Argentina. Parspina pimelodellae n. sp. is characterised by having: (i) a body length/width ratio of 1:3.6–5.3 at the level of the ventral sucker; (ii) 21 oral spines; (iii) an oral sucker larger than the ventral sucker, with a sucker width ratio of 1:0.6–0.7; (iv) a postcaecal region of 16–19% of the body-length; (v) a compact, transversely elongate ovary, anterior to and well separated from the testes; (vi) small, branched vitelline follicles, extending from the level of the ventral sucker to the anterior margin of the ovary; and (vii) a large seminal vesicle situated posterodorsal to the ventral sucker. A key to the species of Parspina is presented.     

Karyotype characterization of three species of the genus Trichomycterus (Teleostei,Siluriformes) from Iguaçu river basin

Three species belonging to the genus Trichomycterus were collected from Igua?u river basin and analyzed from the cytogenetic point of view. Although the species studied had the same diploid number 2n = 54 chromosomes and fundamental number 108, they differed in their karyotypic formulae. C-band patterns showed presence of specific-species markers in T. davisi and T. stawiarski. Results of analysis from the nucleolus organizer region, obtained by silver nitrate staining and CMA3, showed that size heteromorphism observed in this region may be due to gene duplication. Evolution aspects of the Trichomycteridae family and the presence of B chromosome in T. davisi are discussed.     

Ultrastructure of the germ cells in the testis of matrinxã, Brycon cephalus (Teleostei, Characidae)

This study describes at ultrastructural level the germ cells in the testis of matrinx? (Brycon cephalus) raised in captivity. The specimens 'matrinx?' were maintained in four breeding tanks of 200 m(2), at the Aquaculture Research Center at Vale do Ribeira-CEPAR, from Fishery Institute, in Pariquera-A?u City, S?o Paulo, Brazil. The samples were collected from March 1994 to February 1996. The testis has been classified as tubular unrestricted spermatogonial type, in which four stages of germ cells can be distinguished as follows: spermatogonia, spermatocytes (primary and secondary); spermatids and spermatozoa.     

Genetic variability of Brycon henni (Characiformes: Characidae) in the middle basin of Nare and Guatapé Rivers, Magdalena River system, Colombia

Brycon henni is a native species in Magdalena's River basin, and because of its cultural and economic importance, is strongly overexploited. This study aimed to describe the genetic variability and population structure of this species from Nare and Guatapé rivers basins. A total of 195 individuals were collected and DNA extractions were obtained from muscle and blood tissue. Fourteen primers were evaluated with the RAPD technique, being four of them polymorphic, and produced 66 different fragments (63% polymorphism). Besides, using the molecular variance (AMOVA) analysis, the population structure was described for all sites (phi(ST) = 0.297, phi(ST) = 0.163; Nare and Guatapé river basins, respectively), and suggested the importance of the migratory behaviour of the species in the genetic differentiation. Genetic distances among sampled sites showed that most of the genetic differentiation occurred between sites Guatapé and El Cardal with respect to the others. A Mantel Test demonstrated a correlation between genetic and geographic distances (r = 0.431 both of the basins evaluated; r = 0.377, Nare river middle basin), and suggested isolation by distance. The outcomes obtained in this study have valuable implications in species conservation and the genetic variability of natural populations of B. henni, and should be complemented with morphological analyses.     

A molecular phylogeny of the freshwater-fish genus Rasbora (Teleostei: Cyprinidae) in Sri Lanka reveals a remarkable diversification—And a cryptic species

The diversity of the freshwater-fish genus Rasbora (Cyprinidae) on Sri Lanka (five species) is high compared with the four species reported from the peninsula of India, from which the island's cyprinid fauna is derived. The paucity of characters by which species of Rasbora can be phenotypically distinguished renders field identification difficult, adversely affecting the estimation of populations and distributions, with consequences for conservation and management, increasing also the risk of taxonomic inflation. From a sampling of 90 sites across Sri Lanka and based on phylogenetic and haplotype analyses of sequences of cox1 and cytb mitochondrial, and rag1 and irbp nuclear markers, we review the species diversity and phylogeography of Rasbora on the island. Molecular analyses recover, in addition to the five species previously reported, a new (cryptic) species: Rasbora adisi sp. nov. Uncorrected pairwise cox1 genetic distances between species range from 2.0 to 12.3 percent. The Sri Lankan diversification derives from a common ancestor which arrived from India during a sea-level low-stand in the mid-Miocene (15.1 Ma [95% HPD: 11.5–19.8 Ma]), when the present-day island was subaerially connected to the Indian subcontinent by a broad isthmus. This gave rise to a clade comprising five species—R. adisi sp. nov.,Rasbora armitagei, Rasbora microcephalus, Rasbora naggsi and Rasbora wilpita—with a crown age of 9.9 Ma (95% HPD: 7.1–13.3 Ma) and to a clade comprising Indian and Sri Lankan populations of Rasbora dandia, which themselves are reciprocally monophyletic. Morphological analysis of 334 specimens discriminates between most species which, however, are most reliably diagnosed by chromatic characters. The four endemic species exhibit a pattern of inter-basin dispersal via headwater capture, followed by vicariance, explaining the high diversity of the genus on the island.     

A new Chondrostoma species from the Büyük Menderes River Basin,Turkey (Teleostei: Cyprinidae)

In a study of the fishes of the Büyük Menderes River Basin, Aegean region of Turkey, two populations of Chondrostoma were found which showed clearly distinctive characters: the population from the Upper B. Menderes (I??kl? Lake) was attributed to C. meandrense Elvira, 1987, while the population from the Çine Stream in the Lower B. Menderes River basin proved to be a hitherto undescribed species: Chondrostoma turnai sp. n. Altogether 24 metric and 7 meristic parameters were compared. The new species is distinguished from C. meandrense and all other cogeners by a combination of the number of lateral line scales, the number of scale rows between the lateral line and the dorsal-fin origin, the number of scale rows of the lateral line and pelvic-fin origin, and the number of gill rakers on the first gill arch.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:811C213D-BEDD-4C8C-AE57-BFFA7964781A     

Pseudorascora parva (Teleostei, Cyprinidae), an invasive species, a new vector for the maintenance and dissemination of anguillicolosis in France?]

Pseudorasbora parva (Pisces, Cyprinidae) is an invasive species from eastern Asia. Known in France since 1983, it has only been observed since 1993 in the Rh?ne delta where large populations occur. 203 specimens of that fish species have been examined for L3-larvae of Anguillicola crassus. 35% of the fish were found to be infected.     

Allozyme differentiation of two populations of the genus Neoplecostomus Eigenmann & Eigenmann, 1888 (Teleostei, Loricariidae) from the upper Paraná River basin, Brazil

Allozyme electrophoresis was used to examine 12 enzymatic systems in two populations of the genus Neoplecostomus from the Paraná River basin. Samples of Neoplecostomus sp. 1 were collected in Paraitinguinha stream of the Tietê River basin, in the municipality of Salesópolis, São Paulo State, and those of Neoplecostomus sp. 2 from São Domingos stream of the Rio Grande River basin, in the municipality of Muzambinho, Minas Gerais State. The genetic variability of the two populations was estimated by Nei’s expected heterozygosity and was considered lower than average for populations of freshwater fish. The proportion of polymorphic loci was low (only 5.26% for the locus Idh). The low frequency of heterozygosity for both populations revealed a high fixation of alleles for each locus. Homozygote excess was observed in both populations. The values of Nei’s genetic identity and the presence of loci with different allele frequencies in both populations may imply that the two populations belong to different species. The genetic variability between populations was compared to other data for loricariids.     

First partial cranium of Togocetus from Kpogamé (Togo) and the protocetid diversity in the Togolese phosphate basin

Earliest cetaceans (whales) originated from the early Eocene of Indo-Pakistan, but the group dispersed through most of the oceans of the planet by the late middle to late Eocene. This late Eocene global distribution indicates that important dispersal events took place during the middle Eocene (Lutetian), a globally undersampled time interval that is well documented in the Togolese phosphate series. We report here the first discovery of a partial cetacean cranium from middle Eocene deposits of Togo (West Africa). A 3D model of the cranium and teeth was reconstructed in order to reveal hidden anatomical features. The dental and cranial characteristics of the Togolese specimen recall those of protocetid taxa described in Africa, Asia, and North America, but also display significant differences. In particular, we show that the new specimen shares a number of morphological features with the Togolese taxon Togocetus. Such a hypothesis is further supported by a cladistic analysis including 45 taxa and 167 morphological characters, which recovers the new specimen close to Togocetus as the first offshoot of protocetids. Phylogenetic analysis including all the protocetids remains of Kpogamé confirms the singular diversity of the Togolese phosphate basin, and enables to examine potential connections with faunas from contemporaneous localities in Africa.     

Phylogeography of Schizothorax o’connori (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo River, Tibet

Schizothorax o’connori is endemic to the Yarlung Tsangpo River on the Tibetan Plateau. We assessed the relative impacts of historical and contemporary factors in organizing genetic variation in S. o’connori populations using mitochondrial cytochrome b sequences. We analyzed 191 samples from 11 populations and identified 78 haplotypes. The phylogenetic analyses and analysis of molecular variance all supported the same conclusions of two well-differentiated east–west phylogroups, separated by the Tsangpo Great Gorge. The split between the two clades accounted for 58% of the genetic variance observed among the examined samples. Waterfalls as effective barriers played an important role in shaping the phylogeographical structure of this species. Analyses of migration rates revealed that upstream dispersal was limited crossing waterfalls. Our study revealed substantial spatial and temporal variation in the influence of landscape features on contemporary patterns of genetic structure in S. o’connori. Interglacial range expansions clearly left their mark on contemporary populations above the Tsangpo Great Gorge.     

Reproductive strategy of a small endemic cyprinid, the Yarqon bleak (Acanthobrama telavivensis), in a mediterranean-type stream

A mediterranean-type climate exists in five widely separated regions; the Mediterranean basin, parts of western North America, parts of western and southern Australia, southwestern South Africa and parts of central Chile. Streams in these regions feature seasonal disturbances of contrasting hydrology with high predictability of the timing of flooding and drying but low constancy. We would expect fish living in these streams to avoid scouring flow and breed after cessation of the flood period. The aim of the present study was to examine the adaptation of the Yarqon bleak, Acanthobrama telavivensis, an endemic cyprinid in the coastal streams of Israel, to mediterranean-type stream (mediterranean—written with a small m, is used in connection with climate or ecological region and is distinguished from Mediterranean that is used in a geographical context, referring to the Mediterranean basin.) conditions. For that we studied its reproductive strategy (age at maturity and life span, gonad activity, oocyte maturation, spawning activity and habitats, appearance of juveniles), in a major costal stream (Yarqon). Our findings show that the Yarqon bleak exhibits life history traits attuned with a mediterranean-climate hydrologic regime. It breeds in late winter and early spring, a window of opportunity between flash floods and habitat desiccation. Being a multiple spawner allows the fish to compensate for the potential loss of part of its reproductive output due to scouring flows of late floods. The ability of the Yarqon bleak to spawn on different substrate-types enables it to take advantage of different stream conditions that pertain in different years. The fish attains pre-adult size (ca. 33–42 mm) within the first year, prior to drying out of most stream reaches, and matures by the beginning of the second year (males >41; females >42 mm). The cost of these tactics is a short life span (4–5 age groups). The reproductive strategy of the Yarqon bleak falls into the category of in-channel breeding but, unlike the case suggested by a low flow recruitment model, the fish breed during the period of flood cessation, a transitional time between high and low flows, rather than at the time of low flow. Breeding at this time of the year in mediterranean-type streams puts early stages somewhat at risk of being washed away by late floods, but gains them a longer period of growth under favorable conditions. We suggest an additional positive tradeoff that should be investigated: the reduced competition with age 0 of other fish that breed later in the season. This suggested model of recruitment during the period of flood cessation seems appropriate for fish in streams with seasonal contrasting flows of high predictability but low constancy.