A New and Fast Technique to Generate Offspring after Germ Cells Transplantation in Adult Fish: The Nile Tilapia (Oreochromis niloticus) Model

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The occurrence of Austrodiplostomum compactum (Lutz, 1928) (Digenea: Diplostomidae) metacercariae in the eyes of loricariid fish (Siluriformes: Osteichthyes: Loricariidae) from Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Infection by Austrodiplostomum compactum metacercariae in fish from the Nova Avanhandava reservoir, Tiete river, São Paulo State, Brazil.

This study aimed to evaluate the infection by the Austrodiplostomum compactum metacercariae in fishes from the Nova Avanhandava Reservoir, low Tiete river, São Paulo State, Brazil. The parasites were collected from eye (aqueous and vitreous humor), fixed in AFA solution and stained with carmine. The morphometric analysis was performed using a computerized system for analysis of images QWin Lite 2.5 (Leica). Prevalence, mean intensity of infection and abundance of infected fish were calculated. of the 22 species of fish registered, five were infected by metacercariae: Hoplias malabaricus, Metynnis maculatus, Plagioscion squamosissimus, Satanoperca pappaterra and Schizodon imparts. of the 627 fish evaluated, 34% were infected. A higher prevalence was observed in P. sqnamosissionis and S. pappaterra. Schizodon nasutus and M. maculatus are new hosts reported for A. compactum metacercariae.

Fish, Tatui river basin, state of São Paulo, Brazil.

The Tatui river hydrographic basin locates in low Sorocaba river basin in São Paulo state, Brazil. A relatively high diversity of fish species was noticed at that place, whose habitats are also presumed to be diversified. The Tatui river is an important tributary of Sorocaba river, with great number of smaller streams and marginal lagoons. Fishes were collected using gill-nets, purse seines, sieves and traps, line and hook, every month during one year (from May 2009 to April 2010). Fish species were 51, including seven orders and 18 families. Characiformes and Siluriformes were the most represented with respectively 26 and 14 species.

Effects of a small fish cage farm on zooplankton assemblages (Cladocera and Copepoda: Crustacea) in a sub-tropicalreservoir (SE Brazil).

In Brazil, the environmental impacts of fish cage farming in water reservoirs have not been well studied. As this activity is being increasingly practiced, investigations on the impacts of this practice are strongly needed. The goal of this study was to investigate the effects of a small cage tilapia farm on zooplankton assemblages in an oligo/mesotrophic reservoir (Jurumirim Reservoir, Paranapanema River). Zooplankton, limnological variables, and water samples were obtained trimonthly during a year at two sample sites, one was located adjacent to the cage farm and the control area was located one kilometer away from it. Eighteen species were identified and Cladocera was the dominant group. The same species of microcrustaceans were identified at both sites. Among the ecological attributes studied, only evenness showed a tendency towards being higher in the control site. Significant differences between studied variables in the sites were observed only for material in suspension. The results of the study indicate that, during the studied period, the cage farm did not generate detectable changes in the zooplankton assemblages and their ecological attributes. However, small differences in some limnological variables could be an indication of some environmental changes associated with the fish farm system.

Fish cytogenetic research: Advances, applications and perspectives

Methods developed since 1976 for harvesting, preparing and banding fish chromosomes are now commonly used for taxonomic and phylogenetic studies, genetic control and chromosome manipulations in fish breeding and in monitoring aquatic pollutants by examining chromosomal aberrations. These studies have chiefly concerned common temperate freshwater species; the same procedures, when applied to marine and coldwater fish, often provide unsatisfactory results, especially in cell culture. A concerted effort should be made in marine fish, and to develop molecular cytogenetic methods to provide a more powerful tool to study chromosomal evolution. © 1991 BRILL.

Feeding patterns in a fish community of Baia da Onça, a floodplain lake of the Aquidauana River, Pantanal, Brazil

The stomach contents of 24 species of fish and unidentified species from four genera in a floodplain lake of the Pantanal were studied. Fish were collected during the dry season when the lake was isolated from the main river. A community food ingestion index (feeding index weighted by consumer biomass, FIWCB, where 0 < FIWCB < 1) was calculated to quantify feeding patterns. Detritus and algae ingested by Curimatidae were responsible for 46.5% of the FIWCB, while that for algae ingested by Loricariidae (armoured catfish) accounted for 13.2%. The importance of detritus in fish diets is discussed as a strategy for shortening food chains, thereby increasing community efficiency, and as a consequence, fish biomass. It was learnt that the main route of energy flow in this perennial lake was through the detritus chain. The floodplain lakes function as a dry season feeding ground for small-sized species of fish, which are potential prey for the more highly valued larger species of fish.

The effect of ions and adenosine nucleotides on the activity of lactate dehydrogenase from the epaxial muscle of fish

Lactate dehydrogenase was partially purified from the epaxial muscle of Piaractus mesopotamicus (pacu) and its hybrid Piaractus mesopotamicus x Colossoma macropomus (tambacu). This preparation was used for kinetic studies carried out at pH 6.0 and 7.5. It was also used for the study of the inhibition properties of adenosine nucleotides = ATP, ADP, AMP =, divalent ions Ni2+, Cu2+, Co2+ and the anions oxamate and oxalate.

Increased B chromosome frequency and absence of drive in the fish Prochilodus lineatus

The neotropical freshwater fish species Prochilodus lineatus (Pisces, Prochilodontidae) shows 2n = 54 chromosomes plus supernumerary microchromosomes ranging in number from zero to seven among different animals. The transmission rates of B chromosomes were studied by the analysis of the parental and F1 generations in 10 controlled crosses performed with specimens from a natural population. The mean transmission rate observed for B chromosomes (k(B) = 0.511) was consistent with that expected from a regular meiotic behaviour orbs in both sexes and with the theoretical value under a Mendelian mode of transmission (0.5). Possible explanations for the dramatic increase in B frequency observed in this population during the last 10 years are discussed, bearing in mind the current absence of drive.

The dietary regime of detritivorous fish from the River Jacaré Pepira, Brazil

The diet of detritivorous fish was analysed at four distinct habitats in a tropical river during the wet and dry seasons. Two methodologies were used to determine the diet of the fish: (1) the direct analysis of the stomach contents; and (2) the use of stable carbon isotopes. Both methods indicated food partitioning among the fish. The stomach contents showed what the fish had ingested when captured and the 13C isotope indicated what it had assimilated over a long period of time. The 13C isotope suggested the existence of sectional differences in the feeding of the detritivorous fish along the river. Plants employing the C4 photosynthesis pathways seem to have little influence on the diet of these fish. This method proved to be more appropriate for the detection of the main food sources of the captured fish.

Nucleotide sequence of 5S rDNA and localization of the ribosomal RNA genes to metaphase chromosomes of the Tilapiine cichlid fish, Oreochromis niloticus

In this study, we report the cloning and nucleotide sequence of PCR-generated 5S rDNA from the Tilapiine cichlid fish, Oreochromis niloticus. Two types of 5S rDNA were detected that differed by insertions and/or deletions and base substitutions within the non-transcribed spacer (NTS). Two 5S rDNA loci were observed by fluorescent in situ hybridization (FISH) in metaphase spreads of tilapia chromosomes. FISH using an 18S rDNA probe and silver nitrate sequential staining of 5S-FISH slides showed three 18S rDNA loci that are not syntenic to the 5S rDNA loci.

Morphologically differentiated sex chromosomes in neotropical freshwater fish

A general survey of the occurrence of morphologically differentiated sex chromosomes in the neotropical freshwater fishes is presented. The total number of 32 occurrences involving simple XX-XY and ZZ-ZW, and multiple X1X2Y, XY1Y2 and ZW1W2 sex chromosome systems is described, with comments on the aspects of sex chromosome evolution in this fish fauna. The occurrence of different sex chromosome systems in related species of the same genus, or in different populations of the same nominal species, involving male and sometimes female heterogamety, and differences in the molecular composition of sex-linked heterochromatin, are considered as indicative of the early stage of sex chromosomes evolution in fish.

Influence of artificial reefs on fish assemblage of the Barra Bonita Reservoir (São Paulo, Brazil)

This paper deals with the effects of introduced artificial reefs on the diversity of freshwater fish communities in lentic and lotic zones of a very impacted river in southeastern Brazil. To accomplish this goal, artificial reefs were introduced, in December 1997, in the Barra Bonita reservoir and in the lotic zone immediately below the dam. Fish diversity was always higher in the lotic zone than in the reservoir. Accordingly, fish diversity near the artificial reefs was consistently higher than in the control areas. We propose that the higher environmental complexity in the lotic zone, as compared to the reservoir, is incremented in areas where artificial reefs were introduced; also, we present that, in both areas, diversity is mainly affected by the introduction of artificial reefs.

Synaptonemal complex analysis in the fish species Piaractus mesopotamicus and Colossoma macropomum, and in their interspecific hybrid

The surface-spreading technique for visualization of whole cell synaptonemal complex (SC) complements was employed to study the chromosome synapsis in spermatocytes of P. mesopotamicus, C. macropomum and in their interspecific hybrid (tambacu) with the main objective to analyze possible errors in chromosome pairing that could result in hybrid sterility. SC analysis showed that the parental species P. mesopotamicus and C. macropomum have 27 bivalents homogeneously synapsed. The SC in spermatocytes from the hybrid tambacu showed gross meiotic configurations in all cells analyzed. The spermatocytes exhibited a few chromosomes or well synapsed chromosome segments, while many chromosome segments did not have any synapsis. This result, allied to other genetical and cytogenetical evidence, reinforces the hypothesis that the hybrid tambacu is sterile. Further studies involving other aspects, such as behavior and physiology, should be conduced before the introduction of these hybrids in rivers and lakes.

RAPD analysis in the Neotropical fish Brycon lundii: Genetic diversity and its implications for the conservation of the species

Random amplified polymorphic DNA (RAPD) technique was used to examine the genetic variability on an endangered Neotropical fish species, Brycon lundii, collected on two regions with distinct environmental conditions in the São Francisco River (Brazil), downstream from a hydroelectric station. Using decamer oligonucleotides as single primers in Polymerase Chain Reaction (PCR), genetic similarity index, mean allele frequency and mean heterozigosity were estimated, revealing variations between samples from the two regions. Moreover, a fragment of about 1200 base pairs was found in 100% of the examined animals collected at the region closer to the hydroelectric dam, while its frequency was much lower (27.3%) within the sample from the second collecting site, 30 km downstream from the dam, indicating a possible correlation between genetic variation and geographical area. A dendogram representing the relationships among genotypes was obtained, demonstrating at least two major clusters of animals. Based on the data, a model of population structuring in Brycon lundii is suggested. The described approach holds great promise for further analyses and gives support to biodiversity maintenance and recovery efforts of B. lundii.