Early social environment and the fighting behaviour of young Oreochromis niloticus (Pisces, Cichlidae)

This study examines the influence of early experience with different forms of aggressive behaviour on the fighting behaviour of young fish. Fry of the cichlid fish, Oreochromis niloticus, were raised from hatching in small groups consisting of a normal individual (the test fish) and either mutant conspecifics lacking the dorsal fin and thereby the ability to perform fin displays, or normal ones. Following a 63-day period of development in groups the test fish were confronted in their home tanks with an unfamiliar normal fish for 10 min. The fighting behaviour of the test fish was analyzed considering their previous group type (mutant or normal) and rank (alpha or beta). There was no difference between test fish in the rate and sequence of behaviour patterns used in fighting. However, test fish that had developed in mutant groups were rarely the first to bite in contests and had a longer latency to biting following the first bite of the stimulus fish than rest fish with normal experience. This finding is attributable to the form of aggressive behaviour experienced by the test fish during development but not to existing differences in the amount of aggression previously experienced, nor to previous rank, sex, or size relative to the stimulus fish. The results suggest that early experience influenced decision making by the test fish during the fight. The involvement of the fin displays and the possible mechanism of this influence are discussed.

The aggressive behavior of Nile tilapia introduced into novel environments with variation in enrichment

Many studies show environmental enrichment is correlated with benefits to captive animals; however, one should not always assume this positive relationship given that enrichment increases the amount of resources that a territorial animal must defend and possibly affects its aggressive dynamics. In this study, we tested if environmental enrichment affects aggressive interactions in the aggressive fish Nile tilapia (Oreochromis niloticus). We compared fights staged between pairs of male tilapia of similar size (= matched in resource holding potential) in a novel arena that was either barren or enriched, to examine whether enrichment enhances territory value in line with theoretical predictions, with the potential for compromised welfare. We evaluated time elapsed until the first attack (latency), frequency of aggressive interactions and fight duration. We detected fight dynamic differences at the pair level. Higher resource value generated increased aggression but had no effect on fight duration or latency. This conclusion is in line with game theory predictions concerning resource value and contradicts the theory that enrichment of the environment will serve welfare purposes. (C) 2010 Elsevier GmbH. All rights reserved.

Aggressiveness Overcomes Body-Size Effects in Fights Staged between Invasive and Native Fish Species with Overlapping Niches

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chemical communication of handling stress in fish

We investigated whether juveniles of the nocturnal fish jundia (Rhamdia quelen) and the diurnal fish Nile tilapia (Oreochromis niloticus) are able to chemically communicate stress to conspecifics. Groups of 8 fish were reared in tanks under recirculated water (water exchanged among all the tanks) for each species. Fish were handled in half of the tanks (stressor fish) and whole-body cortisol concentrations were compared among handled fish, non-handled fish exposed to water from the handled fish, and non-handled control fish held with no water communication. For each treatment cortisol concentrations were determined before exposure to the stressor (basal levels) and after 1, 2, 4, 8, and 24 h. Basal levels of cortisol confirmed fish were unstressed in the beginning of the experiment. Cortisol was increased in the stressor fish 1 h after handling. Fish receiving water from the stressor fish increased cortisol levels later (2 h after the stressor fish were handled). As the isolated control group maintained cortisol levels unchanged throughout the experiment, we concluded that some chemical factor was released by the stressed fish in the water and thus stressed the conspecifics. This pattern was similar for both unrelated species, thus suggesting that this communication might have evolved earlier in fish and reinforcing the biological value of this kind of information. Published by Elsevier B.V.

5S rDNA characterization in twelve Sciaenidae fish species (Teleostei, Perciformes): depicting gene diversity and molecular markers

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

Localization of 5-methylcytosine in metaphase chromosomes of diploid and triploid pacu fish, Piaractus mesopotamicus (Pisces, Characiformes)

The distribution of 5-methylcytosine (5-MeC) was investigated in fish chromosomes by indirect immunofluorescence using a highly specific 5-MeC monoclonal antibody. Diploid and artificially produced triploid specimens of the pacu fish, Piaractus mesopotamicus, were analyzed. The strong immunofluorescent signals were coincident with the heterochromatic regions of both diploids and triploids in a pattern that matched the C-banding pattern. In the euchromatin, heterogeneous labeling was observed along the chromatids. The weakness of this labeling hindered comparison of the fluorescence labeling of homologous chromosomes from diploid and triploid individuals. However, no striking differences were observed. The possibility that the euchromatin labeling by the 5-MeC antibody is related to the occurrence of mildly repetitive sequences in the genome of Piaractus is discussed.

Dynamics of 5S rDNA in the tilapia (Oreochromis niloticus) genome: repeat units, inverted sequences, pseudogenes and chromosome loci

In higher eukaryotes, the 5S ribosomal DNA (5S rDNA) is organized in tandem arrays with repeat units composed of a coding region and a non-transcribed spacer sequence (NTS). These tandem arrays can be found on either one or more chromosome pairs. 5S rDNA copies from the tilapia fish. Oreochromis niloticus, were cloned and the nucleotide sequences of the coding region and of the non-transcribed spacer were deter-mined. Moreover, the genomic organization of the 5S rDNA tandem repeats was investigated by fluorescence in situ hybridization (FISH) and Southern blot hybridization. Two 5S rDNA classes, one consisting of 1.4-kb repeats and another one with 0.5-kb repeats were identified and designated 5S rDNA type I and type II, respectively, An inverted 5S rRNA gene and a 5S rRNA putative pseudogene were also identified inside the tandem repeats of 5S rDNA type I. FISH permitted the visualization of the 5S rRNA genes at three chromosome loci, one of them consisting of arrays of the 5S rDNA type I, and the two others corresponding to arrays of the 5S rDNA type II. The two classes of the 5S rDNA. The presence of pseudogenes, and the inverted genes observed in the O. niloticus genome might be a consequence of the intense dynamics of the evolution of these tandem repeat elements. Copyright (C) 2002 S. Karger AG, Basel.

Cytogenetic analysis of three species of the genus Haemulon (Teleostei : Haemulinae) from Margarita Island, Venezuela

This paper describes the karyotype analysis of Haemulon aurolineatum, Haemulon bonariensis and Haemulon plumierii, by Giemsa staining, C-banding, Ag-staining and fluorescent in situ hybridization (FISH), to locate the 18S and 5S rRNA genes. Diploid modal count in the three species was 2n = 48 acrocentric elements. Except for pair 24, which exhibited an unmistakable secondary constriction in all three species, it was not possible to classify them as homologous to each other because differences in chromosome size were too slight between adjacent pairs within a size-graded series. Ag-NOR clusters were located in pair 24 in the three species with signal located on the secondary constriction of these chromosomes. C-banding demonstrated that the three species share the same distribution pattern of the constitutive heterochromatin with centromeric heterochromatic blocks in the 23 chromosome pairs and a pericentromeric block in pair 24 which is coincident with the NORs. FISH experiments showed that 18S rDNA sequences were located coincident with the Ag-NOR site in the three species; however, differences in both the number and chromosome distribution of 5S-rDNA cluster were detected among them. Our data suggest that chromosome evolution of Haemulon has been preserved from major changes in the karyotypic macrostructure, whereas microstructural changes have occurred.

Deep barcode divergence in Brazilian freshwater fishes: the case of the Sao Francisco River basin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

DNA barcodes discriminate freshwater fishes from the Paraiba do Sul River Basin, São Paulo, Brazil

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

Fishes of the Atlantic Rainforest of Boraceia: testimonies of the Quaternary fault reactivation within a Neoproterozoic tectonic province in Southeastern Brazil

The upper portion of the Rio Guaratuba, located in the Serra do Mar coastal range of Southeastern Brazil, shows biological and geological evidences of being captured and diverted away from its original course in the direction of the Parana River Basin to become a coastal river due to the Quaternary activity of NW-trending faults. Despite draining directly to the Atlantic Ocean, the upper portion of the Guaratuba still maintains an ichthyofauna that is typical of the adjoining Parana River Basin rather than the characteristic fish fauna of the Brazilian coastal drainages. The fish fauna of the upper Guaratuba is an evident testimony of the tectonic process that allowed the faunal interchange between the upland basins and the coastal drainages that probably has been taking place in Southeastern Brazil throughout the long geological history of the passive Brazilian continental margin.

Reduction of a native fish fauna by alien species: an example from Brazilian freshwater tropical lakes

The consequences of introducing Cichla cf. monoculus Spix & Agassiz, Astronotus ocellatus (Agassiz) and Pygocentrus nattereri Kner into lakes in the River Doce basin, Brazil, on richness, diversity and efficiency of aquatic macrophytes as natural refugia to native fishes was investigated. Samples were taken from lakes with and without alien fishes in areas with and without aquatic macrophytes. The presence of alien fishes reduced richness and diversity of the native fish community. The refugia function, which could be attributed to the clustering of aquatic macrophytes, does not exist in these lakes probably because the alien fishes exploit such habitats for reproduction. Since introductions threaten the native fish diversity of the region, studies on regional dispersion and factors that minimise the spread of alien fishes are needed.

Small-scale fisheries in the middle River Tocantins, Imperatriz (MA), Brazil

The description of the small-scale fisheries in the middle River Tocantins and their dynamics, in a full year cycle, was made out using questionnaires when interviewing fishermen at Imperatriz market. The landed fish exhibited a seasonal pattern related to the hydrological cycle, fishing effort and species diversity. Curimata, Prochilodus nigricans Agassiz, is the most important commercial fish. The fishing gears used in the area are castnets, gillnets, longlines and beach seines. Thirty-six percent of fish landed were caught exclusively by beach seine which mainly targets curimata. Alterations in the physical and biological characteristics of the middle River Tocantins due to the building of the Tucurui dam (2850 km(2) total area) allowed the mapara, Hipophthalmus marginatus Valenciennes, to colonise this area. During the closed season for nets, Siluriformes are the target of the fisheries, caught exclusively by longlining.

Fish community alterations due to pollution and damming in Tiete and Paranapanema rivers (Brazil)

The Tiete River crosses the metropolitan region of São Paulo (Brazil) and receives a large amount of pollution, in contrast to Paranapanema River which runs in a less populated area. In the inferior portions of the basins of these rivers, a series of reservoirs has been built for hydroelectric energy generation which improve the water quality due to the decantation of suspended soils and aeration in the water spills.Twenty-nine sampling sites were established along the two rivers and in each sampling site, two groups of eight gillnets were used with standardized sizes in two seasons: winter (dry season: June-September 1994) and summer (rainy season: December-March 1995). The fishes were measured and weighed.Twenty-five parameters related. to the water were recorded. PCA and cluster analysis helped to identify two groups of sampling sites. The first one corresponds to the rainy season samples, while the second corresponds to the dry season samples, so evidencing strong seasonal environmental variation. However, the dry season group is still divided into polluted and non-polluted sites, showing that during drought there are larger effects of pollutant concentration due to the decreased flow.A total of 415 kg of fish were caught, corresponding to 8324 individuals belonging to 64 different species, in 22 families and four orders of Teleostei. The largest catches occurred in the middle Tiete River. The catches in the reservoirs of the Tiete River, during the rainy season are superior to those of the dry season. on the other hand, sampling sites located in running water presented an inverse pattern with the largest catches in the dry-season. In river Paranapanema, catches are lower than in the Tiete River, except in Rosana Reservoir during the rainy season. Fish diversity was shown to be a good-indicator of environmental stress. In Tiete River an expressive fall in species richness was detected in the polluted stretches, with dominance of one or two species. In the intermediary stretches, the presence of rapids increases the amount of dissolved oxygen, allowing the development of the most abundant and diverse fish community of the river. Fish communities in the reservoirs of the inferior stretch of Tiete River are more diverse. on the other hand, the damming of the superior reaches of Paranapanema River provoked a decrease in diversity. 0 the whole, types of local fish communities detected, showing different compositions and specific abundances, revealed different ecological situations. A discriminant analysis revealed that the parameters of the water influencing the fish community were: dissolved oxygen, conductivity, nitrogen (nitrate, ammoniacal and albuminoid), phosphate, alkalinity, hardness and iron. Copyright (C) 2003 John Wiley Sons, Ltd.

The goatfish Pseudupeneus maculatus and its follower fishes at an oceanic island in the tropical west Atlantic

The influence of a substratum-disturbing forager, the spotted goatfish Pseudupeneus maculatus on the assemblage of its escorting, opportunistic-feeding fishes was examined at Fernando de Noronha Archipelago (tropical west Atlantic). Followers attracted to spotted goatfish foraging singly differed from followers of spotted goatfish foraging in groups in several characteristics. The larger the nuclear fish group, the greater the species richness and number of individuals of followers. Moreover, groups of foraging spotted goatfish attracted herbivores, not recorded for spotted goatfish foraging singly. The size of follower individuals increased with the size and the number of foraging spotted goatfish. The zoobenthivorous habits of the spotted goatfish and its ability to disturb a variety of soft substrata render it an important nuclear fish for several follower species of the reef fish assemblage at Fernando de Noronha. (c) 2006 the Authors Journal compilation (c) 2006 the Fisheries Society of the British Isles.