Estratégia reprodutiva de um rivulídeo não anual em um banhado perene

Atlantirivulus riograndensis (Costa & Lanés, 2009) is a fish registered to the basin of Patos lagoon and the adjacent coastal plains in southern states of Rio Grande do Sul and Santa Catarina, Brazil, found in shallow water courses with that have large quantities of aquatic vegetation and forest edges. The objective of this study was to investigate the reproductive strategy and tactics of this species including the sex ratio, the length at first maturity, spawning type, fecundity and the possible associations among reproduction and abiotic factors. Sampling of specimens occurred in perennial wetlands within the Banhado dos Pachecos wildlife refuge, in the city of Viamão, state of Rio Grande do Sul, Brazil, which is a conservation unit that belongs to an area of environmental protection in the Pampa Biome. The capture of 30 A. riograndensis specimens per month occurred from January to December of 2012. A total of 188 females and 172 males were captured and the total sex ratio was 1:1 in the sampled population. Sexual maturity of the species occurs after 13.59 and 11.92 mm (SL) for females and males, respectively. Both a multiple spawning and a long reproductive period (since August to March) were confirmed by the presence of post-ovulatory follicles that were observed through histological analysis and the values of the gonadosomatic index in females considered spawning capable. The average absolute fecundity of the species is of 19.33 (± 6.18) vitellogenic oocytes in mature ovaries. No significant relationship was found between mean GSI and the abiotic data. Reproductive tactics presented by A. riograndensis indicate a species with an opportunistic reproductive strategy, following the pattern of other species of the Rivulidae family.Estratégia reprodutiva de um rivulídeo não anual em um banhado perene. Atlantirivulus riograndensis (Costa & Lanés, 2009) é uma espécie de peixe registrada para a bacia da laguna dos Patos e planícies costeiras adjacentes, nos estados do Rio Grande do Sul e sul de Santa Catarina, Brasil, encontrada em corpos d’água rasos, com grande quantidade de vegetação aquática e em bordas de mata. O objetivo deste estudo consistiu em investigar a estratégia e as táticas reprodutivas desta espécie, incluindo a proporção sexual, o comprimento de primeira maturação, o tipo de desova, a fecundidade e possíveis associações entre a reprodução e fatores abióticos. As amostragens de exemplares da espécie ocorreram em um banhado perene no Refúgio da Vida Silvestre Banhado dos Pachecos, município de Viamão, estado do Rio Grande do Sul, Brasil, que constitui uma área de proteção ambiental em uma unidade de conservação no bioma Pampa. A captura de trinta indivíduos de A. riograndensis por mês, ocorreu de janeiro a dezembro de 2012. Foram amostradas 188 fêmeas e 172 machos e a proporção sexual total foi de 1:1 na população amostrada. A maturação sexual da espécie ocorre a partir de 13,59 e 11,92 mm (CP) para fêmeas e machos, respectivamente. As análises histológicas demonstraram uma desova parcelada com a presença de folículos pós-ovulatórios em fêmeas consideradas aptas a desovar e um período reprodutivo longo, de agosto até março, confirmado pelos valores do índice gonadossomático. A fecundidade média absoluta da espécie foi de 19.33 (± 6.18) oócitos vitelogênicos em ovários maduros. Não houve relação significativa entre as médias de IGS e os dados abióticos. As táticas reprodutivas apresentadas por A. riograndensis indicam uma espécie com estratégia reprodutiva oportunista, seguindo o padrão das demais espécies da família Rivulidade

Reproduction and feeding of the electric fish Brachyhypopomus gauderio (Gymnotiformes: Hypopomidae) and the discussion of a life history pattern for gymnotiforms from high latitudes

The reproductive biology and feeding habits of the electric fish Brachyhypopomus gauderio were studied. The species has seasonal reproductive behavior, with breeding occurring during the Southern Hemisphere spring and summer, and having a positive relation with the photoperiod variation. Brachyhypopomus gauderio was defined as a fractional spawner, with low relative fecundity and high first maturation size. Sexual dimorphism was registered, males undergoing hypertrophy of the distal portion of caudal filament. The results on reproductive biology herein obtained are in agreement with data concerning gymnotiforms from Southern Brazil and Uruguay, pointing to an ecological pattern for the species from high latitudes, differing from species with tropical distribution. According to the analysis of the food items, B. gauderio feed mainly on autochthonous insects, likewise the other gymnotiforms previously investigated, leading to conclude that there is no variation on the diet of the species of the order related to climatic conditions or even to habitat of occurrence

Diet and body shape among populations of Bryconamericus iheringii (Otophysi: Characidae) across the Campos Sulinos ecosystem

Alterations in natural landscapes, mainly caused by anthropic pressures, have been threatening the world’s biomes, including aquatic environments and its biota. This study describes the diet of Bryconamericus iheringii, and how its body shape relates to environmental variables in populations of 22 streams. A wide array of food items were found, mainly composed of allochthonous plants (50.5%) and autochthonous invertebrates (25.2%). Even though food items remained almost the same, the predominant food group significantly differed among streams, mainly in relation to environmental characteristics. There was variation in body shape primarily associated with body depth and length of the pre-dorsal region; however, these differences did not correspond with streams. PLS-CA analyses indicated that environmental characteristics, such as substrate type, percentage of marginal vegetation have some influence over food items availability but not on body shape. This may be because B. iheringii is a non-specialist species capable of prey switching based on availability due to an intermediate body shape suited for generalist feeding habits.Alterações em paisagens naturais, principalmente as causadas por pressão antrópica, tem ameaçado os biomas mundiais, incluindo ambientes aquáticos e sua biota. Este estudo descreve a dieta de B. iheringii e como seu formato corporal se relaciona com variáveis ambientais, em populações de 22 riachos. Uma grande variedade de itens alimentares foi encontrada, principalmente compostos por plantas alóctones (50,5%) e invertebrados autóctones (25,2%). Ainda que os itens alimentares tenham permanecido quase os mesmos, o grupo alimentar predominante diferiu significativamente entre riachos, principalmente devido a características ambientais. Ocorreu variação no formato corporal principalmente associado com profundidade do corpo e comprimento da região pré-dorsal; entretanto, tais diferenças não corresponderam aos agrupamentos por riacho. A análise PLS-CA indicou que as características ambientais, tais como tipo de substrato, porcentagem de vegetação marginal exercem alguma influência sobre a disponibilidade dos itens alimentares, mas não sobre o formato corporal. Isso pode ocorrer por B. iheringii ser uma espécie não especialista com capacidade de mudar suas presas de acordo a com disponibilidade das mesmas, isto, devido ao seu formato corporal intermediário adequado a hábitos generalistas

Diet and body shape among populations of Bryconamericus iheringii (Otophysi: Characidae) across the Campos Sulinos ecosystem

Alterations in natural landscapes, mainly caused by anthropic pressures, have been threatening the world’s biomes, including aquatic environments and its biota. This study describes the diet of Bryconamericus iheringii, and how its body shape relates to environmental variables in populations of 22 streams. A wide array of food items were found, mainly composed of allochthonous plants (50.5%) and autochthonous invertebrates (25.2%). Even though food items remained almost the same, the predominant food group significantly differed among streams, mainly in relation to environmental characteristics. There was variation in body shape primarily associated with body depth and length of the pre-dorsal region; however, these differences did not correspond with streams. PLS-CA analyses indicated that environmental characteristics, such as substrate type, percentage of marginal vegetation have some influence over food items availability but not on body shape. This may be because B. iheringii is a non-specialist species capable of prey switching based on availability due to an intermediate body shape suited for generalist feeding habits.Alterações em paisagens naturais, principalmente as causadas por pressão antrópica, tem ameaçado os biomas mundiais, incluindo ambientes aquáticos e sua biota. Este estudo descreve a dieta de B. iheringii e como seu formato corporal se relaciona com variáveis ambientais, em populações de 22 riachos. Uma grande variedade de itens alimentares foi encontrada, principalmente compostos por plantas alóctones (50,5%) e invertebrados autóctones (25,2%). Ainda que os itens alimentares tenham permanecido quase os mesmos, o grupo alimentar predominante diferiu significativamente entre riachos, principalmente devido a características ambientais. Ocorreu variação no formato corporal principalmente associado com profundidade do corpo e comprimento da região pré-dorsal; entretanto, tais diferenças não corresponderam aos agrupamentos por riacho. A análise PLS-CA indicou que as características ambientais, tais como tipo de substrato, porcentagem de vegetação marginal exercem alguma influência sobre a disponibilidade dos itens alimentares, mas não sobre o formato corporal. Isso pode ocorrer por B. iheringii ser uma espécie não especialista com capacidade de mudar suas presas de acordo a com disponibilidade das mesmas, isto, devido ao seu formato corporal intermediário adequado a hábitos generalistas

Seasonality and interspecific competition shape individual niche variation in co‐occurring tetra fish in Neotropical streams

The drivers of intraspecific niche variation and its effects on species interactions are still unclear, especially in species-rich Neotropical environments. Here, we investigated how ecological opportunity and interspecific competition affect the degree of individual trophic specialization and the population niche breadth in tetra fish. We studied the four ecologically similar species (Psalidodon aff. gymnodontus, P. aff. paranae, P. bifasciatus, and Bryconamericus ikaa) in subtropical headwater streams (three sites with two co-occurring species and three sites with only one species). We sampled fish in two contrasting seasons (winter/dry and summer/wet) and quantified their trophic niches using gut content analysis. Psalidodon bifasciatus was the only species distributed over all the sampled streams. We observed seasonal differences in population trophic niche breadth of P. bifasciatus just when this species co-occurred with P. aff. gymnodontus. These findings confirm the complex nature of the effects of interspecific competition, depending, for instance, on the identity of the competitor. The degree of individual specialization of P. bifasciatus was higher in the winter, and it was not influenced by the presence of another species. Conversely, the other two Psalidodon species studied presented greater individual specialization in the summer, when fish consumed a higher proportion of allochthonous items (terrestrial insects and seeds), and there were no effects only for B. ikaa. Herein, our results suggest that seasonality in food-resource availability is a major driver of niche variation and it has the potential to play an important role in how these similar tetra species interact and coexist.info:eu-repo/semantics/publishedVersio

Reproduction in Hemiancistrus punctulatus Cardoso & Malabarba, 1999 (Siluriformes: Loricariidae): a lotic neotropical fish faced with habitat change due to reservoirs

Aspectos da biologia reprodutiva de Hemiancistrus punctulatus foram abordados, sendo realizadas amostragens de dezembro de 2000 a fevereiro de 2002, período antecedente à instalação de uma hidrelétrica no rio Forqueta, sistema da Laguna dos Patos. O período reprodutivo, determinado através da variação do Índice gonadossomático (IGS) e da frequência relativa dos estádios de maturação gonadal, ocorreu entre os meses de outubro e fevereiro. A fecundidade média absoluta encontrada foi de 130,33 ovócitos e a fecundidade relativa média foi de 2,75 ovócitos por grama de peso total da fêmea. A distribuição da frequência absoluta dos diâmetros dos ovócitos vitelinados revela que esta espécie possui desova total. A proporção sexual observada na população estudada foi de 1:1, com a tendência dos machos apresentarem maiores tamanhos que as fêmeas.Palavras-chave: Peixes, sistema hidrográfico da Laguna dos Patos, Ancistrini.Characteristics of the reproductive biology of the fish Hemiancistrus punctulatus were examined. Samples were collected December 2000 to February 2002, prior to the installation of a hydroelectric dam on the Forqueta River, in the Laguna dos Patos hydrographic system, in southern Brazil. The reproductive period was October to February, determined by the gonadosomatic index (GSI) and the relative frequency of gonad maturity stages. Average absolute fecundity was 130.33 oocytes and average relative fecundity was 2.75 oocytes g-1 of total female weight. This species lays all eggs simultaneously as shown bythe absolute diameter frequency distribution of the vitellinate oocytes. The sex ratio was 1:1 with males tending to be larger than females.Key words: Fish, Laguna dos Patos hydrographic system, Ancistrini

Evidence of niche partitioning under ontogenetic influences among three morphologically similar siluriformes in small subtropical streams

Ontogenetic influences in patterns of niche breadth and feeding overlap were investigated in three species of Siluriformes (Heptapterus sp., Rhamdia quelen and Trichomycterus poikilos) aiming at understanding the species coexistence. Samplings were conducted bimonthly by electrofishing technique from June/2012 to June/2013 in ten streams of the northwestern state of Rio Grande do Sul, Brazil. The stomach contents of 1,948 individuals were analyzed by volumetric method, with 59 food items identified. In general Heptapterus sp. consumed a high proportion of Aegla sp., terrestrial plant remains and Megaloptera; R. quelen consumed fish, and Oligochaeta, followed by Aegla sp.; while the diet of T. poikilos was based on Simuliidae, Ephemeroptera and Trichoptera. Specie segregation was observed in the NMDS. Through PERMANOVA analysis feeding differences among species, and between a combination of species plus size classes were observed. IndVal showed which items were indicators of these differences. Niche breadth values were high for all species. The niche breadth values were low only for the larger size of R. quelen and Heptapterus sp. while T. poikilos values were more similar. Overall the species were a low feeding overlap values. The higher frequency of high feeding overlap was observed for interaction between Heptapterus sp. and T. poikilos. The null model confirmed the niche partitioning between the species. The higher frequency of high and intermediate feeding overlap values were reported to smaller size classes. The null model showed resource sharing between the species/size class. Therefore, overall species showed a resource partitioning because of the use of occasional items. However, these species share resources mainly in the early ontogenetic stages until the emphasized change of morphological characteristics leading to trophic niche expansion and the apparent segregation observed