Changes in the activity budget of the fiddler crab Leptuca uruguayensis throughout the reproductive period in temperate estuaries.

Animal reproductive success implies the performance of several behaviours, such as courting, mate searching, copulation, offspring production and care. These behaviours usually have high energetic and ecological costs. Therefore, to maximise their reproductive success, animals should make choices throughout their lives, such as deciding how much energy to invest in different activities, according to their conditions and needs. In temperate estuaries, the fiddler crab L. uruguayensis has a short reproductive period, with two synchronous spawning events. Considering that reproductive behaviours incur high energetic cost to fiddler crabs, we estimated how this species manages its activity budget throughout the reproductive period, to quantify trade-offs between the time spent on reproductive behaviours versus time spent on other activities. By analysing videos of females and males recorded in the field at different moments of the reproductive period, we observed that pre-copulatory behaviours, such as female wandering and male waving were more intense at the beginning of the reproductive period, suggesting that most matings occurred before the first spawning event but not before the second one. The ecological conditions during the breeding season and the individual strategies adopted by males and females mostly determine when and how much time to spend on courtship behaviours, and behavioural plasticity can be expected whenever the conditions change. The strategy used by L. uruguayensis for energy management, females' ability to store male gametes and environmental temperatures might have been the main factors determining the relative time spent in courtship behaviours during the reproductive period.

Female energy dynamics in the southernmost fiddler crab: Mixed breeding strategy in Leptuca uruguayensis.

At the south of its geographical distribution, the fiddler crab Leptuca uruguayensis shows two population spawning events, with more than 65 % of the females being ovigerous. The aim of this study was to assess the energy dynamics in L. uruguayensis females to estimate how they mix the capital and the income breeding strategies in the first and second spawns of the short reproductive season. The relationship between the hepatosomatic (HIS) and gonadosomatic (GSI) indices was used to assess the contribution of the hepatopancreas to ovary maturation, as indicative of the capital breeding strategy, whereas the feeding rate and the energy available in the food resource (sediment) were estimated to assess the importance of energy intake in ovary maturation, as indicative of the income breeding strategy. Before the first spawn, a significant negative relationship between the HSI and GSI (p < 0.001) and an increase of 28.2 % in the feeding rate were recorded. This suggests that the first spawn was mainly supported by energy reserves in the hepatopancreas, indicating that females used mostly the capital breeding strategy. After the first spawn, total lipid content in the hepatopancreas decreased by 33 %. On the days before the second spawn, the relationship between the HSI and GSI showed a negative but not significant (p = 0.125) trend, whereas the feeding rate increased even more. This suggests that the intense feeding activity provided the most important energetic source for ovary re-maturation, indicating that females used mostly the income breeding strategy. Also, in the second spawn, the GSI was 24.1% smaller, a fact that affected female fecundity and weight of the egg clutches, which were respectively 12 % and 11 % lower than in the first spawn. However, the energy supply allocated to each embryo was equivalent in both spawns. This study shows how L. uruguayensis females mixed the capital and income breeding strategies to take advantage of all available resources to produce two spawns in a short reproductive season.

Factors Modulating the Female Reproductive Performance of the Fiddler Crab Leptuca uruguayensis with Short Reproductive Season.

AbstractThis study aimed to evaluate the factors modulating the female reproductive performance of the fiddler crab Leptuca uruguayensis (Nobili, 1901) during the short reproductive season of a temperate population. We proposed two modulating factors: the age of females (young and old) and the periods of the reproductive season (beginning, middle, and end); we then evaluated the fecundity, reproductive output, egg volume, and biochemical composition of eggs. The fecundity of L. uruguayensis was affected by the size of females, a variable related to their age. Although young females showed lower fecundity, the reproductive output was not affected by the age or by the periods of the reproductive season, suggesting a constant reproductive effort, proportional to female size. The egg volume decreased, and carotenoid content increased at the end of the season for both female ages, probably as a consequence of variations in food availability and changes in the breeding strategies during the season. However, the content of protein and lipids in the egg clutches decreased at the end of the season only in old females spawning for the second time in the season. The main differences in the reproductive parameters were recorded between the beginning and the end of the reproductive season, probably because in these periods females exclusively use one of the breeding strategies. Finally, we determined that both factors, that is, female age and the periods of the short reproductive season, can modulate the reproductive performance of L. uruguayensis in temperate estuaries.

Feeding preference of the South American endemic anomuran Aegla platensis (Decapoda, Anomura, Aeglidae).

In order to determine the feeding preference of Aegla platensis in streams and the importance of microorganisms in its detritivore diet, we carried out two experiments designed to evaluate the food preferences of A. platensis (1) among leaves with different levels of microbial colonization and (2) among insect larvae (Chironomidae, Simuliidae, Hydropsychidae) and microbially conditioned leaves. A. platensis preferred animal over plant food items; when only leaves were offered, this aeglid preferred the leaves with higher levels of microorganism conditioning.

The correlation between subordinate fish eye colour and received attacks: a negative social feedback mechanism for the reduction of aggression during the formation of dominance hierarchies.

Eye darkening has been linked to social status in fish. The subordinate's eyes darken, while the eyes of the dominant fish become pale. Although this phenomenon has been described in salmonid fishes and in the African cichlid Nile tilapia Oreochromis niloticus, it is unclear whether eye darkening correlates with a reduction in aggressive behaviour. Thus, we evaluated the link between social status and eye darkening. We evaluated whether the eye colours of subordinate fish correlate with the frequency of received attacks in a neotropical fish, the pearl cichlid Geophagus brasiliensis. We paired pearl cichlids and quantified both the aggressive behaviour and the eye darkening of each fish. As has been described for Nile tilapia and Atlantic salmon, a clear-cut hierarchical relationship formed, where dominance and subordination were associated with pale and dark eye colours, respectively. Initially, eye colour darkening was positively correlated with the frequency of received attacks; however, a negative association occurred following eye darkening, in which the intensity of aggressive interactions decreased. Thus, fish that initially received a high number of attacks signalled subordination more rapidly and intensely (rapid and dramatic eye darkening), thereby inducing a negative social feedback mechanism that led to reduced aggression.

Macroinvertebrados bentônicos como indicadores do impacto ambiental promovido pelos efluentes de áreas orizícolas e pelos de origem urbana/industrial / Benthic macroinvertebrates as indicators of environmental impact promoted by rice crop flood and by urban/industrial effluents

Os macroinvertebrados bentônicos têm sido amplamente utilizados como bioindicadores de qualidade ambiental. O objetivo deste estudo foi comparar a qualidade da água que sai de uma área com cultivo de arroz irrigado (água de drenagem) com a água de irrigação, oriunda do Rio Gravataí, em um ponto na grande Porto Alegre. Este estudo de monitoramento foi conduzido na Estação Experimental do Arroz, pertencente ao Instituto Rio Grandense do Arroz (IRGA), em Cachoeirinha, Rio Grande do Sul (RS), ao longo da safra de 2006/2007. Uma camada de 5cm de solo contendo macroinvertebrados bentônicos foi amostrada, utilizando um Corer (78,54cm²), na fonte de irrigação da lavoura (Rio Gravataí e Canal de Irrigação) e no receptor de seus efluentes (Canal de Drenagem). Além disso, o oxigênio dissolvido (O2) na água foi registrado em cada ponto. O material foi filtrado em uma peneira com malha de 0,5mm, fixado, triado e identificado. A abundância, riqueza, biodiversidade e equitabilidade foram avaliadas e comparadas entre os pontos amostrados. Tais parâmetros ecológicos demonstraram uma comunidade mais estruturada e complexa no canal de drenagem que no canal de irrigação e no Rio Gravataí, indicando que a qualidade ambiental é melhor no ponto que recebe a água que passa pela lavoura que nos pontos de entrada da água. Portanto, a comunidade de macroinvertebrados bentônicos neste estudo sugere que os efluentes produzidos pelas cidades e indústrias, como os presentes na bacia hidrográfica do Rio Gravataí, em especial da Grande Porto Alegre, são mais agressivos aos ambientes aquáticos que os efluentes drenados de uma lavoura manejada de acordo com as recomendações técnicas para a cultura.

The macroinvertebrates have been used as indicators of environmental quality. The objective of this study was to compare the quality of water which drains from the rice flooded crop (drainage water) with the irrigation water, sourced from Gravataí River, near the Porto Alegre City, using benthonic macroinvertebrate community as bioindicator. This study was carryout at the Rice Experiment Station of IRGA, in Cachoeirinha (RS), during the 2006/2007 harvest. A layer of 5cm soil, containing benthonic macroinvertebrate was sampled, using a Corer (78.54cm²), at the irrigation source (Gravatai River and Irrigation Channel) and at the effluents receptor (Drainage Channel). Oxygen dissolved (O2) in water also was registered in each point. The sampled material was filtered in a mesh sieve with f 0.5mm and fixed. The macroinvertebrates were identified and the ecologic parameters as abundance, richness, diversity and evenness were evaluated and compared among the sample points. Such ecologic parameters showed a more complex and structured community at the drainage channel, than at irrigation channel, and at Gravatai River, indicating that the environmental features is better in the point which received the water that pass through the crop, than at the irrigation points. Therefore, the benthic macroinvertebrate community in this study suggests that effects generated by cities and industries of Porto Alegre region are more aggressive to aquatic environments than that promoted by rice crop managed according to the technical guidelines.