RESUMO
Aeglids are freshwater anomurans that are endemic from southern South America. While their population biology at the species-level is relatively well understood, intraspecific variation within populations has been poorly investigated. Our goal was to investigate the population biology of Aegla platensis Schmitt, 1942 from the Uruguay River Basin, and compare our data with data from other populations. We estimated biometric data, sex ratio, population density and size-class frequencies, and frequencies of ovigerous females and juveniles, from the austral spring of 2007 until autumn 2008. Sexual dimorphism was present in adults, with males being larger than females. Furthermore, males and females were significantly larger than previously recorded for the species. The overall sex ratio was 1.33:1 (male:female), and population density ranged from 1.8 (spring) to 3.83 ind.m-² (winter). Data from this population differ from published information about A. platensis in almost all parameters quantified except for the reproductive period, which happens in the coldest months, and a population structure with two distinct cohorts. Difference among studies, however, may be in part due to methodological differences and should be further investigated in order to determine their cause. In addition to different methodologies, they may result from ecological plasticity or from the fact that the different populations actually correspond to more than one species.(AU)
Assuntos
Animais , Anomuros/classificação , Anomuros/fisiologia , Distribuição Animal , Biodiversidade , Caracteres Sexuais , BrasilRESUMO
Aeglids are freshwater anomurans that are endemic from southern South America. While their population biology at the species-level is relatively well understood, intraspecific variation within populations has been poorly investigated. Our goal was to investigate the population biology of Aegla platensis Schmitt, 1942 from the Uruguay River Basin, and compare our data with data from other populations. We estimated biometric data, sex ratio, population density and size-class frequencies, and frequencies of ovigerous females and juveniles, from the austral spring of 2007 until autumn 2008. Sexual dimorphism was present in adults, with males being larger than females. Furthermore, males and females were significantly larger than previously recorded for the species. The overall sex ratio was 1.33:1 (male:female), and population density ranged from 1.8 (spring) to 3.83 ind.m-² (winter). Data from this population differ from published information about A. platensis in almost all parameters quantified except for the reproductive period, which happens in the coldest months, and a population structure with two distinct cohorts. Difference among studies, however, may be in part due to methodological differences and should be further investigated in order to determine their cause. In addition to different methodologies, they may result from ecological plasticity or from the fact that the different populations actually correspond to more than one species.
Assuntos
Animais , Anomuros/classificação , Anomuros/fisiologia , Biodiversidade , Caracteres Sexuais , Distribuição Animal , BrasilRESUMO
This study evaluated oxygen consumption (MO(2)) and diel activity in Aegla longirostri, Trichodactylus panoplus and Parastacus brasiliensis (three species of freshwater decapods that occur in sympatry), under two different conditions of O(2) availability, limited and constant; and searched for the existence of a relationship between these two variables. The Kruskal-Wallis test showed that in all the species, MO(2) was higher under constant O(2) availability; T. panoplus and P. brasiliensis showed an oxygen-dependent pattern, while A. longirostri showed higher MO(2) values and less variation in the values between the treatments, indicating a higher and more oxygen-independent metabolism. P. brasiliensis was more active in constant O(2). A. longirostri was more active in limited O(2) and did not show a clear diel activity in any case, showing behavioral changes when in unfavorable conditions. The Spearman's rank correlation analysis did not indicate any relationship between MO(2) and activity. These results indicate a higher metabolism in A. longirostri. The less demanding metabolisms of P. brasiliensis and T. panoplus allow these species to occupy environments that are unavailable to A. longirostri due to differences in dissolved-oxygen concentrations.