Seasonal changes in the somatic indices of the freshwater silverside, Odontesthes bonariensis (Teleostei, Atheriniformes) from a Neotropical shallow lake (Argentina).

The study object was an Odontesthes bonariensis (Valenciennes, 1835) population of a characteristically shallow lake from the pampasic region. Over one year, zooplankton and fish samples were collected monthly. As a function of time and gender, several indices were investigated (relative weight, mesentery fat index, gonadosomatic index, hepatosomatic index and somatic index) and were related to zooplanktonic community dynamics, the main energy food source for this species. The results indicate that the seasonal information contained in the weight compartments is most important in mesentery fat, gonads and liver. The zooplankton availability modulates reserves (fat) behaviour and physiologic activity (liver), determining spawn intensity. Thus, in spring spawns, with higher zooplankton availability, mature individuals of the population, males and females, transfer energy from the food to the gonads. In autumn spawns, they use the fat reserves for gonad ripening.

Seasonal changes in the somatic indices of the freshwater silverside, Odontesthes bonariensis (Teleostei, Atheriniformes) from a Neotropical shallow lake (Argentina) / Mudanças sazonais nos índices somáticos do Odontesthes bonariensis (Teleostei, Atheriniformes) em uma lagoa da região Neotropical (Argentina)

The study object was an Odontesthes bonariensis (Valenciennes, 1835) population of a characteristically shallow lake from the pampasic region. Over one year, zooplankton and fish samples were collected monthly. As a function of time and gender, several indices were investigated (relative weight, mesentery fat index, gonadosomatic index, hepatosomatic index and somatic index) and were related to zooplanktonic community dynamics, the main energy food source for this species. The results indicate that the seasonal information contained in the weight compartments is most important in mesentery fat, gonads and liver. The zooplankton availability modulates reserves (fat) behaviour and physiologic activity (liver), determining spawn intensity. Thus, in spring spawns, with higher zooplankton availability, mature individuals of the population, males and females, transfer energy from the food to the gonads. In autumn spawns, they use the fat reserves for gonad ripening.

O objeto do estudo foi a população Odontesthes bonariensis (Valenciennes, 1835) de uma lagoa característica da região dos pampas argentinos. Durante um ano, recolheram-se mostras mensais da comunidade zooplanctônica e da população de peixe-rei. Pesquisaram-se vários índices (peso relativo e os índices de gordura mesentérica, gônado-somático, hepato-somático e somático) em função do tempo e do sexo, relacionando-os com a dinâmica de comunidade de zooplâncton, a principal fonte de energia para esta espécie. Os resultados indicam que a informação sazonal contida nos compartimentos de peso é muito importante na gordura mesentérica, nas gônadas e no fígado. A disponibilidade do zooplâncton modula as reservas (gordura), o comportamento e a atividade fisiológica (fígado), determinando a intensidade da desova. Assim, na desova de primavera, com disponibilidade mais elevada do zooplâncton, a maioria dos indivíduos maduros da população, machos e fêmeas, transferem energia do alimento às gônadas. No outono os peixes usariam principalmente as reservas de gordura para a maduração gonadal.

Prevalence of enteroparasites in a residence for children in the Córdoba Province, Argentina.

A study of the prevalence of enteroparasites in a population belonging to a substitute home that gives shelter to orphaned and homeless children was done using conventional methods of analysis. This home is located in Córdoba Province, Argentina, and has the following characteristics: It has nine houses located inside the main plot of ground, that shelter 139 individuals, and 25 houses outside this plot distributed randomly in Unquillo city and that shelter 257 individuals. The overall parasitic infection, pathogen and commensal organisms included, yielded 84.8% and the prevalence of the most important parasites was: Enterobius vermicularis (43.4%), Giardia lamblia (23.0%), Ascaris lumbricoides (13.1%), Entamoeba coli (45.5%), Blastocystis hominis (44.4%) and Endolimax nana (34.6%). We also analyzed the population dividing it according to the residence place (inside or outside the plot), age and sex of the individuals. In reference to the location of the patients, A. lumbricoides and E. coli showed significant prevalence in the individuals living inside the plot (p < 0.001 and p < 0.005, respectively) and of B. hominis in those living outside the main plot (p < 0.005). Results indicated a greater parasitism level in the outside residents (61.5%, p < 0.001). When the individuals were studied according to sex, no significant difference was observed, except for E. vermicularis that showed greater prevalence in the male sex (p < 0.04). When the individuals were grouped according to age ranges, a greater prevalence in individuals from 5 to 14 years was noticed (p < 0.01). In this study is also included an analysis of the multiparasitism level that comprises the whole population.