Population dynamics of Heterocypris incongruens (Ramdohr, 1808) (Ostracoda, Cyprididae) in relation to diet type (algae and organic waste) and amount of food

Abstract

Population growth patterns of the ostracod, Heterocypris incongruens have been studied using the green alga, Scenedesmus acutus or organic waste from a water treatment plant as food, and using dry weight equivalents of 5.8, 11.6, and 23.2 μg ml −1 for 50 days. H. incongruens, in our study, reproduced only parthenogenetically. The colour of the eggs and the carapace valves differed depending on the type of food. Populations cultured on the algae appeared bright orangecoloured, while those on organic waste were pale yellow. Regardless type and concentration of food, H. incongruens had a long lag phase of about 3 weeks, after which the exponential phase began that continued for the next 20 to 30 days. In treatments containing an algal diet, the density of H. incongruens increased with the increase of food level from 5.8 to 11.6 μg ml −1 . However, a further increase in food density did not result in a higher peak of abundance. In the treatments containing organic waste, population density was higher (about 1.6 ind. ml −1 ) at 5.8 and 11.6 μg ml −1 , but it decreased to half this density with a further increase in the amount of food (23.2 μg ml −1 ). The rate of population increase (r) of H. incongruens ranged from 0.03 to 0.07 per day, depending on food type and concentration. RESUMENSe estudiaron los patrones de crecimiento poblacional del ostrácodo Heterocypris incongruens utilizando el alga verde Scenedesmus acutus o desechos orgánicos de una planta de tratamiento de aguas residuales como alimento bajo diferentes densidades (como los equivalentes de peso seco de 5,8, 11,6 y 23,2 μg ml −1 ) durante 50 días. H. incongruens en nuestro estudio sólo se reproduce partenogenéticamente. El color de los huevos y las valvas de los ostrácodos difiere dependiendo del tipo de alimentos. Los cultivados en alga presentaron un color naranja brillante, mientras que los cultivados con residuos orgánicos mostraron un color amarillo pálido. Independientemente del tipo de alimento y la concentración, H. incongruens presentó una larga fase de adaptación de aproximadamente 3 semanas. Una vez que la fase exponencial se inició, esta tuvo una duración de 20 a 30 días. En los tratamientos de la dieta que contienen algas, la densidad de H. incongruens aumentó cuando se elevó la concentración de alimento de 5,8 a 11,6 μg ml −1 . Sin embargo, al incrementar la densidad en los alimentos no se reflejó en las abundancias máximas de la población de H. incongruens. Dentro de los tratamientos que contienen residuos orgánicos, la densidad de población fue mayor (alrededor de 1,6 ind. ml −1 ) a 5,8 y 11,6 μg ml −1 , pero se redujo a la mitad con mayor aumento de la densidad de los alimentos (23,2 μg ml −1 ). La tasa de aumento de la población (r) variaron entre 0,03 a 0,07 por día, dependiendo del tipo de alimentos y la concentración.

Demographic responses of Heterocypris incongruens (Ostracoda) related to stress factors of competition, predation and food

“…different species of the same or different taxa occur in space and time; Brachionus calyciflorus and B. havanaensis are frequently reported together in eutrophic tropical systems (alva-martínez et al, 2009). With regard to this study, Heterocypris incongruens (ostracoda) and Simocephalus vetulus (Cladocera) often co-occur in temporary bodies of water, shallow ponds and fountains (Juárez-Franco et al, 2009;Fernández et al, 2012). in degraded environments, positive interactions such as facilitation, could be an additional cause for organisms to remain in such conditions.…”

“…on the simultaneous consumption of cyanobacteria by the zooplankton, works undertaken have focused on the competition between species, and it is worth noting that the organisms utilized belonged to the same taxa; these studies generally conclude that one species excludes the other due to competition (alva-martinez et al, 2009) because they share similar characteristics in their life cycles and utilize their food resource in the same form. in this study, organisms from different taxa were used, H. incongruens (ostracoda) and S. vetulus (Cladocera), because both species frequently co-occur in temporary water bodies, shallow water, ponds and fountains (Juárez-Franco et al, 2009;Fernández et al, 2012). Both organisms have similar feeding habits, but different life cycles.…”