Abstract
The aim of this study was to examine whether the presence of non-toxic filamentous cyanobacteria can cause egg abortion in Daphnia. To test this hypothesis, we fed females of Daphnia pulicaria with the green alga Scenedesmus obliquus from birth until eggs were laid in the brood chamber. Gravid Daphnia females were then exposed to media containing either S. obliquus or filaments of a non-toxic strain of the cyanobacterium Cylindrospermopsis raciborskii. The females were then observed throughout the whole period of egg development and all events of egg abortion were recorded. Experiments were conducted at three temperatures: 16, 20, and 24°C. In the presence of cyanobacteria, the proportion of aborted eggs ranged from 2.6 to 12.9%, compared with 0–1.8% in the green algae treatment. The number of aborted eggs, but not the number of egg-aborting females, tended to increase at higher temperature. Our data indicate that interference by non-toxic cyanobacterial filaments may affect the reproductive success of Daphnia, not only through suppression of their fecundity, but also via an increase in the number of aborted eggs. Therefore, the reproductive rate of Daphnia based on the fecundity of females may be overestimated in situations where filamentous cyanobacteria are present.
Highlights
Cyanobacteria are an inadequate food source for zooplankton (Lampert, 1987; deBernardi & Giussani, 1990)
The aim of this study was to examine whether the presence of non-toxic filaments of cyanobacteria may lead to egg abortion in Daphnia, and if this can be associated solely with the poor capacity of Daphnia to handle cyanobacterial filaments
Our results indicate that the presence of non-toxic filamentous cyanobacteria can cause abortion of eggs
Summary
Cyanobacteria are an inadequate food source for zooplankton (Lampert, 1987; deBernardi & Giussani, 1990). Toxic cyanobacteria may affect Daphnia reproduction by suppressing its fecundity and by increasing the number of aborted eggs or causing egg/ embryo malformation and/or decomposition (Reinikainen et al, 1995; Claska & Gilbert, 1998; Gustafsson et al, 2005; Dao et al, 2010). Threlkeld (1979) found that egg degeneration occurred when the presence of cyanobacteria was combined with higher temperature
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