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Interspecific hybridization in sympatric species of Daphnia inhabiting lakes in northeastern Poland

Brzeziński T., Fronk J., Trzcińska-Danielewicz J., Dawidowicz P.

Oceanological and Hydrobiological Studies

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2012

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Vol. 41, No. 2

1-6

EN

Populations of three sympatric species (Daphnia cucullata, Daphnia galeata, and Daphnia hyalina (Daphnia longispina complex)) inhabiting three lakes in northeastern Poland (Roś, Mikołajskie, Wigry) were checked for interspecific hybrids. Hybrid Daphnia coexisting with parental individuals were detected in each of the investigated lakes. Several classes of hybrids (F1, F2, backcrosses), including D. cucullata×galeata×hyalina individuals, have been detected. Hybrids constituted a substantial (13%-38%) part of the total abundance of individuals of the D. longispina complex. Deficiency of heterozygotes (hybrids) detected may indicate the existence of barriers for gene flow between the sympatric Daphnia taxa.

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Phenotypic plasticity within Daphnia longispina complex : differences between parental and hybrid clones

Pijanowska J., Bernatowicz P., Fronk J.

Polish Journal of Ecology

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2007

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Vol. 55, nr 4

761-769

EN

The mechanism that enables the coexistence of apparently very similar species is fundamental in understanding the diversity of natural communities. The ranges of reactions of the three Daphnia clones in the presence of toxic compounds and fish kairomones were studied in laboratory. The ranges were based on differences in body length, spine length and fecundity (number of eggs in a brood chamber) during first three reproductions. The ranges of reactions of the three clones differed dramatically. The range of D. galeata and D. hyalina hardly overlapped, while that of a D. galeata x hyalina hybrid clone was significantly broader than the ranges of either parental species. The observed diversity of ranges of reactions probably enables the coexistence of closely related species in the variable environment of natural lakes.

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The fate of the ephippia - Daphnia dispersal in time and space

Pietrzak Barbara, Slusarczyk Miroslaw

Polish Journal of Ecology

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2006

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Vol. 54, nr 4

709-714

EN

When conditions deteriorate, freshwater cladocerans from the genus Daphnia switch to production of diapausing eggs encased in chitinous shells called ephippia. Ephippia may serve for temporal escape and recolonisation of the habitat or for geographical dispersal and colonization of other habitats. While dormancy and dispersal of ephippia have been well studied, initial factors determining the fate of the ephippia have remained unknown. We first consider the fate of an ephippium that sinks to the bottom of the water body, where it enriches the egg bank present in the sediments. We then discuss the potential and evidence for dispersal of ephippia, which is probably facilitated by their flotation on the water surface. Finally, we concentrate on the moment of the release of the ephippium showing a likely mechanism that determines its further fate - temporal or spatial dispersal - and we demonstrate it to be accomplished through maternal behaviour.

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Adaptive changes in morphology of Daphnia filter appendages in response to food stress

Bednarska Anna

Polish Journal of Ecology

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2006

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Vol. 54, nr 4

663-668

EN

Morphological adaptations of Daphnia filtration apparatus in response to unsuitable food conditions are examined and set against earlier published data. To maximize food gathering under limiting food conditions, Daphnia can respond morphologically by plastic changes in the size and structure of its filter apparatus. Under low food quantity and/or poor quality, the area of Daphnia filter screen increases and the mesh size decreases.