Thicker filaments of Aphanizomenon gracile are more harmful to Daphnia than thinner Cylindrospermopsis raciborskii.

Lukasz Wejnerowski,Slawek Cerbin,Marcin Krzysztof Dziuba

doi:10.1186/s40555-014-0084-5

Lukasz Wejnerowski, Slawek Cerbin + Show 1 more

Open Access

https://doi.org/10.1186/s40555-014-0084-5

Copy DOI

Journal: Zoological Studies	Publication Date: Jan 3, 2015
Citations: 31	License type: CC BY 4.0

Affiliation: Adam Mickiewicz University in Poznań

Abstract

Filamentous cyanobacteria are known to negatively affect the life history of planktonic herbivores through mechanical interference with filtering apparatus. Here, we hypothesise that not only the length but also thethickness of cyanobacterial filaments is an important factor shaping the life history of Daphnia. To test our hypothesis, we cultured Daphnia magna with non-toxin-producing strains of either Aphanizomenongracile orCylindrospermopsisraciborskii.The former possesses wide filaments, whereas the latter has thinner filaments. The strain of A. gracile has two morphological forms differing in filament widths. The exposure to the thicker A. gracile filaments caused a stronger body-length reduction in females at maturity and a greater decrease in offspring number than exposure to the thinner C. raciborskii filaments. The width of filaments, however, did not significantly affect the length of newborns. The analysis of mixed thick and thin A. gracile filament width distribution revealed that D. magna reduces the number of thinner filaments, while the proportion of thicker ones increases.Also, the effects of cyanobacterial exudates alone were examined to determine whether the changes in D.magna lifehistory were indeed caused directly by the physical presence of morphologically different filaments and not by confounding effects from metabolite exudation. This experiment demonstrated no negative effects of both A. gracile and C. raciborskiiexudates. To our knowledge, this is the first study that demonstrates that the thickness of a cyanobacterial filament might be an important factor in shaping D. magna's life history. At a given biomass, thicker filaments of A. gracile were more detrimental to D. magna than thinner ones of C. raciborskii. There was also a strong interaction between species of the cyanobacterium and filament biomass, where species with thicker filaments and at higher biomass had the strongest negative impact on D. magna life history.

Highlights

Filamentous cyanobacteria are known to negatively affect the life history of planktonic herbivores through mechanical interference with filtering apparatus
Mothers fed A. gracile were much smaller at maturity than those in C. raciborskii treatments, regardless of the biomass (Figure 1b)
Mothers grown at a high biomass of A. gracile (High-Aph) had smaller sizes in comparison to those grown in Low-Cyl and High-Cyl conditions (Tukey’s HSD test: P < 0.0001, P = 0.001, respectively)

Summary

Introduction

Filamentous cyanobacteria are known to negatively affect the life history of planktonic herbivores through mechanical interference with filtering apparatus. Von Elert et al (2003) observed that the growth rate of D. galeata that were fed filaments enriched with sterols was nearly equal to the growth rate of daphnids that were fed Scenedesmus obliquus These contradictory data have been at least partially explained by Gliwicz (1990a), who found that the growth and reproduction of daphnids are strongly suppressed above a critical concentration of filaments. Another supporting example is the study by Soares et al (2009) that demonstrated that only a high biovolume of Cylindrospermopsis raciborskii can reduce the somatic growth of D. magna

Methods

Results

Discussion

Conclusion