Interspecific Differences between D. pulex and D. magna in Tolerance to Cyanobacteria with Protease Inhibitors

Abstract

It is known that cyanobacteria negatively affect herbivores due to their production of toxins such as protease inhibitors. In the present study we investigated potential interspecific differences between two major herbivores, Daphnia magna and Daphnia pulex, in terms of their tolerance to cyanobacteria with protease inhibitors. Seven clones each of D. magna and of D. pulex were isolated from different habitats in Europe and North America. To test for interspecific differences in the daphnids’ tolerance to cyanobacteria, their somatic and population growth rates were determined for each D. magna and D. pulex clone after exposure to varying concentrations of two Microcystis aeruginosa strains. The M. aeruginosa strains NIVA and PCC− contained either chymotrypsin or trypsin inhibitors, but no microcystins. Mean somatic and population growth rates on a diet with 20% NIVA were significantly more reduced in D. pulex than in D. magna. On a diet with 10% PCC−, the population growth of D. pulex was significantly more reduced than that of D. magna. This indicates that D. magna is more tolerant to cyanobacteria with protease inhibitors than D. pulex. The reduction of growth rates was possibly caused by an interference of cyanobacterial inhibitors with proteases in the gut of Daphnia, as many other conceivable factors, which might have been able to explain the reduced growth, could be excluded as causal factors. Protease assays revealed that the sensitivities of chymotrypsins and trypsins to cyanobacterial protease inhibitors did not differ between D. magna and D. pulex. However, D. magna exhibited a 2.3-fold higher specific chymotrypsin activity than D. pulex, which explains the observed higher tolerance to cyanobacterial protease inhibitors of D. magna. The present study suggests that D. magna may control the development of cyanobacterial blooms more efficiently than D. pulex due to differences in their tolerance to cyanobacteria with protease inhibitors.

Microbial players involved in the decline of filamentous and colonial cyanobacterial blooms with a focus on fungal parasitism

“…Smaller zooplankton species (cyclopoid copepods, Bosmina and rotifers) were not impacted by microcystin, which is consistent with a study showing that the smallest species of cladocerans and copepods were not, or only slightly, affected by cyanobacteria (Guo and Xie, ). Moreover, zooplankton communities from eutrophic habitats exhibit physiological adaptations to cyanotoxins, such as detoxification capability (Schwarzenberger et al ., ; Kuster and von Elert, ). For example, following prior exposure to toxic cyanobacteria, Daphnia pulicaria and Daphnia magna strive even at high concentration of microcystins (Sarnelle and Wilson, ; Sarnelle et al ., ).…”

Evaluation of the Ecotoxicological Effects of Microcystis aeruginosa and Cylindrospermopsis raciborskii on Ceriodaphnia dubia Before and After Treatment with Ultrasound

“…The present work did not consider other metabolites produced by cyanobacteria, such as protease inhibitors, and structural variations of the MCs, such as MC-RR, MC-LR, MC-YR, MC-LF, MC-LW (Dörr et al 2010;Bortoli et al 2014;Rastogi et al 2014), STXs, andGTXs (Ferrão-Filho et al 2010;Wiese et al 2010;Carneiro et al 2013). Kuster and Elert (2013) verified a negative effect in the development of D. pulex after exposure to different concentrations of the two lineages of non-MC producing M. aeruginosa, which contained the inhibitor chymotrypsin or trypsin.…”

Phenotypic plasticity in threeDaphniagenotypes in response to predator kairomone: evidence for an involvement of chitin deacetylases

“…Daphnia pulex clone Gerstel was isolated from a pond in northern Germany (Koch et al, 2009). Daphnia pulex clone Münster was originally isolated from a pond in Münster (Gievenbeck), Germany; it was used in a study by Kuster and von Elert (2013).…”