5α-cyprinol sulfate, a bile salt from fish, induces diel vertical migration in Daphnia

Abstract

Prey are under selection to minimize predation losses. In aquatic environments, many prey use chemical cues released by predators, which initiate predator avoidance. A prominent example of behavioral predator-avoidance constitutes diel vertical migration (DVM) in the freshwater microcrustacean Daphnia spp., which is induced by chemical cues (kairomones) released by planktivorous fish. In a bioassay-guided approach using liquid chromatography and mass spectrometry, we identified the kairomone from fish incubation water as 5α-cyprinol sulfate inducing DVM in Daphnia at picomolar concentrations. The role of 5α-cyprinol sulfate in lipid digestion in fish explains why from an evolutionary perspective fish has not stopped releasing 5α-cyprinol sulfate despite the disadvantages for the releaser. The identification of the DVM-inducing kairomone enables investigating its spatial and temporal distribution and the underlying molecular mechanism of its perception. Furthermore, it allows to test if fish-mediated inducible defenses in other aquatic invertebrates are triggered by the same compound.

Knowing the Enemy: Inducible Defences in Freshwater Zooplankton

“…In general, there are some suspected substances for kairomones that are commonly used for intraas well as interspecific information transfer. Invertebrates often release peptides or peptide-based substances [14,225,226], while vertebrates seem to release bile salts that induce a defence in prey species [227,228]. Aliphatic sulphates released from Daphnia have been found to induce defences in algae [229].…”

“…Recently, Hahn et al [227,234] identified and described a fish factor that induces diel vertical migration in Daphnia as 5'α-cyprinolsulfate, a bile salt excreted by carp (Cyprinus carpio) and roach (Rutilus rutilus) during digestion. They also stressed that this bile salt may be a general kairomone in cyprinid fish, although it also seems to exist in smaller concentrations in rainbow trout (Oncorhynchus mykiss).…”

“…They also stressed that this bile salt may be a general kairomone in cyprinid fish, although it also seems to exist in smaller concentrations in rainbow trout (Oncorhynchus mykiss). This implies that there are different bile salts or substances with a similar structure that may act as kairomones and derive from other fish orders [227,234]. Bile salts are a common by-product of the digestion process in all vertebrates, thus explaining why predators are not able to control production and excretion of these substances [228].…”

Estimation of the propensity for sexual selection in a cyclical parthenogen

“…However, little is known about mating in Daphnia. Unlike 78 copepods (Lonsdale et al 1998), and even though Daphnia respond behaviorally and phenotypically 79 to several chemical cues such as fish kairomones (Hahn et al 2019), there is no evidence for sex 80 pheromones that males use to find their mate (Crease and Hebert 1983;Winsor and Innes 2002). Yet, 81 male swimming behavior seems to be optimized to find an appropriate mate (Brewer 1998) and 82 mating is not random as males capture sexually active females (i.e.…”

Harmful alga trades off growth and toxicity in response to cues from dead phytoplankton

“…Both the copepod Acartia hudsonica and the cladoceran Daphnia magna recognize diurnal predatory fishes and avoid them through diel vertical migration. A. hudsonica employs visual and mechanical cues (Bollens et al 1994), whereas D. magna utilizes chemical cues (Loose and Dawidowicz 1994;Hahn et al 2019). Other Daphnia spp.…”