One Kairomone and Multiple Effects in Daphnia Species—5α-Cyprinol Sulfate Induces Morphological Defenses in the Invasive Species Daphnia lumholtzi

Abstract

Recently, the first chemical cues, which induce defenses in freshwater zooplankton of the genus Daphnia have been identified. Still it is unknown how general these so-called kairomones are and if they are perceived by and thereby benefitting invasive species. We here report the chemical identity of the fish-derived chemical signal that induces morphological defensive structures in the invasive species Daphnia lumholtzi. We used bioassay-guided isolation (LC-MS) of incubation water of fish and identified the bile salt 5α-cyprinol sulfate (5α-CPS) as the kairomone. We confirmed this finding by bioassays, in which D. lumholtzi was exposed to purified 5α-CPS sulfate from fish bile and showed that 10 pM 5α-CPS induces significantly elongated helmets and spines in relation to body length. These results identify on one hand another Daphnia species besides Daphnia magna, which is responding to this particular fish-borne kairomone, and on the other hand they reveal another defense that the kairomone induces besides diel vertical migration (DVM). Taken together a high evolutionary conservancy of the molecular mechanism behind inducible defenses in Daphnia spp. against fish can be deduced. It is reasonable to expect that 5α-CPS is involved in further predator—prey communication between Daphnia and fish, which may be of special ecological relevance with regard to invasive species as D. lumholtzi.

Fish predation risk alters the microbiota of Daphnia in the process of inducing its life‐history defence traits

“…In the present study, the presence of predation risk decreased the α diversity (mainly Shannon index) of D. magna gut microbiota with increasing Daphnia instar. The stress responses of D. magna were similar to those in vertebrates, which are primarily regulated by stress-released hormones (Fischer et al, 2014;Hahn & von Elert, 2022). In vertebrates, primary hormone responses trigger endocrine responses, which are associated with gut-microbiota composition and diversity (Qi et al, 2021;Vijay-Kumar et al, 2010;Zhang et al, 2015).…”

Epidermal oxysterols function as alarm substances in zebrafish

“…Interestingly, 5CS has been shown to act as a kairomone that induces diel vertical migration and the morphological defenses of Daphnia to avoid predators. 49 , 50 Likewise, chondroitin sulfates derived from the tissues of sharks, sturgeon, and C. elegans all induced weak fear responses in zebrafish. 13 5DS has the same bile salt backbone, albeit with an unprecedented adduct of sulfated methylene on C-24.…”

Novel Epidermal Oxysterols Function as Alarm Substances in Zebrafish

“…5CS is the dominant bile alcohol sulfate of cypriniform fish (including zebrafish) 47 , and is likely released from injured individuals of this taxonomic group, which is known to use alarm substances. Interestingly, 5CS has been shown to act as a kairomone that induces diel vertical migration and the morphological defenses of Daphnia to avoid predators 48,49 . Likewise, chondroitin sulfates derived from tissues of sharks, sturgeon, and C. elegans all induced weak fear responses in zebrafish 13 .…”