Predator‐specific inducible morphological defenses of a water flea against two freshwater predators

Abstract

The expression of inducible morphological defenses in Daphnia in response to a single predator is a well-known phenomenon. However, predator-specific modifications of the same defensive traits as an adaption to different predator regimes is so far only described for Daphnia barbata. It is unknown if this accounts only for this species or if it is a more widespread, general adaptive response in the genus Daphnia. In the present study, we therefore investigated whether a clone of the pond-dwelling species Daphnia similis responds to different predatory invertebrates (Triops cancriformis; Notonecta maculata) with the expression of predator-specific modifications of the same defensive traits. We showed that Triops-exposed individuals express a significantly longer tail-spine, while body width decreased in comparison to control individuals. Additionally, they also expressed inconspicuous defenses, that is, significantly longer spinules on the dorsal ridge. The Notonecta-exposed D. similis showed a significantly longer tail-spine, longer spinules and a larger spinules bearing area on the dorsal ridge than control individuals as well. However, a geometric morphometric analysis of the head shape revealed significant, predator-specific changes. Triopsexposed individuals expressed a flattened head shape with a pronounced dorsal edge, while Notonecta-exposed individuals developed a high and strongly rounded head.Our study describes so far unrecognized inducible defenses of D. similis against two predators in temporary waters. Furthermore, the predator-dependent change in head shape is in concordance with the 'concept of modality', which highlights the qualitative aspect of natural selection caused by predators. K E Y W O R D Shead shape, morphometry, phenotypic plasticity, predator-prey interactions

Thwarting predators? A three-dimensional perspective of morphological alterations in the freshwater crustacean Daphnia

“…Even with the help of scanning electron microscopy, all three dimensions of the alterations can be depicted, but again only distance measurements were performed to describe potentially defensive morphologies, preventing a comprehensive analysis [ 17 ]. Also a PCA based approach with which the outline of shapes was compared is still limited to only 2 dimensions [ 28 ].…”

Pricklier with the proper predator? Predator‐induced small‐scale changes of spinescence in Daphnia

“…While the benefit of the abovementioned predator-induced large-scale defenses of Daphnia has been shown in many cases (Diel et al, 2020), there is a lack of knowledge regarding alterations of small-scale structural changes, such as spinules, in response to predator cues. In some Daphnia, for example, D. barbata and D. similis, morphological changes of spinescence in response to predator cues were already discussed as an inducible morphological defensive trait (Fryer, 1991;Hebert & Grewe, 1985;Herzog & Laforsch, 2013;Ritschar et al, 2020).…”

Coping with antagonistic predation risks: Predator‐dependent unique responses are dominant in Ceriodaphnia cornuta

“…Daphnia galeata prefers deeper habitats under fish predation risk, while inhabits upper water layers under Chaoborus predation risk (Dodson, 1988). In addition, general responses, such as the development of an elongated tail spine, are observed in Daphnia in response to fish, Triops , and Notonecta (Gu, Qin, Lu, et al, 2020a; Ritschar et al, 2020). Consistent with inducible defensive traits, both general and specific responses appear at the molecular level; for instance, in Daphnia magna , actin and tubulin expression is decreased under Chaoborus larvae or fish predation risks (Pijanowska & Kloc, 2004), ribosomal protein and vitellogenin expression is increased under fish predation risk (Effertz et al, 2015), and cuticle protein expression is increased but vitellogenin expression is decreased under Triops predation risk (Otte et al, 2014).…”