Divergent developmental patterns of induced morphological defenses in rotifers and Daphnia: Ecological and evolutionary context

Abstract

Induced morphological defenses commonly develop in some loricate rotifers as greatly increased spine development and in many species of the cladoceran genus Daphnia as an alteration in the shape and size of its head, producing helmets, crests, and neck spines. This restructuring of the shape of these animals during development, which reduces their vulnerability to a variety of planktonic predators, involves a series of developmental challenges and potential evolutionary constraints for each specific type of defense. In this review, we examine these challenges and the divergent developmental patterns that evolved in rotifers and Daphnia in response to the particular forms of predation pressure they face in their lake and pond environments. These patterns involve differences in the sensitivity of various developmental stages to predator kairomones, the timing of when the defense is present during postembryonic development, the ability to reverse the induced defense if the predator disappears from the community, and the effect of water temperature on the induction process. The type of developmental pattern associated with each induced defense appears to have been shaped by natural selection to effectively protect the animal, at minimal cost, from the specific kind of predation pressure to which it is commonly subjected.

Ecology of predator-induced morphological defense traits in Daphnia longispina (Cladocera, Arthropoda)

“…Despite recent progress in investigating the Chaoborus capture process, the mechanism of the predator-defensive role of the neckteeth is still not fully understood (Weiss et al 2018a;Kruppert et al 2019), and although being inducible, the costs for developing neckteeth may be modest (Tollrian and Dodson 1999). However, neckteeth development is often accompanied by other, seemingly more costly, traits such as an elongated tail spine, increased pedestal size, and increased carapace thickness, strength, or stiffness Riessen et al 2012;Rabus et al 2013;Kruppert et al 2017;Riessen and Gilbert 2019). Nevertheless, the similarity in neckteeth and pedestal expression in D. pulex and D. longispina as observed in this study (Appendix 3) suggests that these induced morphological defense traits are evolutionarily very efficient in protecting against predation from Chaoborus larvae.…”

“…Neckteeth formation is most studied within the D. pulex complex (see above), but is also described for other species or species complexes (e.g. Boronat and Miracle 1997;Lüning-Krizan 1997;Sell 2000;Benzie 2005;Kotov et al 2006;Riessen and Trevett-Smith 2009;Juračka et al 2010Juračka et al , 2011Riessen and Gilbert 2019). Neckteeth (single, multiple, and rosettes) have also been reported in both pond and lake populations of the D. longispina complex (Juračka et al 2011), covering formerly named D. rosea (Sell 2000(Sell , 2006, which is now assigned to the D. longispina group (Petrusek et al 2008).…”

“…Various species of Daphnia possess diverse anti-predator responses. For example, Daphnia exposed to fish predation commonly exhibit vertical migration behavior or changes in life history traits; while Daphnia exposed to invertebrate predators exhibit species-specific responses such as conspicuous helmets, spines, crests or neckteeth (Brehm 1909;Tollrian and Dodson 1999;Lass and Spaak 2003;Weiss et al 2012;Riessen and Gilbert 2019).…”

“…Neckteeth, also referred to as neck spines or Nackenzähne, are small extensions from the dorsal head margin. They are induced typically in early developmental stages as a specific defense against the predatory larvae of the "phantom midge", Chaoborus spp., in several Daphnia species (Juračka et al 2011;Riessen and Gilbert 2019). In particular, D. pulex has been used as a model system to study the causes, effects, and consequences of neckteeth induction (e.g.…”

“…Neckteeth in Daphnia spp. occur in various forms and shapes, from single teeth to multiple teeth in rows or a rosette ("crowns", Juračka et al 2011), and are often accompanied by other defensive traits like elongated tail spines, increased body width, or more hidden defenses such as increased carapace thickness, strength, and stiffness Riessen et al 2012;Rabus et al 2013;Kruppert et al 2017;Riessen and Gilbert 2019). The induction of these traits in multiple species and species complexes within the genus Daphnia poses several interesting questions related to ecological-evolutionary interactions.…”