Predator induction of crests in morphs of the Daphnia carinata King complex

Abstract

Temperature, turbulence, oxygen, and notonectid predators (Anisops calcaratus) were studied experimentally as possible factors influencing crest growth in six different forms of the Daphnia carinata complex. Predators were the most potent influence, inducing crest development in four of the morphs. Temperature had only a secondary effect which may have been indirect. When the notonectids were partitioned off from the Daphnia in the same container, crest development still resulted, suggesting that the stimulus was a water-soluble secretion from the predator. If the notonectids were starved this secretion was either not produced or was ineffective. Experiments showed that predators could induce crest development in adult daphnids that were initially uncrested and that a sustained stimulus from the predator was necessary if crested juvenile Daphnia were to produce crested adults. Under experimental conditions, daphnids with a crest were less susceptible to notonectid predation (mainly because of superior evasion powers) than were those without one. Results of a regression analysis of field data were broadly consistent with experimental results, especially in indicating that predation was a potent factor influencing crest development, and the distribution and abundance of morphs.

Inducible defenses: The relevance of chemical alarm cues in Daphnia

“…We used three Daphnia species for our induction experiments, all well known for inducible morphological defenses. Daphnia cucullata develop high helmets (Agrawal et al 1999, Laforsch andTollrian 2004), Daphnia longicephala produces huge crests (Grant and Bayly 1981), and Daphnia lumholtzi show a remarkable elongation of their head and tail spines (Tollrian 1994). Using D. cucullata as a model system, we also investigated whether the cues are concentration dependent and whether they are species specific.…”

Do Hatchery-Reared Blue Crabs Differ from Wild Crabs, and Does it Matter?

“…For both blue crabs and conch, the hatchery environment may impact shell/carapace shape by failing to provide the necessary cues or stimuli for proper development of predator defenses (Delgado et al, 2002;Davis et al, 2004). Inducible defenses, triggered by the presence of a predator, have long been noted to affect the morphology of prey species, most famously in freshwater Daphnia spp., where presence of a predator stimulates the lengthening of dorsal spines (Grant and Bayly, 1981). However, induction of morphological changes has not been reported in many cultured species, including penaeid shrimp and other portunid crabs.…”

Dopamine is a key regulator in the signalling pathway underlying predator-induced defences inDaphnia

“…[23] (electronic supplementary material, figure S2A) and D. longicephala forms enlarged crests when threatened by the heteropteran backswimmer Notonecta spec. [6] (electronic supplementary material, figure S2B). …”

“…Prominent examples of inducible defences are the various defensive morphological traits observed in the model freshwater crustacean Daphnia. Several Daphnia species display spectacular morphological defences [2,3] including crowns of thorns [4], spines [5], crests [6] and helmets [7 -9]. All these defensive strategies are induced via predator-specific chemical cues known as kairomones.…”