Neckteeth formation in <i>Daphnia pulex</i> as an example of continuous phenotypic plasticity: morphological effects of <i>Chaoborus</i> kairomone concentration and their quantification

Tollrian, Ralph

doi:10.1093/plankt/15.11.1309

Cited by 223 publications

(225 citation statements)

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“…Some control juveniles in the first instar, and very few in the second instar, developed neckteeth, although they were reared in control medium (Fig. 2E), which is in agreement with Tollrian (1993). Juveniles reared in kairomone medium produced neckteeth from the first to the fourth instar stages (Fig.…”

Section: Licl Treatmentsupporting

confidence: 82%

Identification of the Precise Kairomone-sensitive Period and Histological Characterization of Necktooth Formation in Predator-induced Polyphenism inDaphnia pulex

2013

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Many organisms have the ability to alter their development in the presence of predators, leading to predator-induced defenses that reduce vulnerability to predation. In the water flea Daphnia pulex, small protuberances called 'neckteeth' form in the dorsal neck region in response to kairomone(s) released by predatory phantom midges (Chaoborus larvae). Although previous studies suggested that kairomone sensitivity begins when chemoreceptors begin to function during embryogenesis, the exact critical period was unknown to date. In this study, we investigated the period of kairomone sensitivity and the process of necktooth formation in D. pulex through extensive treatments with pulses of kairomone(s). First, we described the time course of embryogenesis, which we suggest should be used as the standard in future studies. We found the kairomone-sensitive period to be relatively short, extending from embryonic stage 4 to postembryonic first instar. We observed cell proliferation and changes in cell structure in response to the kairomone treatment, and propose a model for necktooth formation. Preliminary LiCl treatment suggests the Wnt signaling pathway involved in crest formation as a candidate for the molecular mechanism underlying this process. Our study provides basic insight toward understanding the mechanisms underlying adaptive polyphenism in D. pulex.

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Section: Licl Treatmentsupporting

confidence: 82%

Identification of the Precise Kairomone-sensitive Period and Histological Characterization of Necktooth Formation in Predator-induced Polyphenism inDaphnia pulex

2013

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“…The most striking adaptation is 'neckteeth', comprising a neck pedestal and a series of spikes that arise during juvenile (second and third) instars as a result of maternal and embryonic exposure to the kairomone (e.g. [16,18]). The neckteeth, similar to many defences induced in rotifer predation systems (for review, see [19]), confers a survival benefit to juveniles, which are the preferred prey of Chaoborus [20,21].…”

Section: Methodsmentioning

confidence: 99%

Phenotypic convergence along a gradient of predation risk

et al. 2010

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A long-standing question in ecology is whether phenotypic plasticity, rather than selection per se, is responsible for phenotypic variation among populations. Plasticity can increase or decrease variation, but most previous studies have been limited to single populations, single traits and a small number of environments assessed using univariate reaction norms. Here, examining two genetically distinct populations of Daphnia pulex with different predation histories, we quantified predator-induced plasticity among 11 traits along a fine-scale gradient of predation risk by a predator (Chaoborus) common to both populations. We test the hypothesis that plasticity can be responsible for convergence in phenotypes among different populations by experimentally characterizing multivariate reaction norms with phenotypic trajectory analysis (PTA). Univariate analyses showed that all genotypes increased age and size at maturity, and invested in defensive spikes (neckteeth), but failed to quantitatively describe whole-organism response. In contrast, PTA quantified and qualified the phenotypic strategy the organism mobilized against the selection pressure. We demonstrate, at the whole-organism level, that the two populations occupy different areas of phenotypic space in the absence of predation but converge in phenotypic space as predation threat increases.

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“…Many cladoceran species form predator-induced defenses (reviewed in Tollrian and Dodson 1999). Because no detectable effect of chemical stimuli of crushed conspecifics could be demonstrated in Daphnia pulex (Walls and Ketola 1989;Parejko and Dodson 1990) and Daphnia galeata mendotae (Stirling 1995), most researchers working on inducible defenses in daphnids focused on predator kairomones as cues (e.g., Krueger and Dodson 1981;Hanazato 1991;Laforsch and Tollrian 2004).…”

mentioning

confidence: 99%

Inducible defenses: The relevance of chemical alarm cues in Daphnia

Laforsch¹,

Beccara²,

Tollrian³

2006

Limnol. Oceanogr.

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106

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Many aquatic organisms use chemical cues to recognize predators and to activate inducible defenses. In zooplankton, most of these cues are thought to be kairomones released by specific predators. However, in several other organisms, e.g., fish and amphibians, alarm signals from conspecifics also provide reliable cues. We tested whether alarm substances also act as chemical cues in Daphnia and assessed their relevance compared with predator kairomones. Water-borne cues from macerated conspecifics altered morphology in all Daphnia species tested (Daphnia cucullata, Daphnia longicephala, and Daphnia lumholtzi). However, kairomones released by feeding predators had distinctly stronger effects. In D. cucullata, we tested for the relevance of predator diet and found that the increase in relative helmet length was most pronounced when the predator was fed with conspecifics instead of heterospecifics. Cross-species experiments with alarm substances also revealed that D. cucullata is more sensitive to info-chemicals from macerated conspecifics than to chemical cues from D. magna. Unspecific alarm cues together with cues released by predators consuming prey may form a blend of chemicals that indicates predation risk and activates inducible defenses in nature.

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Neckteeth formation in Daphnia pulex as an example of continuous phenotypic plasticity: morphological effects of Chaoborus kairomone concentration and their quantification

Cited by 223 publications

References 0 publications

Identification of the Precise Kairomone-sensitive Period and Histological Characterization of Necktooth Formation in Predator-induced Polyphenism inDaphnia pulex

Identification of the Precise Kairomone-sensitive Period and Histological Characterization of Necktooth Formation in Predator-induced Polyphenism inDaphnia pulex

Phenotypic convergence along a gradient of predation risk

Inducible defenses: The relevance of chemical alarm cues in Daphnia

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