Dawn Vaughn's Publications

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Dawn's publications
university of washington, department of biology, friday harbor laboratories

Vaughn, D. 2009. Predator-induced larval cloning in the sand dollar Dendraster excentricus: Might mothers matter? The Biological Bulletin 217:103-114 (PDF) (cover) Vaughn, D. and R. R. Strathmann. 2008. Predators induce cloning in echinoderm larvae. *Science* (14 March 2008) 319:1503 (PDF) Vaughn, D. 2007 Predator-induced morphological defenses in marine zooplankton: A larval case study. *Ecology* 88:1030-1039 (PDF) McDonald, K. A. and D. Vaughn. in press. An abrupt change in food environment induces cloning in Dendraster excentricus plutei. The Biological Bulletin Vaughn, D. in review. Why run and hide when you can divide? Evidence for cloning and reduced size as an adaptive inducible defense Vaughn, D. and J. D. Allen. in prep. The peril of the plankton. Integrative and Comparative Biology
ABSTRACTS OF SELECTED PUBLICATIONS
A crab larva (the predator) and a larval snail (the prey) lying near its dorsal spine. The snail larva is of the periwinkle Littorina scutulata. (photo by D. Vaughn)	Predator-induced morphological defenses in marine zooplankton: A larval case study (Ecology 88:1030-1039) *Abstract.* While there are numerous reports of predator-induced morphological defenses for freshwater zooplankton, freshwater larvae, and benthic marine animals, a literature search revealed no reports of predator-induced morphological defenses for marine zooplankton. Rarity of predator-induced morphological defenses in marine zooplankton would imply a difference in predation risks, whereas the presence of such plasticity in defenses would imply that risks are modified by developmental responses. This study reports a predator-induced change in defenses and vulnerability of a marine planktonic larva. Specifically, when reared in the presence of zoea larvae of Cancer spp., veliger larvae of the intertidal snail Littorina scutulata developed significantly smaller shell apertures and rounder shells than did cohort veligers reared in the absence of predator cues. Pair-wise predation trials demonstrated that veligers reared with caged zoeas throughout development had greater survival than predator-naive veligers during short-term exposure to zoeas. The results indicate that some marine larvae develop predator-induced morphological defenses. If so, predators on marine larvae and other zooplankton are not so diverse as to preclude plasticity in development of defensive structures. This result introduces a range of testable hypotheses on developmental plasticity that reduces vulnerability of planktonic larvae and other marine zooplankton to predators.

Predators induce cloning in echinoderm larvae (Science 319:1503)

Abstract. While larval cloning is well-documented in echinoderms, identified stimuli for cloning are limited to those associated with conditions favorable for growth and reproduction. Our research demonstrates that larvae also clone in response to cues from predators. Predator-induced clones were smaller than uncloned larvae, suggesting an advantage against visual predators. Our results offer a new ecological context for asexual reproduction: rapid size reduction as a defense. Although asexual propagation (cloning) is a widespread reproductive strategy of plants and animals, we know of no other report of cloning at any life stage in response to chemical stimuli indicating risk from predators.

Sand dollar larvae in the process of cloning.
Scale = 100 um. (photo by D. Vaughn)

The cover of The Biological Bulletin, issue 217 (2), features the 30th plate from Ernst Haeckel’s Kunstformen der Natur (Artforms of nature) (1904). Here Haeckel depicts echinoids (sea urchins and sand dollars) at various stages of development – planktonic larva, metamorphosed juvenile and benthic adult.

Predator-induced larval cloning in the sand dollar Dendraster excentricus: Might Mothers Matter? (The Biological Bulletin 217 (2))

Abstract. Predator-induced cloning in echinoid larvae, with reduced size as a consequence of cloning, is a dramatic modification of development and a novel response to risks associated with prolonged planktonic development. Recent laboratory studies of pluteus larvae (plutei) of Dendraster excentricus demonstrate that exposure to stimuli from predators (i.e., fish mucus) induces cloning, reduced size and decreased vulnerability to some planktivorous predators. However the timing and incidence of cloning and size reduction of unrelated conspecific plutei differed across experiments. A variable cloning response suggests effects of such factors as cue quality, egg provisioning, maternal experience, and genetic background, indicating that the potential advantages of cloning as an adaptive response to predators are not available to all larvae. This study tested the hypothesis that cloning in D. excentricus plutei is maternally-influenced. Plutei from three half-sibling larval families (different mothers, same father) were exposed to fish mucus for nine days during early development. Cloning was inferred in a percentage of plutei from each family, however the rate and success of cloning differed significantly among the larval half-siblings. Unexpectedly, all mucus-treated plutei were smaller and developmentally delayed when compared to all plutei reared in the absence of a mucus stimulus. Thus, while the results from this study support the hypothesis of an influence of mothers on cloning of larval offspring, reduced larval size was a uniform response to fish mucus and did not indicate an effect of mothers. Hypotheses of the developmental effects of fish mucus on larval size with or without successful cloning are discussed.

When Predaceous Foes Meet Their Match: Predator-Induced Defenses in Marine Invertebrate Larvae (Dissertation)

Abstract. Many organisms inhabit unpredictable environments. The difficult adaptive challenges facing these organisms are met in a variety of ways. For some, environmental uncertainty favors flexibility in phenotypic traits allowing fine-tuning of the phenotype to better match present conditions. Inducible defenses are phenotypically plastic traits that alter the interactions between predators and prey. Induced defensive responses are well-documented in varied habitats to a diversity of predators and throughout ontogeny and include alterations in behavior, life histories and morphologies.

Despite the pervasiveness of predator-induced defenses exhibited by diverse plants and animals in both terrestrial and aquatic environments, there are few reports of predator-induced defensive morphologies and shifts in life histories in marine zooplankton, including the planktonic larvae of marine organisms. Rarity of these types of responses in marine zooplankton would imply a difference in predation risk compared to those experienced by freshwater zooplankton and benthic marine adults, whereas the presence of such plasticity in defenses would imply that risks are modified by developmental responses.

In this dissertation I report predator-induced morphological change and life history shifts in the planktonic larvae of diverse marine organisms, representing three clades of Metazoans. Specifically, stimuli from predators induced a more protective shell morphology in larval gastropods (Lophotrochozoans), asexual reproduction (cloning) and reduced size in larval sand dollars (Deuterostomes), and accelerated development in larval crabs (Ecdysozoans). Taken together, these data demonstrate that plasticity of defensive responses occurs in phylogenetically distinct marine zooplankton and suggest that developmental responses of marine zooplankton to predators may be common.

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