Modular phenotypic plasticity: divergent responses of barnacle penis and feeding leg form to variation in density and wave-exposure

Neufeld, Christopher J.

doi:10.1002/jez.b.21395

Cited by 8 publications

(11 citation statements)

References 43 publications

(64 reference statements)

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“…Although previous work in insects showed that development of genitalia are canalized and show little evidence of plasticity (House and Simmons 2007), experiments in barnacles showed that genitalia can respond in a phenotypically plastic manner to wave action (Neufeld and Palmer 2008), and social environment, in which individuals grow shorter penises when colonies are more dense (Hoch 2009;Neufeld 2011). Similarly, we have found that some species of ducks have phenotypically plastic male genitalia in at least some species in response to their social environment (PLR Brennan, K Zyscowski, and RO Prum, unpubl.…”

Section: Distinguishing Between Mechanisms Of Genital Coevolutionmentioning

confidence: 99%

Mechanisms and Evidence of Genital Coevolution: The Roles of Natural Selection, Mate Choice, and Sexual Conflict

Brennan

Prum

2015

Cold Spring Harb Perspect Biol

114

145

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Genital coevolution between the sexes is expected to be common because of the direct interaction between male and female genitalia during copulation. Here we review the diverse mechanisms of genital coevolution that include natural selection, female mate choice, male -male competition, and how their interactions generate sexual conflict that can lead to sexually antagonistic coevolution. Natural selection on genital morphology will result in size coevolution to allow for copulation to be mechanically possible, even as other features of genitalia may reflect the action of other mechanisms of selection. Genital coevolution is explicitly predicted by at least three mechanisms of genital evolution: lock and key to prevent hybridization, female choice, and sexual conflict. Although some good examples exist in support of each of these mechanisms, more data on quantitative female genital variation and studies of functional morphology during copulation are needed to understand more general patterns. A combination of different approaches is required to continue to advance our understanding of genital coevolution. Knowledge of the ecology and behavior of the studied species combined with functional morphology, quantitative morphological tools, experimental manipulation, and experimental evolution have been provided in the best-studied species, all of which are invertebrates. Therefore, attention to vertebrates in any of these areas is badly needed.

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Section: Distinguishing Between Mechanisms Of Genital Coevolutionmentioning

confidence: 99%

Mechanisms and Evidence of Genital Coevolution: The Roles of Natural Selection, Mate Choice, and Sexual Conflict

Brennan

Prum

2015

Cold Spring Harb Perspect Biol

114

145

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“…With few neighbors, barnacles have shorter feeding legs (Lopez et al. ; Neufeld ) and longer penises (Neufeld ). In this situation, shorter feeding legs may help barnacles cope with the reduced boundary layer, and longer penises may help them reach more distant neighbors.…”

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confidence: 99%

Cuticle and muscle variation underlying phenotypic plasticity in barnacle feeding leg and penis form

Neufeld

Rankine

2012

Invertebrate Biology

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Abstract. Many aspects of barnacle body form are known to be developmentally plastic. Perhaps the most striking examples of such plasticity occur in their feeding legs and unusually long penises, the sizes and shapes of which can change dramatically and adaptively with changes in conspecific density and local water flow conditions. However, whether variation in overall appendage form is mirrored by structural responses in cuticle and muscle is not known. In order to determine how structural variation underlies phenotypic plasticity in barnacle appendages, we examined barnacles occurring at low and high population densities from one wave-protected and one wave-exposed site. We used histological sectioning and fluorescence microscopy of feeding legs and penises to compare cuticle thickness, muscle thickness, and muscle organization, and artificial penis inflation to compare penis extensibility. We observed striking differences in cuticle thickness, muscle thickness, and muscle organization between sites that differed in water velocity, but we found no clear differences associated with variation in conspecific density. Penis extensibility also did not differ consistently between sites. These results are consistent with an adaptive explanation for much of the remarkable and complex variation in barnacle feeding leg and penis morphology among sites that differ in water velocity.Additional key words: Balanus glandula, cirri, wave exposure Rocky shores are among the most extreme and variable hydrodynamic environments on earth. On wave-exposed shores, the maximum velocity of breaking waves can exceed 25 m s À1, while in nearby protected bays, water velocity may be two orders of magnitude slower, never exceeding 10 cm s À1 (Denny 1988;Denny et al. 2003). Adding to this extreme spatial variability, water velocity at any one place can change dramatically as waves break and recede, and it may also vary significantly throughout the year due to the frequency and severity of storm events (Denny 1988). Surprisingly, despite this widespread variation in water velocity over space and time, a diverse assemblage of plants and animals thrives under these extreme conditions.Intertidal barnacles are one particularly successful group that attains large population sizes on rocky shores worldwide. These small sessile crustaceans are filter feeders that use six pairs of modified biramous thoracic legs, called cirri, to capture particles from the surrounding water. In most acorn barnacles, the last three pairs of cirri align to form a fan-like structure that is extended into the water column, while the first three pairs of cirri are used to filter smaller particles and to clean larger particles from the extended cirri (Anderson 1994). Barnacles extend these feeding legs by increasing hydrostatic pressure generated within a closed circulatory system, and retract them with a bundle of striated muscle fibers that runs from the base to the tip of each ramus (Anderson 1994). However, filter feeding poses a challenge to many intertidal barnacles...

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“…; Marchinko ; Marchinko & Palmer ; Chan & Hung ; López et al. , , ; Hoch , , ; Neufeld ; Neufeld & Palmer ; Neufeld & Rankine ; Table ). However, we did note variation in cirrus and penis morphology with respect to tidal height.…”

Section: Discussionmentioning

confidence: 97%

“…; Marchinko ; Marchinko & Palmer ; Chan & Hung ; López et al. , , ; Hoch ; Neufeld ; Neufeld & Rankine ), which show dramatic morphological differences between environments and which had a large proportion of the variance in morphology explained by environmental variables (Table ). The barnacles from this study may lack such strong responses because they use a different feeding strategy and thus respond to the risks of crashing waves differently.…”

Section: Discussionmentioning

confidence: 99%

Effects of tidal height and wave exposure on cirrus and penis morphology of the acorn barnacle Tetraclita stalactifera

Hoch

Reyes

2015

Invertebrate Biology

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Exposure to wave action and other environmental factors can alter the morphology of intertidal barnacles. We tested several hypotheses on the causes of morphological variation in the cirri and penises of the barnacle Tetraclita stalactifera at sites differing in wave exposure, at different heights in the intertidal zone, and at different levels of population density. Unlike many other acorn barnacle species, cirrus and penis characteristics did not correspond to differences in wave exposure or crowding. However, barnacles from higher tidal elevations had thicker cirri and thicker penises than those from lower elevations. Because of reduced time submerged at higher elevations, increased thickness may be a means of compensating for reduced feeding and mating opportunity by allowing for continued feeding and mating attempts during periods of greater wave action. Our observations of differences in cirrus and penis morphology suggest that phenotypic plasticity in penis and cirrus characteristics are adaptations shared by the species T. stalactifera and other acorn barnacles, but that T. stalactifera responds differently to environmental stimuli than do other species.

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Modular phenotypic plasticity: divergent responses of barnacle penis and feeding leg form to variation in density and wave-exposure

Cited by 8 publications

References 43 publications

Mechanisms and Evidence of Genital Coevolution: The Roles of Natural Selection, Mate Choice, and Sexual Conflict

Mechanisms and Evidence of Genital Coevolution: The Roles of Natural Selection, Mate Choice, and Sexual Conflict

Cuticle and muscle variation underlying phenotypic plasticity in barnacle feeding leg and penis form

Effects of tidal height and wave exposure on cirrus and penis morphology of the acorn barnacle Tetraclita stalactifera

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