The effects of parasitism on sex allocation of a hermaphroditic acorn barnacle

Sex allocation theory predicts the adaptive allocation of resources to male versus female reproduction in simultaneous hermaphrodites in response to individual characteristics or environmental factors. Because parasites uptake resources from their hosts, their presence could affect the sex allocation of the hosts. We investigated the effects of infestation status and infestation intensity by the rhizocephalan barnacle Boschmaella japonica on reproduction, including sex allocation, of the host intertidal barnacle Chthamalus challengeri. Feeding activity was also examined as a factor related to resource intake. Both male and female reproductive investment decreased with increasing parasite infestation, and the sex allocation of large-infested hosts was more male-biased than that of large uninfested hosts. Moreover, in contrast to the model prediction that male investment does not change under resource limitation, male investment decreased in infested hosts whose resources were taken by pa..., , , # The effects of parasitism on sex allocation of a hermaphroditic acorn barnacle

[https://doi.org/10.5061/dryad.7wm37pw2q](https://doi.org/10.5061/dryad.7wm37pw2q)

## Description of the data and file structure 

Purpose: This study was conducted to reveal the effects of infestation status and infestation intensity by the rhizocephalan barnacle *Boschmaella japonica* on the feeding activities, reproduction (including sex allocation), and mating group size of the host intertidal barnacle *Chthamalus challengeri*.

Methods: We collected five boulders with barnacles attached at mid-tidal level on a rocky shore in Shirahama, Wakayama, Japan, in May 2019. We placed these boulders individually in aquaria and recorded behavior (i.e., number of feeding activities) for 5 min on a digital camera. We later fixed all individuals in 99.5% ethanol and then randomly selected uninfested and infested individuals and measured the following traits. Missing data given as NA.

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