DOI: 10.5061/dryad.7wm37pw2q
title: Data from: The effects of parasitism on sex allocation of a hermaphroditic acorn barnacle

description: 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 parasites. This
 reduction in male investment could be explained by changes in mating group
 size since infested hosts have shorter penises and consequently can access
 fewer mating partners.
description: # 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. ### Files and variables **Name of columns** 1\)         ID: host barnacles ID (individuals have same number across the datasets) 2\)         Infestation status (1 = infested, 0 = uninfested) 3\)         Incubation status (1 = brooding, 0 = nonbrooding) 4\)         Externae: number of parasites 5\)         Area of all externae: area of all parasites on same host [mm<sup>2</sup>]  6\)         Area per externa [mm<sup>2</sup>] 7\)         Testis and seminal vesicles: volume of testis and seminal vesicles [mm<sup>3</sup>] 8\)         Feeding activities: number of cirral beats as barnacles feed by moving their feeding legs, (called cirri) up and down 9\)         Body size: dry wight of operculum (shell of scutum and tergum) [mm<sup>2</sup>] 10\)      Penis length [mm] 11\)      Penis diameter [mm] 12\)      Eggs: number of eggs 13\)      Major axis of an egg [mm] 14\)      Minor axis of an egg [mm] 15\)      Volume of each egg capsule: calculated as an ellipsoid: ⁴⁄₃π × major axis × ½ minor axis × ½ minor axis × ½ [mm<sup>3</sup>] 16\)      Female investments: volume of all eggs calculated as number of eggs × volume of each egg capsule [mm<sup>3</sup>] 17\)      *k* times longer penis length: host penis length (PL) in uninfested condition multiplied by each elongation rate (*k* = 1.5, 1.82, and 2.0), calculated as PL × *k* [mm] 18\)      *k* MGS: 1 + the number of conspecifics reachable by the length of each elongated penis (*k* = 1.5, 1.82, and 2.0) 19\)      *k* times longer penis length of infested condition: host penis length in infested condition (PL − 0.386) multiplied by each elongation rate (*k* = 1.5, 1.82, and 2.0), calculated as (PL − 0.386) × *k* [mm] 20\)      *k* MGS of infested condition: 1 + the number of conspecifics reachable by the length of each elongated penis (*k* = 1.5, 1.82, and 2.0) 21\)      Difference in *k* MGS: number of uninfested MGS − number of infested MGS for each elongation rate (*k* = 1.5, 1.82, and 2.0) 22\)      Picture-ID: The ID of the image used to measure the host penis length and diameter, and the area per externa and the total area of all externae on the same host. 23\)      Video-ID: The ID of the video used to observe and measure feeding activities.  **Information of each dataset file** 1\)         Main data.csv: contains host ID, infestation status and intensity (number and total area of parasites), host body size, feeding activities, male investments (penis length and diameter, volume of testis and seminal vesicles) and female investments (incubation status, number of eggs, major axis and minor axis of an egg, and volume of an egg and all eggs). 2\)         Area of per externa.csv: contains host ID, infestation status, total area of parasites, area per parasite, and host body size. 3\)         Mating group size.csv: contains host ID, host penis length of uninfested and infested conditions at each elongation rate (natural, 1.5, 1.82, and 2.0), mating group size at each elongation rate, difference in mating group size between uninfested and infested conditions and host traits (infestation status and intensity [number of and total area of parasites], host body size, feeding activities, male investments [penis length and diameter, volume of testis and seminal vesicles] and female investments [incubation status, volume of all eggs, number of eggs, major axis and minor axis of an egg, and volume of an egg]).  **Information for the R-scripts (R v. 4.1.2)** 1\)         Analysis.main data.R: contains analysis of the infestation effects on the host body size, feeding activities, male and female investments, sex allocation, and the area of all externae using the dataset file Main data.csv. 2\)         Analysis.Area of per externa.R: contains analysis of the area per externa using the dataset file of Area of per externa.csv. 3\)         Analysis.Mating group size.R: contains analysis of the reduction of mating group size 4\)         Hypothesized fitness gain curves: contains writing instructions for Fig. 1. **Raw data (JPG and MOV files)** The names of the JPG and MOV files correspond to the information in the “Picture-ID” and “Video-ID” columns, respectively, of the Excel file “Dryad_JEB_tamechika_data2.xlsx”. To identify the host barnacles in the MOV files, please refer to the PDF file “Behavior-identification.pdf”. The host barnacle IDs in the PDF file “Behavior-identification.pdf” correspond to the information in the “ID” column of the Excel file “Dryad_JEB_tamechika_data2.xlsx” and the CSV files (i.e., “Main data.csv”, “Area of per externa.csv”, and “Mating group size.csv”).