DOI: 10.5061/dryad.ksn02v7gm
title: A sensory investment syndrome hypothesis: Personality and predictability are linked to sensory capacity in the hermit crab Pagurus bernhardus

description: Correlated phenotypic traits (i.e., syndromes) may manifest as
 associations between different behavioural types or between behavioural
 and non-behavioural phenotypes. While research on syndromes is extensive,
 correlations involving behavioural type and sensory morphology have yet to
 be investigated. Sensation is essential in decision-making and should be
 correlated with behavioural phenotypes involved in risk response,
 including boldness. We investigated correlations between boldness and
 sensory capacity in Pagurus bernhardus hermit crabs, taking repeat
 measures of startle response durations to assess hermit crab personality
 and predictability. The correlation between startle response and the
 sensillar density (i.e., number of sensilla per unit surface area) of both
 chelipeds was assessed using Bayesian-fitted double hierarchical general
 linear models (DHGLMs). Negative correlations between these two traits
 support the existence of a syndrome linking sensory capacity and
 behavioural type, hereafter distinguished as a ‘sensory investment
 syndrome’. Increasing sensillar density on the major claw also
 corresponded with reduced within-individual variation, or predictability,
 in startle response duration. By demonstrating a correlation between a
 sensory and a behavioural phenotype, our results demonstrate the
 importance of considering sensory morphology and performance in
 behavioural ecology and show how sensory investment syndromes may be
 linked to support behavioural strategies that help to maximise fitness.
description: # A sensory investment syndrome hypothesis: Personality and predictability
 are linked to sensory capacity in the hermit crab *Pagurus bernhardus*
 Dataset DOI: [10.5061/dryad.ksn02v7gm](10.5061/dryad.ksn02v7gm) ##
 Description of the data and file structure The following data files were
 used to investigate the potential for a correlation between a behavioural
 phenotype (boldness) and sensory morphological phenotype (sensillar
 density or the number of sensilla per unit chelar surface area) in the
 common hermit crab *Pagurus bernhardus*. Morphological data were collected
 by scanning electron microscopy and image analysis. Behavioural phenotype
 (animal personality and predictability) data were collected by collecting
 repeat measures (n=11) of the startle response durations for individual
 hermit crabs*.* Data were analysed using Bayesian-fitted DHGLMs. ### Files
 and variables #### File: SensoryStartle.R **Description:** R code used to
 analyse data from the attached .csv file  #### File: SensoryStartle.csv
 **Description:** Datasheet with all variables analysed in this research
 study #### File: fit\_MJC\_file.rds **Description:** The output for the
 brms() model examining the effect of major chelar (MJC) sensillar density
 on hermit crab startle response duration (SRD) #### File:
 fit\_MNC\_file.rds **Description:** The output for the brms() model
 examining the effect of minor chelar (MNC) sensillar density on hermit
 crab startle response duration (SRD) #### File: fit\_mass\_file.rds
 **Description:** The output for the brms() model examining the effect of
 crab mass on hermit crab startle response duration (SRD) ##### Variables *
 crab_ID: Unique ID assigned to each focal *P. bernhardus* hermit crab *
 site: Field collection site (Mount Batten, Plymouth, Devon, UK, and
 Hananfore, Looe, Cornwall, UK) * hcsx: Hermit crab sex (female vs. male) *
 hcmss: Hermit crab mass (g) * shmss: Shell mass (g) provided to each focal
 crab * SRD_no: The startle response number (0 = initial through 10 =
 final) for each hermit crab * SRD: The startle response duration (s) for
 each hermit crab * includeRPT: Include (1) or exclude (0) from the
 analysis; reasons for exclusion are elaborated in the Methods section of
 the paper, but include death and autotomy. * MJC_SEM: Was a scanning
 electron micrograph of the major cheliped generated for this individual
 hermit crab (1 = Yes, 0 = No) * single sensilla: The number of single
 sensilla identified on the major cheliped's dorsal surface. * dublet
 sensilla: The number of double sensilla identified on the major
 cheliped's dorsal surface. * triplet sensilla: The number of triple
 sensilla identified on the major cheliped's dorsal surface. *
 sensillar bundle: The number of bundled sensilla identified on the major
 cheliped's dorsal surface. * TOTAL_SENSILLA: The total number of
 sensilla identified on the major cheliped's dorsal surface. * MJC
 chelar area: The surface area of the major cheliped * density total: The
 total sensillar density of the major cheliped (total sensilla / chelar
 area) * MNC_SEM: Was a scanning electron micrograph of the minor cheliped
 generated for this individual hermit crab (1 = Yes, 0 = No) *
 MNC_SINGLE: The number of single sensilla identified on the minor
 cheliped's dorsal surface. * MNC_DOUBLET: The number of double
 sensilla identified on the minor cheliped's dorsal surface. *
 MNC_TRIPLET: The number of triple sensilla identified on the minor
 cheliped's dorsal surface. * MNC_BUNDLED: The number of bundled
 sensilla identified on the minor cheliped's dorsal surface. *
 MNC_TOTAL: The total number of sensilla identified on the minor
 cheliped's dorsal surface. * MNC chelar area: The surface area of the
 minor cheliped * MNC_SENS_DENSITY: The total sensillar density of the
 minor cheliped (total sensilla / chelar area) * premoult_death: Did the
 hermit crab die before moulting (necessary for SEM methodology) but after
 all 11 startle responses had been collected? (1 = Yes, 0 = No) *
 fit_MJC_file: The output for the brms() model examining the effect of
 major chelar (MJC) sensillar density on hermit crab startle response
 duration (SRD) * fit_MNC_file: The output for the brms() model examining
 the effect of minor chelar (MNC) sensillar density on hermit crab startle
 response duration (SRD) * fit_mass_file: The output for the brms() model
 examining the effect of crab mass on hermit crab startle response duration
 (SRD) ## Code/software All data were analysed in R (version 4.4.1) with
 RStudio (version 2024.09.0+375). Figures were generated with ggplot2
 (version 3.5.1). Linear mixed effects models were analysed using lme4
 (version 1.1-35.5) and lmerTest (version 3.1-3). The DHGLM was fitted
 using a Bayesian approach with the ‘brms’ package (version 2.22.0). ##
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