Among-individual behavioural variation in the ornamental red cherry
shrimp, Neocaridina heteropoda
Abstract
Personality variation, defined as among-individual differences in
behaviour that are repeatable across time and context, is widely
reported across animal taxa. From an evolutionary perspective,
characterising the amount and structure of this variation is useful
since differences among individuals are the raw material for adaptive
behavioural evolution. However, behavioural variation among-individuals
also has implications for more applied areas of evolution and ecology –
from invasion biology, to ecotoxicology, and selective breeding in
captive systems. Here, we investigate the structure of personality
variation in the red cherry shrimp, Neocaridina heteropoda, a popular
ornamental species that is readily kept and bred under lab conditions
and is emerging as a decapod crustacean model across these fields, but
for which basic biological, ecological, and behavioural data is limited.
Using two assays and a repeated measures approach, we quantify
behaviours putatively indicative of shy-bold variation and test for
sexual dimorphism and/or size-dependent behaviours (as predicted by some
state-dependent models of personality). We find moderate to high
behavioural repeatabilities across traits. Although strong
individual-level correlations across behaviours are consistent with a
major personality axis underlying these observed traits, the
multivariate structure of personality variation does not fully match a
priori expectations of a shy-bold axis. This may reflect our ecological
naivety with respect to what really constitutes bolder, more risk prone,
behaviour in this species. We find no evidence for sexual dimorphism and
only weak support size-dependent behaviour. Our study contributes to the
growing literature describing behavioural variation in aquatic
invertebrates. Furthermore, it lays a foundation for further studies
harnessing the potential of this emerging model system. In particular,
this existing behavioural variation could be functionally linked to
life-history traits, invasive success, and serve as target of artificial
selection or bioassays. It thus holds significant promise in applied
research across ecotoxicology, aquaculture, and invasion biology.