PT  - JOURNAL ARTICLE
AU  - Keita Harada
AU  - Katsushi Kagaya
TI  - Customizing material into embodied cap by sponge crab
AID  - 10.1101/330787
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 330787
4099  - http://biorxiv.org/content/early/2019/02/07/330787.short
4100  - http://biorxiv.org/content/early/2019/02/07/330787.full
AB  - Getting camouflaged with environmental material can improve survivability of animals. How animals select and fit some material into their body design remains unclear. To address the question, we examined the cap making behavior of the sponge crab, Lauridromia dehaani that carries a natural sponge as a cap. We analyzed their preference to the size of artificial sponge, the whole area size of the cap that the crabs cut off, and its hole size of the caps that the crabs customize to make it suitable for their body. Three different sizes of artificial sponge were given to the crabs experimentally so that they chosen one sponge among them. We video recorded the process of the cap making behavior, and measured the size of caps. Although a particular fixed behavioral pattern was observed in the cap making behavior, the choice and hole size considerably varied even in a single individual. To fully consider the individuality, we constructed statistical models including hierarchical models. We infered the posterior distributions of the parameters in several models, and built up the predictive distributions of the models by a Bayesian approach. The model selection based on WAIC (Widely-Applicable Information Criterion) and posterior information from the models revealed that large individuals tended to choose large sponges with the variability specific to each individual. Furthermore, the individual-specific tendency was found in the relationship of the carapace width and the cap hole size. These analyses imply that the crabs update the cap making behavior by recalibration, given that they have to molt to become large. These findings might give a new insight into body extending capability of crustaceans.