overall

Hyastenus sp as well as other species belonging to the same family are well known for masking themselves with algae, sponges and small pieces of other invertebrates that may be available in their habitat (Wicksten, 1993; Stachowicz and Hay, 1999; Stachowicz and hay, 2000). They do this by using their chelipeds to collect and attach these materials on the surface of their bodies. Algae, bryozoans and sponges usually remain alive and growing (Woods and McLay, 1994). This masking behavior may be associated with camouflage, chemical defenses and food storage (Sato and Wada, 2000; Stachowicz and Hay, 1999; Thanh et al., 2003).

Feeding

Species of Hyastenus, as well as other species belonging to Epialtidae, are mostly herbivores (Wicksten, 1993; Stachowicz and Hay, 1999; Stachowicz and hay, 2000).  By attaching algae on their carapace, they may be able to consume this food during stressing conditions, such as absence of food resources or high activity of predators that force them to be hidden instead of searching for food. Thus, the decorating behavior would act as a food storage mechanism (Kilar and Lou, 1986; Woods and McLay, 1994).

Defense system

The behavior of decorating themselves can also be understood as a fundamental method of protection. First, the decoration works as a camouflage, making the animals look similar to the background, which conceals them and helps to avoid predation (Wicksten, 1993; Stachowicz and Hay, 1999; Stachowicz and hay, 2000). Another strategy of defense is selecting specific seaweeds that are unpalatable to other omnivores due to the presence of chemicals and secondary metabolites ( Stachowicz and Hay, 1999; Stachowicz and hay, 2000). Both camouflage and chemical defenses act as protection for these small animals against predators (Stachowicz and Hay, 1999; Thanh et al., 2003).