Grooming behaviors and fouling of the spider crab Libinia dubia (Decapoda: Epialtidae)

Abstract

Body fouling has been reduced by grooming behaviors. In decapods, grooming has been focused on gills, sensory structures, and jointed appendages. In this study, grooming behaviors of the spider crab, Libinia dubia H. Milne-Edwards, 1834, were examined; this brachyuran crab decorates and camouflages body regions by attaching materials onto hooked setae. The relationship between grooming and these camouflaged body regions was unknown. Six observational and experimental studies examined the grooming frequency, duration of grooming behaviors, body regions groomed, variance of these behaviors in the presence of another individual, and the efficiency of these grooming behaviors at removing gill fouling. Sensory and respiratory structures were groomed most frequently and for the longest duration, not body regions with decorations and hooked setae. Crabs in isolation exhibited the highest grooming time budget (5.22%). The presence of another conspecific decreased the grooming time budget (0.67%), and primary actions (e.g., fighting, displaying, mating) became priority. Ablation of a gill-grooming appendage did not impact fouling on gills. Grooming as a secondary action was supported. Reasons for not grooming body regions with hooked setae were discussed. Spider crabs had a lower time budget for grooming compared to most decapods, but similar to another brachyuran.

Setal descriptions, locations, and abundances: Their impacts on decorating behaviors in the spider crab Libinia (Crustacea: Epialtidae)

“…All setal types observed in this study are described in Libinia and in body regions decorated in spider crabs (Berke & Woodin, 2009; Hultgren & Stachowicz, 2011; Szebeni & Hartnoll, 2005; Wortham & Jedlicka, 2019). While Szebeni and Hartnoll (2005) estimated 2.6 setal types per species of spider crabs, the spider crabs in this study have more setal types (8) than this previously reported average.…”

“…While research has suggested that larger individuals do not decorate due to the lack of predation (Guinot & Wicksten, 2015; Hultgren & Stachowicz, 2009), Libinia individuals are smaller than the carapace widths reported in these previous studies (CW >10 cm). Wortham and Jedlicka (2019) also reported that in Tampa Bay, predators exist that feed on spider crabs (Springer & Woodburn, 1960). A lack of hooked setae may be driving decreases in decorating behaviors, while not decreasing the ability to camouflage.…”

“…Large individuals do retain pappose setal types, which hold decorations; large individuals retain the ability to decorate, just by a different mechanism, and rely on euphorbia pappose setae instead of hooked setae. The non‐hooked setae are fouled and cover much of the exoskeleton, possible providing a secondary camouflage option as suggested in Wortham and Jedlicka (2019). Having another option for holding decorations might enable large individuals to still employ a type of camouflage; it is unlikely that disruptive camouflage is a strategy employed by larger individuals.…”

“…The two species used in this morphological study are decorating spider crabs from the Family Epialtidae: Libinia emarginata Leach, 1815 (Figure 1a) and Libinia dubia Milne Edwards, 1834 (Figure 1b,c). These species have hooked setae and non‐hooked seate on their carapace and walking legs (Hultgren & Stachowicz, 2009; Rorandelli et al, 2007; Stachowicz & Hay, 1999; Wortham & Jedlicka, 2019). Libinia species are difficult to distinguish, although key physical indicators can be used (Corrington, 1927; Brownell et al, 1977; Wass, 1955; Williams, 1984; Figure 1).…”