Behavior of the burrowing shrimp Alpheus macellarius in varying gravel substrate conditions

The behavior of the male snapping shrimp, Alpheus macellarius (Decapoda: Alpheidae), was studied in tank experiments with four levels of gravel content for five consecutive days. Markov-chain type analyses identified significant behavioral states that were grouped into six behavioral classes (Wandering, Surveying, Grooming and Foraging, Resting, Hidden). Significant trends in the durations and frequencies of the classes were found across days and periods, with shrimps mainly wandering and burrowing during the first day. Grooming, foraging and resting became more frequent during succeeding days. Shrimps built burrows in the morning and then groomed and foraged mostly in the afternoon. This periodicity implies a greater priority for the shrimp to construct and maintain a burrow rather than forage. Gravel content did not significantly influence burrowing behavior, but marked variations were noted in burrowing success, burrow structure and stability. Animals in 15% and 25% gravel substrates produced more burrows of greater complexity, which lasted longer than those of the shrimps in 0% and 5% gravel setups. Feeding was mainly sediment scavenging suggesting the predominance of a deposit-feeding trophic mode. Modifications in burrow construction and adaptations in burrowing and feeding indicate the ability of A. macellarius to respond to different environmental conditions.