Burrow Morphology of Alpheid Shrimps: Case Study of Alpheus brevicristatus and a Review of the Genus.

The Alpheus brevicristatus De Haan, 1844 is one of the commonest shrimp species inhabiting the tidal flats in Japan. This species is sometimes accompanied by the facultative symbiotic goby, Acentrogobius spp. Here, we investigated the burrow morphology of A. brevicristatus in a tidal flat of Uranouchi Inlet, Kochi Prefecture, Japan. We also reviewed existing literature on alpheid burrow morphology using the resin casting technique, to determine how burrows vary in the presence and absence of gobies. Nine burrows were casted in situ using polyester resin. All burrows were long, but shallow in structure, with several funnel-shaped openings and short cul-de-sac branches. This species appears to use several burrow openings to access the sediment surface for feeding with high efficiency. Gobies were not associated with all burrows cast; however, 1-3 individuals of the small alpheid shrimp Athanas japonicus Kubo, 1936 were entombed in seven of the casts. A review of 12 studies on the burrow morphology of 16 Alpheus species based on resin casting techniques showed wide variation in burrow characteristics, such as burrow depth, length, and number of openings. Our findings suggest that burrow structure is influenced by species-specific characteristics and sediment type. The possibility that the presence of the symbiotic goby affects the burrow morphology of Alpheus shrimp is discussed.