The Effect of Sand Particle Size on the Burrowing Ability of the Beach Mysid Gastrosaccus psammodytes Tattersall

Laboratory studies on the burrowing rates of the mysid shrimp, Gastrosaccus psammodytes , in a series of well-sorted sediments, determined whether (1) burial times were dependent on grain size and (2) if natural population distribution may be influenced by grain size on beaches. Burial times were tested in nine well-sorted sediments with grain size ranging from 90 to 2000mu m. Large individuals (i.e. gravid females) were used. G. psammodytes burrowed fastest in 125–1000mu m sand with mean burial times less than 1·6s. Burial time increased to approximately 2s in 90–125mu m sand. G. psammodytes could not burrow in grain sizes coarser than 1000mu m. G. psammodytes has been reported to occur on beaches with grain sizes ranging from 90 to 500mu m but are uncommon on beaches with coarser sand. It appears that population distribution may be influenced by grain size that is probably not related to the animalsʹ burial time ability, but rather their inability to burrow completely into coarse sand. Indirectly, grain size may also influence the morphodynamic state of a beach and therefore food availability since coarse-grained beaches tend to be reflective with little surf production.