Snapping shrimp (Alpheus heterochaelis & A. normanni)
Two species of snapping shrimp, A. heterochaelis and A. normanni , collected near Beaufort, North Carolina, during June 1982, and then held in the laboratory, used their major chelae to crush and consume juveniles of the hard clam Mercenaria mercenaria. Snapping shrimp (19.1 to 39.4 mm in total body length [TL]) ate clams in the largest size-class (15.1 to 20.0 mm in shell length), but preferred smaller clams when offered equal numbers in this large size-class and in each of three smaller size-classes. Female snapping shrimp, regardless of species, exhibited a statistically higher predation rate than males when the results of five separate experiments were combined. The major chelae of the females of specimens of A. heterochaelis (>32.0 mm TL) were smaller than those of equal size males. Alpheus heterochaelis (19.1 to 27.2 mm TL) had a larger major chela for a given body length than did specimens of A. normanni; however, predation rates of the two species were not significantly different. The number of clams crushed was related to both the size of the major chelae and total body length for A. normanni, but not for A. heterochaelis. Alpheus spp. inflict two types of shell damage which are identical to those caused by blue crabs. These results imply that previous studies may have overestimated the importance of crab predation and underestimated or ignored the importance of predation by snapping shrimp.