Population Dynamics of the Sponge-Dwelling Alpheid Synalpheus longicarpus, with Observations on S. brooksi and S. pectiniger, in Shallow-Water Assemblages of the Eastern Gulf of Mexico

Abstract

Investigations were conducted on species composition, population dynamics, and ecological interactions of alpheid shrimps associated with the loggerhead sponge Spheciospongia vesparia in shallow-water assemblages of the eastern Gulf of Mexico. Three species, Synalpheus brooksi, S. pectiniger, and the numerically dominant S. longicarpus were found in coexistence. Biomass and numbers of all three species found within the sponge were directly proportional to increasing sponge volume. Dominance of S. longicarpus, a eurythermal tropical species, is attributed to successful year-round reproduction. S. brooksi and S. pectiniger are fugitive species in this particular association. The latter species are able to colonize the habitat, but seasonal temperature minima by depressing egg production limit their ability to coexist in greater abundance. Coexistence of the three shrimp species appears to coincide with a wide degree of niche overlap. Potential competition for limited available space within the host may be intense and, combined with the differing reproductive success of each species, may be of considerable importance in determining population size and species composition of the associates.