Title

Characteristics Contributing to Invasiveness of the Asian Shore Crab, Hemigrapsus sanguineus

Date of Completion

January 2011

Keywords

Biology, Ecology|Psychology, Behavioral Sciences|Biology, Physiology

Degree

Ph.D.

Abstract

In the marine environment, unique challenges directly impact an invasive species' establishment, including salinity preference and tolerance, ability to find food, utilization of shelter and space, response to mates, and avoidance of competition and predation. By quantifying these factors, one can predict where a potential newly introduced invader could become established and develop management strategies to curb its spread in the new area. ^ In data collected in Rhode Island, spatial patterning of Hemigrapsus sanguineus changes with season, showing increased aggregation during winter months in the intertidal zone. In laboratory trials, preference for intermediate-sized rock shelter persists in H. sanguineus regardless of temperature, with a specific preference for larger rock, which is consistent with limb loss patterns. ^ To test the cohabitation response of adult H. sanguineus to conspecific and heterospecific (green crab Carcinus maenas), we quantified presence of H. sanguineus in artificial shelters deployed intertidally and subtidally in Long Island Sound (CT), replicated in the laboratory, and determined interspecifc and intraspecific competition of crabs of different carapace size ratios in the laboratory. H. sanguineus avoided likely competitors, as did other benthic species in the community of either the H. sanguineus or C. maenas treatment. Laboratory direct competition trials show H. sanguineus uses shelter more often than its competitor, and is more likely to cohabitate with conspecifics. ^ H. sanguineus tolerates a wider range of salinities and is more likely to adequately defend shelter from competitors within the mid and upper intertidal. H. sanguineus shows low mortality across a broad range of salinities, has little change in hemolymph osmolality and Na/K ATPase activity over a short-term salinity shock, and behaviorally distinguishes between salinities when presented with a choice, regardless of acclimation salinity. ^ The combination of the effects of the behavioral dominance of H. sanguineus for shelter with its ability to withstand salinity changes give it a unique ability to maintain valuable intertidal shelter from predators and competitors during changes in tides and freshwater events, and make it a more efficient invader by allowing it to gain a foothold early in its life cycle and persist. ^