Study of shore crab response to intertidal stimuli
Since its itroduction to the New Jersey shore in 1988, the western Pacific shorecrab Hemigrapsus sanguineus has spread to inhabit rocky intertidal locations along theAtlantic coast from Massachusetts to North Carolina (McDermott 1998). Many reasonshave been proposed to explain the rapid spread of this non-indiginous species. Forexample, it has been shown that H. sanguineus has longer spawning periods along themid-Atlantic coast than it does in its natural habitat in the western Pacific Ocean, due toa more favorable climate (Epifanio et al 1998). For this reason, these crabs are able tospawn more times per season than indigenous crabs, providing one possible hypothesis For this species to expand its range along the Atlantic coast, it will need to havewide tolerances to temperature and salinity. In 1998 Epifanio found that The purpose of this study is to show the tolerance and behavioral responses of H.sanguineus to varying water and air temperatures, and water salinity concentrations. It isbelieved that these crabs will be very tolerant to the various extreme conditions that theywill be put through. It is the ability
Thedifferences between the number of crabs that chose submersion versus emersion wasstatistically signifigant (Chi-square test, chi-square=9. Next, water of varying salinities were produced. The water was addedslowly, and frequently checked with a salinity refractometer until the desired salinity of15 parts per thousand was obtained. Greater survival ofjuveniles to reproductive maturity allows for the population of H. The field trip was conducted at low tide. In the first trial 15 fish food pellets were added to each containerin order to provide the crabs with food, and hopefully reduce cannibalism. Being that the numberof crabs missing was small and consistent by size, the missing crabs did not effect theoutcome of this comparison. In addition, the experiments abovecould be repeated in conditions where the crabs are fed periodically. The container was once againdraped with plastic mesh. A onegallon acrylic container was placed in the center of the five gallon container. Five large and fivesmall crabs were also added to the styrofoam container. sanguineus to survive in extreme environmental conditions. The number of crabsmissing was the same for the adult and juvenile crab experiments. While no crabs were found dead in waters with salinities of 30 and 40 partsper thousand, 7 of 30 (23%) crabs were found in the waters with salinities of 15 parts perthousand, and 18 of 30 (60%) crabs were found dead in the waters with salinities of fiveparts per thousand (Table 1).
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