Study Of Crabs To Intertidal Stimuli :: essays research papers

INTRODUCTION- 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 measure per season than indigenous crabs, providing one possible hypothesisfor their population explotion.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 peeing and a ir temperatures, and water salinity concentrations. It isbelieved that these crabs will be truly tolerant to the various extreme conditions that theywill be put through. It is the ability of these crabs to survive in these unfavorablesituations that is key to their success. This experiment was also knowing to prove thehypothesis that the tolerance of H. sanguineus to various environmental factors increaseswith size.METHODS AND MATERIALS-In February 2000, a field trip was taken to Crane Neck Point to collect stretch forthspecimens for the experiment. The field trip was conducted at low tide. The watertemperature was approximately 3 degrees Celcius, with the air temperature slightly abovefreezing (0-1 degree Celcius). Live crabs were obtained by overturning rocks in theintertidal zone. Hemigrapsus sanguineus was found at all levels of the intertidal zone,although their numbers increased as one moved toward the waterline. The crabs werecollected with no tubercle toward size. The si zes of the specimens collected werefound to range from 0.5 to 4.2 cm. The crabs were collected in a plastic five gallonbucket. Water was added to the bucket to keep the crabs from dehydrating. The crabswere taken back to the lab, where they were kept in the plastic five gallon buckets for afew weeks until the experiment began. Air hoses were added to the buckets in order tooxygenate the water. The water was changed, as necessary. The first experiment conducted was the experiment regarding water temperatureand salinity tolerances. The objective was to conduct an experiment that would providemeasurable data on the tolerance of H.