Study Of Crabs To Intertidal Stimuli :: essays research papers

INTRODUCTION-   Ã‚  Ã‚  Ã‚  Ã‚   Since its itroduction to the New Jersey shore in 1988, the western Pacific shore crab Hemigrapsus sanguineus has spread to inhabit rocky intertidal locations along the Atlantic coast from Massachusetts to North Carolina (McDermott 1998). Many reasons have been proposed to explain the rapid spread of this non-indiginous species. For example, it has been shown that H. sanguineus has longer spawning periods along the mid-Atlantic coast than it does in its natural habitat in the western Pacific Ocean, due to a more favorable climate (Epifanio et al 1998). For this reason, these crabs are able to spawn more times per season than indigenous crabs, providing one possible hypothesis for their population explotion. For this species to expand its range along the Atlantic coast, it will need to have wide 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 is believed that these crabs will be very tolerant to the various extreme conditions that they will be put through. It is the ability of these crabs to survive in these unfavorable situations that is key to their success. This experiment was also designed to prove the hypothesis that the tolerance of H. sanguineus to various environmental factors increases with size. METHODS AND MATERIALS-   Ã‚  Ã‚  Ã‚  Ã‚  In February 2000, a field trip was taken to Crane Neck Point to collect live specimens for the experiment. The field trip was conducted at low tide. The water temperature was approximately 3 degrees Celcius, with the air temperature slightly above freezing (0-1 degree Celcius). Live crabs were obtained by overturning rocks in the intertidal zone. Hemigrapsus sanguineus was found at all levels of the intertidal zone, although their numbers increased as one moved toward the waterline. The crabs were collected with no distinction toward size. The sizes of the specimens collected were found to range from 0.5 to 4.2 cm. The crabs were collected in a plastic five gallon bucket. Water was added to the bucket to keep the crabs from dehydrating. The crabs were taken back to the lab, where they were kept in the plastic five gallon buckets for a few weeks until the experiment began. Air hoses were added to the buckets in order to oxygenate the water. The water was changed, as necessary.   Ã‚  Ã‚  Ã‚  Ã‚  The first experiment conducted was the experiment regarding water temperature and salinity tolerances. The objective was to conduct an experiment that would provide measurable data on the tolerance of H.