Gastropod Movement: Other Studies Compared With Mine


           Gastropod movement in the intertidal is the object of intrigue for many ecologists. Their paths can seem almost random and finding similarities in movement patterns between species can be extremely difficult. It can also be difficult to predict movement based on patterns of distribution for some species. Chapman (2000) has done a study comparing the movement of three intertidal gastropods and the only similarity found among the three species was that they were able to move greater distances on simple topographic sites than on complex topographic sites, and this was only determined after two weeks. There was no determination of variation in directionality among the three gastropods. This study is part of a larger study looking at whether spatial patterns of the habitat or differences between species had more effect in determining the movement of the animals. But the most important lesson from this study was the importance of replication and trials across more periods of time. It also demonstrated the difficulty in finding similarities in movement patterns among different species. My study is more interested in looking at motivations for movement across the intertidal rather than patterns of movement, but by gaining a better understanding of these patterns we can better infer as to why they show such patterns. Focusing on similarities in the motivation of different species to move may be useful in identifying the patterns of movement across different habitats.


           In another study I found, Crowe (1996) looks at how patterns of dispersal in an intertidal gastropod might be useful in predicting patterns in the gastropodís movement. The snails he studied, Bembicium, were generally found in association with oyster beds and he found that juvenile patterns of dispersal could be used to predict their movement, but since adults were less dependent on the shelter of the oysters these patterns could not be used to predict the movement of adults. Using patterns of dispersal to predict movement reflects on the motivation of the organism to move. Finding clues about the benefits of the dispersal pattern, in this case Bebicium finds shelter and protection in the oyster bed, can indicate what the motivation might be for the movement. My study showed, to some degree, that you could predict the movement of Batillaria minima based on their dispersal in the intertidal. Even when the snails were too far away from the rock to head directly for it, they still eventually moved either to a vertical surface or another rock in the tide pool. One could also conclude from my study that the weather must be taken into account, on a cloudy day the snails did not move in the same patterns as on a sunny day. There was no way to predict their movement on a cloudy day. Also, I did not do any analysis of size or age, but I could estimate from my visual take on size distribution while counting the snails, I would say this is not a factor for Batillaria minima.


    Another study done in my Ecology of Atlantic Shores class, by Matt Chmielewski, looks at the movement of the gastropod Nerita versicolor in and out of tide pools. Chmielewskil looks at the retention of snails within a tide pool and its relationship to salinity. His results suggest salinity may be a motivation for the movement of Nerita between tide pools. To check out this study, click here.


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