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http://www.gastropods.com/Shell_Images
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Taxonomy

Kingdom ANIMALIA
Phylum MOLLUSKA
Class GASTROPODA
Order CAENOGASTROPODA
SuperFamily CERITHIACEA
Family POTAMIDIDAE
Genus BATILLARIA
Species MINIMA

Physical characteristics of a habitat can greatly affect the spatial and temporal patterns of distribution and abundance of the organism (4). Past studies done by other Clark students at this site have noted the trend of B. minima to aggregate (12,13), but there was no study done to determine which rocks were most populated. Because the rocks that snails were found aggregated around physically differed, I wanted to know if there was preference to any specific characteristics of the rocks. I was also interested to see the extent of the density of the aggregations, and if this was dependent on the characteristics of the rock. If the size, shape, and color of the rocks differed and I wanted to see if these characteristics could determin the density or patterns of aggregation. Because most B. minima that I initially observed were around the rocks or under the rocks, I wanted to also see if there was a statistical difference between the concentrations of snails under the rocks compared to on top of the rocks.
Chapman and Underwood (1996) found that the intertidal gastropod, Littorina unifasciata, increased in aggregation when their enviromnet was dry. They showed that gastropods aggreagated to prevent dessication (3).
Because the tide pool had very little input from the ocean, I recorded the water temperature and weather conditions. This was because I wanted to rule out any changes in concentration or aggregation that could be contributed to temperature changes.

The "little black snails" that I observed in a tidal pool turned out to be Batillaria minima. They feed on algae and detritus (8) and is about 5-21 millimeters in length (6). Its geographical range is from South Florida to Brazil and to Bermuda (6), and it inhabits the mid to high tide range zone (7) often in highly salinic conditions (8). Upon close inspection of course, not all of these snails were black; they showed various color morphs and degrees of hue. Most were black, or all black with some lighter coloring. The operculum of the B. minima is orange-brown. It becomes translucent at the margins, is round and multi spiraled. The apex is usually eroded. Three spiral cords cross coarse axial ribs on each whorl forming small nodules (10).