Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Clustering in Littorina planaxis
Student Author(s): Miyamato, Alan
Pages: 21
Location: Final Papers Biology 175H
Date: June 1964
Keywords: periwinkle
littorina
Abstract: High density groups of Littorina planaxis found in cracks, concavities and around protruding quartz crystals were found to be of fluctuating numbers and constantly changing membership. Persistence of clusters in cracks was found to be greater than in the sligher irregularities, largely due to their greater size. No relation could be found between cluster sizes and any environmental variable, but the percentage of population clustered was found to be inversely proportional to the wetness of the rock. Increases in percentage clustered was most noted at dawn, and the maximum percentage clustered was recorded during the daylight hours on dry rock. Snails were found to be trapped by shade on drying rock, but they ignore the difference in light intensity when the rock is wet. Mucus trails are hypothesized to be a means of directing snail traffic to the cluster-prone areas. Application of heat was foundto increase percent-age of snails clustered. Possible adaptive advantages: better chance of surviving dessication, mechanical protection from waves.