Hopkins Marine Station Student Paper

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Title: Observing the low activity rate of Macclintockia scabra: a consideration of potential movement cues: location, splash, and light exposure
Student Author(s): Pennington, Leslie
Faculty Advisor(s): Watanabe, Jim
Pages: 22
Location: Final papers Biology 175H
Date: June 2002
Abstract: Previous reports on the behavior of Macclintockia scabra have implied that the intertidal limpet moves every time it is wetted by the incoming tide. In a three-week study on the potential effects of location, splash and light level on limpet movement, frequency of movement (number of instances individual limpet moved divided by the number of instances limpet was wet ­ averaged over all observed limpets) was calculated to be 12%. This is based on 2660 field observations on seventy-nine limpets, dispersed among three sites, differing in degree of wave exposure. I also made 600 observations on twenty-five limpets that had established home scars on rocks transported to the laboratory. Frequency of movement in the lab was 15%. A two-factor analysis of variance (ANOVA) was carried out on frequency of movement, with degree of splash and field site as the two factors. Data from during the day and at night had to be analyzed separately because all possible combinations of "splash", "site" and "light level" did not occur during my field study. Frequency of movement did not differ significantly among sites. No movement was observed at low tide in either the lab or field. An increased frequency of movement was found to accompany a corresponding increase in splash level, both at night and during the day. However, lab results showed a decreased frequency of movement when limpets were submerged rather than sprinkled by a spray bar. A significantly greater amount of movement (25%) was seen at night than during the day (7%) ­ a finding that could be due to the higher nighttime tidal heights. Lab results showed no significant difference in day and night movement frequency. In a separate experiment, limpets were exposed to an artificial high tide, during a normally low tidal period. The limpets responded by producing a significantly lower-than-normal frequency of movement (8%). 10/15 tidal simulations resulted in a movement frequency of zero. My findings suggest that Macclintockia scabra may use a combination of splash level, light, and other as yet identified "tidal-timing" cues to induce movement. Location appears to play a less significant role.