. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 4a. Number of D variabilis clams in the laboratory jumping in response to knocking sounds relative to time of day and tide. Noon is n; midnight is m. Clams were most responsive around the time of high tide and showed no response around the time of low tide. Clams responded for only three to five tidal cycles after they had been taken from the beach. The pattern shown is a compilation of several collections (represented by different symbols) taken on different days from the same beach. Room lights were continuously on
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 4a. Number of D variabilis clams in the laboratory jumping in response to knocking sounds relative to time of day and tide. Noon is n; midnight is m. Clams were most responsive around the time of high tide and showed no response around the time of low tide. Clams responded for only three to five tidal cycles after they had been taken from the beach. The pattern shown is a compilation of several collections (represented by different symbols) taken on different days from the same beach. Room lights were continuously on in this experiment. In the 2 additional days of experiments, performed during falling tides with several other synthesized low- frequency stimuli, jumping responses were consistent with those already described. Specifically, the number of clams responding increased with loudness, log (P<,), and de- creased with increasing time after high tide (multiple regression, P < ; loudness variable: P < , time variable: P < n = 35). A cumulative total of 147 responses were observed in 35 trials during those 2 days. On these 3 days of experiments, clams responding to sounds jumped only if they were less than 14 cm from the speaker, and most responding clams were less than 5 cm from the speaker face. The proximity of responding clams to the sound source raises the possibility of near- field effects (complicated wave interference patterns), which would complicate interpretation of the responses. A near field exists (close to a vibrating piston in an infinite baffle, an approximation to the geometry' of the speaker: Kinsler el 1982. inter alia} only if the diameter ( m) of the speaker is greater than the sound's wavelength. For an 832-Hz sound the wavelength is m (wavelength = speed of sound divided by frequency, speed of sound in coarse silt sea bottoms assumed = 1540 m/s; Kinsler etai, 1982). The speaker is even smaller compared to the longer wavelengt
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
