. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BURROWING IN THE VENERIDAE Further sequences of movements follow rapidly at more or less equal time intervals. This period, during which the time/sequence remains more or less constant, ends when the shell reaches a position where the hinge margin is level with the surface of the substratum. Up to this time only the first siphonal move- ments of the digging sequence have occurred. The second series of siphonal movements described earlier are included in subsequent sequences, and these later sequences occupy progressively lon
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BURROWING IN THE VENERIDAE Further sequences of movements follow rapidly at more or less equal time intervals. This period, during which the time/sequence remains more or less constant, ends when the shell reaches a position where the hinge margin is level with the surface of the substratum. Up to this time only the first siphonal move- ments of the digging sequence have occurred. The second series of siphonal movements described earlier are included in subsequent sequences, and these later sequences occupy progressively longer time intervals (Fig. 2). The time pattern of repetition of sequences during the digging period was repeated in whole or in part by all members of the Veneridae examined. The fullest records were obtained with those animals which burrow more deeply, where the number of sequences making up the digging-period was greater. Deeper burrowing is apparently achieved by quicker repetition of the characteristic sequences and an increase in the number of movement sequences/period, and is 3 Ul I-. B NUMBER OF SEQUENCE IN THE DIGGING PERIOD FIGURE 2. Analysis curves of time/sequence (mins.) for one complete digging-period for Venerupis decussata (A). The time interval between the final downward movement and the second extension of the siphons (see text) is also shown for each sequence (B). associated with large size (Mercenaries) or with the possession of elongated siphons (Dosinia). In those species such as Venus casina, with short siphons, where the normal habit is to He near the surface of the substratum with the posterior end of the shell exposed, the burrowing-period consists of the initial fixation and downward movements only and ceases when the ligament margin is more or less level with the surface of the substratum. If the change-in-depth/sequence is analyzed in the same way, a similar although opposite pattern appears. Depth/sequence falls off progressively as the time/sequence
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
