The Biological bulletin (20379034365)

Title: The Biological bulletin

Identifier: biologicalbullet188mari (find matches)

Year: [1] (s)

Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983

Subjects: Biology; Zoology; Biology; Marine Biology

Publisher: Woods Hole, Mass. : Marine Biological Laboratory

Contributing Library: MBLWHOI Library

Digitizing Sponsor: MBLWHOI Library

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ARM WAVING IN SEA LILIES 91

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Figure 2. Video sequence of characteristic arm waving behavior in Endo.\ocnnii.\ parrac (A-C) Sequential steps of the effective stroke. (D) Maximum arm extension. (E-F) Recovery stroke. mis maclearanus, stand erect with arms drooping down near the stalk (Fig. 1 A). In a current, these same species form their arms into a parabolic fan for feeding (Fig. IB; see also Macurda and Meyer, 1974, 1976), though the uppermost few arms of the fan may sometimes be ex- tended straight up into the water column. All three species have been observed with individual arms waving up and down rapidly (Fig. 1A, 1C). In dense populations, large numbers of individuals have been observed to engage in arm-waving behavior simultaneously (Fig. ID), particu- larly after several minutes of illumination by the sub- mersible. Although we have occasionally observed arm flicking or waving in animals with their arms extended in the feeding posture, arm-waving behavior has been observed more commonly in animals with drooping arms. The arm is moved rapidly away from the stalk, sweeping outward and upward until it is fully extended above or to the side of the calyx (Fig. 2). The arm pauses only briefly at the end of the stroke before reflexing downward more slowly to its initial position. This entire movement may take as little as 2 s or as much as 21 s. Frequency histograms of the durations of effective and recovery strokes (Fig. 3) show that the recovery strokes were more variable and often longer than the effective strokes, but the two distri- butions overlapped substantially. For individual strokes, the ratio of the effective component to the recovery was nearly always greater than 1 (Fig. 4). and the difference between the durations of paired effective and recovery strokes was highly significant (paired Student's / test, 54d.f., i = 5.75, P < 0.0000). The arms were flexed through arcs ranging from a few degrees to more than 180 degrees. Most arms were flexed only once before an- other arm was brought into play. Often, one arm was flexed while another on the same animal was in its re- covery stroke. Examination of histological sections of the arm of E. parrae revealed the presence of large dorsal (oral) longi- tudinal muscles linking the arm segments (Fig. 5). These muscles, which are described elsewhere (Hyman, 1955) as flexor muscles, are clearly responsible for the flexure of the arms. There are no opposing longitudinal muscles, but large ligaments are found ventral (aboral) to the flexor muscles (Fig. 5). The recovery phase of arm waving must

биологический бюллетень книжные иллюстрации биология зоология Морская биология морская биологическая лаборатория изображения из интернет-архива

1825

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