. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 462 K. P. SEBENS N AGONISTIC ALL ANEMONES 40 30 20 10 4 5 678 9 10 II • 12 13 14 15 16 17 18 DIAMETER (cm) FIGURE 2. Sizes of Anthopleura xanthogrammica that displayed agonistic behavior (acrorhagal inflation) compared to the size distribution of all anemones mapped during the basal diameters were found to be immature (juveniles) in this and an earlier study (Sebens, 198Id) while most individuals above that size had obvious male or female gonads. Anemones with cm basal diameters displayed 19 agonistic behavior
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 462 K. P. SEBENS N AGONISTIC ALL ANEMONES 40 30 20 10 4 5 678 9 10 II • 12 13 14 15 16 17 18 DIAMETER (cm) FIGURE 2. Sizes of Anthopleura xanthogrammica that displayed agonistic behavior (acrorhagal inflation) compared to the size distribution of all anemones mapped during the basal diameters were found to be immature (juveniles) in this and an earlier study (Sebens, 198Id) while most individuals above that size had obvious male or female gonads. Anemones with cm basal diameters displayed 19 agonistic behaviors out of 88 anemones observed (22%) and anemones > 10 cm displayed 35 such encounters out of 90 anemones (38%). Clearly juveniles are unlikely to participate in agonistic encounters either as aggressor or as defender, while adults do so frequently. A chi-squared test was performed on juvenile and adult categories assuming as the null hypothesis that agonistic behavior would be observed equally in both groups. The hypothesis must be rejected (x2 = , P 10 cm) and small (<10 cm) adults. One hypothesis for the low incidence of agonistic behavior in juveniles results from their small size and perimeter: the probability of contacting other anemones would be lower among smaller individuals compared to larger individuals. However, small anemones move more frequently (Sebens, 1981b, this study) and could experience even more contacts per unit time than do the adults. For all natural agonistic interactions, the size of the aggressor was plotted against that of the anemone that had been attacked (Fig. 3). In some cases the initiation of aggression could have been missed and only the response seen. However, most ob- servation periods began soon after the tide covered the anemones and continued for several hours. In only two cases was there a responding inflation and application of acrorhagi by the attacked anemone. Others may have done so after the period of observation, meanin
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
