. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CRINOID REPRODUCTION 225 250-J 200- 0) £ D « lOCh u o 50H 50% D 1972 M M. N D 1974 FIGURE 2. Fluctuation in the size-frequency structure of post-pachytene oocytes of C. japonica. Each of the eleven average frequency polygons was constructed from cytometric data from the number of females shown above the polygon. The thickened segments of the horizontal axis indicate the presence of oogonia and spireme oocytes. Arrows I and II mark, respectively, the spawnings of the first and third weeks of October 1973. Within each ovary, t
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CRINOID REPRODUCTION 225 250-J 200- 0) £ D « lOCh u o 50H 50% D 1972 M M. N D 1974 FIGURE 2. Fluctuation in the size-frequency structure of post-pachytene oocytes of C. japonica. Each of the eleven average frequency polygons was constructed from cytometric data from the number of females shown above the polygon. The thickened segments of the horizontal axis indicate the presence of oogonia and spireme oocytes. Arrows I and II mark, respectively, the spawnings of the first and third weeks of October 1973. Within each ovary, the entire population of post-pachytene oocytes grew as a single generation (also called a cohort of oocytes). The growth of all oocytes as a single generation is rarely encountered in echinoderms, having previously been re- ported only for the asteroid Patiriclla regularis (Crump, 1971) and possibly also for the asteroid Astcrias nibcns (Schlieper, 1957). This rare pattern of oocyte growth is certainly not a characteristic of crinoids in general, since the ovaries of most species contain more than one oocyte generation (Holland, unpublished observation). In any female of C. japonica collected from late winter through early fall, the diameters of the largest and smallest oocytes differed by at least 80 //,. This wide range in oocyte diameters within each oocyte population was not an artifact caused by our sampling method, since similar ranges were found in random samples of unsectioned oocytes teased from fixed ovaries. Presumably, in each oocyte popula- tion, the largest cells were the first produced and thus the oldest, while the smallest cells were the last produced and thus the youngest; the following analysis of growth rates depends on the acceptance of the foregoing presumption. Instantaneous relative t/roi^tlt rates of post-pachytene oocvtcs The growth of two oocytes is shown in Figure 3. The curve at the left is for the largest (and presumably the first-produced) oocyt
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
