. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 196 MICHAEL MAZURKIEWICZ Lj (fl ID a: ce 80 - 70- 60 - 50- 40- 30- 20 - 10- 0. r 20 - 1 5 - 10 - 5 20 40 60 80 100 120 140 160 NUMBER OF DAYS AFTER FERTILIZATION 180 200 FIGURE 7. Growth of Laeoncrcis cufocri in laboratory cultures at 22 ± 3° C 30r/fr. Values plotted are means of 12-24 individuals. and In worms with less than 30 setigers, the miclgut can he readily distinguished from the hindgut on the hasis of pigmentation and general form. The midgut is yellow, relatively broad, and highly expanded ; the hindgut is colorle
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 196 MICHAEL MAZURKIEWICZ Lj (fl ID a: ce 80 - 70- 60 - 50- 40- 30- 20 - 10- 0. r 20 - 1 5 - 10 - 5 20 40 60 80 100 120 140 160 NUMBER OF DAYS AFTER FERTILIZATION 180 200 FIGURE 7. Growth of Laeoncrcis cufocri in laboratory cultures at 22 ± 3° C 30r/fr. Values plotted are means of 12-24 individuals. and In worms with less than 30 setigers, the miclgut can he readily distinguished from the hindgut on the hasis of pigmentation and general form. The midgut is yellow, relatively broad, and highly expanded ; the hindgut is colorless, relatively narrow, highly sinuous, and sometimes doubles back on itself. The hindgut elongates more than the midgut. Thus in the 30-setiger juvenile, the midgut occupies the fifth to twelfth metastomial segments, while the hindgut occupies the 13th to 30th metastomial segments. Beyond the 30-setiger stage, distinction between mid- and hindgut requires histological examination. Growth under laboratory conditions As noted previously, the growth of laboratory-reared worms was highly variable beyond the 4-setiger larval stage and individual variation became progressively greater as cultures aged. Unfortunately, the culture techniques which were used did not allow for careful control of the quality and quantity of food. Therefore, it is impossible to judge if the variability in growth was inherent or due to dif- ferences in food conditions. Consequently, growth of laboratory-reared worms was followed by noting the earliest appearance of a given life history stage and its corresponding length (Table II). A sigmoid growth curve resulted when either length or segment-formation was used as an indicator of growth (Fig. 7). Thirty-two specimens (17 females, 15 males) of the F! generation were success- fully reared to sexual maturity and spawned after 168-192 days of development. The F2 generation of worms appeared identical in morphology to those of the FI generation. Sexually matur
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
