. The Biological bulletin. Biology; Zoology; Marine biology. FUNCTION'S OF SWIMMING SETAE 100 175. 50 100 s s Figure 3. Per cent filtering area. Setal spacing in /mi for 4, 7, and 10 mm filtering height specimens of C. laeviuscula (solid lines I and C. natalensis (broken lines) as determined by equations in Table II. Nearshore particle distribution (shaded) indicates the percentage of particles between 20 and 97 /mi that is larger than the SS value. postulated that the presence of swimming setae indicated that filter-feeding was the primary means of acquiring food (Caine, 1974, 1976, 1977). Ho
. The Biological bulletin. Biology; Zoology; Marine biology. FUNCTION'S OF SWIMMING SETAE 100 175. 50 100 s s Figure 3. Per cent filtering area. Setal spacing in /mi for 4, 7, and 10 mm filtering height specimens of C. laeviuscula (solid lines I and C. natalensis (broken lines) as determined by equations in Table II. Nearshore particle distribution (shaded) indicates the percentage of particles between 20 and 97 /mi that is larger than the SS value. postulated that the presence of swimming setae indicated that filter-feeding was the primary means of acquiring food (Caine, 1974, 1976, 1977). However, it now appears that this was an overgeneralization. The relative importance of periphyton to the two species investigated is indi- cated in their survival on algal substrata. C. laeviuscula survived on those suhstrata supporting dense epiphyte growths but did not survive on those substrata lacking epiphytes (red and brown algae). Several factors could explain the failure of C. laeviuscula to maintain itself on these substrata in the field, including algal release of specific toxic substances, algal microhabitats occurring outside the caprel- lid's tolerance limits, selective predation, emigration, or lack of food. In con- trolled laboratory experiments, only the release of specific toxic substances and lack of food remain possible explanations. Due to the species survival with the addition of colonial diatoms, it is contended here that death is due to the lack of periphyton on the substrata. Similarly, the survival of C. natalensis on these algal substrata indicates the relative unimportance of periphyton to this species and reliance on suspended particles and filter-feeding. The mechanism (s) whereby periphyton is retarded or excluded from the algae is beyond the scope of this project, but Sieburth and Conover (1965) have found that tannins released from brown algae retard the survival of algal, including diatom, and hydrozoan epibionts. By comparing the nearshore parti
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