. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 90 J. DAVID GEORGE MAX SAND. 1963 1964 FIGURE 23. Maximum-minimum temperatures for the sea water overlying the sampling site (open circles, broken line) and for the mud-sand 1 cm. below the surface (solid circles, unbroken line). Arrows mark (A) the onset of gamete production, and (B) the time of spawning. Sudden temperature changes seemed ineffective as a spawning stimulus (cf. Cirrifonnia tentacitlata—George, 1964). On the other hand sudden changes of salinity such as occur over a tidal cycle at the sampling site induced s
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 90 J. DAVID GEORGE MAX SAND. 1963 1964 FIGURE 23. Maximum-minimum temperatures for the sea water overlying the sampling site (open circles, broken line) and for the mud-sand 1 cm. below the surface (solid circles, unbroken line). Arrows mark (A) the onset of gamete production, and (B) the time of spawning. Sudden temperature changes seemed ineffective as a spawning stimulus (cf. Cirrifonnia tentacitlata—George, 1964). On the other hand sudden changes of salinity such as occur over a tidal cycle at the sampling site induced some spawning in ripe worms. Since spawning can be prevented by keeping the temperature at a constant low level it is unlikely that spawning occurs as a result of a biological clock mechanism or lunar periodicity. The fact that eggs are not fertilizable nor cleavage possible below 5%c is of interest, since 3-setiger larvae are able to live at a salinity of (although not grow), and adults can tolerate a salinity of for an indefinite period. A similar phenomenon has recently been reported for Nereis diversicolor by Smith (1964), although in these worms the range of tolerance for cleavage and successful gastrulation is narrower than for fertilization. It is likely that the susceptibility of early development stages of the worm to low salinities limits the spread of reproductively viable individuals into the upper reaches of estuaries. At Lawrence- town adults were found living permanently in areas where the salinity never rises to 5%c. These worms were presumably either passively transported there as larvae or had reached there by active swimming in the adult phase (it has already been noted that the adults are good swimmers). It is unlikely that these worms migrate back to areas of higher salinity during the breeding period, and they are probably non-reproductive individuals. A burst of phytoplankton occurred during April of both 1963 and 1964 and. Please note that t
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
