. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 32 F. J. GRIFFIN ET AL. 9a » b^* \^ If I. S-J. Figure 9. Representative images, obtained by video frame capture, from cultures of Clupea pallasi embryos maintained at three salinities. In the 14 ppt (a) and 28 ppt (b) cultures, larvae, empty (transparent) chorions of hatched larvae, and chorions (darkened, opaque) from which embryos have not hatched are evident. In the }<5 ppt culture (c), a hatched scoliotic larva with a bent tall, a partially hatched larva, and chorions of unhatched embryos are Bar = 1 mm. or
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 32 F. J. GRIFFIN ET AL. 9a » b^* \^ If I. S-J. Figure 9. Representative images, obtained by video frame capture, from cultures of Clupea pallasi embryos maintained at three salinities. In the 14 ppt (a) and 28 ppt (b) cultures, larvae, empty (transparent) chorions of hatched larvae, and chorions (darkened, opaque) from which embryos have not hatched are evident. In the }<5 ppt culture (c), a hatched scoliotic larva with a bent tall, a partially hatched larva, and chorions of unhatched embryos are Bar = 1 mm. or subspecies differences are reported to exist within C harengiis. which overall possesses a broader fertilization and developmental salinity tolerance range than C. pallasi (see Blaxter and Holliday, 1963: Ojaveer, 1981: Haegele and Schweigert, 1985). The comparison of salinity toler- ance curves for fertilization in San Francisco Bay C. pal- lasi and C. h. memhras from Airisto Sound supports this possibility. Alternatively, the differences may reflect physiological, nongenetic responses to the different salin- ity regimes to which the fish are exposed. Pacific herring that reproduce in the San Francisco Bay estuary constitute the southernmost eastern Pacific population of C. pallasi. isolated by a large geographical distance from other Pa- cific populations (Haegele and Schweigert, 1985). The fish migrate from oceanic waters of the eastern Pacific into the San Francisco Bay estuary where salinities fluc- tuate both seasonally and annually (2-32 ppt). dependent on both natural precipitation and freshwater diversions by humans (Peterson et 1989). In contrast, the C. h. membras population that reproduces in Airisto Sound resides in lowered salinity waters (4-10 ppt) of the Baltic Sea throughout the year (Haapala and Alenius, 1994). The fact that the salinity tolerance range for fertil- ization in C. h. membras has not narrowed suggests that the position of the range
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