. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. REPRODUCTIVE BEHAVIOR OF LEPTASTERIAS POLARIS 37 2 °C 0Male spawning induced by decreasing temperature ©Active sperm in the -^ water column (moving at ® Female spawning stimulated by sperm in the water column. ©Aggregation and settling of sperm (resting state) Spterm reactivated by fresrrty-soawned oocytes " rtilizationT? ® Brooding and embryonic development Figure 4. Schematic illustration of spawning behavior for male and female Lcplastvrias polans, showing the relation between them. cerning the induction of spawning
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. REPRODUCTIVE BEHAVIOR OF LEPTASTERIAS POLARIS 37 2 °C 0Male spawning induced by decreasing temperature ©Active sperm in the -^ water column (moving at ® Female spawning stimulated by sperm in the water column. ©Aggregation and settling of sperm (resting state) Spterm reactivated by fresrrty-soawned oocytes " rtilizationT? ® Brooding and embryonic development Figure 4. Schematic illustration of spawning behavior for male and female Lcplastvrias polans, showing the relation between them. cerning the induction of spawning could be made in the course of our experiments. A few isolated male spawnings occurred during minimum daylength (<9 h) when water temperature was around 2°-3°C (first sight of sperm fil- aments) in late December (Fig. 2), but most spawnings were observed in January as the temperature fell further. The temperature fluctuated between 2° and 4°C (Fig. 2) throughout the following weeks of spawning, and gamete release seemed to be closely related to these variations. The same spawning pattern was observed in control group 2, maintained in natural temperature and total darkness, whereas no spawning occurred in control group 1, kept at steady temperature and photoperiod. As a result of the seasonally low primary production, the tanks provided with seawater from the estuary, where spawnings were recorded, contained virtually no phytoplankton. Salinity continuously fluctuated between 26 and 32%o without any consistent increasing or decreasing trends (data not pre- sented). During qualitative observations, the presence of sperm filaments seemed to be correlated with subsequent female spawning within a few hours. Complementary ex- periments conducted in replicates showed that the intro- duction of sperm in the water induced spawning of several females in the controlled environment (control group 1), therefore minimizing the importance of temperature in female spawning. No male
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
