of response from these organisms during- the 

 eclipse indicated that the lowered light inten- 

 sity or duration of totality, or both, were not 

 sufficient to stimulate the kind of movement 

 observed after dark. 



30m. 



i^M^fivi '^'^^sBii \^Mi 



Figure 9. — Echo soundings before and after sunset 

 (2000 hr.). 



COMPARISON WITH OBSERVATIONS 

 FROM OTHER ECLIPSES 



The observations presented in this paper 

 show some agreement with those of previous 



workers, but the responses recorded for some 

 species were not the same. Considering the 

 variables such as light intensity, duration of 

 totality, and the variation in experimental de- 

 sign, these differences are not surprising, but 

 they should be equated. 



Mori (1939) conducted carefully designed 

 experiments on several species, and made de- 

 tailed observation on others, including the 

 sandhopper, Orchestia sp. He concluded that 

 sandhoppers "were apparently not affected by 

 the eclipse," yet he does mention that a few 

 individuals were exposed "towards the end of 

 totality ....," exhibiting their normal cre- 

 puscular behavior, but this activity lasted only 

 a few seconds before the animals retreated into 

 hiding. Totality during the 1936 eclipse in 

 Japan lasted 2 minutes, and began at 1519 

 when illuminance under normal conditions is 

 high. As Mori stated, the inactivity may be 

 explained by the fact that the change of light 

 intensity at totality was too rapid ; but he also 

 cautioned that factors such as humidity and 

 atmospheric pressure might have been the con- 

 trolling influences. He also reported on ob- 

 servations from the aquarium of the Akkesi 

 Marine Biological Laboratory, ". . . shrimp, a 

 flat fish, a young salmon, a trout, and a herring 

 were all indifferent to the eclipse, whereas a 

 crab, which is quiet on ordinary days, began to 

 move, and a bullhead appeared from the shady 

 tangle of weeds when it became darker and 

 hid again when it became lighter in just the 

 same way as seen on ordinary days and 

 nights." 



In reference to light-dark cycles, Biinning 

 (1964) stated that deviations from the natural 

 frequency of an organism could "necessarily 

 have an entirely different relationship to the 

 light and dark period than normally. For ex- 

 ample, if the dark period is too short, the 

 organism with its own cycle length does not 

 have time enough within the dark period to 

 reach the usual physiological state typical of 

 night." He also stressed that sometimes the 

 beginning of the light period has a greater 

 influence on the timing of responses during 

 dark than the beginning of the dark period 

 itself. 



MARINE ORGANISMS DURING SOLAR ECLIPSE 



267 



