620 



ECOLOGY AND BEHAVIOR 



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DAYS BEFORE DEATH 



24 



Figure 4 Alterations in hematocrit values of captive 

 Squalus acanthias. 



channels), and eosinophils II (coarse granules rarely found in circulating 

 blood). 



During the experimental periods, lymphocytes became infrequent in the 

 circulating blood, and lymphocytic concentrations in the spleen decreased in 

 size. Large numbers of mature eosinophils II, polymorphs, and (with increas- 

 ing frequency) eosinophils I appeared in all hematopoeitic centers. Throm- 

 bocytes in the blood and thrombocytic mitoses in the spleen increased at 

 first and then decreased in number. Reticuloendothelial cells of the sheathed 

 arteries of the spleen appeared greatly enlarged; mitoses were occasionally 

 observed. These cells often contained dark pigment granules or large, pale- 

 staining inclusions (Zenker's or Bouin's fixed tissue). 



Physiological Observations 



Table 5 presents the results of assays of sera from freshly caught animals 

 during 1971 and 1973. Data quoted here are within the range of values 

 reported for Squalus body fluids by other authors (Maren 1967; Burger 

 1967; Murdaugh and Robin 1967). Differences significant at the 0.01 level 

 (Student T-tests) exist in serum levels of glucose, cholesterol, and proteins at 

 the time of capture between the wild populations of the two experimental 

 seasons. The summer of 1971 was relatively cool and cloudy; air tempera- 

 tures averaged 15.8°C during June and 20. 2° C in July. Potential food 

 sources included large numbers of mackerel, cod, hake, herring, and eu- 

 phausiid crustaceans. During the experimental period of 1973, air tempera- 

 tures averaged 18.7°C in June and 21.3°C in July (U.S. Department of 

 Commerce, Environmental Data Service), and food fish were scarce in the 

 area. Thus the relatively depressed blood glucose and cholesterol levels of 

 animals in 1973 may be related to increased temperature and decreased food 

 supply. Cholesterol generally declines during starvation, and low serum levels 



