FASTING CONFINEMENT EFFECTS ON SHARKS 633 



study, rises in serum sodium and chloride were accompanied by interrenal 

 hypertrophy and histological alterations in the rectal gland, which suggest a 

 decrease in its secretory activity. 



The chemical structure of the interrenal secretion is controversial In a 

 series of papers (Idler and Truscott 1966; Idler and Truscott 1969; Grimm, 

 O'Halloran, and Idler 1969; Truscott and Idler 1968; Truscott and Idler 

 1972; Idler, Freeman, and Truscott 1967; Idler 1969) the major steroid 

 produced has been described as a unique form 1-a-OH-corticosterone. The 

 interrenal organ of Squalus acanthias was reported to produce predom- 

 inantly 1-a-OH-corticosterone, along with fractional amounts of corti- 

 costerone. However, Bern, deRoos, and Biglieri (1962) and Simpson and 

 Wright (1970) reported little or no 1-a-OH-corticosterone and stated that the 

 interrenal gland produced predominantly corticosterone and deoxycorti- 

 costerone. 



As none of the aforementioned studies reported significant Cortisol or 

 cortisone production, the glucocorticoid competence of elasmobranch 

 interrenal secretions may be questioned. The lack of extensive liver lipid 

 mobilization, the decline in serum protein and glucose, and the preferential 

 utilization of tissue proteins during starvation in elasmobranchs parallel the 

 responses of other vertebrates to hyposecretion of glucocorticoids. 



Although interrenal secretion probably decreased as death approached, it 

 should be noted that both the alterations in the histological appearance of 

 the rectal gland and hematopoeitic system and the rising serum sodium and 

 chloride levels were consistent until the moment of death. Both cytological 

 and metabolic changes appeared immediately after introduction to the pens, 

 when the interrenals appeared most active; thus the lack of glucocorticoid 

 activity was not due simply to interrenal insufficiency. 



Extracts of elasmobranch interrenals have been shown to possess powerful 

 mineralocorticoid activities, but no glucocorticoid properties, when admin- 

 istered to adrenalectomized rodents (Idler, Freeman, and Truscott 1967; 

 Idler, O'Halloran, and Home 1969). Both mineralocorticoid activity and a 

 significant anti-inflammatory response accompanied the histological indica- 

 tions of interrenal secretion in the present study. 



If we assume that interrenal secretions would produce a similar response 

 in other vertebrates, the steroid must have a unique structure, since no 

 adrenal steroid or combination found in higher vertebrates would produce 

 high mineralocortoid , and anti-inflammatory activities in the absence of 

 significant gluocorticoid activity (Frieden and Lipner 1969). It may be 

 hypothesized that this hormone evolved in concert with the reliance upon 

 liver lipids for buoyancy regulation; however, limiting the accessibility of 

 lipids maintains the hydrodynamic efficiency of the animal but severely 

 restricts its ability to tolerate prolonged inanition. 



Figure 10 is -a summary of the proposed interactions of factors affecting 

 captive elasmobranchs. These have been defined as: 



1. "Chronic stresses" associated with the conditions of confinement (such 

 environmental variables as crowding, aggressive interaction, temperature, and 

 starvation); these have been discussed in detail previously, and 



