The effect of 16 weeks starvation and 6 weeks refeeding on the size and chemical composition of the hepatopancreas of 2 size classes of C. destructor (20–40 g and 40–60 g) maintained at 2 temperatures (10°C and 25°C) was investigated under laboratory conditions. The response to starvation was not influenced by size class. In fed animals, the wet hepatosomatic index (HSIw-%) and dry hepatosomatic index (HSId-mg/g) increased to 7% at week 2 and 36 mg/g at week 10 respectively, whereas in starved animals HSIw and HSId decreased to 2.6% and 3.6 mg/g at week 10 respectively. Hepatopancreas moisture (HM-%) of fed animals decreased to 51% after 10 weeks, whereas in starved animals it increased to a maximum of 81% after 2 weeks. In fed animals, hepatopancreas lipid (HL-mg/g), protein (HP-mg/g), and ash (HA-mg/g) reached a maximum of 30 mg/g at week 10, 7.8 mg/g at week 6, and 2 mg/g at week 4 respectively. Hepatopancreas carbohydrate (HNFE-mg/g) in fed animals fluctuated considerably. In starved animals, HL did not significantly change for the first 4 weeks, and a minimum of 0.5 mg/g occurred at week 8. In contrast, HP decreased for the first 2 weeks to 3 mg/g, and HNFE decreased for 4 weeks to 0.67 mg/g after which no significant change occurred. Ash levels in starved animals generally decreased for 12 weeks to 0.36 mg/g. Low temperature reduced the rate of utilization of hepatopancreas nutrients. About 7 months of starvation at 10°C is required for the hepatopancreas to become nutritionally depleted. Refeeding starved animals resulted in an increase in wet and dry hepatosomatic indices and all hepatopancreas nutrients and a decrease in hepatopancreas moisture. Complete recovery of the hepatopancreas of starved animals following refeeding, to levels recorded in the fed control animals, was recorded for the HSIw, HA, and HNFE. The various hepatopancreas condition indices used here are discussed in relation to their practical value and accuracy in predicting animal condition, and a classification is presented. The adaptive significance of hepatopancreas size and nutrient storage capacity is also discussed.
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Vol. 20 • No. 3