Energetics variation of the striped clam Eurhomalea exalbida (Chemnitz, 1795) in Ushuaia Bay, Beagle Channel (54 deg 50 min S)

摘要

The processes of energy transfer in the clam Eurhomalea exalbida Chemnitz, 1795 can be analyzed by measuring the seasonal variations in energy content with respect to the reproductive characteristics of the population. The energy content of three organ groups of E. exalbida (gonad, digestive gland and gastrointestinal tract-foot (FV); adductor muscles (M); and gills-mantlesiphons (GMS), was measured using calorimetry in monthly samples of the Ushuaia Bay population for a year. The relative condition index was also measured monthly for the three organ groups. No relationship, was found between the energy content per gram (kJ/g ash free dry weight) of the organ groups FV, M and GMS and the size of the adult organisms. The mean values for the twelvemonth experimental period for FV were very similar for males and females with 20.55 +- 1.10 kJ/g for males and 20.26 +- 0.91 kJ/g for females; for M they were 20.68 +- 0.65 kJ/g for males and 20.76 +- 0.76 kJ/g for females; and for GMS they were less than for the other two organ groups, with values of 20.02 +- 1.09 kJ/g for males and 20.02 +- 0.84 kJ/g for females. An analysis of the energy content data and the relative condition index (RCI) measured at monthly intervals throughout the year revealed significantly lower values for FV in November (p < 0.05), which is believed to be linked to the greater gametic emission in this month. In contrast, no significant differences over time were found in the energy content or relative condition index of eitherM or GMS. The relative stability of the energy content and RCI of M and GMS over time suggests that there were no changes in the proportion of their biochemical components and no changes in the mass of the organs, hence Eurhomalea exalbida does not havean energy reservoir and the energy used in reproduction may be extracted directly from the food consumed.