Ovary growth and protein levels in ovary and fat body during adult-wintering period in the red mason bee, Osmia rufa

Winter months are supposed to be a crucial period for the development of the reproductive system, especially ovaries, in Osmia rufa females. During 7 months of the wintering period (from September till March), the length and width of terminal oocytes and protein concentrations in ovary and fat body tissue extracts of red mason bee females, O. rufa, were studied. Our observations indicate statistically significant differences in the size of terminal oocytes for three different periods of over-wintering: September-October, November-January and February-March. Ovary growth was fast in the September-October period; it slowed down in November-January, and then increased again in February-March. Time-dependent changes were noted also in the number of oocytes and protein concentrations in ovary and fat body tissue during all wintering periods. During all winter months the number of oocytes progressively increased, but a statistically significant increase was only noticed for the periods September-October and February-March. Similarly, during the first two months (September-October) and the last three (February-April) we observed major changes in protein concentration in ovary and fat body tissue. Our results indicate that adult diapause in O. rufa varies to some extent in comparison to the other insects, probably because the the ovary is not fully inhibited during wintering, including the diapause period. These results allow a better understanding of the wintering strategies, including the diapause period, and may be useful for improving rearing methods of this economically important species.