Environmentally Controlled Sex Expression in Meloidodera floridensis

A. C. Triantaphyllou, H. Hirschmann


Larvae of Meloidodera floridensis develop as females after feeding on pine roots, but become males under conditions of starvation. Seventy to 80% of the larvae kept in tap water at 23 C for 4 months underwent one or two molts, developing as males, and more than 50% became adult males. Ninety-six percent of the larvae that entered pine roots became females and only 4% developed as males. There is evidence that the latter did not feed on the roots. In comparison with tap water, solutions of cholesterol, testosterone propionate and[beta]-estradiol did not significantly affect the percentage of larvae that developed into males. Larvae kept in soil without a host plant did not develop into males. Most of them exhausted their energy supply and died without undergoing any development. We conclude that sex expression in M. floridensis is to a large extent controlled by environmental factors. Under natural conditions of feeding on a host plant, larvae develop as females according to their genetic constitution (thelytokous organism). Under conditions of starvation, however, sexual differentiation proceeds toward the male direction, probably as a result of alteration of the hormonal balance of the larvae and the subsequent activation of different sites of genetic function. Key Words: postembryogenesis, development, hormones.

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