No evidence of androgenic hormone from the testes of the glowworm, Lampyris noctiluca.

The widely accepted concept, stating that insects have no true sex hormones, and that primary as well as secondary sex characteristics are controlled by the genetic inventory of each single cell, is challenged by the report of Naisse, J. [1966a. Contrôle endocrinien de la différenciation sexuelle chez l'Insecte Lampyris noctiluca (Coléoptère Malacoderme Lampyride). I. Rôle androgène des testicules, Arch. Biol. Liège, 77, 139-201] on the discovery of an androgenic hormone in the glowworm, Lampyris noctiluca. This case is of special interest, since it may point to an ancestral mode of sex differentiation in arthropods, considering that androgenic hormones have been discovered and characterized in crustaceans. With the intention to further characterize the androgenic hormone in the glowworm, and to establish a bioassay, we tried to repeat Naisses's transplantation experiments, according to which, androgen producing testes implanted into female larvae should masculinize the female's gonads and all other female features of the sexually strongly dimorphic pupae and beetles. We found, however, that larval development of the glowworm proceeded differently than reported by Naisse, and that sexing of larvae was not possible. Therefore, "blind" transplantations had to be performed. The results of our experiments showed, however, unequivocally, that an androgenic hormone, allegedly synthesized by the apical tissue of larval testes, was not involved in sex differentiation. We found, that in transplants, where testes and ovaries were even located closely to each other, both matured and formed spermatozoa in the testes and vitellogenic oocytes in the ovaries. Masculinization of ovaries was never observed, and the sex of the recipient was always in accordance with the sex of its own gonads. We therefore conclude that Lampyris noctiluca does not synthesize an androgenic hormone in the larval testes, and that sex differentiation is probably regulated as in other insect species. (The apical testis tissue of the glowworm was previously shown to represent progenitors of spermatogonial cyst cells [Balles, S., Maas, U., Sehn, E., Dorn, A., 2002. Testis differentiation in the glowworm, Lampyris noctiluca, with special reference to the apical tissue. J. Morphol. 251, 22-37].).