(Evolutionary transformation of testes and ovaries in booklice, birdlice, and sucking lice (Psocoptera, Phthiraptera: Mallophaga, Anoplura)

摘要

Evolutionary changes in the number and relative position of follicles in testes and ovarioles in ovaries of Psocoptera and Phthiraptera are analyzed. In the superorder Psocidea, oligomerization plays the leading role in the evolution of ovarioles: their number gradually decreases from 5 to 3 ovarioles per ovary. A hypothetical occurrence of three variants of follicle arrangement in testes, namely the three-follicular successive, three-follicular fan-shaped, and unifollicular ones is suggested and discussed. These variants are morphogenetically associated in the three-step morphocycle. The choice between each of the three states is determined by one of three variants affected by the hypothetical morphogenetic factor. The action of this factor can be switched from one variant to another, being evolutionarily labile and reversible; the mosaic distribution of variants in the phylogeny confirms this assumption. In Phthiraptera, the psocid factor responsible for the formation of fan-shaped and unifollicular testes is blocked. In Amblycera, the most primitive group of Mallophaga, testes are formed by three follicles arranged successively. In Ischnocera, a more advanced group, and their derivative Anoplura, testes are bifollicular, bearing opposite-pointed follicles; such an arrangement can be accounted for by the reduction of the apical follicle. The opposite-pointed bifollicular testes, typical of Ischnocera-Anoplura, may posses separate follicular bases or bases connate at base. The factor governingthe fusion of follicular bases is assumed to be identical to that governing the fusion of follicles in proscids. In the lice phylogeny, the alternation of pedunculate and basally fused follicles is observed. An evolutionary scenario is proposed, which accounts for all the data being analyzed.