EVOLUTIONARY ASPECTS OF ABERRANT MEIOSIS IN SOME PENTATOMINAE (HETEROPTERA)

The normal males of most animals may now and then produce a few sperms that carry an abnormal number of chromosomes. In the great majority of cases these are the result of a mitotic accident that occurred somewhere in the course of development. However, there are some species in which aberrant sperms are not accidental but are produced regularly in a certain region of all testes. Conditions such as these have been encountered in 21 species belonging to the insect Family of Pentatomidae (Heteroptera) and, more specifically, to the Subfamily Pentatominae. In most such species one entire compartment or lobe of every testis produces nothing but sperms with aberrant chromosome numbers. So bizarre are the meiotic deviations through which this is brought about that the testicular compartment in question has been called the "harlequin lobe." All the evidence indicates that such sperms very rarely produce viable offspring and they therefore play at most an indirect role in the hereditary mechanism of the species. Nevertheless they are produced in huge numbers and it is an interesting question how so wasteful a feature could have become establsihed in so many species. The cytological features of the harlequin meiosis have been treated elsewhere (Schrader, 1960) and the present account is primarily concerned with the evolutionary aspects of the harlequin lobe.