Artificial Activation of the Egg in a Gynogenetic Spider Beetle

Abstract

IN a recent communication in Nature by Moore, Woodroffe and Sanderson¹, it was shown that the spider beetle Ptinus latro Fab. exists only as females and that these require to be inseminated by males of the allied Ptinus hirtellus Sturm in order to produce viable eggs. Insemination by sterilized males was ineffective. The details of the cytological phenomena involved were communicated at the Tenth International Congress of Entomology, 1956 ². Since no conclusions could be reached as to whether the sperm enters the yolk of the P. latro egg, it is proposed to carry out experiments using labelled sperm and autoradiography. Meanwhile, the following is a report on results of experiments on artificial activation of the virgin egg. The methods employed involved cold and heat treatments, exposure to ether vapour, and puncturing with a fine glass needle, but the best results were obtained with the needle puncture method or traumatization. It was found that the maturation division proceeded as far as telophase (Fig. 1) in 50–60 per cent of the 200 eggs treated. Eggs were squashed in aceto-orcein from 10 to 120 min. after puncture and it was observed that the maturation division is complete usually after 30 min. However, no onset of cleavage was seen up to 2 hr., after which time the eggs tend to dry up. In untreated eggs from virgin females, the development is usually blocked at the first metaphase (Fig. 2). The chromosomes may remain in this stage up to a period of five days, and then degenerate. From the remarkably high percentage of eggs activated by traumatization, it seems reasonable to assume that the role of the sperm in initiating activation is mainly of a physical nature. Further work is in progress and will be reported elsewhere.