INCIDENCE AND ORIGIN QF ANDROGENETIC MALES IN X-RAYED HABROBRACON EGGS

¹ University of Pennsylvania

1. 1.57 per cent of Habrobracon eggs X-rayed in first meiotic metaphase (14,420 r-28,840 r) and laid by treated females mated to untreated males develop into androgenetic males. These will develop after any dose up to 54,000 r although lethal dose for the egg chromosomes in this stage is 2400 r. Cytological study of 294 such eggs (14,420 r-36,050 r) shows that three were undergoing androgenetic cleavage while three others were possibly preparing for it. A maximum of six, or 2.04 per cent, does not differ significantly from androgenetic survivors, and it must be concluded that androgenetic embryos at doses used are as viable as embryos developing in untreated eggs.

2. Chromatin bridges which appear in meiotic division II after treatment in first meiotic metaphase retard and distort the egg pronucleus, occasionally to such a degree that the sperm pronucleus cleaves and develops into a normal fertile haploid male with paternal traits only. The almost complete absence of these bridges after treatment in first meiotic prophase will explain the failure of androgenetic males to develop in these eggs.