Production of androgenetic diploid loach by cold-shock of eggs fertilized
with diploid sperm
Diploid androgenotes were produced without egg irradiation in the loach, Misgurnus
anguillicaudatus. Eggs of wild-type diploid females were fertilized with diploid sperm of
a neo-tetraploid male and then cold-shock treated at 3 C (range, 0.5 C) for 30 minutes
just after fertilization to eliminate the female nucleus. After hatching, ploidy status of the
hatched larvae was analyzed by flow cytometry, which revealed putative diploid androgenotes
as well as larvae possessing other ploidies. Five independent microsatellite DNA
Introduction
Teleost eggs are normally ovulated at the metaphase of
the second meiosis (M II). At this point, the eggs are
physiologically mature and are spawned outside of the
female to accept sperm for fertilization in ambient water.
Such reproductive traits of most teleosts provide the
potential for chromosome manipulation, such as induced
polyploidy (increase in the number of chromosome sets),
gynogenesis (all-female inheritance), and androgenesis
(all-male inheritance). Androgenesis is also defined as the
development of progeny carrying chromosomes exclusively
transmitted from the male parent. Three types of
androgenesis have been recognized to date: (1) obligate
androgenesis (or paternal apomixis); (2) spontaneous
androgenesis; and (3) artificial androgenesis [1]. In obligate
markers were genotyped to confirm all-male inheritance of the resultant diploid larvae.
The mean SD yield rate of diploid androgenetic larvae to total eggs used was 12.29
3.25% in the cold-shock group and 22.23 13.42% in the UV-irradiated group (P > 0.05).
No diploid androgenetic larvae were detected in the intact control group. To our knowledge,
this is the first report demonstrating successful induction of diploid androgenotes
without egg irradiation in fish.