Induction of diploid androgenetic and mitotic gynogenetic Nile tilapia (Oreochromis niloticus L.)

Abstract

Androgenesis is a potentially valuable technique for recovering fish from gene banks composed of cryopreserved sperm, developing inbred lines, and analyzing patterns of inheritance. The procedure for producing diploid organisms whose nuclear DNA is wholly of paternal origin is dependent on: (1) the denucleation of "host" eggs, and (2) the inhibition of the first mitotic division in order to double the haploid sperm chromosome complement following fertilization of host eggs. Denucleation of tilapia (Oreochromis niloticus L.) eggs was carried out using UV irradiation. Treatment durations of 5-8 min (total dose of 450-720 J/m(2)) produced acceptable yields of viable denucleated eggs [22.9±1.6% (±SE) of controls] as estimated by the survival of haploid androgenetic tilapia to 48 h post-fertilization. Successful mitotic inhibition was accomplished using a heat-shock of 42.5 °C for 3-4 min, applied at 2.5-min intervals from 22.5 to 30 min post-fertilization (mpf). The mean survival of androgenetic diploid fish to yolk-sac absorption for treatment groups varied from 0.4% to 5.3%, relative to the controls. Differences in the suceptibility of eggs from different females to UV irradiation were a significant factor in the overall yield of androgenetic diploids. Paternal effects did not significantly influence the androgenetic yield, suggesting that individual males would not be selected against. For comparative purposes mitotic gynogenetic "mitogyne" diploids were produced from UV-irradiated sperm. Mean survival to yolk-sac absorption varied from 0.5% to 10.64%, relative to controls. Similar optima for androgenetic and gynogenetic induction were found in the period 25-27.5 mpf (minutes post-fertilization). Induction treatments would appear to be operating on the same developmental events in both these techniques, and the results suggest that the UV irradiations used do relatively little damage to the eggs beyond nuclear inactivation. The results indicate that the production of androgenetic O. niloticus is possible on a consistent basis and that the application of this technique may be useful in quantitative and conservation genetics.

Comparison of temperature shock timing to induced artificial mitotic gynogenesis and androgenesis in common tench

“…Intra-species androgenesis conducted in this experiment also did not result in an increased survival rate of the offspring. A similar relationship between the time before the thermal shock (42°C, duration 4 min) was applied after fertilization was observed by Myers et al (1995) who conducted mitotic andro-and gynogenesis in Nile tilapia (Oreochromis niloticus). The authors found that the highest survival rate of andro-and gynogenetic offspring of Nile tilapia could be achieved when a thermal shock was applied 25 min (androgenesis) and 27.5 min (gynogenesis) after spermiation and with eggs incubated at 28°C.…”

“…A similar relationship was observed in this study for tench; this means that a thermal shock applied to stop the first mitotic division in inducing androgenetic development should be applied earlier than when gynogenetic development is induced. Meanwhile, Myers et al (1995) noted that the shock applied in order to duplicate genetic material in a diploid zygote should be earlier than in a haploid (andro-or gyno-genetic) zygote. The cause of the differences in the timing of the first division in a diploid zygote (androgenetic and gynogenetic) has not been identified.…”

“…The cause of the differences in the timing of the first division in a diploid zygote (androgenetic and gynogenetic) has not been identified. It may be attributed to a delay in mitosis in haploid (1n) organisms compared to diploid (2n) organisms (Myers et al 1995). The cause of the earlier division in an androgenetic zygote than in a gynogenetic zygote remains unknown.…”

Genetic Inactivation of Dace, Leuciscus Leuciscus (L.), Gametes Using UV Irradiation

“…These doses were higher than those recognized as optimum UV oocyte treatment for common carp (2500 J m ) by Lin and Dabrowski (1998), and were similar to those reported by Kucharczyk et al (1998) ). Viable UV doses for different species might result from differences in chorion structure, egg size and shape, as well as the position of the female pronucleus (Myers et al, 1995).…”

Validation of clonal line females for sex determination studies in nile tilapia Oreochromis niloticus L.

“…Phenotypic (morphological) markers can be used if the trait is based on a recessive allele (Galbusera et al, 2000) and such characteristics have been used to assess inheritance in gynogenetic fish such as common carp (Nagy et al, 1978) and tilapia (Don and Avtalion, 1988;Varadaraj 1990;Myers et al, 1995). However, such morphological markers are rare (Ezaz et al, 2004a), and confirmation using biochemical or molecular markers is required to allow the unambiguous identification of inheritance.…”