Assessment of fitness components in transgenic Japanese medaka as a model to assess environmental risk in genetically modified organisms

Liza V Jimenez, Purdue University

Abstract

The objective of this research was to establish methods to estimate the fitness components needed to predict the potential for transgenic organisms to spread in a wild population. Three transgenic (TR) lines of Japanese medaka (Oryzias latipes) were used, one microinjected with a human growth hormone gene construct (hGH) and two injected with a salmon growth hormone gene construct (400 and H67). Using a static fitness estimation protocol for all three TR lines, pairs of different genotype combinations were crossed to estimate relative viability, average age at sexual maturity, average fecundity, average fertility, and body mass for both TR and wild type (WT) fish. Using a dynamic fitness estimation protocol (hGH line only), groups of mixed genotypes of each sex were crossed with individuals of the same genotype of the opposite sex to estimate the mating advantage of transgenic males and females relative to wild type. TR-hGH fish were similar to WT individuals in body weight, but had a relative viability of 20% of that of WT fish. TR-hGH females were more fecund than WT females, on average (hGH = 24 ± 1.83 eggs, N = 14; WT = 19 ± 0.62 eggs, N = 16, F = 4.52, P = 0.04), but TR-hGH males were similar in fertility to WT males (84 ± 1.65% compared to 86 ± 1.43%; t = 0.49; P = 0.63). TR-hGH offspring attained sexual maturity sooner than WT offspring did (58.5 ± 1.79 days and 64.3 ± 1.27 days, respectively; t = 2.56; P = 0.01). There was no significant mating advantage of TR-hGH males over WT males (X2 = 3.75 < χ 2.05(3) = 7.82). TR-400 fish were nearly twice as heavy as WT individuals (400 = 129 mg and WT = 64 mg), but had a relative viability of 16% of that of WT fish. TR-400 females were significantly less fecund than WT females, on average (16 ± 0.53 eggs, N = 15 and 19 ± 0.62 eggs, N = 16, respectively; F = 8.30, P = 0.00), but TR-400 males were similar in fertility to WT males (85 ± 1.62% compared to 86 ± 1.43%; t = −0.45; P = 0.65). TR-400 offspring attained sexual maturity sooner than WT offspring did (59.5 ± 3.24 days and 64.3 ± 1.27 days, respectively; t = 1.39; P = 0.11). TR-H67 fish were up to 1.33 fold heavier than WT individuals (H67 = 106 mg and WT = 89 mg), but had a relative viability of 36% of that of WT fish. TR-H67 females were less fecund than WT females (17 ± 0.51 eggs, N = 17 and 19 ± 0.62 eggs, N = 16, respectively; F = 4.66, P = 0.03), but again TR-H67 males were similar in fertility to WT males (84 ± 1.94% compared to 86 + 1.43%; t = −0.69; P = 0.49). TR-H67 offspring attained sexual maturity at a similar age as WT offspring (61.6 ± 1.94 days compared to 64.3 ± 1.27 days; t = 1.27; P = 0.27).

Degree

Ph.D.

Advisors

Howard, Purdue University.

Subject Area

Aquaculture|Fish production|Genetics|Zoology|Environmental science

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