Sexually Dimorphic Growth Stimulation in a Strain of Growth Hormone Transgenic Coho Salmon (Oncorhynchus kisutch)

Characterization of sexual size dimorphism in mandarin fish and association with igfbp-5a/b regulation

Mandarin fish (Siniperca chuatsi) is an important cultured fish in East Asia that shows sexual size dimorphism (SSD), with females growing faster than males when reaching marketable size. However, the regulatory mechanism of SSD is not clear. To characterize SSD of mandarin fish and its association with gh/igf1/igfbp-5 expression, gonadal developmental atlas of the females and the males were described, and growth parameters and serum levels of E2 and T, as well as the relative expression levels of gh, igf1, and igfbp-5a/b mRNAs, were determined. The results showed that the logistic growth equation of body mass and total length of female and male were W(♀) = 667.57/(1 + e^(4.19 - 1.24*t)), W(♂) = 582.71/(1 + e^(4.07 - 1.27*t)), L(♀) = 31.47/(1 + e^1.95 - 1.08*t)), L(♂) = 26.20/(1 + e^(2.56 - 1.5*t)). The month of inflection points for body mass for females and males were 3.37 mph and 3.20 mph, respectively, when the body mass were 333.79 g and 291.36 g. The month of inflection points for total length growth were 1.80 mph and 1.70 mph, respectively, when the total length were 18.52 cm and 16.28 cm. At 1.5-2.0 mph, SSD was not clearly demonstrated. At 3.0 mph, the body mass of the females was significantly higher than that of the males (P < 0.05), Serum E2, brain gh, and liver igf1 expression of the females was significantly higher than that of the males (P < 0.05); T content of the males was significantly higher than that of the females (P < 0.05). At 4.0 months of age, the body mass of the females was highly significantly higher than that of the males (P < 0.01), Serum E2, brain gh, and liver igf1 expression of the females was highly significantly higher than that of the males (P < 0.05); T content of the males was significantly higher than that of the females (P < 0.05). With the continuous development of gonads, muscle and liver igfbp-5a and -5b expression generally tend to increase in females and males, while igfbp-5a showed a gradual increasing trend, and igfbp-5b expression showed a trend of decreasing and then increasing. Male igfbp-5a/b expression was significantly higher than female at the age of 3.0-4.0 months (P < 0.05). This work verified that the females had faster growth rate since 3.0 mph compared to the males, which may be related to higher E2 levels in females leading to higher igf1 level, through inhibition of igfbp-5a/b expression.

Production of all-male non-transgenic zebrafish by conditional primordial germ cell ablation

Many fish species exhibit remarkable sexual dimorphism, with males possessing numerous advantageous traits for commercial production by aquaculture such as faster growth rate, more efficient food energy utilization for muscle development, and better breeding performance. Several studies have shown that a decrease in the number of primordial germ cells (PGCs) during early development leads predominantly to male progeny. In this study, we developed a method to obtain all-male zebrafish (Danio rerio) by targeted PGC ablation using the nitroreductase/metronidazole (NTR/Mtz) system. Embryos generated by female heterozygous Tg(nanos3:nfsB-mCherry-nanos3 3'UTR) and male wild-types (WTs) were treated with vehicle or Mtz. Compared to vehicle-treated controls, 5.0 and 10.0 mM Mtz treatment for 24 h significantly reduced the number of PGCs and yielded an exclusively male phenotype in adulthood. The gonads of offspring treated with 5.0 mM Mtz exhibited relatively normal morphology and histological characteristics. Furthermore, these males were able to chase females, spawn, and produce viable offspring, while about 20.0% of males treated with 10.0 mM Mtz were unable to produce viable offspring. The 5.0 mM Mtz treatment protocol may thus be suitable for large-scale production of fertile male offspring. Moreover, about half of these males were WT as evidenced by the absence of nfsB gene expression. It may thus be possible to breed an all-male WT fish population by Mtz-mediated PGC ablation.

Comparison of growth performance among channel-blue hybrid catfish, ccGH transgenic channel catfish, and channel catfish in a tank culture system

Fish is an essential source of high-quality protein for people worldwide. The present study was designed to compare the growth performance among the channel-blue hybrid catfish, channel catfish transgenic for the channel catfish growth hormone (ccGH) cDNA driven by the antifreeze protein promoter from an ocean pout Zoarces americanus (opAFP-ccGH), and non-transgenic channel catfish control. Mean body weight of channel-blue hybrid catfish was 15.80 and 24.06% larger than non-transgenic channel catfish control at 4 and 18 months of age, respectively. However, transgenic opAFP-ccGH channel catfish were 5.52 and 43.41% larger than channel-blue hybrid catfish and 22.19 and 77.91% larger than their controls at 4 and 18 months of age, respectively. Significant differences in mean body weight between the sexes within all genetic types were found. Males were larger than females (P < 0.001). However, mean body weight of non-transgenic males was not larger than transgenic opAFP-ccGH females or male and female hybrid catfish. Condition factor of transgenic opAFP-ccGH channel catfish was higher (P < 0.05) than that of full-sibling, non-transgenic channel catfish and hybrid catfish. The mean percentage body weight gain of GH transgenic channel catfish was 559%, the channel-blue hybrid catfish was 384.9% and their non-transgenic controls channel catfish was 352.6%.

Growth Differences of Growth Hormone Transgenic Female and Male Channel Catfish, Ictalurus punctatus, Grown in Earthen Ponds to Sexual Maturation

This study compared growth performance between female and male transgenic channel catfish, Ictalurus punctatus, containing channel catfish growth hormone full-length cDNA driven by the ocean pout antifreeze protein promoter, opAFP-ccGH, the rainbow trout metallothionein promoter, rtMT-ccGH, or both constructs, and their non-transgenic siblings in earthen ponds at 16 and 48 months of age. Body weight between the transgenic and their non-transgenic siblings differed (P < 0.001) at all ages. Transgenic F₂ opAFP-ccGH grew 1.51- to 2.58-, F₂ rtMT-ccGH grew 1.44- to 2.99- and F₁fish transgenic for both constructs grew 1.36- to 2.92- fold larger than their non-transgenic sibling controls, depending upon age and sex. Body weight of the transgenic GH males was significantly higher than those of the transgenic GH females at 16 months of age (P < 0.001). However, body weight of the transgenic GH females was significantly higher (P < 0.001) compared with those of the transgenic GH males at 48 months of age, but not for the double transgenics (P > 0.05). In the case of non-transgenic GH siblings, males were larger than females at both 16 and 48 months of age (P < 0.001). Sexually dimorphic responses to GH transgenes were the opposite after sexual maturation. When critically low dissolved oxygen levels were encountered, survival of transgenic male and female opAFP-ccGH channel catfish was lower than that of controls (P = 0.004), as well as rtMT-ccGH females (P = 0.11), which is not surprising since the largest fish are most likely to succumb during an oxygen depletion.