Genetic covariation in production traits of sub-adult black bream Acanthopagrus butcheri after grow-out

Predicting the suitability and reliability of traits associated with juvenile growth as indirect selection criteria for choosing future broodstock requires accurate and repeatable estimates of genetic (co)variation for growth traits at different ages. We compared juvenile wet weight of black bream Acanthopagrus butcheri (Munro) at 6 months of age with wet weight, dressed weight, fillet yield and gonad weight in tagged individuals at 18 months of age, following 12 months of farm grow‐out. Fish survival and tag retention was high, and there was significant among‐family variation for all traits. The phenotypic correlations among wet weight, dressed weight and fillet yield at 18 months of age were very high (0.93–0.97) and similar to their genetic correlations (0.96). Importantly, the phenotypic correlations between wet weight at 6 months and wet weight, dressed weight and fillet yield at 18 months were high (0.63–0.65), and so too were their genetic correlations (0.66–0.73), indicating the potential for using wet weight in the hatchery as a selection criterion for improved weight and meat yield of fish at harvest. Gonad weight shared little or no phenotypic or genetic correlation with these other traits, suggesting that selection for faster growing fish will not affect fecundity or sexual maturation rate. It appears, however, that cultured black bream do become sexually mature more rapidly than wild fish, as 78% of all fish harvested in this study had developing or mature gonads, whereas less than 50% of fish in wild populations are reproductively mature by the same age. Precocious sexual development may lead to uncontrolled spawning in grow‐out ponds and a potential loss of selection gains.     

Characterization of molecular variants of GnRH, induction of spermiation and sex reversal using salmon GnRH-A and domperidone in the protogynous diandric fish, Synbranchus marmoratus Bloch, (Teleostei, Synbranchidae)

This paper studies the molecular variants of gonadotropin-releasing hormone (GnRH) present in the brain of the protogynous swamp eel, Synbranchus marmoratus, and the effects of the administration of salmon GnRH analogue (sGnRH-A) and the dopamine receptor antagonist, domperidone (DOM) on final maturation and gamete release in this species. Evidence for the presence of two GnRH variants, sGnRH and cIIGnRH were obtained by reverse phase high-pressure liquid chromatography (RP-HPLC) and radioimmunoassay with different antisera. The effects of treatment with sGnRH-A+DOM were checked by three ways: oocyte and milt release by stripping, histological analysis of the gonadal tissue, and androgen serum levels at different times throughout the experiment. In males, spermiation was induced after three weeks of treatment. In the female group, sGnRH-A+DOM did not induce ovulation at the end of the experiment. Histological analysis of the gonads from the female group showed evidence of sex reversal. All the treated fish had elevated androgen serum levels from the third week, with respect to control fish. In all cases, serum estradiol levels were undetectable. These results suggest that treatment with sGnRH analog and DOM induce sex reversal in female and spermiation in males. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of water temperature and growth variation on the sex ratio of experimentally reared eels

In a controlled experiment, elvers (Anguilla anguilla L.) were reared for 137 weeks at 17, 20 and 26°C. Most eels with macroscopically sexable gonads were males. The proportions of females were 14% of sexable individuals at 26°C and 7–8% at 17 and 20°C. During the first 15 weeks, 20–50% of initial numbers were lost, but this early mortality was not significantly size selective. In spite of a long term experiment, a significant number of the survivors never attained a sexable size. Nongrowers (7–9 cm) were still alive nearly three years after being caught as glass eels. Among the earliest fast growers, 5% females, or less, were found. The proportion of females increased in later grading groups, but the pattern of increase did not indicate that males and females have separated mean ranks in a fixed growth hierarchy. Water temperature influenced observed sex ratios, but probably not through direct influence on the sex differentiation. Some alternative hypotheses, dealing with population density and individual growth status, are discussed.     

The cytochrome P450 system of Atlantic salmon (Salmo salar): II. Variations in hepatic catalytic activities and isozyme patterns during an annual reproductive cycle

A group of Atlantic salmon (Salmo salar) was followed through their first year of maturation and spawning. At monthly intervals, starting with juvenile fish in December, 5–7 fish of each sex were killed, and liver and plasma were sampled. The last sampling point was of spawning fish in November a year later. Variables in the cytochrome P450 (P450) system were studied in hepatic microsomes, and estradiol 17 was measured in the plasma of females to assess the maturational status. The P450 1A1-mediated 7-ethoxyresorufin O-deethylase (EROD) started at high levels in winter, but decreased to non-detectable activities in pre-spawning females. Decreases, but not to the same extent, were also observed during this period in total cytochrome P450, cytochrome b₅, NADPH-cytochrome P450 reductase, and in the content of two immunochemically determined P450 isozymes. At the same time, LSI levels increased in maturing females (starting in July), and GSI levels increased in both sexes (starting in May). Sex specific differences were observed in pre-spawning fish in September and October, with levels of total P450, b₅, NADPH-cytochrome P450 reductase, EROD and P450 isozymes significantly lower in females. At the same time, plasma estradiol-17 levels reached peak values in females. The results point to the important role of sex steroids such as estradiol-17 as major factors in the regulation of final sexual maturation. However, this study also indicates that there may be estradiol-17 independent events of equal importance in the early stages of gonadal maturation that may involve the P450 system. The changes observed in the P450 system (as a major drug and steroid metabolizing system) of Atlantic salmon during sexual maturation may be of importance both in the endogenous transduction of hormonal signals, and as a pharmacological basis for designing therapeutic treatment of diseases in the aquaculture industry.Parts of this work were presented at the 5th International Symposium on Responses of Marine Organisms to Pollutants, April 1989 in Plymouth, United Kingdom (Larsen and Goks\/oyr 1989).     

中华绒螯蟹副性征的研究

在解剖、测量性成熟和未成熟中华绒螯蟹外部形态和性腺之基础上,试用“双百分率法”和“差异显著性检测法”对中华绒螯蟹的副性征进行了研究。结果表明,性成熟后的雌、雄中华绒螯蟹均具有较明显的副性征。     

Effects of (D-Ala6, Pro9N ethylamide) — LHRH on plasma levels of gonadotropin, 17α,20β-dihydroxy-4-pregnen-3-one and testosterone in male goldeye (hiodon alosoides Rafineque)

Male goldeye were treated with (D-Ala⁶, Pro⁹-N ethylamide) — LHRH (LHRH-A) in saline or a silastic pellet (100 µg.kg^–1 body weight) and changes in plasma gonadotropin (GtH), 17,20-dihydroxy-4-pregnen-3-one (17,20P) and testosterone (T) levels were determined by radioimmunoassay. LHRH-A increased plasma GtH levels, with the response to LHRH-A in saline being of much greater magnitude and duration than the response to silastic pellet implants. Seasonal differences were found in the response to LHRH-A. Spermiated fish were the most responsive, recrudescing fish the least, and regressed fish displayed an intermediate response. Plasma 17,20P levels were elevated in response to LHRHA in fish of all sexual stages although the magnitude of the increase was not related to the magnitude of the increase in GtH levels. Treatment with LHRH-A also resulted in a transitory increase in plasma T levels. The endocrine control of GtH and steroid secretion in goldeye is discussed in relation to studies in cyprinids and salmonids. Address for reprint requests: Department of Zoology, University of Alberta, Edmonton, Alberta T6G 2E9 Canada.     

2013年杭州市萧山区松墨天牛成虫林间种群动态的监测研究

2013年4—10月对浙江省杭州市萧山地区南部马尾松与松阔次生混交林林中松墨天牛的种群数量动态进行了监测,结果表明,松墨天牛在萧山地区南部松林中1年只发生1代,成虫活动期为5月中旬至9月下旬,6月下旬为成虫羽化高峰期,2个监测点所诱获的松墨天牛成虫种群个体的雌、雄性比为1.51:1和1.73:1。     

安义瓦灰鸡早期生长规律研究

通过对不同羽速基因及不同性别安义瓦灰鸡的早期生长规律进行研究,结果表明:不同性别安义瓦灰鸡的早期生长规律有较大差异(P<0.01),不同羽速基因安义瓦灰鸡的早期生长规律差异不显著;安义瓦灰鸡的生长速度与出壳重无关,出壳重只影响其育雏期的体重;性别对体重的影响较晚,且公鸡大于母鸡。     

利用分离的奶牛X精子冷冻精液生产体内性控胚胎试验

采用常规精液和分离的X精子冷冻精液对115头超数排卵的青年和经产荷斯坦母牛人工输精生产体内性控胚胎。结果表明,利用2支和3支性控精液给超排青年母牛输精,头均分别获得6.8枚±4.8枚和6.3枚±3.2枚可用胚胎,与常规精液的超排效果(7.2枚±5.2枚)无明显差异;利用2支和3支性控精液给超排经产母牛输精,头均可用胚胎分别为7.5枚±4.5枚和8.6枚±5.6枚,与常规精液的超排效果(6.1枚±3.2枚)相比,分别增加23%(P>0.05)和41%(P>0.05),无显著差异,但解冻后性控精子会明显影响经产母牛的受精率;对用性控精液输精生产的12枚抽样胚胎采用LAMP法进行性别鉴定并移植,结果获得了91.7%的雌性率和36.4%的受胎率。结果提示,X精子的分离过程会在一定程度上影响受精率,用分离的X精子冷冻精液对超排母牛进行人工授精生产体内性控胚胎是可行的。     

我国作物病虫害生物防治研究与应用最新进展

本文总结了近5年来我国在作物病虫害生物防治研究和应用方面的最新进展, 包括作物害虫、病害(真菌、细菌和病毒病)和线虫的生物防治、植物免疫和昆虫性信息素的研究和应用, 以及新方法和新技术在作物病虫控制中的应用。同时, 与国外的研究进展进行了比较, 指出了存在的主要问题、发展趋势与对策建议。