北京地区宽鳍(魚巤)的生长及食性

2004-2006年,作者对分布于北京市怀柔水库上游入库河流怀沙河和怀九河宽鳍鱲的生物学进行了研究。结果显示:北京地区宽鳍鱲年龄组成较小,雄鱼最大3龄,雌鱼最大2龄。体长和体重相关关系式为:W=9×10-6L3.1947(r=0.9784),其种群呈异速增长。1龄组雌雄鱼体长和体重无显著差异,2龄组雄鱼体长和体重显著大于雌鱼,可能与雌鱼性成熟后生长速度减慢有关。雄鱼VonBertalanffy生长方程为:Lt=121.56×(1-e-0.3718(t 0.6272)),最大体长121.56mm;Wt=41.16×(1-e-0.3718(t 0.6272))3,最大体重41.16g;生长拐点tr=2.41龄;雌鱼最大为2龄,未能拟合VonBertalanffy生长方程。丰满度和饱食指数均呈周年变化,这可能与水温变化和繁殖期的影响有关。北京地区的宽鳍鱲为植食性,主要摄食硅藻,取食具选择性,且获得的食物量与藻类的多度一定程度上正相关。雌雄性比接近1∶1,1冬龄性成熟;繁殖期5-7月,5月份成熟系数最高。与嘉陵江种群相比,北京种群体长、体重均小于嘉陵江种群;食性上,前人研究认为嘉陵江种群为肉食性,但经我们重新鉴定,嘉陵江种群也为植食性,个别肉食性食物成分可能是随摄食的藻类带入的;在年龄组成、种群增长方式、性比及繁殖特性上,未发现二者有明显差异。基于北京地区宽鳍鱲的生物学特性,结合该地区的环境特点,我们建议通过控制捕捞数量、选择最适捕捞时间、保护原有生境来维持北京地区宽鳍鱲资源的可持续利用。     

性类固醇激素对黄颡鱼雌雄生长二态性的影响

为了研究性类固醇激素在雌雄生长二态性中(Sexual Size Dimorphism, SSD)的作用, 文章分析了性类固醇激素对雌雄生长、性腺发育和能量代谢的影响。结果显示: 17β-雌二醇(17β-estradiol, E₂)显著抑制黄颡鱼的生长, 且E₂显著促进能量在肝脏中的分配, 但在摄食量上无显著影响, 所以E2对黄颡鱼生长的抑制是能量分配的差异引起, 而不是能量获取差异引起。17α-甲基睾丸酮(17α-Methyltestosterone, MT)显著促进雌鱼生长, 但抑制雄鱼生长, MT能显著促进黄颡鱼摄食和肝脏的能量分配, 显著抑制卵母细胞的发育和卵巢的能量投入。本研究发现MT通过促进摄食, 抑制卵巢发育并且减少性腺发育的能量投入, 从而促进雌鱼生长; E₂能够显著增加雌雄鱼在肝脏中能量的投入, 最终抑制雌雄生长。实验结果只能部分解释实验中观察到的生长差异现象, 因此我们需要更进一步从能量的摄入、分配及消耗三方面来研究雌雄生长的二态性。     

广州地区人工湖食蚊鱼的种群特征

为调查广州地区人工湖泊食蚊鱼的分布以及探究不同生境要素下食蚊鱼的生长繁殖特点和种群特征,于2012 年5 月-7月份对广州地区6 区19 个人工湖进行实地考察,发现所考察的人工湖均有食蚊鱼的分布。利用捕捞量比较其中4 个人工湖食蚊鱼种群数量,结果显示水体相对富营养化的月湖食蚊鱼数量比其余3 个人工湖高出39.5-43.1 倍。比较4 个人工湖食蚊鱼的形态、摄食、相对怀卵量以及种群结构等指标,结果显示月湖食蚊鱼肥满指数显著低于其余3 个人工湖,而肝体指数和消化道饱满指数却显著高于其余3 个人工湖。同时,月湖雌鱼的相对怀卵量也显著高于其余3 个人工湖,其种群中幼鱼所占比例最大,成鱼中雄鱼所占比例大于雌鱼。反映了水体饵料生物丰富条件下,更有利于食蚊鱼的摄食和繁殖,种群结构低龄化,呈快速增长型。     

白鲟年龄鉴定及其生长的初步研究

以齿骨和胸鳍条为年龄鉴定材料,通过其骨磨片比较研究,结果显示用胸鳍条鉴定白鲟的年龄较为可靠。所收集的６６尾白鲟样品中,根据胸鳍条鉴定年龄,幼鲟８尾,１－３龄。成鱼５８尾中,雄鱼３３尾,最低６龄,最高１１龄,多数个体为８－９龄。雌鱼２５尾,最低７龄,最高１７龄,多数为１０－１２。白鲟生长速度快,特别在第一年其长度生长最为突出。当年１０月份的幼鱼全长达５３－６１ｃｍ,１龄鱼平均全长７５ｃｍ。推算结果表明雌雄鱼在性成熟前生长无明显差异,性成熟后,雌鱼的长度及重量均大于相同年龄雄鱼。采用ＶＢＧＦ描述白鲟全长及体重的增长。     

人工养殖中华鲟后备亲鱼摄食和 生长的周年变化

实现全人工繁殖是中华鲟(Acipenser sinensis)物种保护的重要途径,建立中华鲟人工养殖亲鱼群体是人工繁殖的基础条件。本文以自然变温条件下人工培育的中华鲟后备亲鱼(年龄15龄,体长183~235 cm,体重71.5~180.5 kg,n=14)为研究对象,每天对摄食行为进行观察记录,每月对生长指标进行检查测量,通过持续12个月的跟踪观测,开展后备亲鱼摄食和生长特征研究。结果显示,后备亲鱼摄食比例、摄食频次具有明显的月际变化特征,均存在极显著差异(P<0.01),雌鱼、雄鱼均具有相似的周年变化规律,雌雄摄食比例仅9月存在显著差异(P<0.05),雌雄摄食频次同月均无显著差异(P>0.05);后备亲鱼配合饲料日饵率和鲜活饵料日饵率均呈现先下降后升高的变化趋势,配合饲料日饵率10月最低,为0.02%,1月最高,为0.19%,鲜活饵料日饵率6月最低,为0.12%,4月最高,为0.99%;配合饲料的年均摄食比例仅为18.39%±17.61%,鲜活饵料的年均摄食比例为62.57%±15.63%,配合饲料和鲜活饵料摄食比例存在极显著差异(P<0.01),可见实验对象对鲜活饵料具有明显摄食偏好;配合饲料日饵率、鲜活饵料日饵率、总摄食率、雌鱼摄食率、总摄食频次和雌鱼摄食频次与水温存在显著负相关关系(P<0.05);后备亲鱼体周长、体重、肥满度均呈现先下降后上升的变化趋势,呈现生长缓慢特征,不同月份肥满度存在显著差异(P<0.05),其他生长指标不同月份间比较无显著差异(P>0.05)。在中华鲟后备亲鱼培育管理中,应注意加强水温调控,提供适宜养殖条件,减少人为干扰,改善摄食和生长效果。本研究对中华鲟后备亲鱼养殖技术的改进具有参考价值。     

三倍体虹鳟性转换及性腺发育的研究

用高温刺激法获得三倍体虹鳟幼鱼。从开始投饵起,分别投喂含有不同浓度17β-雌二醇(0～60μg/μg)的饵料,持续60天,获得了93%～100%的高三倍体雌性率(对照组的雌性率为52%)。三倍体雄鱼可观察到其精子形成,但性腺成熟度较相对的二倍体差;三倍体雌鱼的生殖细胞多停留在偶线期到粗线期,未发现有性成熟个体。实验结果推测,三倍体虹鳟雌鱼的不育现象看来不是由于雌雄基因组的组成差异而致,更可能是由于三组染色体造成对虹鳟卵巢发育更大的阻力。雌二醇处理对三倍体虹鳟幼鱼的生长和成活没有明显的影响。     

三倍体Gong鳟性转换及性腺发育的研究

用高温刺激法获得三倍体Gong鳟幼体。从开始投饵起,分别投喂含有不同浓度17β－雌二醇（0－60μg/μg）的饵料,持续60天,获得了93％－100％的高三倍体雌性率（对照组的雌性率为52％）。三倍体雄鱼可观察到其精子形成,但性腺成熟度较相对的二倍体差;三倍体雌鱼的生殖细胞多停留在偶线期到粗线期,未发现有性成熟个体。实验结果推测,三倍体Gong鳟雌鱼的不育现象看来不是由于雌雄基因组的组成差异而致,更可能是由于三组染色体造成对Gong鳟卵巢发育更大的阻力。雌二醇处理对三倍体Gong鳟幼鱼的生长和成活没有明显的影响。     

食蚊鱼昼夜摄食节律观察

以分时段采样法研究入侵物种食蚊鱼的夏季昼夜摄食节律。食蚊鱼夏季种群内有雌鱼、雄鱼和幼鱼三个不同的摄食类群,这三个类群的摄食节律差异明显。雌鱼摄食节律成双峰型,第一高峰在10:00,而最高峰在22:00,此时肠道食物团平均重量11.70±11.60mg,饱满指数为190.22±155.61。幼鱼也成双峰型,分别在6:00和18:00有两个摄食高峰,以清晨6:00为最高,肠道食物团平均重1.08±1.09mg,饱满指数为128.44±105.49。雄鱼则成单峰型,摄食高峰出现午后14:00左右,肠道食物团平均重0.71±0.96mg,饱满指数为71.80±107.65。食蚊鱼不同摄食类群间的摄食高峰交错出现,是其协调种内关系,降低种内竞争的一种有效行为机制。     

投喂策略对黄颡鱼生长和繁殖的影响

实验设置饱食投喂(AS)、80%饱食(80AS)、50%饱食(50AS)及先饥饿34d后再饱食投喂31d (HAS)四个处理组,饲养初重(86.6±0.41) g的雌性黄颡鱼(Pelteobagrus fulvidraco) 65d,于实验中期(34d)和实验结束时取样,以探究投喂策略对黄颡鱼母本生长性能和繁殖能力的影响。实验结果显示:80AS组、50AS组和HAS组的总摄食量基本符合实验设计的比例且显著低于AS组。在实验结束时, 80AS组的增重率和体重与AS组无显著差异, HAS组体重显著低于AS组并与80AS组无显著差异,生长未能达到同期饱食水平。各组在实验结束时的肌肉粗脂肪和粗蛋白含量均随投喂水平降低而降低,性腺粗脂肪和粗蛋白则无显著差异,据此可以推测母本将营养优先供给性腺而非肌肉。实验末期AS组和80AS组卵直径无显著差异,均显著高于50AS组并低于HAS组,表明饥饿后恢复摄食对卵的发育有补偿效应。实验结束时各处理组的绝对繁殖力和相对繁殖力未受到投喂策略的显著影响。80AS、50AS及HAS组的star、sf-1、3β-hsd和cyp19a1基因表达由中期的显著低于AS组上调...     

瓣结鱼的繁殖习性以及精子的活力与寿命

经组织学观察,研究了性成熟瓣结鱼的性腺发育的周期性变化,并初步分析了瓣结鱼的和。其繁殖盛期在４月下旬到５月上旬,繁殖群体♀：♂＝１：９．１,繁殖季节具有雌雄二态性,雄鱼绝大多数在２龄性成熟,雌鱼多在３性成熟。不同浓度的ＮａＣｌ溶液对精子活力和寿命有较大影响,成熟精子在０．４５－０．５５％的ＮａＣｌ溶液中剧烈运动时间最长,平均为１７２．５秒。     

Effect of individual and group rearing on age and size at maturity of male mosquitofish, Gambusia affinis

Age and size at sexual maturity were significantly greater for male mosquitofish, Gambusia affinis Baird and Girard, reared in sib-groups than for their sibs reared individually. Age at sexual maturity averaged 43.3 and 62.1 days for individually- and group-reared males, respectively, a 43% difference; final length and weight at maturity were 7.7 and 34.2% greater, respectively, for group-reared males than for their individually-reared sibs. The results were consistent among 30 families that represented the progeny of 30 wild-caught females. The observed differences may be attributable to behavioural interactions affecting the neuroendocrine control of the maturation process, as suggested by previous studies of Xiphophorus .     

Organizational–Activational Concept Revisited: Sexual Differentiation in an Atherinomorph Teleost

Because of its numerous sexually dimorphic characters, the Western mosquitofishGambusia affinis affinisis an excellent vertebrate system for addressing questions concerning sexual differentiation. In this review, the actions and limits of gonadal sex steroids, specifically testosterone, on the development of the sexually dimorphic anal fin and its axial and appendicular support are described. Data from our laboratory show that the critical period in this species for the anterior transposition of the male anal fin and its appendicular support occurs during the late embryonic period and that this differentiation of the male phenotypic genital areaduring the critical period is regulated by androgen.     

Androgen dependent development of a modified anal fin, gonopodium, as a model to understand the mechanism of secondary sexual character expression in vertebrates

Male external genitalia show structural variations among species. Androgenic hormones are essential for the morphological specification of male type copulatory organs, while little is known about the developmental mechanisms of such secondary sexual characters. Western mosquitofish Gambusia affinis may offer a clue to the sexual differentiation researches, because they show a prominent masculine sexual character for appendage development, anal fin to gonopodium (GP) transition, and its formation could be induced in early juvenile fry by exogenously supplied androgens. We show that GP development is promoted by androgen dependent augmentation of sonic hedgehog (Shh) expression. Two AR cDNAs were cloned and identified as ARalpha and ARbeta from western mosquitofish. Both ARs were predominantly expressed in the distal region of outgrowing anal fin rays. Exposure of fry to androgen caused anal fin outgrowth concomitant with the Shh induction in the distal anal fin ray epithelium. When AR signaling was inhibited by its antagonist flutamide in fry, the initial induction of the Shh was suppressed accompanying retarded anal fin outgrowth. Similar suppression of anal fin outgrowth was induced by treatment with cyclopamine, an inhibitor of Shh signaling. These observations indicate that androgen dependent Shh expression is required for anal fin outgrowth leading to the formation of a genital appendage, the GP in teleost fishes. Androgen-induced GP formation may provide insights into the expression mechanism regulating the specification of sexual features in vertebrates.     

The western mosquitofish (Gambusia affinis affinis): a new laboratory animal resource for the study of sexual dimorphism in neural circuits

The western mosquitofish (Gambusia affinis affinis) is a useful model for the study of sexual dimorphism and the neural circuits associated with sexual differentiation. This is largely because of its anal fin, which undergoes radical postnatal transformation in males. Understanding the neural mechanisms involved in this process may also help elucidate basic principles of the nervous system. The authors describe the mosquitofish as a model for research and present guidelines for the care and use of this species.     

A male poecillid's sexually dimorphic body plan, behavior, and nervous system

Here we review the literature of a male poecillid's sexually dimorphic body plan, behavior, and nervous system, including work dating from the mid 1800s to the mid 1990s as well as work in press or in preparation for publication. Rosa-Molinar described the remodeling of the sexually dimorphic anal fin appendicular support, confirmed earlier claims about the development of the male and female secondary sex characteristics in the Western Mosquitofish, Gambusia affinis and provided for the first time direct embryonic evidence suggesting that remodeling of the sexually dimorphic anal fin appendicular support is biphasic. The first process begins in embryos and proceeds similarly in immature males and females; the second process occurs only in males and results in the anterior transposition of the anal fin and its appendicular support to the level of vertebra 11 [Rosa-Molinar E, Hendricks SE, Rodriguez-Sierra JF, Fritzsch B. 1994. Development of the anal fin appendicular support in the western mosquitofish, Gambusia affinis (Baird and Girard, 1854): a reinvestigation and reinterpretation. Acta Anat 151:20-35.] and the formation of a gonopodium used for internal fertilization. Studies using high-speed video cameras confirmed and extended Peden's and others' observations of copulatory behavior. The cameras showed that circumduction is a complex movement combining in a very fast sequence abduction, extension and pronation, S-start-type fast-start (defined as torque-thrust), and adduction movements. Recent work on the nervous system demonstrated dye-coupling between motor neurons and interneurons via gap junctions, suggesting an attractive substrate for the rapid motions involved in poecillid copulatory reflexes.     

Evidence for the secondary sexual development of the anal fin in female kokanee salmon Oncorhynchus nerka

This study examines whether the anal fin undergoes secondary sexual development similar to other reproductive traits in salmonids. This hypothesis was tested by comparing the anal‐fin size of female kokanee salmon Oncorhynchus nerka that were in the early and late stages of sexual development. Females in an advanced stage of maturation had significantly larger anal fins relative to females in an early state of maturation (+4–7%), indicating that the anal fin undergoes secondary sexual development. The magnitude of this secondary growth was comparable with snout length (+9–10%), which is known to undergo secondary sexual development in female salmonids. When morphological trait dimensions were compared between the sexes, the anal fin was the only morphological trait found to have a female‐biased sexual size dimorphism. This is the first study to show that the anal fin of female salmonids undergoes secondary sexual development.     

Effects of Ration on Growth and Reproductive Investment from Larva to Sexual Maturity in the Female Cyprinid Minnow,Tanichthys albonubes

Somatic growth and reproductive investment in female Tanichthys albonubes (Cyprinidae) individually cultured at the laboratory from larva to sexual maturity were examined under low, medium, and satiation food rations. All the 72‐day post‐hatch fish reached sexual maturity under all rations. The standard length, wet body mass, dry ovarian mass, dry liver mass, condition factor, energy content, and number of vitellogenic oocytes were all increased with ration levels. However, food conversion efficiency decreased with ration. There were no significant differences in total number of oocytes per female between rations. The species is a continuous batch‐spawner. The size‐frequency distributions of oocyte diameters showed a continuous pattern, ranging from 0.03 to 0.70 mm, at different rations. The proportion of energy intake allocated to growth decreased with ration levels. Only 3.29–4.60% of energy intake was stored in the ovary. These biological and energetic characteristics allow this fish to reach first maturity with low food intake, although it produced fewer vitellogenic oocytes at lower rations. This property enables T. albonubes survive in its native habitats where food is not only scarce, but also variable temporally and spatially. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Site selection and attachment duration of Anodonta woodiana (Bivalvia: Unionacea) glochidia on fish hosts

The relationship between parasitic glochidia of Anodonia woodiana (Unionidae: Anodonti-nae) and potential fish hosts was investigated in the laboratory. Intensity of parasitism was highest on the exotic fish Gambusia affinis , lower on the native species Puntius semijascio-latus and Metzia takakii , and least on Rhodeus sinensis . Glochidia generally attached at fin margins, particularly the pectorals and caudal. In Gambusia affinis , the incidence of glochidia on the pectorals was higher than would be expected on the basis of ratios between fin margin lengths. Apparently, the role of the pectoral fins in locomotion makes them more liable to glochidial contact, thereby increasing their susceptibility to attachment.
The duration of glochidial attachment was shortened as temperatures increased. Mean values ranged from 14-4 days at 15°C to 6 days at 27°C. At 33°C glochidia rapidly detached and metamorphosis was unsuccessful. Significantly, water temperatures in A. woodiana habitats in Hong Kong rarely exceed 30°C.     

孕激素暴露致食蚊鱼形态雄性化的生物学效应

目的：研究不同浓度孕酮（ PRO）暴露对雌性食蚊鱼（ Gambusia affinis）的形态雄性化生物学效应。方法将性未成熟的雌性食蚊鱼个体分别静水暴露于0.5、5、50和500 nmol/L不同浓度的PRO实验组中,并设置对照组和平行组。持续暴露42 d后观察与测定食蚊鱼的体长、体重、臀鳍第3鳍条和第14,15,16椎肋骨形态雄性化变化等指标,同时观察卵巢发育状况。结果食蚊鱼暴露42 d后,与对照组相比,50和500 nmol/L实验组食蚊鱼的体长（ BL）有极显著减少（分别P＜0.01）;无论是低浓度组还是高浓度组,暴露实验后体重（ BW）都有显著性或极显著下降（P＜0.05或P＜0.01）;PRO暴露对食蚊鱼身体健康指数（CF）的影响,只有在5 nmol/L浓度时差异有显著性（P＜0.05）;500 nmol/L浓度处理后,第3臀鳍条分节数（FJ）、长度（FL）和最宽处宽度（FW）差异有显著性（P＜0.05）,表明形态雄性化变化明显;其他浓度组则无明显区别（P＞0.05）;500 nmol/L PRO实验组中,雌性食蚊鱼的第14,15,16椎肋骨的L值、D值和L：D值都出现极显著性差异（分别P＜0.01）,表明形态雄性化变化明显;组织切片观察揭示,暴露组食蚊鱼卵巢中的卵母细胞发育受到不同程度的抑制,II、III时相卵母细胞胞核发生肿胀现象。结论孕激素暴露诱导雌性食蚊鱼形态雄性化的生物效应十分明显。     

Effects of 17alpha-ethynylestradiol on sexual development of male western mosquitofish (Gambusia affinis)

Juvenile male western mosquitofish (Gambusia affinis) were exposed to different concentrations of 17alpha-ethynyl estradiol (EE2) in the diet during the period of sexual maturation. A clear inhibiting influence of EE2 on sexual development was apparent. The proportion of males in each treatment group that failed to complete gonopodial development during the 150-day observation period increased significantly with EE2 concentration. There were significant nonlinear trends toward shorter gonopodia in groups exposed to higher EE2 concentrations. Vitellogenin (VTG) was detectable in the blood of all fish exposed to 1.0 or more micro/g food and the concentration increased dramatically with increasing EE2 exposure. A significant negative association was seen between EE2 concentration and spermatophore counts. This study has demonstrated deleterious effects of EE2 exposure on sexual maturation and several indirect measures of reproductive fitness. It supports the biological relevance of vitellogenin in the blood and reduced gonopodium length as biomarkers for estrogen exposure and endocrine disruption in mosquitofish.