卵胎生入侵种食蚊鱼的两性异形和雌性繁殖输出

检测了卵胎生入侵种食蚊鱼(Gambusia affinis)繁殖期个体大小和形态特征的两性异形以及雌性繁殖输出。结果表明,繁殖期,雌性个体的数量显著大于雄性个体,雌性个体的体长显著大于雄性个体,食蚊鱼属于偏向雌性的两性异形。以体长为协变量的One-way ANCOVA及后续的Tukey's检验显示,特定体长食蚊鱼的雌性个体的头宽、眼间距、体宽和体重均显著大于雄性个体;头长和尾鳍长的两性间差异不显著。6个形态特征变量的主成分分析(Eigenvalue≥1)发现,前2个主成分共解释65.1%的变异。头宽、眼间距、体宽和体重在第一主成分有较高的正负载系数(解释45.4%变异),头长在第二主成分有较高的负负载系数(解释19.7%变异)。食蚊鱼的繁殖输出与母体个体大小的线性回归显示,窝仔数和窝仔重均与母体体长、体重呈显著的正相关;食蚊鱼的繁殖输出与母体局部特征的线性回归显示,窝仔数和窝仔重均与母体头宽、眼间距和体宽呈显著的正相关。窝仔数与后代个体的平均体长呈显著的正相关、与后代个体的平均体重相关不显著,后代个体大小与数量不发生权衡。食蚊鱼繁殖期的性别比例、个体大小和局部形态特征的两性异形受生育力选择、性选择、生态位分化、食物竞争等多种选择压力的作用,也有利于该物种种群扩张和快速入侵。     

食蚊鱼消化系统的组织学观察

食蚊鱼的消化道由口咽腔、食道、肠和肛门组成。口咽腔内有味蕾分布。食道粘膜为复层扁平上皮,粘膜内有粘液细胞。肠可分为前后两段,皱襞高度、肌层厚度有差异。消化腺包括肝脏和胰腺。肝小叶不明显,雌雄肝脏的显微结构不同。胰腺呈弥散型,一部分分布在肝脏内,另一部分和消化道伴生。讨论了食蚊鱼消化系统的特点与食性的关系。     

冷箭竹生殖特性研究

１９８１－１９９０年对冷箭竹（Ｂａｓｈａｎｉａｆａｎｇｅｎｉａ）开花、结实、种子萌发、幼苗更新复壮等生殖特性进行了观察。冷箭竹开花周期为４５－５５年,开花持续期约１０年,１９８３年盛花期测定茎秆上着生花序的长度平均为１７０．８ｃｍ,每１茎秆上的小花数为１２８０．３枚,每朵小花从开放至萎蔫的持续期约６天,花药持续开裂时间为０．７７天,花粉生活力达９６．７％,柱头承受花粉时间为２．３天,雌蕊子房发育为果实平均为３５８６粒／ｍ￣２,未受粉的瘪粒为１３９９４粒／ｍ￣２。种子生活力为２７．６％,种子发芽率为１５％－２０％,当年生幼苗成活率为７６％－９３％。     

摄食水平对不同性别食蚊鱼仔幼鱼生长发育的影响

在实验室27℃水温下,研究了少食、中食和饱食三个摄食水平对0至25日龄雌雄食蚊鱼(Gambusia affinis)的生长发育特征和饵料利用效率的影响。26d饲养实验结束后,对试验鱼摄食和生长指标、臀鳍分化、性成熟及饵料转换效率进行分析。结果显示:到臀鳍开始分化时,饱食组雄鱼的累计摄食总能量和生长速度开始小于雌鱼,且随日龄的增加差异加大;随摄食水平的增加,0日龄仔鱼到臀鳍分化和性成熟的时间缩短。至实验结束,各摄食组的雄鱼均形成发育完善的生殖足,性腺都达到成熟状态;而雌鱼性成熟迟于雄鱼,且其性成熟更易受到摄食水平的影响,饱食组只有约50%的个体达到性成熟,少食组的卵母细胞则均处在小生长期。随着摄食水平的增加,雌雄鱼的体长、体重和干物质特定生长率均呈明显上升趋势,而干物质饵料转化效率则呈明显下降趋势;实验结束时,雌鱼的生长指标和干物质饵料转化率均大于雄鱼。以上结果表明,伴随臀鳍的分化,食蚊鱼在摄食、生长、发育、性成熟和应对食物丰度变化上表现出显著的性别差异。     

食蚊鱼摄食特性及其与浮游动物和环境因子的关系

2008年11月—2009年4月,利用分时段采样法对广州暨南大学明湖内食蚊鱼在秋季(11月)、冬季(12—2月)、春季(3—4月)3个季节的摄食特性进行了研究,探讨其与湖内浮游动物群体数量动态、光照和水温的关系。结果表明:食蚊鱼主要以浮游动物为食,对枝角类和桡足类有较强的选择性;明湖日平均水温与浮游动物日平均丰度在3个季节间有显著差异,而食蚊鱼消化道饱满指数的差异不显著;食蚊鱼消化道饱满指数在这3个季节的变化与浮游动物丰度、水温、光照在这3个季节的变化无明显的相关;无论哪个季节,食蚊鱼在白天时段(10:00—18:00)的消化道饱满指数均高于夜间(22:00—6:00),表现出白天高峰型的摄食节律;光照是影响食蚊鱼昼夜摄食节律的主要因素,而水温、浮游动物丰度的昼夜变化与食蚊鱼的昼夜摄食节律没有显著相关。     

食蚊鱼生态入侵的研究进展

食蚊鱼原产于中、北美洲,由于被认为可用以控制蚊子,而于20世纪初被世界各地大量引种,现已成为全球性分布的外来入侵种之一。尽管食蚊鱼的控蚊效果尚存争议,但有一点却成不争事实,即该外来入侵种已经对世界各地的土著物种（无脊椎动物、鱼类和两栖类等）、生态系统以及水体环境都构成了巨大的影响。本文从食蚊鱼的生物学特性、入侵机制、控蚊效果和生态效应等4方面对目前有关该外来入侵种的研究结果进行了归纳和总结,并为该物种的管理和控制提出了建议性策略和措施,以期为中国的外来入侵种研究及其管理和控制提供基础资料及参考依据。     

食蚊鱼对罗非鱼仔鱼捕食一例

本文报道了在广州地区某一半自然水体中发现的入侵物种食蚊鱼(Gambusia affinis)对另一入侵物种罗非鱼(Oreochromis sp)仔鱼捕食现象一例。在一尾体长24.10mm的雌性食蚊鱼消化道中发现3尾罗非鱼仔鱼,其体长分别为6.68 mm、5.85 mm、5.67 mm。     

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。     

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。     

华北驼绒藜种群数量动态与生殖特性的相关性

采用立木级法研究华北驼绒藜种群的大小级结构,利用各龄级的存活数编制种群静态生命表和存活曲线,构建时间序列预测图对种群数量动态过程进行预测,利用生活史特征观察结果分析其生殖对策,探讨了生殖特性与种群动态的关系。结果表明:华北驼绒藜种群幼龄和老龄级个体数较少,中龄级个体数量较多,呈稳定或衰退趋势;种群生命表和存活曲线的分析表明,尽管生境条件不同,但存活曲线基本接近DeeveyⅢ型;种群数量的时间序列预测表明,华北驼绒藜种群会随时间推移,呈现老龄级株数先增加后减少的趋势,种群稳定性长期维持困难;生活史特征表明,华北驼绒藜在长期进化过程中形成了兼具r-对策和k-对策的双重特性来维持种群的相对稳定。良好的生殖适应性是物种发展的关键,华北驼绒藜种群年龄结构、生命表、存活曲线以及时间序列预测图反映出其种群数量动态与生殖特性具有密切的相关性,传粉系统效率低、胚胎发育过程营养失调、种子向幼苗的转化率低以及种群更新对母株的依赖性强等生殖生物学特性与种群动态相吻合;生境恶劣和人为干扰也成为其种群发展的制约因素。     

The effects of sublethal concentrations of five organophosphorus insecticides on temperature tolerance, reflexes, and orientation in Gambusia affinis affinis (Pisces: Poeciliidae)

Gambusia affinis were exposed to the insecticides ABATE®, fenthion, chlorpyrifos, methyl parathion, and malathion for 24 h at concentrations of 1, 5, and 10 ppb and for 48 h at 5 ppb. The thermal tolerance was lowered significantly for male and female G. affinis by the toxicants methyl parathion and chlorpyrifos at 5 and 10 ppb with 24 h exposure. Activity was restricted with fish exposed to methyl parathion and chlorpyrifos at concentrations of 10 ppb for 24 h and at 5 ppb for 48 h.     

Exposure to pesticides impairs the expression of fish ornaments reducing the availability of attractive males

Ornament magnitude often reflects a local balance between sexual selection and other sources of natural selection opposing their elaboration. Human activity may disrupt this balance if it modifies the costs of producing, maintaining or displaying the ornaments. When costs are increased, a shortage of acceptable partners may ensue, with consequences commensurate with how stringent (and effective) the process of mate choice is. Here, we show that the expression of ornaments in the viviparous amarillo fish (Girardinichthys multiradiatus) is influenced by embryonic exposure to low concentrations of an organophosphorus insecticide. Male ornamental fin size, dimorphic yellow coloration and display rates were all compromised in exposed fish, but unaffected in their paternal half-sibling controls and in their sisters (morphology and colour). Exposure resulted in smaller fish of both sexes, thus the differential effect by sex was restricted to attributes such as fin size only above the naturally selected magnitude shown by females. Father phenotype predicted offspring morphology of controls, but not of exposed males, which were discriminated against by both control and exposed females. Since stringent female mate choice can result in females refusing to mate with suboptimal mates, this sub-lethal developmental effect can reduce the effective population size of amarillo fish populations.     

Sexually selected sexual selection: Can evolutionary retribution explain female ornamental colour?

By preferring mates with increasingly costly ornaments or courtship displays, females cause an escalation of male reproductive costs. Such increased costs should promote male selectivity based on fecundity‐linked female attributes, leading to female ornamentation in species with traditional sex roles. Consequently, female ornamentation should evolve more frequently in taxa where male reproduction is costly than in comparable taxa where it is cheaper. We assessed the prevalence of female ornamental colouration in two clades of viviparous cyprinodontid fish: the Goodeinae, where stringent female choice imposes male mating costs, and the Poeciliinae, whose males can circumvent female mate choice. We found that although in the Poeciliinae female ornamental colour is a correlated, but paler version of male coloration, females of the Goodeinae often display vivid ornamental colours that are distinct from those of males. Thus, male and female ornaments are not (phylo)genetically correlated in the Goodeinae. Furthermore, phylogenetic signal on male and female colour is clearly detectable in the Poeciliinae, but absent in the Goodeinae, suggesting that ornamental colour of males and females in the latter may be the consequence of selection. Given that enforceable female choice has promoted male ornaments, we propose that evolutionary retribution has promoted distinct female ornaments in the Goodeinae.     

小型哺乳动物的繁殖投入与繁殖成功率

动物的繁殖活动关系到整个种群的生存与灭绝, 繁殖投入和繁殖成功率是繁殖生态学研究的重要内容。从繁殖投入的划分入手, 综述了小型哺乳动物的繁殖投入和繁殖成功率之间的关系及其影响因素、分子生物学技术在繁殖生态学中的应用等, 阐述了小型哺乳动物能够根据自身的状态调整每次繁殖活动中的时间投入和能量分配, 采取不同的繁殖对策。这些繁殖对策是长期自然选择的结果, 其目的都是为了最大限度地提高自身的适合度。并且指出分子生物学技术在繁殖生态学中的应用将大大加快这一研究领域的快速发展。     

Foraging costs drive female resistance to a sensory trap

Male ornaments can evolve through the exploitation of female perceptual biases such as those involved in responding to cues from food. This type of sensory exploitation may lead to confusion between the male signals and the cues that females use to find/recognize food. Such interference would be costly to females and may be one reason why females evolve resistance to the male ornaments. Using a group of species of viviparous fish where resistance to a sensory trap has evolved, we demonstrate that females exposed to an ornament that resembles food have a diminished foraging efficiency, that this effect is apparent when foraging on a food item with which the ornament shares visual attributes, and that not all species are equally affected by such confusion. Our results lend support to the model of ornamental evolution through chase-away sexual conflict.