海月水母精巢发育及排精过程的观察

采用实验生态学及显微观察的方法研究了海月水母(Aurelia sp.)的精巢发育及其排精过程,并对其精子活力进行了测定。结果表明:在水温20~22℃的条件下,海月水母碟状体经过40 d生长,达到伞径(7.50±0.71)cm、体重(28.70±6.60)g时,精巢出现并生长发育;经过60 d生长,达到伞径(11.77±0.51)cm、体重(83.54±10.36)g时,精巢发育成熟并开始排精;生长90 d后,精巢开始出现退化,当生长110 d时,精巢退化完全。在精巢发育过程中,其宽度和长度分别伴随海月水母伞径的增长而增宽和伸长,并出现折叠现象。海月水母的排精路线为:精子先粘附于精子细丝上,从精巢排出,继而经过胃循环沟、胃口腕沟,最后由口腕基沟排出体外。在水温22℃、盐度30、p H 8.0的条件下,海月水母精子活力随时间延长而降低,其快速运动时间和寿命分别为4 h 30 min和10 h。本研究结果显示,在适宜的环境条件下,海月水母精巢发育迅速,排精路线与过程相对简单,其精子活力强、寿命长,这种高效的生殖策略为其暴发奠定了基础,这或许也是海月水母能在地球上存活年代久远的原因之一。     

温度、盐度对海月水母碟状体生长及存活的影响

海月水母为我国近海主要大型灾害水母种类之一,当自然环境适宜其生长与繁殖时,易出现暴发性的增殖现象,严重破坏了我国近岸海洋生态系统的稳点与平衡。采用实验生态学方法,研究了温度(2.5、5、7.5、10、15、20、25、27.5、30℃)和盐度(15、20、25、30、35、40)对海月水母碟状体存活与生长的影响,实验共进行30d。结果显示,在实验设置的温盐范围内,温度、盐度均显著影响碟状体的存活与生长。在盐度15-35条件下,海月水母碟状体可以在温度2.5-25℃存活,在15-25℃范围内可正常生长;在温度20-25℃和盐度20-30条件下适宜海月水母碟状体生长,其中温度20℃和盐度25条件下海月水母碟状体特定生长率达到最大。与盐度相比,温度对碟状体的影响较大,在盐度15-35条件下,随着温度的升高,碟状体的伞径逐渐增大,其碟状体形态向水母体形态的转变速度加快。在达到临界点25℃时,若继续升高温度,碟状体的生存率与生长率显著下降。温度与盐度对海月水母碟状体的生存与生长具有明显的交互效应,碟状体在实验过程中表现出在较低温度条件下提高了对较高盐度的适应性。研究表明,温度、盐度的变化显著影响碟状体的生长与存活,直接导致碟状体种群数量变动,进而影响成熟水母体种群数量。结论为进一步探索大型水母暴发的生态环境机理提供重要科学依据。     

环境因子对海月水母生长发育影响的研究进展

海月水母是一种广泛分布的世界性近岸种,也是我国近海海域大型水母优势种之一.近年来海月水母在世界各地频繁暴发,对海洋生态系统和沿岸经济、社会发展带来了很大危害.海月水母有复杂的生活史(营附着生活的螅状体世代和营浮游生活的水母体世代)和多种无性生殖(出芽生殖、横裂生殖、足囊生殖等)及有性生殖方式.环境因子影响海月水母生活史的各个阶段,如浮浪幼虫阶段、螅状体阶段、碟状体阶段等.这些生长阶段尤其是早期生长阶段的状态(如附着、分布、扩散等)会进一步影响海月水母的种群动态.本文以海月水母生活史为主线,系统总结分析了国内外关于环境因子对其生活史各阶段的影响,提出了一些值得进一步深入研究的问题,以期为我国近海海域水母暴发关键因子的研究提供借鉴.     

温度和食物水平对海月水母螅状体无性繁殖的影响

水母暴发给近岸人类的生活、渔业资源以及海洋生态系统带来影响。这些近岸海域暴发的水母可以通过有性繁殖和无性繁殖来维持或扩大水母种群数量。在水母生活史中,螅状体的无性繁殖是决定水母体数量的关键阶段,因此对此阶段进行研究。设置了4个温度水平(9、12、15、18℃)、3个食物水平(5个卤虫/螅状体、20个卤虫/螅状体、40个卤虫/螅状体),在12个组合条件下研究温度和食物水平对海月水母螅状体无性繁殖能力和方式的影响。研究结果表明,在海月水母螅状体繁殖子体的各种方式中,匍匐茎生殖是主要的繁殖方式,出芽生殖次之,纵向分裂以及足囊出现几率极低。食物对海月水母螅状体产生总子体数影响显著,温度的影响不显著,食物水平越高,海月水母螅状体繁殖子体的能力越强。食物和温度对螅状体发生横裂均有影响,但温度对螅状体横裂的影响更大。温度对螅状体的横裂率影响显著,食物影响不显著。碟状体的释放发生在12、15、18℃的条件下,温度是影响海月水母螅状体通过横裂生殖释放碟状体数量的最重要因素。可见在螅状体无性繁殖阶段,温度和食物对繁殖方式的影响各不相同。     

福建东山岛海域霞水母的渔业生物学研究

1994年4～9月调查结果表明,东山湾海域霞水母的密度高峰期出现在6月25日～7月10日,生物量高峰期在7月10～8月5日;群体的伞径分布范围15～580mm,平均247．48mm,体重分布范围0．4～10250g,平均1274g;高次方程模拟的伞径生长方程式为Φt=15．1726+16．7204t+0．1926t2-0．0014t3—0．0004t4,指数高次方程模拟体重生长方程式为logeWt=-0．6885+1．3397t-0．0959t2+0．0034t3—0．00005t4;以生物经济学原理确定合理开捕为7月15日,合理开捕伞径为360mm．还讨论了表层水温和盐度与霞水母生物量和密度的关系及其资源开发等问题．     

光倒刺鲃的年龄与生长的初步研究

研究了光倒刺鲃(Spinibarbus hollandi)的年龄与生长规律,结果表明:光倒刺鲃鳞片年轮特征主要为疏密切割型。体长与鳞长呈直线相关L=44.44R-11.69,体重与体长呈指数函数相关W=0.0258L2.9125,4龄以前生长较快,生长指标高,体长指标高,体长和体重的相对增长率大,其生长规律可用Von Bertalanffy方程表达:Lt=67.3[1-e-0.2018(t-0.1338)],Wt=5441.44[1-e-0.2018(t-0.1338)]3。体重生长曲线的拐点位于t=5.678,拐点体长Lr=45.313cm,拐点体重Wr=1660.885g。光倒刺鲃雌性一般在3~4龄性成熟,雄鱼3龄时性成熟。     

池养条件下似刺鳊(鱼句)早期发育阶段的摄食与生长特性

对人工培育的似刺鳊(鱼句)(Paracanthobrama guichenoti)仔鱼、稚鱼和幼鱼的生长与摄食节律进行了研究.结果显示,在1~70日龄间,似刺鳊(鱼句)全长平均日增长率为3.55%,体重平均日增长率为11.26%,头长/全长值随着13龄的增长而变小.全长(L,mm)与体重(M,mg)的关系式为M=0.001 2 L2-0.056 4L+0.650 4;体重(M,mg)与日龄(D,d)的关系式为M=0.004 3 e0.0936D;全长(L,mm)和日龄(D,d)的关系式为L=0.015 4 D2-0.012 8 D+8.196 5.在饵料充足的条件下,20日龄晚期仔鱼全天均有很高的摄食发生率,小高峰出现在8:00时;40日龄稚鱼则表现出明显的昼夜摄食节律,属于典型的白天摄食类型,日摄食率2.337 6%.20 13龄仔鱼和40日龄稚鱼饱食后分别经6 h、5 h整个消化道排空.在水温25℃及饥饿空胃状态下,10日龄仔鱼只经3 d即开始出现死亡个体,经5 d全部死亡;20日龄仔鱼经6 d开始出现死亡个体,经9 d全部死亡;40 13龄稚鱼经7 d才开始出现死亡个体,10 d后全部个体均死亡.     

珠江水系倒刺鲃生长的初步研究

对采集于珠江水系西江及北江流域的倒刺(Spinibarbus denticulatus denticulatus)样本进行了年龄鉴定和性腺组织学观察,并对鳞长、卵径等进行了测定。结果表明,倒刺鳞片的年轮特征为疏密切割型,新年轮出现时期主要在4~6月。体长和体重呈幂函数关系,西江和北江可分别用公式WX=2.498 4×10-2L2.999 6(r=0.956 1)和WB=1.373 3×10-2L2.815 9(r=0.925 3)表示。根据生长阶段分析,雌性倒刺的性成熟年龄为5龄,5龄以前为幼鱼生长阶段,5~10龄为成鱼生长阶段。雄性倒刺的性成熟年龄为3龄。3龄以前为幼鱼生长阶段,3龄以上为成鱼生长阶段。倒刺的繁殖季节为4~6月份。     

阿拉善荒漠区五趾跳鼠不同年龄组体重与体尺特征的关系模型

啮齿动物年龄的划分对研究其年龄结构和种群数量变化等生态学特征具有重要的意义。利用体重来划分年龄组不仅对于野外实验研究方便快捷,而且能够较为真实地反映年龄与其形态特征指标的关系。五趾跳鼠（Allactaga sibirica）是我国北方分布较为广泛的啮齿动物之一,对其年龄组进行划分,是了解其生活史特征的有效方法。本文利用系统聚类法对2012至2014年在内蒙古阿拉善荒漠区捕获的五趾跳鼠体重进行分析,将五趾跳鼠划分为3个年龄组,Ⅰ龄组体重62 ~ 80 g（包括80 g）,Ⅱ龄组体重80 ~ 110 g（不包括80,但包括110 g）,Ⅲ龄组体重 > 110 g;并建立五趾跳鼠体重（W,g）与4个体尺特征指标体长（LB,mm）、尾长（LT,mm）、后足长（LP,mm）及耳长（LE,mm）的关系模型：Ⅰ龄组WⅠ =﹣1.032 + 0.137LB + 0.259LT,R2 = 0.244,AIC =﹣50.394 1,F = 0.005;Ⅱ龄组WⅡ = 0.072 + 0.099LB + 0.060LT + 0.214LP,R2 = 0.212,AIC =﹣131.021 5,F = 0.001。结果表明,五趾跳鼠的体尺指标在整个生长发育过程中并不是统一生长的,在特定阶段固定的体尺指标会开始生长。耳长在Ⅰ龄时已经完成生长或生长速度减缓;体长与尾长在Ⅰ龄时与体重具有较强的关系,在Ⅱ龄时生长速度减慢;后足长在Ⅱ龄时与体重关系较强,且生长速度加快;Ⅲ龄时体长、尾长和后足长停止生长或生长速度缓慢。荒漠区五趾跳鼠体重与体尺特征关系模型直观地反映了年龄与体尺特征的生长发育关系。     

高体近红鲌的生长与繁殖

高体近红鲌为长江上游的特有鱼类,以2008年5—11月从赤水河赤水市江段采集的540尾高体近红鲌标本为材料,对其生长与繁殖特性进行了研究和分析。结果表明:高体近红鲌鳞片年轮结构呈疏密切割型,年龄特征显著。种群由1—4龄共4个年龄组组成,其中以2龄个体为主。体长分布主要集中在100—160 mm;体重分布主要集中在20.0—50.0 g。总性比为♀∶♂=1.30∶1。体长与鳞径呈直线关系,体长和体重呈幂函数关系且幂指数接近3,基本符合匀速生长类型,体长和体重Von Bertalanffy方程分别为Lt=217.38(1-e-0.2867(t+0.757))和Wt=118.151-e-0.2867(t+0.757)2.8103;生长拐点为2.85龄,拐点对应的体长和体重分别为Lt=140.09 mm,Wt=34.37 g。雌雄初次性成熟年龄均为1龄;繁殖高峰期为6—7月。Ⅳ期雌鱼的绝对繁殖力为950—8655粒,平均值(3087.90±1602.15)粒;体长相对繁殖力FL为10.00—56.20粒/cm,平均值(24.26±10.16)粒/cm;体重相对怀卵量FW为66.08—197.67粒/g,平均值(116.49±32.05)粒/g;卵径频率分布显示高体近红鲌为一次产卵类型。       

Do respiratory metabolic rates of the scyphomedusa Aurelia aurita scale isometrically throughout ontogeny in a sexual generation?

We measured the respiration rate of Aurelia aurita payingspecial attention to the relationship between its metabolic ratesand body mass throughout ontogeny of the jellyfish in a sexualgeneration. Two different regression lines between respirationrates and body dry weight were obtained in ephyra to young medusa(bell diameter 4.2–19 mm, 0.07–14 mg dry weight) and medusa(BD17-120 mm, 12-2100 mg DW), at respective temperatures of 10 and15 °C. The cut off point of the metabolic rates was foundat the developmental stage just being metamorphosed into medusashape (BD 12–20 mm). The slope value of medusa respiration ratewas close to isometric scaling (0.9), whereas that of ephyra toyoung medusa was lower (0.6). Ecological implications of allometricscaling in the early developmental stages of ephyrae and metephyraeare discussed.     

大型水母幼体生长的影响因子研究进展

21世纪以来,中国东、黄海,韩国西海岸以及日本海连年发生大型水母暴发现象,对海洋渔业的生产活动以及海洋生态系统带来巨大的影响。水母暴发形成机制非常复杂,解释其发生机理并有效预报是目前急待解决的问题。大型水母的生活史中有明显的世代交替现象,受精卵,浮浪幼虫,螅状体,足囊,横裂体到碟状体的幼体发育阶段属无性世代,幼蜇发育到成蜇阶段属有性世代。在早期生活史中,螅状体的足囊繁殖与横裂生殖是大型水母无性繁殖的重要方式,对其成体的数量形成至关重要。综述了国内外有关温度、盐度、光以及营养条件对大型水母早期发育阶段的影响研究进展,研究表明温度是影响螅状体发育以及足囊繁殖和横裂生殖的最主要的环境因子;盐度、光和营养条件在适温范围内,均对螅状体和横裂生殖有一定的影响,其上下限随水母种类和发育阶段有所变化。展望了大型水母早期幼体研究的发展趋势,如环境因子对不同种类的大型水母幼体生长机理的影响、多个环境因子对幼体的综合作用、动态的环境因子与大型水母幼体之间的关系等。     

Organization of the subumbrellar musculature in the ephyra,juvenile, and adult stages of Aurelia aurita Medusae

We used fluorescently labeled phalloidin to examine the subumbrellar musculature of the scyphozoan jellyfish Aurelia aurita in a developmental series from ephyra to adult medusa. In the ephyra, the swim musculature includes a disc‐like sheet of circular muscle, in addition to two radial bands of muscle in each of the eight ephyral arms. The radial muscle bands join with the circular muscle, and both circular and radial muscle act together during each swim contraction. As the ephyra grows into a juvenile medusa, arms tissue is resorbed as the bell tissue grows outward, so eventually, the ephyral arms disappear. During this process, the circular muscle disc also grows outward and the radial muscle bands of the arms also disappear. At this time, a marginal gap appears at the bell margin, which is devoid of circular muscle cells, but has a loose arrangement of radial muscle fibers. This marginal gap is preserved as the medusa grows, and contributes to the floppy nature of the bell margin. Radial distortions in the circular muscle layer involve muscle fibers that run in random directions, with a primarily radial orientation. These are believed to be remnants of the radial muscle of the ephyral arms, and the distortions decrease in number and extent as the medusa grows. Since the mechanics of swimming changes from drag‐based paddling in the ephyra to marginal rowing in the adult medusa, the development of the marginal gap and the presence of radial distortions should be considered in terms of this mechanical transition.     

The ontogeny of swimming behavior in the scyphozoan, Aurelia aurita. I. Electrophysiological analysis.

1. Electrical correlates of behavioral activity were observed in the lip and tentacles of the polyp, but none were detected during column contraction. The tentacles are the most electrically active tissue, and the potentials are conducted along the length of the tentacle, but conduction to other parts of the animal were not observed. 2. Although the tentacles of the polyp and the rhopalia of the medusa are probably homologous, the development of pacemaker activity during strobilation is not a smooth transition from tentacle contraction potentials (TCPs) to marginal ganglion potentials (MGPs). This result indicates that each pacemaker activity develops de novo. 3. Two types of behavior were observed in the polyp: local responses, and coordinated activity which involved integrated responses in several body parts. The coordinated responses indicate that neurological coordination can take place in the polyp. Furthermore, feeding and spasm in the ephyra are similar to feeding and the protective response in the polyp. This similarity suggests that both coordinated responses in the polyp are coordinated by interneural facilitation in the diffuse nerve net (DNN) as in the ephyra. 4. Swimming in the ephyra is a medusoid behavior but feeding and spasm are coordinated by the DNN and are polypoid responses. Therefore, the ephyra is a mixture of polypoid and medusoid behaviors. As the ephyra matures into an adult medusa both polypoid responses are lost, but the DNN remains to modulate pacemaker output and control marginal tentacle contractions. As development proceeds from polyp, to ephyra, to medusa, each subsequent stage acquires some new behavior while retaining some aspect from the previous stage.     

Fish assemblage structure in urban streams of Puerto Rico: the importance of reach- and catchment-scale abiotic factors

Cotylorhiza tuberculata is a common symbiotic scyphozoan in the Mediterranean Sea. The medusae occur in extremely high abundances in enclosed coastal areas in the Mediterranean Sea. Previous laboratory experiments identified thermal control on its early life stages as the driver of medusa blooms. In the present study, new ecological aspects were tested in laboratory experiments that support the pelagic population success of this zooxanthellate jellyfish. We hypothesized that planulae larvae would have no settlement preference among substrates and that temperature would affect ephyra development, ingestion rates and daily ration. The polyp budding rate and the onset of symbiosis with zooxanthellae also were investigated. Transmission electron microscopy revealed that zooxanthella infection occurred by the polyp stage. Our results showing no substrate selectivity by planulae and high polyp budding rates in high temperatures suggest increased benthic polyp populations, which would lead to higher medusa abundances. Rates of transition from ephyrae to medusae and the feeding of early medusa stages also increased with temperature. Continuing changes in coastal ecosystems such as future climate warming and marine construction may lead to increased populations of jellyfish to the detriment of fish globally.     

Molecular characterization of aspartylglucosaminidase,a lysosomal hydrolase upregulated during strobilation in the moon jellyfish,Aurelia aurita

The life cycle of the moon jellyfish, Aurelia aurita, alternates between a benthic asexual polyp stage and a planktonic sexual medusa (jellyfish) stage. Transition from polyp to medusa is called strobilation. To investigate the molecular mechanisms of strobilation, we screened for genes that are upregulated during strobilation using the differential display method and we identified aspartylglucosaminidase (AGA), which encodes a lysosomal hydrolase. Similar to AGAs from other species, Aurelia AGA possessed an N-terminal signal peptide and potential N-glycosylation sites. The genomic region of Aurelia AGA was approximately 9.8 kb in length and contained 12 exons and 11 introns. Quantitative RT-PCR analysis revealed that AGA expression increased during strobilation, and was then decreased in medusae. To inhibit AGA function, we administered the lysosomal acidification inhibitors, chloroquine or bafilomycin A1, to animals during strobilation. Both inhibitors disturbed medusa morphogenesis at the oral end, suggesting involvement of lysosomal hydrolases in strobilation.     

闽江口海蜇渔业生态学研究

根据1993年5～9月的调查材料,研究了福建闽江口海域海蜇的渔业生态学。其密度和生物量高峰分别出现在6月20日和7月10日;群体伞径范围为18～546mm,平均328.8mm.体重范围为0.5～9540g,平均2877.4g;伞径为345～485mm的雌性有性繁殖力在1120.6×10⁴～3754.8×10⁴粒,平均2444.7×10⁴粒,有性生殖期在8月初至11月;采用高次方程和指数高次方程分别模拟伞径和体重生长,生长方程为:Φ_t=12.1337+17.7048t+3.1385t²-0.2049t³+0.00302t⁴,log_eW_t=-0.5749+1.4818t-0.0771t²+0.00129t³;以生物经济学原理确定7月20日为合理开捕期,开捕伞径为465.8mm.讨论分析了执行合理开捕期和开捕规格,对保护和合理利用海蜇资源,提高经济效益的重要意义.     

Evolution and development of scyphozoan jellyfish

Scyphozoan jellyfish, or scyphomedusae, are conspicuous members of many ocean ecosystems, and have large impacts on human health and industry. Most scyphomedusae are the final stage in a complex life cycle that also includes two intermediate stages: the larval planula and benthic polyp. In species with all three life‐cycle stages, the metamorphosis of a polyp into a juvenile scyphomedusa (ephyra) is termed strobilation, and polyps can produce one ephyra (termed monodisc strobilation) or many ephyrae (termed polydisc strobilation). In contrast to species with planula, polyp and medusa stages, a handful of scyphozoan species possess modified life cycles with reduced or absent stages. The evolutionary patterns associated with strobilation and life‐cycle type have not been thoroughly investigated, and many studies of ephyra development and strobilation induction are not yet synthesized. Herein, I place the development of scyphomedusae in an evolutionary context. I first review the current evolutionary hypotheses for Scyphozoa. Next, I review what is known about scyphomedusa development across a broad diversity of species, including the first signs of strobilation, the formation of strobila segments, and the morphogenesis of ephyrae. I then review cases where the canonical scyphozoan life cycle has been modified, and take advantage of phylogenetic hypotheses to place these observations in an evolutionary context. I show that the evolution of monodisc strobilation occurred at least twice, and that the loss of intermediate life‐cycle stages occurred several times independently; by contrast, the reduction of the medusa stage appears to have occurred within a single clade. I then briefly review the major natural cues of strobilation induction. Finally, I summarize what is currently known about the molecular mechanisms of strobilation induction and ephyra development. I conclude with suggestions for future directions in the field.     

钵水母水螅体横裂诱发条件及调控机制研究进展

横裂是水螅体世代向水母体世代转变的重要阶段.对水螅体横裂诱发条件及调控分子机制的研究不仅对水母爆发生态学和水母人工繁育具有重要意义,而且对比较研究两栖类、昆虫以及刺胞动物等具有复杂生活史生物的变态分子机制起源也具有很好的理论价值.现有研究表明,诱发水螅体横裂的自然环境因素有温度、光照、盐度和共生虫黄藻等,不同门类水母的横裂方式以及环境诱导因素各不相同.能够诱导水螅体横裂的化学因素有吲哚类化合物、9-顺式维甲酸、碘元素和过氧化氢等,其中吲哚类化合物对绝大多数水母水螅体都有诱导作用.尽管水螅体横裂的分子机制尚未明晰,但对海月水母的研究表明,RxR信号通路以及一种横裂诱导激素前体假定蛋白CL390在水母横裂过程中起着重要的作用,提示水母变态分子机制与两栖类和昆虫在分子水平上存在一定程度的共性.     

Predation potential of the jellyfish Drymonema larsoni Bayha & Dawson (Scyphozoa: Drymonematidae) on the moon jellyfish Aurelia sp. in the northern Gulf of Mexico

The jellyfish Drymonema larsoni bloomed in the northern Gulf of Mexico in the Fall of 2000 and fed voraciously on the moon jellyfish Aurelia sp., especially where they were concentrated in frontal convergence. We evaluated the predation potential of D. larsoni on Aurelia sp. medusa using laboratory and field data. Our data set represents the most complete study to date on the new scyphozoan family Drymonematidae and indicates that D. larsoni may be one of the most effective predators on other jellyfish recorded to date. On average, each D. larsoni medusa contained 2.7 Aurelia sp. prey, but as many as 34. In addition, 94% of moon jellyfish unassociated with D. larsoni showed scarring from previous contact with D. larsoni tentacles. Digestion times for D. larsoni feeding on individual Aurelia sp. ranged from 2 to 3 h and averaged 2.7 h. Potential clearance rates for predation on Aurelia sp. were extremely high (320–1043.5 m³ d⁻¹) and indicate that D. larsoni is potentially an important predator on Aurelia sp. blooms where the species co-occur. When the two species co-occur in numbers, predation by D. larsoni medusae could reduce moon jellyfish blooms, possibly alleviating predation pressure on lower trophic levels utilized by Aurelia sp., such as copepods and the early life history stages of ecologically and economically important fish and invertebrate species.