Aspects of the study of the life cycles of Antarctic copepods
Aspects of the study of the life cycles of Antarctic copepods
复制标题
南极桡足类生命周期研究的各个方面
作者：
S. Schnack
不同的方法来研究南极桡足类的生活史策略的描述，试图在我们现有的知识，新的光。迄今为止，大多数研究都是关于不同季节和不同区域的丰度、水平和垂直分布以及阶段组成。因此，季节性图片必须从不同的年份和采样区域汇编。生理学方法包括对例如产蛋、摄食、呼吸和排泄率、C：N和O：N比率、脂质和蛋白质含量的测量。然而，生理和生化数据仍然很少。本文给出了近15年来在威德尔海东部进行的调查的现场观测结果，而生理参数的数据是基于更广泛的地理区域。在威德尔海东部，8种桡足类占桡足类丰度的95%左右，占桡足类生物量的80%以上。在哲水蚤中，小型物种Microcalanus pygmaeus占66%，而大型物种Calanoides acutus和Calanus propinquus占52%的生物量。物种丰富度冬季最低，夏秋季节最高，而M.侏儒鸟体型细小，全年数量相若。桡足类的垂直分布具有明显的季节性，夏季主要分布在上层，而其它季节则相反。然而，最大浓度的深度层因物种而异。个体发育的垂直迁移在C. acutus，C. propinquus。年龄结构也有季节性差异，最年轻的种群出现在夏季。acutus、尖吻隐翅虫C. propinquus、Ctenocalanus citer或秋季对Gerlachei的影响，而M.俾格迈人在夏季最老。最年轻的桡足类阶段和男性并不总是出现在C。acutus和C. propinquus。与此相反，所有的发展阶段和两性都发生在一年四季的M。gerlachei，M. pygmaeus和C. Citer。性腺成熟的优势哲水蚤物种的收益以及在威德尔海东部的浮游植物生产开始之前。然而，性腺成熟的雌性比例最高，因此最高的产卵率与春季和夏季的生产期相吻合。在秋季，三个较大的品种C. acutus、尖吻隐翅虫C. propinquus和M.杰拉谢勒都花光了。与此相反，两个较小的物种，C。citer和M.俾格迈，在秋天停留在高处。产蛋率在一个地区和一个物种内变化很大。许多桡足类积累了大量的脂质，主要是蜡酯。与此相反，五种（C. propinquus，C. Similimus、Euchirella rostromagna、Stephos longipes和Paralabidocera anarctica）几乎只合成三酰基甘油而不合成蜡酯。脂肪含量具有明显的季节性，秋季最高。代谢活动的季节性差异也很明显，在黑暗的季节最低。桡足类物种对南大洋明显季节性的适应差异很大，大多数南极桡足类在黑暗季节保持活跃。尖哲水蚤似乎是唯一真正滞育的物种。计算了大种赤眼蜂的夏季发育率和冬季死亡率。acutus和C. propinquus表明这两个物种的生命周期都是1年，很少有雌性越冬，并且可能会第二次产卵。相比之下，R更可能有2年的生命周期。千兆。然而，研究的所有物种的生命周期持续时间仍然是不确定的，区域差异是非常可能的。
Different approaches to the study of life cycle strategies of Antarctic copepods are described in an attempt to shed new light on our present knowledge. To date, most studies were carried out on abundance, horizontal and vertical distribution and stage composition during different seasons and in various regions. Hence, the seasonal pictures had to be compiled from different years and sampling regions. The physiological method includes measurements on e.g. egg production, feeding, respiration and excretion rates, C:N and O:N ratios, lipid and protein contents. However, both physiological and biochemical data are still rare. Results of field observations are given in this paper for investigations conducted within the last 15 years in the eastern Weddell Sea, while data of physiological parameters are based on a broader geographical region. In the eastern Weddell Sea, eight copepod species account for about 95% of copepod abundance and for more than 80% of copepod biomass. Within the calanoids, the small species Microcalanus pygmaeus dominates by numbers with 66%, while the large species Calanoides acutus and Calanus propinquus comprise together 52% of the biomass. Species abundance is lowest in winter and highest in summer/autumn, however, seasonal changes in the abundance of M. pygmaeus are small and this species occurs in similar quantities throughout the year. All copepod species show a distinct seasonal vertical distribution pattern and they occur in upper water layers in summer, in contrast to the other seasons. However, the depth layers of maximum concentration differ between species. The ontogenetic vertical migration is most pronounced in C. acutus and relatively weak in C. propinquus. The age structure also shows seasonal differences with the youngest population observed in summer for C. acutus, C. propinquus, Ctenocalanus citer or autumn for Metridia gerlachei, whereas the M. pygmaeus population is oldest during summer. The youngest copepodite stage and the males are not always present in C. acutus and C. propinquus. In contrast, all developmental stages and both sexes occur throughout the year in M. gerlachei, M. pygmaeus and C. citer. Gonad maturation in the dominant calanoid species proceeds well before the onset of phytoplankton production in the eastern Weddell Sea. However, the highest portion of females with ripe gonads and hence highest egg production rates coincide with the productive period in spring and summer. In autumn, ovaries of the three larger species C. acutus, C. propinquus and M. gerlacheiare all spent. In contrast, the percentage of ripe females of the two smaller species, C. citer and M. pygmaeus, stays high in autumn. Egg production rates are highly variable within one region and species. Many copepods accumulate large depots of lipid, mainly wax esters. In contrast, five species (C. propinquus, C. simillimus, Euchirella rostromagna, Stephos longipes and Paralabidocera antarctica) almost exclusively synthesise triacylglycerols and not wax esters. The lipid content exhibits distinct seasonal patterns, and is highest in autumn. A seasonal difference is also obvious in metabolic activities with lowest rates during the dark season. The adaptation to the pronounced seasonality in the Southern Ocean differs greatly between copepod species, and most Antarctic copepods stay active during the dark season. Calanoides acutus seems to be the only true diapause species. Calculations of summer developmental rates and winter mortality rates of the large species C. acutus and C. propinquus suggest that both species have a 1-year life cycle with few females overwintering and probably spawning a second time. In contrast, a 2-year life cycle is more likely in R. gigas. However, life cycle durations of all species studied are still uncertain and regional differences are very probable.