Copepod sex ratio dynamics: the role of predators and food

桡足类性别比例动态：捕食者和食物的作用

• 批准号: NE/G005516/1
• 负责人: Andrew Hirst
• 金额: $ 34.8万
• 依托单位: Queen Mary University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG005516%2F1
• 关键词: Copepod; sex; ratio; dynamics; role

Copepods are free-drifting animal plankton found throughout the ocean in vast numbers. This group plays a critical role in the biochemistry of the upper ocean. They are the dominant grazers of many phytoplankton (free floating plants) and central to the food web, being the food source of many larger predators including some commercial fish. Through their actions they move carbon from surface waters to the deep ocean (the biological pump). In order to quantify and model the biogechemistry of the upper ocean, the mechanisms involved in determining copepod population size need to be understood. Changes in population abundance are determined by fecundity, growth and mortality rates. Whilst there is a strong understanding of copepod growth and fecundity, few field studies on mortality have been undertaken, and a mere handful have attempted to identify the causes of death. Consequently there are fundamental gaps in our understanding of controls on population dynamics in this important planktonic group. In many species the ratio of males and females at the birth is close to 1 (i.e. equal numbers of each) and evolutionary and genetic arguments suggest the same should be true for copepods. However, other factors can then act to alter this intial ratio as the animals age, for example, the males may die faster. Whilst in some copepod species there are equal numbers of the sexes in adults, in others the ratio is highly skewed (with females outnumber males by 10 to 1 or more). Evidence suggests that production of young by adult copepods can be limited by mate encounters, these are controlled by the sex ratio. Sex ratios are therefore both critical in population growth, and they also can give us an insight into the causes of mortality. The adult sex ratio is the result of events in this stage and/or earlier juveniles. Our first objective is therefore to quantify where sex ratio skew is generated. We will do this for populations of 3 chosen copepod species at a site in Southampton Water (UK) over an annual cycle. The copepod species being Acartia discaudata, Pseudocalanus elongatus and Oithona nana. Next, the two likely contributors to adult sex ratio skew will be studied, these are: 1. Differences in feeding rates on males and females by predators In searching for mates the behaviour of males increases the likelihood of their detection and predation. Predation rates on the 3 copepods will be determined in laboratory feeding experiments with 2 pelagic predators (the scyphomedusa Aurelia aurita and the chaetognath Sagitta setosa) over a range of adult copepod prey densities, and male to female ratios. Sex-specific differences in predation rates on marine copepods will be tested. 2. Differences in males and female physiological longevity Many males live for shorter periods than females when they are incubated free from any predators, they have a shorter 'physiological' longevity. This can be related to the fact that many males feed at reduced rates. Males and females of the 3 chosen copepods will be examined across a range of food concentrations and compositions in the laboratory to quantify these differences. At the Southampton Water site the chosen prey and predators co-occur. Over an annual cycle we will estimate mortality rates of the 3 copepods and also perform gut content analysis of the 2 predators to examine their removal rates. By combining field mortality rates, physiological longevity ranges and predator rates on the copepods we will produce a mortality budget. Our work has important implications beyond the local study site. A mathematical model that combines the adult age-survival functions with external (predation) mortality to determining sex ratios will be developed. Combined with global field sex ratios, we will make predictions of the relative control of food and predators. An optimal life-history model will be developed in order for us to examine differences between copepod sexes and families.

桡足类是自由漂流的浮游动物，在整个海洋中大量存在。这一组在海洋上层的生物化学中起着关键作用。它们是许多浮游植物（自由漂浮植物）的主要食草动物，也是食物网的中心，是许多大型捕食者（包括一些商业鱼类）的食物来源。通过它们的活动，它们将碳从表层沃茨转移到深海（生物泵）。为了量化和模拟上层海洋的生物多样性，需要了解决定桡足类种群规模的机制。种群数量的变化取决于繁殖力、生长和死亡率。虽然人们对桡足类的生长和繁殖力有了深入的了解，但很少有人对死亡率进行实地研究，也只有少数人试图确定死亡原因。因此，在我们对这一重要的亚热带种群的种群动态控制的理解方面存在着根本性的差距。在许多物种中，出生时雄性和雌性的比例接近1（即两者数量相等），进化和遗传论据表明桡足类也应该如此。然而，随着动物年龄的增长，其他因素也会改变这种初始比率，例如，雄性可能会死得更快。虽然在一些桡足类物种中，成年人的性别数量相等，但在其他物种中，性别比例高度倾斜（女性数量超过男性10比1或更多）。有证据表明，生产年轻的成年桡足类可以限制配偶的遭遇，这些是由性别比例控制。因此，性别比例对人口增长至关重要，也可以让我们深入了解死亡原因。成年人的性别比例是这个阶段和/或早期少年事件的结果。因此，我们的第一个目标是量化性别比例偏差产生的地方。我们将这样做的人口3选择桡足类物种在一个网站在南安普顿水（英国）在一个年度周期。桡足类为盘尾真哲水蚤、长伪哲水蚤和微小剑水蚤。接下来，将研究两个可能导致成人性别比例偏斜的因素，它们是：1。捕食者对雄性和雌性的摄食率差异在寻找配偶时，雄性的行为增加了它们被发现和捕食的可能性。3桡足类的捕食率将在实验室饲养实验中确定2远洋捕食者（scyphomedusa奥雷利亚aurita和毛颚矢箭虫setosa）在一系列的成年桡足类猎物密度，和男性女性比例。将测试海洋桡足类捕食率的性别特异性差异。2.雄性和雌性生理寿命的差异许多雄性的寿命比雌性短，当它们被孵化时没有任何捕食者，它们的“生理”寿命更短。这可能与许多雄性以降低的速率进食的事实有关。将在实验室中对3种选定桡足类的雄性和雌性进行一系列食物浓度和成分检查，以量化这些差异。在南安普顿水域，选择的猎物和捕食者同时出现。在一年的周期内，我们将估计3种桡足类的死亡率，并对2种捕食者进行肠道内容物分析，以检查它们的去除率。结合现场死亡率，生理寿命范围和捕食率的桡足类，我们将产生一个死亡预算。我们的工作具有重要的意义，超出了当地的研究地点。一个数学模型，结合成年人的年龄生存功能与外部（捕食）死亡率，以确定性别比例将被开发。结合全球野外性比，我们将对食物和捕食者的相对控制进行预测。一个最佳的生活史模型将被开发，以便我们研究桡足类性别和家庭之间的差异。

项目成果

Highlight: on the origin of the sexes.

亮点：关于性别的起源。

• DOI: 10.1093/gbe/evt164
• 发表时间: 2013
• 期刊: Genome biology and evolution
• 影响因子: 3.3
• 作者: Venton D

Female and male gamete mitochondria are distinct and complementary in transcription, structure, and genome function.

• DOI: 10.1093/gbe/evt147
• 发表时间: 2013
• 期刊: Genome biology and evolution
• 影响因子: 3.3
• 作者: de Paula WB;Agip AN;Missirlis F;Ashworth R;Vizcay-Barrena G;Lucas CH;Allen JF
• 通讯作者: Allen JF

Estimating digestion time in gelatinous predators: a methodological comparison with the scyphomedusa Aurelia aurita

估计胶状捕食者的消化时间：与 scyphomedusa Aurelia aurita 的方法学比较

• DOI: 10.1007/s00227-012-2134-z
• 发表时间: 2012
• 期刊: Marine Biology
• 影响因子: 2.4
• 作者: FitzGeorge-Balfour T

Influence of copepod size and behaviour on vulnerability to predation by the scyphomedusa Aurelia aurita

桡足类大小和行为对镰刀鱼捕食脆弱性的影响

• DOI: 10.1093/plankt/fbt077
• 发表时间: 2014
• 期刊: Journal of Plankton Research
• 影响因子: 2.1
• 作者: Fitzgeorge-Balfour T

Female-biased sex ratios in marine pelagic copepods: Comment on Gusmão et al. (2013)

海洋中上层桡足类动物性别比例偏向女性：对 Gusmão 等人的评论。

• DOI: 10.3354/meps10522
• 发表时间: 2013
• 期刊: Marine Ecology Progress Series
• 影响因子: 2.5
• 作者: Hirst A