Reply to Horizons Article "Some ideas about the role of lipids in the life cycle of Calanus finmarchicus" Irigoien (2004): I
Reply to Horizons Article "Some ideas about the role of lipids in the life cycle of Calanus finmarchicus" Irigoien (2004): I
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回复地平线文章《关于脂类在Finmarchicus生命周期中的作用的一些想法》Irigoien (2004)：I
DOI：
10.1093/plankt/fbh112
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发表时间：
2004
影响因子：
2.1
通讯作者：
R. Campbell
中科院分区：
文献类型：
--
作者：
R. Campbell
调节Finmarchicus生活史的生物和非生物因素没有得到很好的描述，Xabier Irigoien(Irigoien，2004)提出了一些关于脂类可能起什么作用的有趣假设。然而，他确实对过冬期间脂质的作用做出了一些令人怀疑的假设。首先，他说“脂肪储存决定滞育深度”。我最近对脂类对浮力深度的影响进行了模拟(Campbell and Dowe，2003)，该模型表明，只有在非常窄的脂类成分窗口中才能获得接近中性浮力的东西。此外，由于脂肪比海水更容易压缩，由脂肪引起的浮力是不稳定的，只有当动物能够相当准确地诊断出它们处于中性浮力的深度时，才能获得准中性浮力(非常低的下沉/上升率)。其次，他说“越冬期间只消耗了储存的脂肪中的一小部分(5%)”。许多对合理不同的种群和良好采样频率的研究表明，在越冬期结束之前，干重或有机质(可能是脂肪)大大减少[例如(马歇尔和奥尔，1958；Comita等人，1966；Tande，1982；Hopkins等人，1984)]。此外，Ingvarsdottir等人测量并模拟了最低呼吸速率。(Ingvarsdottir等人，1999年)意味着在四个月内碳含量损失12%(同样，可能主要是脂肪)(这是保守的，在六个月内损失17.5%)。上述模拟结果(Campbell和Dower，2003)表明，个体的浮力性质对脂质含量非常敏感，只要脂质含量变化1-2%(就这一点而言，这完全在脂质测量的不确定度之内)，浮力性质就可以预期有相当大的变化。所有这些考量(我和艾里戈安的考量)都假定这些动物无法控制它们的浮力。在一些初步的实验中，我观察到金枪鱼改变了它的浮力，并能够在控制海水密度(通过改变盐度)后，或者当通过增加或降低静水压力来控制海水和桡足类的密度时，很快(<；1小时)达到接近中性的浮力。我们知道，Finmarchicus的生活史特征具有相当大的可塑性。在多世代的地区，G1代的一部分越冬，其余的不越冬；有几个阶段被认为是越冬(CIV-CVI)，越冬深度因地理而异。这种可塑性背后的个体行为可能存在相当大的差异，而当前的概念模型往往忽略了这一点。如果这些动物不仅仅是“愚蠢的粒子”，并且能够主动地选择它们的越冬深度，那么脂质在控制那部分生活史方面可能就不那么重要了。这也将带来有选择性的优势。一个个体不需要一定数量的脂肪，而是可以储存最多的脂肪，这有望增加它在越冬期间的存活概率，并增加春季羽化后产生的卵的数量和/或大小。在这种情况下，深度分布可能与其他一些物理或生物因素有关(例如对流混合层的深度，或捕食者的分布)。《浮游生物研究》第26卷第8期第979-980页2004年
The biotic and abiotic factors that modulate the life history of C. finmarchicus are not well described, and Xabier Irigoien (Irigoien, 2004) suggests some interesting hypotheses about what role lipids might play. He does, however, make some questionable assumptions about the role of lipids during overwintering. First, he states that ‘lipid storage determines the diapause depth’. Recent modelling of the effect of lipids on buoyancy depth by myself (Campbell and Dower, 2003) suggests that something approximating neutral buoyancy is only attainable in a very narrow window of lipid compositions. Moreover, since lipids are more compressible than seawater, buoyancy due to lipids is unstable, and a quasineutral buoyancy (very low sinking/ascent rates) can only be attained if the animals are able to diagnose fairly exactly the depth where they are neutrally buoyant. Second, he states that ‘only a small percentage ( 5%) of the stored lipids are consumed during overwintering’. Many studies of reasonably distinct populations and with good sampling frequency have shown a considerable decrease in dry weight or organic matter (presumably lipid) well in advance of the end of the overwintering period [e.g. (Marshall and Orr, 1958; Comita et al., 1966; Tande, 1982; Hopkins et al., 1984)]. As well, the lowest respiration rates measured and modelled by Ingvarsdottir et al. (Ingvarsdottir et al., 1999) imply a loss of 12% of carbon content (again, probably mostly lipid) over a four month period (which is conservative, 17.5% would be lost over a 6 month period). The above mentioned modelling results (Campbell and Dower, 2003) show that the buoyancy properties of an individual are very sensitive to lipid content, and considerable changes in buoyancy properties can be expected with only a 1–2% change in lipid contents (which is well within the uncertainty of lipid measurements, for that matter). All of these considerations (mine and Irigoien’s) assume that these animals cannot control their buoyancy. In some preliminary experiments, I have observed that the calanoid Neocalanus plumchrus altered its buoyancy, and was able to achieve approximately neutral buoyancy quickly (<1 h) following manipulation of seawater density (by altering the salinity), or when the density of both seawater and the copepods was manipulated by increasing or decreasing hydrostatic pressure. We know that there is considerable plasticity in the life history characteristics of C. finmarchicus. In areas with multiple generations, a portion of the g1 generation overwinter while the rest do not; several stages are known to overwinter (CIV–CVI), and the overwintering depth varies geographically. It is perhaps not unlikely that there is considerable variation in individual behaviour underlying that plasticity, and the current conceptual models tend to ignore it. If these animals are more than ‘dumb particles’, and are actively able to select their overwintering depth, then lipids are perhaps less important in controlling that portion of the life history. That would confer selective advantages as well. Rather than needing some ‘right’ amount of lipids, an individual could lay down ‘maximal’ lipid stores, which could be expected to increase its survival probability during overwintering, and the number and/or size of eggs that are produced following emergence in spring. In this case, the depth distribution might be expected to be related to some other physical or biotic factors (e.g. the depth of the convective mixed layer, or the distribution of predators). JOURNAL OF PLANKTON RESEARCH j VOLUME 26 j NUMBER 8 j PAGES 979–980 j 2004