ABSTRACT: Rates of development of the feeding larvae of marine invertebrates may often be limited by inadequate food, extending the length of the larval period and increasing overall larval mortality. A better understanding of the frequency and importance of this phenomenon requires knowledge of the food concentration below which larvae are limited, and above which they are not, as well as estimates of how strongly food supply affects length of the planktonic period. We addressed these issues using larvae of the sand dollar Dendraster excentricus as a model and chl a concentration as a metric of food abundance. We reared larvae in natural seawater collected from coastal southern California (USA), as well as in reduced and supplemented food treatments created from this natural seawater, 6 times from 2017 to 2019 to take advantage of temporal variation in chl a concentration. Larvae showed morphological responses indicative of low food in nature in only 1 of 6 experiments and showed delayed time to 50% metamorphic competence in 2 of 6 experiments. Larvae appeared to be food limited below chl a concentrations of ~2.4-3.0 µg l^-1, but developed at maximal rates at higher food concentrations. Low natural food supplies delayed time to 50% competence by up to 1.25 d. An 11 yr record of chl a concentration in waters of coastal southern California suggests that larvae of D. excentricus are likely food limited in developmental rate throughout much of the year except for late winter to late spring.

中文翻译：

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沙钱树Dendraster excentricus幼虫食物限制的时间变化

摘要：海洋无脊椎动物摄食幼虫的发育速度通常可能受到食物不足，幼虫期延长以及幼虫总死亡率增加的限制。要更好地了解这种现象的发生频率和重要性，就需要了解食物浓度，低于该浓度时，幼虫受到限制，高于或低于该浓度时，以及对食物供应对浮游时间长度的影响程度的估计值。我们使用沙钱树Dendraster excentricus的幼虫作为模型并通过chl a处理了这些问题。浓度作为食物丰度的度量。我们利用从加利福尼亚州南部沿海地区（美国）收集的天然海水以及由这种天然海水制成的减少和补充食品处理方法饲养了幼体，从2017年到2019年进行了6次处理，以利用chl a浓度随时间变化的优势。幼虫仅在6个实验中就有1个显示出自然界中食物不足的形态反应，在6个实验中有2个显示出变态能力延迟到50％的时间。似乎幼虫的食物限制浓度低于chl ，浓度约为〜2.4-3.0 µg l ^-1，但在较高的食物浓度下会以最大的速率发育。天然食品供应不足使时间延迟了50％，至多1.25 d。chl a的11年记录加利福尼亚南部沿海地区水域中的高浓度表明，除冬末至春末外，一年中大部分时间内，偏心线虫的幼虫可能是食物发育受限的食物。