Leibniz Centre for Tropical Marine Research, Fahrenheitsstraße, Bremen, Germany.
University of Bremen, Bibliothekstraße, Bremen, Germany.
PLoS One. 2020 Jan 8;15(1):e0226600. doi: 10.1371/journal.pone.0226600. eCollection 2020.
Since the size of newly hatched larval fish is directly related to egg size, small differences in initial egg size can be critical to survival and further development of offspring. Underlying processes causing size variation in fish offspring are still not entirely understood. In this study we investigated whether the spatial position of an individual egg within a clutch affects size variation in two benthic spawning coral reef fishes, the clownfishes Amphiprion ocellaris and A. frenatus. To evaluate the effects of within-clutch position on embryonic development, egg growth metrics and protein content were analysed on day 2, 5 and 8 after deposition (adp). Additionally the activities of the key metabolic enzymes citrate synthase (CS) and lactate dehydrogenase (LDH) were investigated to evaluate the physiological status of the embryos. Central eggs of A. frenatus were significantly longer and heavier than peripheral eggs only on day 2 and 5 adp (2.07 mg, 2.59 mm vs. 1.84 mg, 2.49 mm). No significant differences were observed in A. ocellaris between eggs originating from a central or peripheral (5 mm from edge) position (1.33 mg, 2.26 mm vs. 1.15 mg, 2,18 mm). Diameter of the eyes did not differ between the two fish species nor between different positions, for any age group. The protein content of eggs (7.5% of wet weight) was independent of age, position and species. Enzymatic activity increased from 2 adp until peak activity was observed for both enzymes on day 8 adp, independent from position. The range of CS- and LDH-activity was 0.3-13.0 and 0.2-71.7 U g-1 wet weight, respectively. Significant differences in enzymatic activity were observed between age groups in both species, which in connection with significantly larger eggs of A. frenatus at day 2 and 5 adp could hint at a better O2 supply of central eggs. Potential implications for captive breeding are given.
由于刚孵化的幼鱼的大小与卵的大小直接相关，因此初始卵大小的微小差异可能对后代的生存和进一步发育至关重要。导致鱼类后代大小变化的潜在过程仍不完全清楚。在这项研究中，我们调查了个体卵在卵堆中的空间位置是否会影响两种底栖产卵珊瑚礁鱼类小丑鱼（Amphiprion ocellaris 和 A. frenatus）的大小变化。为了评估卵堆内位置对胚胎发育的影响，在沉积后第 2、5 和 8 天（adp）分析了卵的生长指标和蛋白质含量。此外，还研究了关键代谢酶柠檬酸合酶 (CS) 和乳酸脱氢酶 (LDH) 的活性，以评估胚胎的生理状态。仅在第 2 和第 5 adp 时，A. frenatus 的中央卵明显比外周卵更长、更重（2.07mg，2.59mm 比 1.84mg，2.49mm）。在 A. ocellaris 中，没有观察到中央卵和外周卵（距边缘 5mm）之间的显著差异（1.33mg，2.26mm 比 1.15mg，2.18mm）。两种鱼类的眼睛直径以及任何年龄组的不同位置之间均无差异。卵的蛋白质含量（湿重的 7.5%）与年龄、位置和物种无关。酶活性从第 2 adp 开始增加，直到第 8 adp 时两种酶均达到峰值活性，与位置无关。CS-和 LDH-活性的范围分别为 0.3-13.0 和 0.2-71.7U g-1湿重。两种物种的酶活性在不同年龄组之间存在显著差异，这与 A. frenatus 在第 2 和第 5 adp 时卵更大有关，可能暗示中央卵的 O2 供应更好。本文给出了对圈养繁殖的潜在影响。
