Nanae Fresh-Water Station, Field Science Center for Northern Biosphere, Hokkaido University, Sapporo, Japan.
Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan.
J Fish Biol. 2020 Apr;96(4):1004-1013. doi: 10.1111/jfb.14291. Epub 2020 Mar 3.
Larval dispersion rather than adult migration generally leads to the worldwide expansion of fishes. Species of the genus Gymnocanthus have expanded geographically while undergoing allopatric speciation. Of this genus, while Gymnocanthus tricuspis inhabits the Arctic Ocean and surrounding area, G. herzensteini and G. intermedius occur around northern Japan. Larval early life histories of G. herzensteini and G. intermedius from northern Japan and G. tricuspis from Unalaska Island were investigated to estimate their dispersal potential during larval stages. The larval and juvenile abundances of G. herzensteini and G. intermedius were highest in May in shallow sandy bottoms below 7 m in depth, and the body sizes were 9.7-34.6 mm notochord length (NL) and/or standard length (SL) in G. herzensteini and 8.4-46.7 mm NL and/or SL in G. intermedius. Two egg masses of G. tricuspis (1.92 ± 0.08 mm in diameter) and hatched larvae (6.20 ± 0.19 mm NL) were collected in March. Compared with other sculpins in previous studies, the body sizes of G. herzensteini and G. intermedius at hatch are large and at settlement are small, while both hatch and settlement sizes of G. tricuspis are much larger. Counting micro-increments between the hatch check and settlement marks in G. herzensteini and G. intermedius demonstrated that the pelagic larval durations for 2 weeks with an immature body suggests that these species cannot disperse widely during the pelagic phase, while pelagic larvae of Arctic species such as G. tricuspis with long pelagic larval durations could disperse.
幼鱼的扩散而非成鱼的洄游通常导致鱼类的全球性扩张。 Gymnocanthus 属的鱼类在经历异域物种形成的同时在地理上扩张。在这个属中，Gymnocanthus tricuspis 栖息在北冰洋及其周边地区，而 G. herzensteini 和 G. intermedius 则分布在日本北部。本研究调查了来自日本北部的 G. herzensteini 和 G. intermedius 以及来自乌纳拉斯卡岛的 G. tricuspis 的幼鱼早期生活史，以估计其在幼鱼阶段的扩散潜力。在水深 7 米以下的浅砂底，G. herzensteini 和 G. intermedius 的幼鱼和幼鱼数量在 5 月最高，体长为 9.7-34.6 毫米神经弓长（NL）和/或标准长度（SL）在 G. herzensteini 中，8.4-46.7 毫米 NL 和/或 SL 在 G. intermedius 中。2 个 Gymnocanthus tricuspis 的卵块（直径 1.92±0.08 毫米）和孵化的幼虫（6.20±0.19 毫米 NL）于 3 月采集。与之前研究中的其他鮟鱇鱼相比，G. herzensteini 和 G. intermedius 的孵化时体长较大，而在定居时体长较小，而 G. tricuspis 的孵化和定居时体长都要大得多。在 G. herzensteini 和 G. intermedius 中，从孵化检查到定居标记之间的微增量计数表明，2 周的浮游幼体期具有未成熟的身体，这表明这些物种在浮游阶段不能广泛扩散，而像 G. tricuspis 这样具有长浮游幼体期的北极物种的浮游幼虫则可以扩散。
