Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Duck Pond Drive, Blacksburg, VA 24061, USA.
J Fish Biol. 2011 May;78(5):1470-91. doi: 10.1111/j.1095-8649.2011.02954.x.
The morphological development of larval cobia Rachycentron canadum from 3 days post hatch (dph) until weaning (27 dph) was examined using S.E.M. Two groups of fish were studied: a control group (CF), reared under standard feeding protocol, and a group in which prey items were enriched with supplemental taurine (4 g l(-1) day(-1) ; TF). TF fish grew faster (P < 0·001), attained greater size (mean ±s.e. 55·1 ± 1·5 v. 33·9 ± 1·0 mm total length) and had better survival (mean ±s.e. 29·3 ± 0·4 v. 7·1 ± 1·2 %) than CF fish. Canonical variance analysis confirmed findings with respect to differences in growth between the treatment groups with separation being explained by two cranial measurements. S.E.M. revealed that 3 dph larvae of R. canadum (in both groups) possess preopercular spines, superficial neuromasts on the head and body, taste buds in the mouth, an olfactory epithelium which takes the form of simple concave depressions, and primordial gill arches. Gill filaments start to form as early as 6 dph and lamellae buds are visible at 8 dph in both groups. In CF fish, the cephalic lateral line system continues its development at 12-14 dph with invagination of both supra- and infraorbital canals. At the same time, a thorn-like or acanthoid crest forms above the eye. At 14 dph, invaginations of the mandibular and preopercular canals are visible and around 22 dph enclosure of all cranial canals nears completion. In CF larvae, however, completely enclosed cranial canals were not observed within the course of the trial, i.e. 27 dph. In TF larvae, grooves of the cephalic lateral line system form 4 days earlier than observed in CF larvae of R. canadum (i.e. at 8 dph), with enclosure commencing at 16 dph, and completed by 27 dph. Along the flanks of 6 dph larvae of either treatment, four to five equally spaced neuromasts delineate the future position of the trunk lateral line. As myomeres are added to the growing larvae, new neuromasts appear such that at 16 dph a neuromast is associated with each myomere. By 27 dph, the trunk lateral line starts to invaginate in CF larvae, while it initiates closure in TF larvae. These findings elucidate important features of the larval development of R. canadum and show that dietary taurine supplementation benefits larval development, growth and survival in this species. Moreover, they suggest a conditional requirement for taurine in larval R. canadum.
使用扫描电子显微镜检查了从孵化后 3 天（3 dph）到断奶（27 dph）的幼鱼圆斑星鲽（Rachycentron canadum）的形态发育。研究了两组鱼：对照组（CF），按照标准喂养方案饲养；实验组（TF），在饵料中添加补充牛磺酸（4 g l(-1) day(-1)）。TF 鱼生长更快（P < 0·001），体型更大（平均值 ± s.e. 55·1 ± 1·5 毫米全长比 33·9 ± 1·0 毫米全长），存活率更高（平均值 ± s.e. 29·3 ± 0·4 比 7·1 ± 1·2 %）。典型方差分析证实了处理组之间生长差异的发现，分离由两个颅测量值解释。扫描电子显微镜显示，圆斑星鲽 3 dph 幼虫（两组均有）具有前鳃盖棘、头部和身体表面的神经嵴、口腔中的味蕾、呈简单凹形凹陷的嗅上皮和原始鳃弓。6 dph 时开始形成鳃丝，两组均在 8 dph 时可见鳃片芽。在 CF 鱼中，12-14 dph 时，头侧线系统继续发育，眶上和眶下管内陷。与此同时，眼睛上方形成刺状或棘状嵴。14 dph 时，可观察到下颌骨和前鳃盖骨的管内陷，大约在 22 dph 时，所有颅管的封闭接近完成。然而，在 CF 幼虫中，在试验过程中没有观察到完全封闭的颅管，即 27 dph。在 TF 幼虫中，头侧线系统的凹槽比观察到的 CF 圆斑星鲽幼虫早 4 天形成（即 8 dph），16 dph 开始封闭，27 dph 完成。在 6 dph 幼虫的两侧，四到五个等距的神经嵴勾勒出未来的躯干侧线位置。随着生长中的幼虫增加肌节，会出现新的神经嵴，因此在 16 dph 时，每个肌节都与一个神经嵴相关。到 27 dph 时，CF 幼虫的躯干侧线开始内陷，而 TF 幼虫的躯干侧线开始闭合。这些发现阐明了圆斑星鲽幼虫发育的重要特征，并表明饮食中添加牛磺酸有益于该物种的幼虫发育、生长和存活。此外，它们表明牛磺酸在幼鱼圆斑星鲽中存在条件需求。
