Larvae and juveniles of long sardine, Triportheus auritus, from the lower Amazon river was described, evaluating ontogenetic changes in their external mor­phology, pigmentation, fin development, morphometry, and meristics. A total of 93 individuals, 83 larvae and 10 juveniles were analyzed, they were captured monthly between 2014 and 2019 in the Amazon river channel and in macrophytes aquatic stands in the alluvial plains located in the lower Amazon River. From each specimen, morphometric and meristic data were measured and then the growth pattern between morphometric variables was analyzed. The larvae have an elongated body in a fusiform shape, superior mouth, simple nostril, pigmented spherical eyes and long intestine, surpassing the median region of the body. Initial pigmentation is scarce, but intensifies through development forming a pattern composed of three longitudinal bands concentrated in the ventral, cephalo-dorsal and lateral line regions. There are also pigments in the mandible, surrounding the mouth, under the swim bladder, intestine and fins. The sequence of complete fin formation is: caudal, anal, dorsal, pectoral and pelvic. The total number of myomeres ranged from 45 to 48 (25–29 preanal and 17–22 postanal). Morphometric relationships indicated differential growth for measurable morphometric parameters, with abrupt growth of snout length, head length and body height in the transition from flexion to postflexion stages. The pre-dorsal distance showed a decrease in the growth rate at the threshold from the larval to the juvenile period. The pre-pectoral and pre-anal distances showed negative allometric growth. In conclusion, the combination of body shape pigmentation pattern and, the formation sequence of fins allow the identification of the genus and coupled with the number of myomeres, morphometric relationships, and ray numbers of the anal fin ensure the differentiation of T. auritus from the other congeneric species. The metamorphosis occurred mainly at the end of the larval period and it is related to changes in the physiological and ecomorphological characteristics of the species.

中文翻译：

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被称为长沙丁鱼 Triportheus auritus (Valenciennes 1850) (Characiformes, Triportheidae) 的新热带鱼的早期发育

长沙丁鱼的幼鱼和幼鱼Triporteus auritus, 来自亚马逊河下游，评估了它们的外部形态、色素沉着、鳍发育、形态测量和分生学的个体发生变化。共分析了 93 只个体、83 只幼虫和 10 只幼鱼，它们在 2014 年至 2019 年期间在亚马逊河道和亚马逊河下游冲积平原的大型水生植物群中每月捕获。从每个样本中，测量形态学和分生数据，然后分析形态学变量之间的生长模式。幼虫体长呈梭形，口上位，鼻孔简单，有色球形眼，肠长，超过体中部。最初的色素沉着很少，但通过发育而加剧，形成由三个纵向带组成的模式，集中在腹侧、头背和侧线区域。下颌骨、嘴巴周围、鳔、肠和鳍下方也有色素。完整鳍形成的顺序是：尾鳍、臀鳍、背鳍、胸鳍和骨盆鳍。肌节的总数从 45 到 48（25-29 个肛前和 17-22 个肛后）不等。形态测量关系表明可测量的形态测量参数的不同增长，在从屈曲到后屈阶段的过渡中，鼻子长度、头部长度和身体高度突然增长。前背距显示从幼虫到幼虫期阈值处的生长速率下降。胸前和肛门前距离显示负异速生长。T. auritus来自其他同类物种。变态主要发生在幼虫后期，与物种生理生态形态特征的变化有关。