Instituto de Investigaciones Marinas y Costeras, Universidad Nacional de Mar del Plata CONICET-FCEyN, Mar del Plata, Argentina.
J Fish Biol. 2021 Mar;98(3):643-654. doi: 10.1111/jfb.14605. Epub 2020 Nov 19.
The family Mugilidae consists mainly of diadromous species, whose reproduction occurs in offshore waters. Pre-juveniles shift their diet in the surf zone (zooplanktophagous to iliophagous). Later, during their recruitment into estuaries, huge changes take place in their digestive system. However, digestive and metabolic characteristics and some morphological traits at recruitment are unknown for Mugilidae. We performed comparative studies on early and late pre-juveniles of Mugil liza recruited in Mar Chiquita Coastal Lagoon (37°32'-37°45'S, 57°19'-57°26'W, Argentina). We determined digestive enzyme activities (intestine), energy reserves (liver/muscle), total/standard length, total weight, intestinal coefficient, hepatosomatic index and retroperitoneal fat. Pre-juveniles exhibited amylase, maltase, sucrase, lipase, trypsin and aminopeptidase-N (APN) activities, which were maintained over a wide range of pH and temperature, and exhibited Michaelis-Menten kinetics. In late pre-juveniles, amylase (422 ± 131 μmol maltose min mgprot ), sucrase (86 ± 14 mg glucose min mgprot ), trypsin (84 ± 9 μmoles min mgprot ) and APN (0.58 ± 0.08 μmoles min mgprot ) activities were higher (42%, 28%, 35% and 28%, respectively) than in the early stage. Also, the intestinal coefficient was higher in late (3.04) compared to early (2.06) pre-juveniles. Moreover, the liver appeared to be a main site of glycogen and triglyceride storage in late pre-juveniles, muscle being the site of storage in early pre-juveniles, exhibiting higher glycogen, free glucose and protein concentrations (92%, 82%, 32%, respectively). The results suggest that pre-juveniles of M. liza exhibit an adequate digestive battery to perform complete hydrolysis of various dietary substrates, availability of energy reserves and morphological characteristics to support their feeding habit and growth after recruitment. Our results represent an important contribution to knowledge of the ecology and digestive physiology of pre-juveniles of Mugilidae in the wild.
鳗鲡科主要由洄游物种组成，其繁殖发生在近海海域。幼鱼在冲浪区改变其饮食（浮游生物食性变为食藻类）。后来，在它们进入河口的过程中，它们的消化系统会发生巨大变化。然而，鳗鲡科幼鱼在进入河口时的消化和代谢特征以及一些形态特征尚不清楚。我们对在马奇奎塔沿海泻湖（37°32′-37°45′S，57°19′-57°26′W，阿根廷）中洄游的早期和晚期幼鱼进行了比较研究。我们测定了消化酶活性（肠）、能量储备（肝/肌肉）、全长/标准长、全重、肠系数、肝体指数和腹膜后脂肪。幼鱼表现出淀粉酶、麦芽糖酶、蔗糖酶、脂肪酶、胰蛋白酶和氨肽酶-N（APN）活性，这些活性在很宽的 pH 和温度范围内得以维持，并表现出米氏动力学。在晚期幼鱼中，淀粉酶（422±131μmol 麦芽糖/min mgprot）、蔗糖酶（86±14mg 葡萄糖/min mgprot）、胰蛋白酶（84±9μmoles/min mgprot）和 APN（0.58±0.08μmoles/min mgprot）的活性较高（分别为 42%、28%、35%和 28%）。此外，晚期幼鱼的肠系数（3.04）高于早期幼鱼（2.06）。此外，肝脏似乎是晚期幼鱼糖原和甘油三酯储存的主要部位，而肌肉是早期幼鱼储存的部位，表现出更高的糖原、游离葡萄糖和蛋白质浓度（分别为 92%、82%、32%）。研究结果表明，鳗鲡科幼鱼具有足够的消化电池，可以对各种饮食底物进行完全水解，具有能量储备，并具有形态特征，以支持它们在进入河口后的摄食习惯和生长。我们的研究结果为鳗鲡科幼鱼在野外的生态和消化生理学知识做出了重要贡献。
