Leptocephalus energetics: metabolism and excretion.
Leptocephalus energetics: metabolism and excretion.
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Leptocephalus 能量学：新陈代谢和排泄。
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
Torres
中科院分区：
文献类型：
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作者：
Bishop;Torres
细头鱼是一种不寻常的透明幼虫，是鳗鱼、骨鱼、大海鲢和瓢虫的典型特征。与所有其他鱼类的幼体不同，细头鱼可以在浮游生物中以幼体的形式存在几个月，然后才蜕变成幼鱼。在它们的休眠阶段，细头绦虫以糖胺聚糖的形式积累能量储备，然后消耗能量来促进变态。因此，leptocephalus的发展战略是根本不同的，从所有其他鱼类在两个方面：它是远远超过持续时间和能量储备的积累。预计leptocephalus发育的不寻常特征将反映在幼虫的能量预算中。本研究描述了能量分配到代谢和排泄，这是能量预算的两个重要组成部分。采用密封瓶呼吸法，在海上直接测定了四种细头鱼（Leptocephali）、尾缘副棘鲷（Paraconger caudilimbatus）、巴利阿里阿里鱼（Ariosoma balearicum）、石生裸胸鱼（Gymnothorax saxicola）和戈氏蛇鳗（Ophichthus gomesii）的代谢率。代谢率的直接测量通过测量中间代谢的两个关键酶乳酸脱氢酶和柠檬酸合酶的活性以及Na（+）/K（+）-ATP酶的活性来证实，Na（+）/K（+）-ATP酶是渗透调节中重要的普遍存在的离子泵。通过对呼吸道孵育中使用的海水进行二次采样，测定排泄率。在所有的试验中使用了每个物种的整个premetamorphic大小范围。质量比耗氧速率、排泄速率和酶活性（y）均随质量（M）的增加而急剧下降，其关系式为y=aM（B），式中a为物种特异常数，-1.74<B<-0.44。在瘦头鱼中，描述特定质量代谢率和质量之间关系的常见异速生长方程的高度负斜率通常在-0.33到0之间，表明随着体型的增加，代谢率会大幅下降。结果表明，活跃代谢组织的比例也随着尺寸的减小而下降，在很大程度上被代谢惰性能量库糖胺聚糖所取代。因此，细头龙可以在最小的代谢损失下长到很大的尺寸，这是一种不寻常的成功的发育策略。
Leptocephali are the unusual transparent larvae that are typical of eels, bonefish, tarpon and ladyfish. Unlike the larvae of all other fishes, leptocephali may remain in the plankton as larvae for several months before metamorphosing into the juvenile form. During their planktonic phase, leptocephali accumulate energy reserves in the form of glycosaminoglycans, which are then expended to fuel metamorphosis. The leptocephalus developmental strategy is thus fundamentally different from that exhibited in all other fishes in two respects: it is far longer in duration and energy reserves are accumulated. It was anticipated that the unusual character of leptocephalus development would be reflected in the energy budget of the larva. This study describes the allocation of energy to metabolism and excretion, two important elements of the energy budget. Metabolic rates were measured directly in four species of leptocephali, Paraconger caudilimbatus, Ariosoma balearicum, Gymnothorax saxicola and Ophichthus gomesii, using sealed-jar respirometry at sea. Direct measurements of metabolic rates were corroborated by measuring activities of lactate dehydrogenase and citrate synthase, two key enzymes of intermediary metabolism, in addition to that of Na(+)/K(+)-ATPase, a ubiquitous ion pump important in osmotic regulation. Excretion rates were determined by subsampling the sea water used in the respiratory incubations. The entire premetamorphic size range for each species was used in all assays. Mass-specific oxygen consumption rate, excretion rate and all enzyme activities (y) declined precipitously with increasing mass (M) according to the equation y=aM(b), where a is a species-specific constant and -1.74<b<-0.44. In leptocephali, the highly negative slope of the familiar allometric equation describing the relationship between mass-specific metabolic rate and mass, normally between -0.33 and 0, showed that a massive decline in metabolic rate occurs with increasing size. The result suggests that the proportion of actively metabolizing tissue also declines with size, being replaced in large measure by the metabolically inert energy depot, the glycosaminoglycans. Leptocephali can thus grow to a large size with minimal metabolic penalty, which is an unusual and successful developmental strategy.