Modest Regulation of Digestive Performance Is Maintained through Early Ontogeny for the American Alligator, Alligator mississippiensis
Modest Regulation of Digestive Performance Is Maintained through Early Ontogeny for the American Alligator, Alligator mississippiensis
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DOI：
10.1086/709443
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发表时间：
2020-06
影响因子：
1.6
通讯作者：
Jarren C Kay;R. Elsey;S. Secor
中科院分区：
文献类型：
--
作者：
Jarren C Kay;R. Elsey;S. Secor
美洲扬子鳄是一种机会主义的食肉动物，随着身体尺寸的增加，食物和食性发生了个体发育的变化。鳄鱼在刚出生时经常以无脊椎动物和小鱼为食，随着它们的成长，它们会逐渐减少以较大的脊椎动物为食。我们假设，扬子鳄在调节肠道功能方面经历了个体发育的变化--在生命早期经常进食的适度调节，以及随着身体大小的增加而减少进食的更广泛的调节。我们通过比较新生、幼年和未成年扬子鳄的代谢率、器官重量、肠道组织学、消化水解酶活性和肠道营养摄取率的餐后反应来检验这一假设。在摄食过程中，所有三个年龄段的扬子鳄的代谢率都经历了快速的增长，在2d内达到顶峰，此后下降到摄食前的速度较慢。比动力作用随体质量增加而增加，相当于进食能量的32%。对于每个龄级，大多数器官的湿质量和干质量不随摄食而变化。对于亚成体扬子鳄，由于胃呈酸性，胃腔内的pH值随禁食时间的延长而发生区域性变化。随着喂养的进行，上皮细胞从假层状结构重塑为层状结构，并被脂滴渗透。摄食没有引起肠道组织厚度的任何显著变化，尽管它确实诱导了亚成体肠道细胞宽度和体积的增加。对于每个年龄段，喂食一般不会导致胰腺胰酶、肠道氨基肽酶以及肠道养分摄取活动和容量的显著变化。由于新生儿表现出较高的摄取率，不同年龄段的群体特定营养摄取率有所不同。在年龄段中，肠道摄取能力随体质量的异速生长(质量指数和lt；1)而变化。在这三个年龄段中，鳄鱼进食和禁食对消化性能的适度调节似乎是个体遗传学上的保守。
The American alligator, Alligator mississippiensis, is an opportunistic carnivore that experiences an ontogenetic shift in food and feeding habits with an increase in body size. Alligators frequently feed on invertebrates and small fish as neonates and transition to feeding less frequently on larger vertebrates as they grow. We hypothesized that alligators experience an ontogenetic shift in the regulation of intestinal performance—modest regulation with frequent feeding early in life and wider regulation with less frequent feeding as they increase in body size. We tested this hypothesis by comparing postprandial responses in metabolic rate, organ masses, intestinal histology, digestive hydrolase activities, and intestinal nutrient uptake rates among neonate, juvenile, and subadult alligators. With feeding, alligators of all three age classes experienced a rapid increase in metabolic rate that peaked within 2 d and thereafter declined more slowly to prefeeding rates. Specific dynamic action increased with body mass and was equivalent to 32% of meal energy. For each age class, the majority of organs did not change in wet and dry mass with feeding. For subadult alligators, luminal gut pH varied regionally due to the acidic stomach, which continued to remain acidic with fasting. With feeding, epithelial enterocytes are remodeled from a pseudostratified to a stratified architecture and become infiltrated with lipid droplets. Feeding did not generate any significant change in the thickness of intestinal tissues, though it did induce an increase in enterocyte width and volume for subadults. For each age class, feeding generally did not result in significant changes in pancreatic trypsin, intestinal aminopeptidase, and intestinal nutrient uptake activities and capacities. Mass-specific nutrient uptake rates varied among age classes due to the higher rates exhibited by neonates. Among age classes, intestinal uptake capacities scaled allometrically (mass exponents <1) with body mass. Across these three age classes, the modest regulation of digestive performance with feeding and fasting for alligators appears to be ontogenetically conserved.