O'Grady Shannon P, Morando Mariana, Avila Luciano, Dearing M Denise
Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
Zoology (Jena). 2005;108(3):201-10. doi: 10.1016/j.zool.2005.06.002. Epub 2005 Aug 10.
A range of digestive tract specializations were compared among dietary categories in the family Liolaemidae to test the hypothesis that herbivores require greater gut complexity to process plant matter. Additionally, the hypothesis that herbivory favors the evolution of larger body size was tested. Lastly, the association between diet and hindgut nematodes was explored. Herbivorous liolaemids were larger relative to omnivorous and insectivorous congeners and consequently had larger guts. In addition, small intestine length of herbivorous liolaemids was disproportionately longer than that of congeners. Significant interaction effects between diet and body size among organ dimensions indicate that increases in organ size occur to a greater extent in herbivores than other diet categories. For species with plant matter in their guts, there was a significant positive correlation between the percentage of plant matter consumed and small intestine length. Herbivorous liolaemids examined in this study lacked the gross morphological specializations (cecum and colonic valves) found in herbivores in the families Iguanidae and Agamidae. A significantly greater percentage of herbivorous species had nematodes in their gut. Of the species with nematodes, over 95% of herbivores had nematodes only in the hindgut. Prevalence of nematodes in the hindgut of herbivores was 2 x that of omnivores and 4 x that of insectivores.
为了验证食草动物需要更复杂的肠道来处理植物性物质这一假设，对铲蜥科不同食性类别的一系列消化道特化特征进行了比较。此外，还对食草习性有利于更大体型进化这一假设进行了验证。最后，探讨了食性与后肠线虫之间的关联。相对于杂食性和食虫性的同属物种，食草性铲蜥体型更大，因此肠道也更大。此外，食草性铲蜥的小肠长度相对于同属物种长得不成比例。各器官维度中食性和体型之间的显著交互作用表明，食草动物的器官尺寸增长幅度比其他食性类别更大。对于肠道中有植物性物质的物种，所消耗植物性物质的百分比与小肠长度之间存在显著正相关。本研究中所检测的食草性铲蜥缺乏鬣蜥科和agamidae科食草动物所具有的明显形态特化特征（盲肠和结肠瓣膜）。食草性物种肠道中有线虫的比例显著更高。在有线虫的物种中，超过95%的食草动物仅后肠有线虫。食草动物后肠中线虫的患病率是杂食动物的2倍，是食虫动物的4倍。
