滆湖鲢和鳙肠道生长格局研究

Intestine Growth Pattern of Chinese Silver Carp and Bighead Carp Sampled from Gehu Lake in Jiangsu Province,China

肠道形态种间差异是动物对食物质量的长期进化响应,本文研究了滆湖鲢(Hypophthalmichthys molitrix)鳙(Aristichthysnobilis)肠长(GL)和肠重(GM)两种肠道形态参数的生长格局,并探讨了它们对鲢鳙食性差异的指示作用。结果表明,滆湖鲢、鳙GL相对身体大小(体长BL和体重BM)、GM相对GL、肠道内含物重(GCM)相对BM均呈正异速生长或增加,鲢鳙GM相对BM分别呈等速和负异速生长。相对肠长(RGL)、ZI指数、相对肠道内含物重指数(RGCM)鲢显著大于鳙,GM/GL比值正好相反,相对肠重(RGM)鲢鳙间无显著差异。根据文献对比及RGL与营养级的经验公式,鲢鳙均为偏浮游植物杂食性鱼类,这与鳙为偏浮游动物食性鱼类的普遍认识不太一致,说明国内需要更多的研究以增加RGL对鱼类食性的指示作用。与鳙相比,鲢从更多且质量较低的食物中满足营养和能量需求的主要机制是增加肠道长度而不是分配更多组织给肠道。肠长能而肠重不能识别体型相似的2个近缘物种(鲢鳙)的食性差异。

Interspecific differences in intestinal morphology are long-term evolutionary responses of animals to food quality.Gut length and mass are two important morphometric characteristics of the digestive tract and used as indicators for interspecific dietary comparisons.It is crucial that gut length and mass grow with body size to meet nutrient and energy needs during maturation.To date,few studies have been reported on quantitative descriptions of growth patterns of gut length and mass for fish in China.Chinese silver carp(Hypophthalmichthys molitrix)and bighead carp(Aristichthys nobilis)are two well-known commercial species in China.They are often used as representative species when applying biomanipulation to control blue-green algal blooms in inland water bodies.However,there are conflicting views on whether they can effectively depress phytoplankton biomass due to controversy over their dietary composition.In this study,the growth of gut length and mass of silver carp and bighead carp in Gehu Lake were compared and differences in their diets were explored.A total of 250silver carps and 253bighead carps were collected from April to October,2015and gut length,gut mass and gut content mass of all specimens were measured.The relationships of log10gut dimensions against log10body size were established using reduced major axis regression.The relationships of gut length to body size(body length and body mass),gut mass to gut length,and gut content mass to body mass of silver carps and bighead carps were positively allometric.The relationship of gut mass to body mass was isometric for silver carps and negatively allometric for big-head carps.Relative gut length(RGL),Zihler′s index(ZI)and relative gut content mass of silver carp were significantly higher than those of bighead carp,while the reverse was found in the ratio of gut mass to gut length.There was no significant difference in relative gut mass between the two carps.In terms of the literature analysis and the empirical formula of the relationship between fish diet and RGL,it could be presumed that the two carps are omnivores with preference for phytoplankton,and that is inconsistent with the general understanding that bighead carp are omnivores with preference for zooplankton.Thus,more research should be conducted on the relationship of RGL to fish diet in China.To meet their nutrient and energy requirements,silver carp depend on a longer gut to digest food of relatively low quality rather than on increased gut mass as in bighead carp.Gut length can be used to identify dietary differences between closely related species,such as silver carp and bighead carp,but gut mass cannot.