关于公鱼属鱼类分类的讨论

本文回顾了公鱼属鱼类的分类历史,讨论了分类存在的问题,提出了赞同把该属分成形态特征和生态习性明显不同的两个种的意见:淡水产卵的定为池沼公鱼(H.olidus(Pallas),海水产卵的定为海公鱼(H.pretiosus(Girard)。     

Specific dynamic action in two body size groups of the southern catfish (<Emphasis Type="Italic">Silurus meridionalis</Emphasis>) fed diets differing in carbohydrate and lipid contents

Specific dynamic action (SDA), the energy costs associated with meal digestion and assimilation, is generally affected by body size and food composition. We assessed the postprandial metabolic response and calculated SDA in two size groups of the southern catfish (Silurus meridionalis), each fed one of two diets, high lipid or high carbohydrate, at a meal size of 4% the body mass. Using a continuous-flow respirometer, we determined the oxygen consumption rate at 2-h intervals until the postprandial oxygen consumption rate returned to the prefeeding level. None of the parameters (resting metabolic rate, Rpeak, factorial ratio, time-to-peak, duration, energy expended on SDA, or SDA coefficient) were significantly affected by diet nor was there an interaction between diet and body mass. Rpeak and energy expended on SDA for the whole fish body were significantly higher in the larger fish than the smaller one in both dietary treatments, whereas no significant effect of body size was found in mass specific values. Factorial ratio (range 3.41 to 3.60), peak time (range 9.6 to 12.7 h), SDA coefficient (range 9.36 to 10.36%), and SDA duration (range 62.0 to 71.0 h) did not significantly differ between body size groups. These results suggest that in S. meridionalis the percentage of assimilated energy allocated to SDA may be independent of the body mass.     

Microtopographic structures facilitate plant recruitment across a saltmarsh tidal gradient

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