title: The effects of fasting on the metabolic interaction between digestion and locomotion in juvenile southern catfish (Silurus meridionalis).
abstract: To investigate the effect of fasting on maintenance metabolism, feeding metabolism and aerobic swimming performance as well as their metabolic interactions in juvenile southern catfish, we measured the following: (1) the postprandial oxygen consumption ((MO₂) response (16% body mass meal size) after 0 (control), 1, 2 and 4 weeks of fasting and (2) the swimming performance of non-digesting and digesting fish after either 0, 1, 2 or 4 weeks of fasting. The fasting groups displayed with lower resting MO₂ (MO₂(rest)), lower peak postprandial MO₂ (MO₂(peak)), larger energy expenditures and longer digestive processes than those of the control groups. The critical swimming speed (U(crit)), the active MO₂ (MO₂(active)) and the metabolic scope (MO₂(active) - MO₂(rest), MS) of both non-digesting and digesting fish all decreased progressively after 1, 2 and 4 weeks of fasting, with those of non-digesting fish decreased more acutely than digesting fish (P<0.05). Digesting fish displayed with a 14%, 23%, 27% and 71% significantly higher MO₂(active) than that of non-digesting fish in the 0-, 1-, 2- and 4-week fasting groups. Digestion only caused a significantly lower U(crit) and MS in both the 0- and 1-week fasting groups (P<0.05). The MO₂ increased greatly with the swimming speed, and digestion caused a higher MO₂ when compared to that of the fasting fish in any groups. The MO₂ of fish in the 4-week fasting group was significantly lower than that of other groups when the swimming speed was the same. In conclusion, both digestive and locomotive functions were down-regulated during fasting. In the 0- and 1-week fasting groups, the decreased MS for swimming during digestion caused a lower U(crit) (i.e., a digestion priority model). However, because the MO₂(active) of digesting fish decreased much more slowly than that of fasting fish, the MS of the 2- and 4-week fasting groups did not change during digestion, and the fish could handle both physiological activities independently (i.e., an additive model).
authors.affiliation: Laboratory of Evolutionary Physiology and Behavior, Chongqing Key Laboratory of Animal Biology, Chongqing Normal University, Chongqing, 400047, China. shijianfu9@hotmail.com
authors.forename: Shi-Jian
authors.initials: SJ
authors.lastname: Fu
authors.forename: Xu
authors.initials: X
authors.lastname: Pang
authors.forename: Zhen-Dong
authors.initials: ZD
authors.lastname: Cao
authors.forename: Jiang-Lan
authors.initials: JL
authors.lastname: Peng
authors.forename: Guanjie
authors.initials: G
authors.lastname: Yan
mesh_terms: D000818:Animals; D002397:Catfishes / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D004063:Digestion; D005508:Food Deprivation; D010101:Oxygen Consumption; D019518:Postprandial Period; D013550:Swimming / Q000502:physiology*