Seasonal digestive/metabolic flexibility in juvenile detritivore marine estuarine-dependent fish Mugil liza (Mugilidae)

Abstract

Many organisms inhabiting heterogeneous habitats with seasonal changes in key environmental factors exhibit digestive/metabolic flexibility at different levels (e.g., biochemical and morphological). However, integrative studies in the wild on groups of ecological and economic importance such as detritivore marine estuarine-dependent fishes while inhabiting estuaries or coastal lagoons are lacking. This study analyzed juvenile Mugil liza Valenciennes, 1836 inhabiting Mar Chiquita Coastal Lagoon (Argentina) caught in autumn (5 °C) and spring (25 °C). We determined: digestive enzyme activities in the intestine; morphological traits; and, energy reserves in liver and muscle. Amylase, lipase, trypsin, and aminopeptidase-N activity increased in spring (270%, 33%, 270%, and 90%, respectively) while maltase and sucrase activity decreased (54% and 55%, respectively). Intestinal coefficient increased (18%) in spring. No changes occurred in hepatosomatic index, glycogen, and free glucose concentration. Triglycerides and protein concentration were higher in spring in both the liver (16% and 41%, respectively) and the muscle (25% and 26%, respectively). The results show a specific and differential modulation of key components of carbohydrate, lipid, and protein metabolism in spring, pointing out the occurrence of seasonal digestive/metabolic flexibility in juvenile Mugil liza in the wild which would allow them to support changes in key external factors.