Variation in respiratory rate and gill morphology in different genetic lineages of Isonychia japonica Ulmer, 1919 (Ephemeroptera: Isonychiidae)

Abstract

Isonychia japonica Ulmer, 1919 in the Japanese Archipelago is composed of two genetic lineages that live in different habitats of river ecosystems in the larval stage: clade J-U inhabits upstream and clade J-D inhabits downstream reaches. Whilst their distribution is well known, their morphology and how they have adapted to these diverse environments remains unknown. In this study, we focus on the physiological characteristics, especially the oxygen consumption, and gill morphology of larvae of these two lineages of I. japonica to infer how they adapt to different environments. Our results indicate that I. japonica of the clade J-U has a higher O2 consumption and is greatly influenced by temperature compared to the clade J-D, which is consistent with the physicochemical characteristics of their habitats. Also we show that the two lineages of I. japonica are not only divergent genetically and in their environmental habitats but also different morphologically and physiologically.