Summary Life history traits of the freshwater calanoid copepod Eodiaptomus japonicus from Lake Biwa were examined in the laboratory. Four different food concentrations (FC, 103, 5 × 103, 104 and 5 × 104 cells mL−1) and two temperature conditions (15 and 25 °C) were used to clarify the combined effects of those two factors on life history traits. A survival rate of more than 70% was observed at the two medium FCs at 15 °C, although survival was <42% at all six of the other food–temperature combinations. Post‐embryonic development times to adult stage in males and females were affected by both FC and temperature; median development times ranged from 28.7 to 37.3 and 31.4 to 35.0 days at 15 °C and 13.7 to 23.9 and 14.3 to 27.7 days at 25 °C, respectively, for males and females. An interaction between the two experimental factors was found only for females, with food shortage being most acute at 25 °C. Clutch sizes also increased with FC at both temperatures and interaction occurred between those two factors. Egg production rates increased with increasing FC similarly at both temperatures without an interaction effect. Adult body size increased with increasing FC at both temperatures: for example, average female prosome length increased from 0.865 mm to 0.922 mm at 15 °C and from 0.799 mm to 0.904 mm at 25 °C. Somatic and population growth rates calculated from the experimental data increased with FC, but the increase was more important at 25 °C. These responses to FC and temperature suggest that both growth and population dynamics of this copepod might be more influenced by food shortage at temperatures >15 °C. Adult body sizes under food‐limited conditions in this study are at the lower end of the range of those observed in situ, while those predicted from in situ temperatures, assuming non‐limiting food conditions, were always larger than those of natural populations. Therefore, food shortage appears to be the most important factor affecting both growth and reproduction of E. japonicus in Lake Biwa.

Fig. S1. Excess activities (Bq g −1 ) of 210 Pb (solid circle) and 214 Pb (open circle) (A) and estimated age (year) (B) of the sediment core collected from the north basin of Lake Biwa.

Three‐spined sticklebacks (Gasterosteus aculeatus L.) of the Camargue region (Rhone delta, northern Mediterranean Sea) occupy coastal mesohaline lagoons and freshwater canals. In this study, the acclimation capacity to different salinities of a population living in freshwater canals was investigated. Freshwater (FW; 5 ‰) individuals were compared to fish acclimated for at least 2 weeks to brackish water (BW; 15 ‰) and seawater (SW; 30 ‰). Blood osmotic pressure and gill Na+/K+‐ATPase (NKA) gene expression of the α1 subunit and α1a and α1b isoforms were determined at these salinities. NKA protein expression in the gill ionocytes and the remodelling of these cells were also investigated through NKA immunolabelling and electron microscopy. Blood osmolalities of fish acclimated to FW, BW and SW were significantly different. Branchial NKA α1a and α1b expressions also differed, with a higher expression of NKA α1b in fish acclimated to SW. Gill ionocytes in fish acclimated to FW were located along the lamellae and at their base and appeared elongated, whereas these cells were restricted to gill filaments in fish acclimated to SW with a round shape. Finally, electron microscopy revealed three different types of apical structures for these ionocytes: a honeycomb‐like structure and a dome shape in FW, and deeply encrypted in SW. This study shows that ionocyte cell type and morphology, and gill NKA expression are salinity‐dependent. This branchial remodelling is directly linked to the physiological homeostatic status reached by the fish. It also highlights that sticklebacks of the Camargue region can rapidly acclimate to different salinities and can easily migrate between FW canals and mesohaline coastal lagoons.