Feeding rate and dissolved nitrogen release rate of Bdellocephala annandalei, an endemic species in Lake Biwa

Abstract

　We experimentally examined the feeding and dissolved nitrogen release rates of Bdellocephala annandalei, which inhabits the benthic region of Lake Biwa. Dead Daphnia pulicaria from Lake Biwa was used as food, and the water temperature was maintained at 7.5 ± 0.3°C, close to the habitat. The feeding rate of B. annandalei was 128.89 ± 28.21 μg mgDW^-1 d^-1 of carbon and 27.27 ± 5.53 μg mgDW^-1 d^-1 of nitrogen. The release rate of dissolved nitrogen was determined for dissolved total nitrogen (DTN) and NH₄-N as 9.23 ± 1.14 μg mgDW^-1 d^-1 and 1.95 ± 0.49 μg mgDW^-1 d^-1, respectively. These are new ecological findings for this species that advance our understanding of its function in nutrient cycling at the benthic region of Lake Biwa. As population density of B. annandalei is declining due to anoxia caused by climate warming, the findings of this study are useful for the conservation of this species and for assessing the risks to the deeper lake ecosystem after population decline.