Author(s)

Takero Sekimoto¹, Yuki Osumi¹, Takashi Shiraki¹, Akane Kobayashi¹, Kentaro Emi¹, Mitsuru Nakajo¹, Masatoshi Moku², Vladimir Kostal³, Chihiro Katagiri⁴, Tetsuo Harada¹

¹Laboratory of Environmental Physiology, Graduate School of Integrated Arts and Sciences, Kochi University, Kochi, Japan.
²Atmosphere and Ocean Research Institute, The University of Tokyo, Tokyo, Japan.
³Institute of Entomology, Biology Center of the Academy of Sciences CR, Ceske Budejovice, Czech Republic.
⁴Division of Life Science and Engineering, School of Science and Engineering, Tokyo Denki University, Hatoyama-cho, Japan.

This study aims, first, to examine the limit for tolerance to lower salinity by an oceanic sea skater, Halobates micans, and , second, to make it clear whether exclusively fresh water Halobatinae species, Metrocoris histrio has salinity tolerance. Adults of H. micans were collected using Neuston Net from the starboard side of R/V MIRAI on a fixed station at 8°S, 80°E, whereas those of M. histrio were collected from a small pond filled with a spring fresh water in Kochi (33°N, 133°E), Japan. Time in survival was measured in starved condition under several salinity conditions: 0‰, 2‰, 4‰, 6‰, 8‰, 9‰ and 10‰ for H. micans; 0‰, 5‰, 10‰, 12.5‰, 15‰ for M. histrio. Half of adults were in coma due to lower salinity under 10‰ and time in survival was less than 10 hours under less than 4‰ for H. micans. Time in survival was half at 5‰ of 80 hours on average at 0‰ as a control and less than 10 hours at 10‰ or higher salinity for M. histrio. Relatively flexible osmo-regulation ability by H. micans would be related to wide variety of salinity condition of surface oceanic water, whereas very limited tolerance even to lower salinity of 5‰ may be permitted by the no chances to be exposed to brackish water in natural habitats of M. histrio. This study showed that salinity tolerance of Halobatinae species would reflect, directly, the salinity condition of their habitats.

Oceanic Sea Skaters, Fresh Water Halobates mican sand Its Closely Related Fresh Water Species, Metrocoris histrio

Sekimoto, T. , Osumi, Y. , Shiraki, T. , Kobayashi, A. , Emi, K. , Nakajo, M. , Moku, M. , Kostal, V. , Katagiri, C. and Harada, T. (2014) Comparative Study of Salinity Tolerance an Oceanic Sea Skater, Halobates micans and Its Closely Related Fresh Water Species, Metrocoris histrio. Natural Science, 6, 1141-1148. doi: 10.4236/ns.2014.614102.