What dose Calyptogena sp. move looking for? ~Behavior observation of Calyptogena sp. in rearing tank~

15th Deep-Sea Biology Symposium (ポスター発表)
Makoto Sugimura, Yuka Koyano, Yoshihiro Suzuki, Miku Ota, Takami Nobuhara, Yukiko Nagai, Takashi Toyofuku

What dose Calyptogena sp. move looking for?
~Behavior observation of Calyptogena sp. in rearing tank~

Makoto Sugimura(1), Yuka Koyano(1), Yoshihiro Suzuki(1), Miku Ota(2), Takami Nobuhara(2), Yukiko Nagai(2), Takashi Toyofuku(2)
 (1) Enoshima Aqurium

[ABSTRACTS] Deep-sea creatures found in chemosynthetic ecosystems are known to have unique trophic acquisition strategy with symbiotic bacteria. Many of these animals receive organic matter produced by intracellular symbiotic bacteria as their main energy source. At Enoshima Aquarium, we developed a chemosynthetic ecosystem tank system (Miyake et al, 2012) that simulating the seep environment in order to study and display deep-sea creatures of chemosynthetic ecosystem. In this study, Calyptogena sp. were collected using the ROV Hyper-Dolphin, operated by the R/V Shinseimaru of University of Tokyo/ JAMSTEC. Sampling site was off Hatsushima Island seep site in Sagami Bay at depths of 855m (35°00.9507 ‘N, 139°13.327’E) on 6th of May, 2016. Calyptogena sp. individuals were then housed in the chemosynthetic ecosystem tank at Enoshima Aquarium. To monitor the daily migration of individuals, we took time lapsed video every 3 minutes from the top of the tank in total of 484 hours 14 minutes. As the result of the observation, we found that Calyptogena sp. individuals moves intermittently, average moving distance of one move was about 3.22 cm/15 min, and the average moving speed was about 0.38 cm/min. On the surface of sediment in the tank, heterogeneously mat-like biofilm cover area considered to be caused by bacteria activity were formed in mosaic pattern and we observed Calyptogena sp. individuals tend to moves along with the outline of the discoloration region. In this biofilm cover area, 50 to 300 μmol of hydrogen sulfide was detected from sediment. From these facts, we inferred that Calyptogena sp. individuals are moving to adopt environmental change, exploring optimal living environments such as suitable level of hydrogen sulfide and condition of bacterial mats. In the future, we would like to investigate further relationship between behavior of clams and environmental condition in order to clarify the ecology of chemosynthetic Calyptogena sp.