Tree Climbing Behavior of the Snail Cerithidea rhizophorarum (Gastropoda : Potamididae)

Abstract

Tree climbing behavior of the snail Cerithidea rhizophorarum A. Adams, 1855 (Gastropoda : Potamididae) was observed in a mangrove forest at the mouth of the Atago River, southern Kyushu, Japan. The forest is dominated by Kandelia candel (L.) Druce and Hibiscus hamabo Sieb. et Zucc. It is the northern limit of distribution of mangroves in the west Pacific. C. rhizophorarum was in the intertidal zone of the tidal flat most of the time but occasionally climbed up the trunks of mangrove trees The number of snails that climbed up trees in 100 m^2 decreased between June and August, but suddenly increased in late August and fluctuated between 1000 and 2000 through January. The number of snails inhabiting the tidal flat kept decreasing from June to December and increased from January through April. A larger proportion of snails moved off the trees in summer than in winter. There was a clear ebb and flow rhythm in the locomotion activity which synchronized with the tidal shift in the summer. Snails tended to fall onto the tidal flat at low tide and to climb up trees at the high tide. Snails aggregated on particular trees regardless of the physical traits of the trees. The climbing behavior of C. rhizophorarum seems to be dependent on both seasons and the ebb and flow rhythm of locomotion.