PhD THESIS

Abstract

Autotomy is defined as the ability to cast off particular portions of the body when under stress. 1 Species of molluscs which exhibit such behaviour include the marine neogastropods Harpa ventricosa, 113 Stom-atella mariei and Cena varia, the opisthobranchs, with species of Oxynoidae and Doridae and the pul-monates Prophysaon coerulium and Hehcarion.' Among the bivalves, species of Solenoidea and Telh-noidea also exhibit autotomy of the siphon.' The fig shell Ficus ficus Linnaeus is a common, subtidal species of sandy or muddy bottoms on the west coast of Taiwan. 3 This study investigated a special autotomy behaviour in F. ficus where a part of mantle is autotomized under mechanical stress. Ficus ficus were collected around the coast of Kaohsiung in Taiwan (Longitude 120°17'E, Latitude 22°38'N). Mechanical and electrical stimuli were tested for their capacity to induce mantle autotomy behaviour in the gastropod. Experiments were carried out in a plastic box (7.5 x 14 x 10 cm) with 0.5 cm seawater level, mechanical stimuli were generated by a file, forceps or stirring the seawater around the non-anaesthetized and anaesthetized snails for 5 min. Snails were anaesthetized by immersing the snails in seawater containing 10% MgCIj for three hours. Electrical pulses were delivered for 1 min from an AgCl electrode, at 2-5, 5, 10 and 20 volt/cm shell length. The autotomy tissues detached from intact snails or from shedding were collected for density determination. In addition, autotomized F. ficus were kept in an aquarium to observe the regenera-tion and the floating fish food (Brand name: Amazon) was used as food.