About storage of tentacles in the pockets of cuttlefishes (Mollusca: Cephalopoda)

Abstract

: Cuttlefishes store their tentacles in the pockets, which are open depressions in the anteroventral surface of the head between the bases of arms III and IV. When cuttlefishes hunt prey, they rapidly extend their tentacles from the pockets towards the prey, catch it using tentacular clubs, retract the tentacles to the pockets, and then hold it to their mouth using their arms. Tentacle storage in the pockets is important for hunting. However, the arrangement of the tentacles in the pockets remains unknown. In this study, I report the arrangement of tentacles in the pockets of pharaoh cuttlefish Sepia pharaonis (Ehrenberg, 1831) and golden cuttlefish Sepia esculenta (Hoyle, 1885) by morphological observation. Two patterns for keeping the tentacles in the pockets were observed. In the first pattern, tentacular clubs were located outside the tentacle pocket openings. The curling of tentacular stalks was less complex than that of the second pattern. In the second pattern, tentacular clubs were completely retained inside the pockets. The curling of the tentacular stalk was more complex than that of the first pattern. In both patterns, the tentacular stalks first turned from the origin towards the oral side and then curled with twisting from the oral side to the aboral side in the pockets. We observed that tentacular stalks did not tangle. This result contributes to understanding the basic morphology of tentacular storage in cuttlefish pockets. Possible causes for the differences between the two patterns are discussed.