Diet movement patterns of Pacific sugar limpet, Patelloida saccharina (Gastropoda: Patellogastropoda: Lottiidae) in response to semi-dinurnal tides of Samal Island, Philippines

Limpets pursue adaptive responses to persist in harsh conditions of tropical intertidal areas. This study investigated the diel movement patterns of a homing limpet species, Patelloida saccharina, subjected to semidiurnal tides at Catagman, Samal Island, Philippines. Field observations from 27 March 2017 to 19 April 2017 showed that during spring tides, activity commenced when limpets were submerged by the flooding tide at night. All limpets returned to their respective home scars just before sunrise and no further activity or movement was observed even during flood tide in the day. No activity was observed during night-time low tide periods of neap tides. Activity commenced at a later time when the limpets were submerged by the incoming tide and ceased prior to exposure from the outgoing of the tide. Results of Chi-square tests suggest that P. saccharina movement patterns were associated with day-night cycles (x(2) = 19.158) and tide type (x(2) = 17.658). However, movement was not directed (x(2) = 0.79718; d.f. = 2; p > 0.05), which may relate to random search for food. Further, Mann-Whitney U tests indicated significant differences in the distance travelled and duration of excursion of limpets between the spring and neap tides. Limpets moved farther and spent a longer time foraging during spring tides than neap tides, although a higher percentage of actively moving limpets was observed during the neap tide. The current study suggests that periods of darkness and submersion are prerequisites to initiate movement of P. saccharina limpets. The substantial literature on limpet behaviour considers that variations in activity pattern are adaptive strategies linked to desiccation. Overall understanding of P. saccharina movement pattern supports this premise that homing mechanism and movement restricted to nocturnal high tides are possible adaptations for survival on tropical intertidal shores of Samal Island.