Synchronized anthesis and predation on pollen in the marine angiosperm Thalassia testudinum (Hydrocharitaceae)

Synchrony in the anthesis of male and female flowers of the hydrophilous dioecious marine angiosperm Thalassia testudinum was studied by following flower buds of 64 staminate and 34 carpellate flowers in situ during night and day to observe the timing of flower opening. Anthesis of female flowers occurred throughout the day, with a slight peak between 15:00 and 17:00 h. The time lapse between initiation of anthesis and full opening of the flowers was similar to 2 to 3 h. Anthesis in male flowers was highly synchronized, and all ripe primordia initiated anthesis within 1 h at dusk at similar to 18:00 h, and pollen was released within 1 to 2 h. Male flowers in anthesis, or briefly after anthesis, were a targeted food source for herbivorous fish and >30% of the staminate flowers were consumed during our observations. The highly synchronized nocturnal pollen release is unusual for an abiotic pollinator, and we hypothesize that this may be a mechanism to ensure fertilization or, alternatively, may be a reponse to avoid pollen predation by fish.