Abstract
Three species of trunkfishes (Ostraciidae) were studied in the waters of Miyakejima, Izu Islands, Japan.Intensive studies of Lactoria fornasini and less detailed, comparative studies of Lactoria diaphanus and Ostracion cubicus revealed that all three species are haremic and seemingly gonochoristic, although only L.fornasini was examined histologically. Lactoria diaphanus and Ostracion cubicus spawn near, the surface in the late afternoon, but Lactoria fornasini spawns 10-20 min after sunset near the substrate.It is hypothesized that predator pressures account for differences between species, and in the femalebiased sex ratios of all three species.The role of ostracitoxin, a lethal stress secretion in the mucus of ostraciid fishes, is discussed in relation to predation.
