Development of Tripedalia binata Moore, 1988 (Cubozoa: Carybdeida: Tripedaliidae) collected from the eastern Gulf of Thailand with implications for the phylogeny of the Cubozoa

Abstract

Box jellyfishes are considered among the most dangerous sea creatures due to the lethal poisonous stings to humans. In order to predict the occurrences of box jellyfishes, it is necessary to understand their ecology and life cycle. The small box jellyfish Tripedalia binata was collected from eastern Thailand, in order to observe its life history, to compare its morphological characters with other cubozoans, and to discuss ecology and phylogeny in the class Cubozoa. Fertilization occurred internally, blastulae developed into planulae. Planulae were bred in the gastral pocket of the female medusa and released into the water. Free swimming planulae settled and metamorphosed into polyps. Adult polyps formed cysts at temperatures below 20°C water deterioration or starvation. Budding occurred in adult polyps, and buds were released after commencement of budding. Complete metamorphosis of a whole polyp into a single medusa occurred. Newly detached medusae were distinguished from those of other cubozoans by the pattern of nematocyst warts on the exumbrella and red chromatophores. The developmental features of T. binata resemble most closely those of T. cystophora and Copula sivickisi. The similarities in all early life cycle stages of those species support the close relationship of these species in the family Tripedaliidae.