First record of an early ephyra of Desmonema glaciale (Cnidaria, Scyphozoa) from the Northern Antarctic Peninsula

Abstract

We report an early ephyra of Desmonema observed for the first time in the central basin of the Bransfield Strait. The specimen, measuring 12.2 mm in diameter, was characterized by four thick and fully developed adradial tentacles, four tentacular buds, poorly developed oral arms, and smooth umbrellar lobes. Its smooth lobes and absence of digitiform oral arm structures (ruling out Ulmaridae) classified it within Semaeostomeae. Furthermore, its tentacle development pattern, marginal lobe shape, and circular musculature confirmed its placement within the genus Desmonema. We analyzed ontogenetic variation in tentacle number among Desmonema species, along with other morphological traits, and identified this individual as Desmonema glaciale. Although adults of this large (<1.2 m bell diameter) scyphozoan medusa are common in Antarctic waters, this record represents the youngest specimen described for the species. The presence of a D. glaciale ephyra highlights the ecosystem's role in the development of gelatinous predators. Detecting early life stages provides insights into reproductive success and population dynamics in changing environments, as jellyfish blooms are increasingly recognized as indicators of ecosystem shifts. This record enhances understanding of cnidarian life cycles and underscores the importance of monitoring early stages to predict ecological responses to climate change.