staurozoa

Staurozoa, commonly known as stalked jellyfish, is a class of cnidarians within the subphylum Medusozoa. Members are sessile, attached to substrata by a stalk, and lack a free-swimming medusa stage that is typical of many other jellyfish. They resemble small jellyfish but are permanently affixed to their habitat.

Morphology and anatomy: Stauromedusans have a polyp-like body organized around a calyx from which numerous tentacles radiate around the mouth. A stalk or peduncle secures the animal to a substrate such as rocks, kelp, or algae. Individual size varies from a few millimeters to several centimeters in height, depending on species. The arrangement of tentacles and the shape of the calyx are diverse across taxa, contributing to a variety of appearances within the group.

Life cycle and reproduction: The life cycle begins with planula larvae that settle on a surface and develop into a stalked polyp. In many species, the polyp produces reproductive structures that give rise to small medusoid forms that remain attached to the stalk rather than becoming free-swimming. Consequently, a free-swimming medusa stage is largely absent in Staurozoa, and reproduction is primarily sexual through planulae, with subsequent development producing new attached individuals.

Habitat and distribution: Staurozoans are found in marine environments worldwide, with a greater diversity in cold and temperate waters. They inhabit shallow coastal regions, often attaching to algae, kelp, rocks, or detritus. They can occur from intertidal zones to deeper shelves, depending on the species.

Taxonomy and systematics: Staurozoa is a distinct class within Medusozoa. The group includes several families and genera, with notable examples such as Haliclystus (family Haliclystidae) and Lucernaria (family Lucernariidae). Molecular studies continue to clarify relationships among staurozoan lineages and their position among medusozoans.