Final answer:
The Helmet Jellyfish feeds by using nematocysts in its tentacles to immobilize prey before digestion which occurs in its gastrovascular cavity.
Step-by-step explanation:
The Helmet Jellyfish, much like other jellyfish, feed as free-swimming, solitary carnivores. They have a mouth opening on the underside of their bell, which is encircled by hollow tentacles that are equipped with nematocysts. These nematocysts are capable of immobilizing prey, which consists of small fish and other marine animals. The jellyfish's mouth leads to a gastrovascular cavity that may be segmented into four interconnected sacs known as diverticuli. This cavity functions not only to digest the prey but also to distribute the nutrients throughout the jellyfish's body through a network of radial canals.
The branched gastrovascular cells play a dual role in increasing the surface area for nutrient absorption and supporting the animal's body structure. Additionally, the scyphozoan jellyfish possess a nerve net and muscle ring that aids in their movement, which coincidentally allows them to draw in their prey as they swim through the water.