tonna

Tonna is a genus of large, predatory sea snails belonging to the family Tonnidae. These marine gastropod mollusks are commonly known as tun shells due to their rounded, inflated shape. Species within the Tonna genus are found in tropical and subtropical waters worldwide, inhabiting sandy bottoms and coral reefs.

Tun shells are characterized by their thick, heavy shells, which often feature prominent spiral ribs and nodules. The aperture is typically large and elongated, with a distinct siphonal canal at the base. The shell color varies among species, but often includes shades of cream, brown, or white, sometimes with darker banding or spotting.

These snails are active predators, feeding on a variety of marine invertebrates, including echinoderms like sea urchins and starfish, as well as polychaete worms. They possess a radula, a ribbon-like structure covered in teeth, which they use to rasp away at their prey. Tonna species are generally slow-moving but effective hunters.

Reproduction in Tonna typically involves external fertilization, with females laying gelatinous egg masses that are attached to the substrate. The larval stage is planktonic, allowing for dispersal. While some species are quite large and conspicuous, others are more elusive, making them challenging to find. Several Tonna species have shells that are collected by hobbyists and sometimes used in decorative crafts.