Tun Shells of the Tonnidae Family
One Tun Shell of the Tonnidae Family can be found in this website:
Grinning Tun, Malea ringens. A representative of the Tonnidae Family of Tun Shells.
Phylogeny: Tun Shells of the Tonnidae Family are gastropod mollusks in the order Littorinimorpha. This order is large and very diverse in shape including snail-like, cowry shaped, and limpet-like. Most are marine species but some are found in freshwater or on land. They all have a twisted shell and a muscular foot that is used for movement. The key characteristic is that they all exhibit torsion, which is a process where the body twists so that the anus, gills, mantle cavity, and reproductive organs all point forward. There are sixteen superfamilies in this large order. The Tonnidae Family is one of nine families in the superfamily Tonnoidea. The Tonnidae Family is fairly small, with no subfamilies, three genera and thirty-five species. Shells in this family are also commonly called Cask Shells or Tonnids.
Description: Tun Shells are medium to large shells that have thin but strong construction. They are named after the wine casks, known as tuns. The shells have a large globose body whorl and a low to moderate spire. Most are sculpted with strong spiral cords or flat ridges. They have a large aperture, which widens with age. In adults the outer lip often begins to flare and thicken. The outer lip is crenulated, matching the exterior sculpture. They have a short, open, siphonal canal and may have a posterior canal. The columella may be twisted. The animals are often too large to retract into their shells and they lack an operculum. These shells have a thin periostracum. The largest shells in this family reach around 30 cm (11.7 inches) in length
Habitat and Distribution: Tun Shells are generally found on and within sand, mud, or shell hash substrates. They live in the intertidal zone, and at depths up to 2,359 m (7,738 feet). They are found worldwide in tropical to subtropical seas. At least four species from this family are found in Mexican waters.
Natural History: Tun Shells bury themselves during the day, often with only their siphon tip showing, and emerge at night to hunt. They prey upon bivalves, gastropods, crustaceans, polychaetes, sipunculids, fish, sea urchins, sea stars, and sea cucumbers. They secrete saliva containing sulfuric acid to paralyze and partially digest their prey. Some species envelope the prey in their large proboscis and swallow it whole. In turn, they are prey for fish, shorebirds, crabs, and other mollusks. Their empty shells are used by octopuses and hermit crabs for housing. Tun Shells are gonochoric and reproduce sexually with internal fertilization. The eggs are laid as ribbon-like masses. Tun Shells are edible and are harvested commercially in some regions. The shells are sought as decorative items and by shell collectors.