Rock Shells of the Muricidae Family

Thirty-four Rock Shells of the Muricidae Family can be found in this website:

Phylogeny: Rock Shells of the Muricidae Family are gastropod mollusks that are in the order Neogastropoda. Neogastropods are characterized by having a long siphon canal, a well-developed siphon notch, and a specialized radula. Many species in this order have a narrow aperture. Neogastropods are primarily marine snails and most of the well-known shell families are in this order. The superfamily Muricoidea is one of seven superfamilies in this order. The Muricidae Family is the only family in this superfamily. The Muricidae Family is very large. It is comprised of ten subfamilies, two hundred genera, and over seventeen hundred species. Shells in this family are also commonly known as Murex Shells (plural Murexes or Murices) or Muricids.

Description: Rock Shells vary widely in appearance. They range from small to large in stature and they may be of thin or solid construction. Some are elongated while others are more globose.  Generally speaking, they have a spindle-shaped (fusiform) outline, with a wide body whorl and a short to moderate spire, though some are limpet-like or elongated. Most (but not all) have a long siphonal canal, which may be open or closed.  Rock Shells are known as some of the most intricately sculpted shells. These shells often have numerous spines or “wings” running along their varices. Their varices are thick ribs that run the length of the shell that form from the thickening of the shell’s outer lip which occurs during periodic rest in the shell’s growth cycles. They may display spines, knobs, or frills. Other species lack varices and instead have spiral ridges. Most shells are white and various shades of brown, or black. Only a few are brightly colored but despite the lack of bright colors, these shells are often striking in their coloration. Their aperture is oval to narrow. The outer lip may be smooth or toothed. The columella is smooth to weakly ridged.  Rock Shells have a corneous operculum and they do not have a periostracum. Scientists use the shape of the radula to differentiate between similar looking species. The largest species in this family is 34 cm (13.4 inches) in height.

Habitat and Distribution: The majority of Rock Shells live on coral, gravel or rock substrates. Some species are found on sand or mud. Rock Shells live in the intertidal zone and to depths in excess of 2,000 m (6,600 feet). They are found worldwide, in tropical to polar seas. Sixty species of the Muricidae Family are found in Mexican waters.

Natural History: Rock Shell are predators, primarily consuming bivalve mollusks. They use a combination of a toxic enzyme that they secrete, to soften the bivalve shell, and their radula to drill or chip a hole into the bivalve. Most of the drill holes are at the bivalve’s margin, where their shell is most vulnerable. Rock Shells drill holes are rougher and more irregular than those from moon snails and other predatory snails. Once the hole is drilled, Rock Shells inject a neurotoxin to kill their prey, which also facilitates shell opening. Some Rock Shell species have a tooth on their outer lip that is used to assist in opening the shell. Rock Shells are also known to eat barnacles, polychaetes, coral polyps, and gastropods. In turn Rock Shells are preyed upon by crabs, fish, shorebirds, and other predatory mollusks. Rock Shells are gonochoric and reproduce sexually with internal fertilization. The eggs are laid in protective capsules. These capsules also contain “nurse eggs”, which are a food source for the developing embryos. Some Rock Shell species have been used commercially to produce a dark purple dye. From early historical times, Mediterranean cultures have utilized the dye found in these snails for dying cloth. Clothes dyed with Royal Purple or Tyrian Purple were considered very valuable. The native populations along the west coast of Mexico have similarly used the dye from Rock Shells for at least five hundred years. The name Murex  stems from the Greek root meaning “purple fish”.