Thylacodes squamigerus

Scaled Worm Snail

Family: Velutinidae · Class: Gastropoda · Order: Littorinimorpha

The Scaled Worm Snail is a marine gastropod mollusk in the family Velutinidae, characterized by its unique tubular, irregularly coiled shell that grows attached to hard substrates. Unlike typical gastropods, this species produces a permanently cemented, worm-like shell that can reach lengths of several centimeters. The shell surface displays distinctive scale-like ridges or lamellae, giving the species its common name. The aperture is circular and the shell color ranges from grayish-white to brown, often matching the substrate on which it grows. Thylacodes squamigerus occurs along the Pacific coast of North America, with its range extending from central California southward to Baja California, Mexico. In California, the species is documented from intertidal and shallow subtidal zones along the coast, particularly in areas with rocky substrates and stable hard surfaces suitable for attachment. The species' distribution appears to be patchy and localized, with populations concentrated in areas providing appropriate settlement substrates. This species inhabits rocky intertidal and shallow subtidal environments, typically in areas with moderate to strong wave action. Scaled Worm Snails require hard substrates such as rocks, shells, or artificial structures for initial larval settlement and subsequent growth. They are commonly found in crevices and on vertical rock faces where they can filter feed effectively. The species occurs from the low intertidal zone to depths of approximately 20 meters, with optimal habitat conditions including areas with good water circulation and plankton availability. As a suspension feeder, Thylacodes squamigerus captures planktonic organisms and organic particles from the water column using ciliary feeding mechanisms. The species produces mucus nets or feeding webs that trap food particles, which are then transported to the mouth via ciliary action. Reproduction involves the release of planktonic larvae that must locate suitable hard substrates for metamorphosis and permanent attachment. Once settled, individuals cannot relocate, making substrate selection critical for survival. The species exhibits protandrous hermaphroditism, with individuals functioning first as males and later developing female reproductive capabilities. Limited information exists regarding the conservation status of the Scaled Worm Snail in California. The species does not appear on federal or state endangered species lists, and no specific population assessments have been conducted. However, like many marine invertebrates dependent on rocky intertidal habitats, populations may face pressures from coastal development, water quality degradation, and climate change effects including ocean acidification and sea level rise. The species' restricted habitat requirements and limited dispersal ability as adults may make populations vulnerable to localized disturbances. Marine protected areas along the California coast may provide some protection for populations within their boundaries, though comprehensive surveys are needed to assess current population status and distribution patterns.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.