Leafy hornmouth • Ceratostoma foliatum
Top: leafy hornmouths with obvious varices. Bottom right: distinctive stalked, yellow egg cases laid by females of this species. Bottom left: underside view of this species. Photos by Bea Proudfoot (top right) and Jenn Burt.
Identification
The three distinctive varices, or “frills” on the shell, the protruding tooth near the anterior end of the aperture (shell opening), and the coarse operculum (the structure that covers the aperture when the snail retreats into its shell) justify this species’ descriptive common name of 'leafy hornmouth.' The interior of the shell is white, while the exterior varies from gray, white, to yellow brown. Another distinguishing feature of this species is that the siphonal canal – a trough-like extension of the aperture – is closed and twisted at the end. Leafy hornmouths are typically 8-8.5 cm long, and can reach 10 cm in length. The whorls in the spire are much smaller than the main body whorl.
Similar Species
Nucella lamellosa is a similarly shaped, grey species of marine snail, however N. lamellosa lacks the large frills and closed siphonal canal characteristic of the leafy hornmouth.
Habitat and Range
This species inhabits exposed rocky intertidal and subtidal zones (up to 65 m), and is typically found in close proximity to barnacles (Semibalanus cariosus and Balanus glandula) and bivalves such as Mytilus trossulus and M. californianus – the primary food source for these carnivorous gastropods. Its range extends from central Alaska to southern California.
Intriguing Information
In order to access its prey, the leafy hornmouth uses its radula to drill through the protective shells of mussels and barnacles, injects digestive enzymes that essentially liquefy the body of the prey, and then simply slurps up the dissolved tissue.
Individuals of this species typically gather en masse in the spring and summer to copulate. Females then proceed to lay their eggs in distinctive yellow, stalked egg cases, each containing about 25-80 eggs. Females generally lay about 40 egg cases per year. Larval development occurs within the capsule, and after about 4-10 months, juvenile leafy hornmouths emerge from the egg cases. This species can live up to 16 years.
The large shell varices are known to have a number of functions related to protection from predators and the environment. When leafy hornmouths are dislodged from a substrate and fall through the water, the varices help them land with their aperture (shell opening) down. This protects them from predation. When exposed to bright light, leafy hornmouths been observed orienting their shells so that the varices provide enhanced shading and light protection to the rest of the shell.
iNaturalist
https://www.inaturalist.org/taxa/116687-Ceratostoma-foliatum
The three distinctive varices, or “frills” on the shell, the protruding tooth near the anterior end of the aperture (shell opening), and the coarse operculum (the structure that covers the aperture when the snail retreats into its shell) justify this species’ descriptive common name of 'leafy hornmouth.' The interior of the shell is white, while the exterior varies from gray, white, to yellow brown. Another distinguishing feature of this species is that the siphonal canal – a trough-like extension of the aperture – is closed and twisted at the end. Leafy hornmouths are typically 8-8.5 cm long, and can reach 10 cm in length. The whorls in the spire are much smaller than the main body whorl.
Similar Species
Nucella lamellosa is a similarly shaped, grey species of marine snail, however N. lamellosa lacks the large frills and closed siphonal canal characteristic of the leafy hornmouth.
Habitat and Range
This species inhabits exposed rocky intertidal and subtidal zones (up to 65 m), and is typically found in close proximity to barnacles (Semibalanus cariosus and Balanus glandula) and bivalves such as Mytilus trossulus and M. californianus – the primary food source for these carnivorous gastropods. Its range extends from central Alaska to southern California.
Intriguing Information
In order to access its prey, the leafy hornmouth uses its radula to drill through the protective shells of mussels and barnacles, injects digestive enzymes that essentially liquefy the body of the prey, and then simply slurps up the dissolved tissue.
Individuals of this species typically gather en masse in the spring and summer to copulate. Females then proceed to lay their eggs in distinctive yellow, stalked egg cases, each containing about 25-80 eggs. Females generally lay about 40 egg cases per year. Larval development occurs within the capsule, and after about 4-10 months, juvenile leafy hornmouths emerge from the egg cases. This species can live up to 16 years.
The large shell varices are known to have a number of functions related to protection from predators and the environment. When leafy hornmouths are dislodged from a substrate and fall through the water, the varices help them land with their aperture (shell opening) down. This protects them from predation. When exposed to bright light, leafy hornmouths been observed orienting their shells so that the varices provide enhanced shading and light protection to the rest of the shell.
iNaturalist
https://www.inaturalist.org/taxa/116687-Ceratostoma-foliatum
References
Charbonneau, N. (2002). Ceratostoma foliatum (Gmelin, 1791). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 2015-10-29.
Harbo, R. M. (1997). Shells & Shellfish of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P.209.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest [electronic version]. Madeira Park, BC: Harbour Publishing.
Authors and Editors
Beatrice Proudfoot and Kelly Fretwell (2015)
Charbonneau, N. (2002). Ceratostoma foliatum (Gmelin, 1791). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 2015-10-29.
Harbo, R. M. (1997). Shells & Shellfish of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P.209.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest [electronic version]. Madeira Park, BC: Harbour Publishing.
Authors and Editors
Beatrice Proudfoot and Kelly Fretwell (2015)