periwinkle snails?
- Thread starter renogaw
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ryanhayes9
Active Member
Identification
The periwinkle has a rounded univalve shell. The dark brown to black shell grows to a little over one inch across. Each turn of a snail’s shell is called a whorl. The main whorl, called the body whorl, of the periwinkle is much larger than the others. The remaining whorls are low-spired compared to most other snails. (A spire is the part of the shell which includes all the whorls above the body whorl.) The operculum of the periwinkle is black and fits perfectly over the shell opening. The common periwinkle is one of our slowest moving snails.
Habitat
This snail lives on any coast with hard surfaces to attach itself to. It is rarely found on mud or sand bottoms. The periwinkle lives only in the intertidal zone. Because the operculum (the “trap door” attached to the foot that is used to cover the shell opening) fits so tightly, the snail is able to survive long periods out of water. During low tide the periwinkle uses a mucous to stick its shell to the rock, then seals the opening shut to keep in moisture until the tide returns.
Introduced Animals
An introduced animal is a non-native species brought here by humans (usually attached to ocean crossing ships) from other parts of the world. The periwinkle is a perfect example of how successful introduced species can become. We have very few native snail types that live in the upper intertidal zone. When this snail arrived from Europe over 100 years ago, it found an empty niche which it filled nicely. Today it is one of the most numerous animals on our shore.
Feeding
The periwinkle is a strict herbivore. It feeds on the algae film which covers the rocks of the intertidal zone. When feeding, even in an aquarium, there can often be seen a trail on the rock as the snail scrapes away the plant growth. In heavily populated areas entire rocky shores can be scraped clean of all growth. Like nearly all snails, the periwinkle uses its tooth-like radula to feed with. Periwinkles only feed during high tide.
Protection
This snail has effective defenses against predators. First, the shell is very hard. Every snail’s “Achilles heel” is its opening (or aperture) The operculum of the periwinkle is fairly thick and seals the opening tightly, keeping crabs, shore birds and other predators from reaching the soft animal inside. Its habit of living high up on the intertidal zone protects it from its most dangerous predator, the sea star. Sea stars cannot live more than a few minutes exposed to air so cannot survive in the periwinkles favorite habitat. If captured by a sea star, the operculum is not match for this predator. (See “Northern Sea Star” entry for how sea stars feed.)
Reproduction
Female periwinkles lay several thousand eggs at a time, all embedded in a mass of gelatin (similar to frog’s eggs). The gelatin soon disintegrates leaving the individual eggs to drift away. They hatch into tiny, shell-less larvae which drift in the currents for several days before growing a shell and settling to the bottom.
In the Aquarium
This species is difficult to keep in captivity. Although hardy and easy to feed, they tend to climb out of the water along the top lip of the aquarium. They then seal themselves shut awaiting high tide (which, of course, never comes) and the snail eventually dries out and dies. Another problem is a strange inability to right themselves if turned upside down. The snails, if not turned over by hand, remain upside down, unable to feed.
The periwinkle has a rounded univalve shell. The dark brown to black shell grows to a little over one inch across. Each turn of a snail’s shell is called a whorl. The main whorl, called the body whorl, of the periwinkle is much larger than the others. The remaining whorls are low-spired compared to most other snails. (A spire is the part of the shell which includes all the whorls above the body whorl.) The operculum of the periwinkle is black and fits perfectly over the shell opening. The common periwinkle is one of our slowest moving snails.
Habitat
This snail lives on any coast with hard surfaces to attach itself to. It is rarely found on mud or sand bottoms. The periwinkle lives only in the intertidal zone. Because the operculum (the “trap door” attached to the foot that is used to cover the shell opening) fits so tightly, the snail is able to survive long periods out of water. During low tide the periwinkle uses a mucous to stick its shell to the rock, then seals the opening shut to keep in moisture until the tide returns.
Introduced Animals
An introduced animal is a non-native species brought here by humans (usually attached to ocean crossing ships) from other parts of the world. The periwinkle is a perfect example of how successful introduced species can become. We have very few native snail types that live in the upper intertidal zone. When this snail arrived from Europe over 100 years ago, it found an empty niche which it filled nicely. Today it is one of the most numerous animals on our shore.
Feeding
The periwinkle is a strict herbivore. It feeds on the algae film which covers the rocks of the intertidal zone. When feeding, even in an aquarium, there can often be seen a trail on the rock as the snail scrapes away the plant growth. In heavily populated areas entire rocky shores can be scraped clean of all growth. Like nearly all snails, the periwinkle uses its tooth-like radula to feed with. Periwinkles only feed during high tide.
Protection
This snail has effective defenses against predators. First, the shell is very hard. Every snail’s “Achilles heel” is its opening (or aperture) The operculum of the periwinkle is fairly thick and seals the opening tightly, keeping crabs, shore birds and other predators from reaching the soft animal inside. Its habit of living high up on the intertidal zone protects it from its most dangerous predator, the sea star. Sea stars cannot live more than a few minutes exposed to air so cannot survive in the periwinkles favorite habitat. If captured by a sea star, the operculum is not match for this predator. (See “Northern Sea Star” entry for how sea stars feed.)
Reproduction
Female periwinkles lay several thousand eggs at a time, all embedded in a mass of gelatin (similar to frog’s eggs). The gelatin soon disintegrates leaving the individual eggs to drift away. They hatch into tiny, shell-less larvae which drift in the currents for several days before growing a shell and settling to the bottom.
In the Aquarium
This species is difficult to keep in captivity. Although hardy and easy to feed, they tend to climb out of the water along the top lip of the aquarium. They then seal themselves shut awaiting high tide (which, of course, never comes) and the snail eventually dries out and dies. Another problem is a strange inability to right themselves if turned upside down. The snails, if not turned over by hand, remain upside down, unable to feed.
ryanhayes9
Active Member
no prolem