Dog Whelks - Western Isles - Hebrides Insects
Dog Whelks - Nucella lapiilus - Small Sea Snails
Dog Whelks aren't just pretty shells - there are sea creatures inside - they are sea snails.
Many can be seen in the Western Isles - Scotland. The shells come in many different sizes and colours from red to green, yellow, orange.
Dog Whelk - A Mollusc
The Dog-whelk is a predatory mollusc found on rocky shores, breakwaters & pier piles. The dog whelk can be separated from other seashore snails by the distinct groove along the shell lip.
Shell Shape
The shell’s exact shape depends on its exposure to wave action, and its colour depends on diet. The radula or tongue is modified for shell boring is assisted by chemical means.
The groove in the shell lip allows water in for breathing. To bore for a barnacle for example can take up to 48 hours.
Feed on Barnacles and Mussels and Limpets
Dog whelks feed on barnacles and mussels. As you can see from the above photograph the shells of the dog whelk can be many colours, Indeed individual that have been feeding on dark mussels - then their shell may be darker in colour. The shell is up to 4cm in length.
Dog whelks release digestive enzymes into its prey, liquidizing it, and then sucking up the liquid. Dog Whelks have a lifespan of 7 years. Eggs are internally fertilized and laid in crevices or beneath boulders during the autumn and early spring.
Dog Whelk - White or Cream
The Animal The animal itself is white or cream coloured with white speckles, and a flattened head. The head has two tentacles, each bearing a eye about one third of the length of the tentacle from its base.
Large Waves & Dog Whelks
Dog Whelk Remains Inactive If there are large waves around and there is an excessive risk of water loss the dog whelk will remain inactive in sheltered locations for long periods.
Eggs - Yellow - Often in Overhangs
The egg capsules of Nucella lapillus are vase shaped, about 8mm high, usually yellow and found attached to hard substrata in crevices and under overhangs
Only a Few Eggs are Fertile
The females lay egg capsules containing lots of eggs only a few of which are fertile.
The rest of them are food for the ones that do hatch. After about 4 months they emerge as small dog whelks
History - Dog Whelks Used in Dyes
In medieval times the dog whelk was used to acquire beautiful red and violet and purple dyes. Fabric for weaving could be dyed directly from the opened whelk.
The dye came from mucus in a gland known as the hypobranchial gland. This chemical substance passes from yellow to green and then on to blue, reds and purples when exposed to air and sunlight. Ancient dyes were made in a vat process, the evidence for which can still be found in Ireland and the Middle East.
Different Number of Chromosomes
Remarkably, dogwhelks from different types of shores have different numbers of chromosomes, even though they are members of the same species. They can interbreed with others found on other shores. Individuals in the same population have even been known to exhibit variation in chromosome number.
1970's - saw dog whelks decimated
Dogwhelk numbers decreased badly in the 1970's as they were poisoned by a side effect of tributyltin (TBT). TBT is a highly toxic chemical found in antifouling paint used on boats.
