These are
easily seen on the nearby Nucella lapillus shoreline.
Class: Gastropoda Order: Neogastropoda Family: Muricidae Genus: Nucella
Distribution They are common on the On the west side of the Atlantic they extend from Long Island rocky coasts of the North in the USA, north along the (eastern) Canadian coastline to Atlantic. They occur on Greenland. On the eastern (European) side they occur from coastlines of both the southern Portugal north through Scandinavia into the Siberian western and eastern side of arctic. They also occupy the coastline of Iceland. this ocean. They are commonly found around the coastline of Nova Scotia.
Habitat In coastal environments the littoral zone extends from the high They occupy the littoral water mark, which is rarely inundated, to shoreline areas that are zone of the North Atlantic, permanently submerged. It always includes the intertidal zone. this being the part of a sea, They occur on both exposed shores and sheltered shores, lake or river that is close to ranging between the 19 °C summer isotherm in the south and the shore. the -1 °C winter isotherm in the north.
Food Nucella possess a radula which is a toothed appendage for Dog whelks are predatory removing flesh, and a mouth on an extensible proboscis. It feeds snails. They feed mostly on either by inserting the proboscis between the shells of bivalves barnacles and mussels. or plates of barnacles and using the radula to rasp flesh, or by Periwinkles, other drilling a small hole in the shell of its prey through which it gastropods and bivalves are inserts its proboscis. It releases digestive enzymes into its prey, also consumed. liquidizing it, and then sucking up the "soup."
Reproduction The male has a large penis situated behind the head on the right They form aggregations and becomes visible when extended. Copulation amongst the seasonally. Spawning group is repeated at intervals, between which a few egg capsules aggregations are formed in are laid, one at a time. Spawning is protracted and ends in the the spring for the purpose fall. Eggs are laid in protective capsules on hard substrata in of fertilization. These damp crevices and under stones. Larger females lay larger contain groups of thirty or capsules, 9 -10 mm high, 3 -4 mm across, however most more adult males and capsules are about 8 mm. They are yellow to brown in colour females. Fertilization is and are vase shaped. Capsules are cemented to the substratum internal. They are by the ventral pedal gland and foot and are sealed with a 'plug' at oviparous. the opposite end. They are usually yellow in colour.
Development They develop to the juvenile stage within The females lay egg the egg capsule. This V-shaped capsule capsules containing lots of measures approximately 1 cm including the eggs only a few of which stalk and exit plug. During the first week are fertile. The remainder, the embryos begin development by feeding about 94%, are food for the on the nurse (unfertilized) eggs. After slowly developing embryos about 4 months individuals emerge as that hatch out after a few juvenile whelks. months.
Characteristics The overall shell shape varies quite widely The shell is rounded with a according to the degree of exposure to pointed spire and a short, wave action of the shore on which a particular population lives. straight siphonal canal (a The body whorl (the largest section of the shell where the groove on the underside of majority of the visceral mass is located) is usually around 3/4 of the shell) and a deep anal the total length of the shell. The aperture is usually crenulated in canal. The external shell mature dog whelks, less often in juveniles. This means finely colour is variable, usually a notched or scalloped. The outer lip is dentate and ridged within. whitish grey, but can be The columella (lip) is smooth. The animal itself is white or orange, yellow, brown, cream coloured with white speckles, and a flattened head. The black, and purple or banded head has two tentacles, each bearing an eye about one third of with any combination of the length of the tentacle from its base. these colours.
Adaptations The mouth and radula are on an extensible Adaptations include a proboscis, which is about the same length as modified radula (a toothed their shell. chitinous structure) to bore They are able to adapt their shell shape, shell holes in the shells of prey, thickness and relative size of the aperture to along with an organ on the vary with wave exposure. foot which secretes a shell- The shell surface can be fairly smooth softening chemical. When a interrupted only with growth lines, or when the snail is living in hole has been formed more sheltered areas the shell surface can be somewhat rough paralysing chemicals and and lamellose. Wave action tends to confine the dog whelk to digestive enzymes are more sheltered shores, however, this can be counteracted, both secreted inside the shell to by adaptations to tolerate it such as the shell and muscular foot break the victim’s soft body and by the avoidance of direct exposure to wave action by down into a ‘soup’ which making use of sheltered microhabitats in rocky crevices. can be sucked out. Many populations are diminishing in Status/Threats various parts of the world. The decline They are predated by birds has been linked to contamination effects when emersed, and by of tributyltin (TBT) compounds used in crabs when immersed. Egg antifouling paints, which cause imposex in capsules are predated by dog whelks. crabs and juvenile lobsters.
Sightings in Nova Scotia Easily seen on many coastal areas.