|Researched by||Dr Harvey Tyler-Walters||Refereed by||Dr John Crothers|
|Other common names||-||Synonyms||Thais lapillus (Linnaeus, 1758)|
The shell is broadly conical, bearing spiral ridges and consisting of a short pointed spire, dominated by the last whorl. The shell is usually up to 3 cm in height by 2 cm broad but may reach up to 6 cm in height (Crothers, 1985). The shell colour is variable, usually white, but may be grey, brown, or yellow, occasionally with contrasting (usually brown) spiral banding. A short, open siphonal canal leads from base of the aperture. The outer lip of the aperture is thin in young specimens, becoming thickened and toothed internally with age. The shell shape, shell thickness and relative size of the aperture vary with wave exposure. In some populations, mainly sublittoral or from the intertidal in North Kent, the growth lines extend outwards to form flounces or ruffles, and this variety of dog whelk is called Nucella lapillus var. imbricata. The animal itself is white or cream coloured with white speckles, and a flattened head. The head bears two tentacles, each bearing a eye about one third of the length of the tentacle from its base. 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.
The taxonomy of Nucella lapillus was reviewed by Crothers (1985) and Kool (1993)
|Phylum||Mollusca||Snails, slugs, mussels, cockles, clams & squid|
|Class||Gastropoda||Snails, slugs & sea butterflies|
|Order||Neogastropoda||Whelks, drills & cone snails|
|Recent Synonyms||Thais lapillus (Linnaeus, 1758)|
|Typical abundance||Moderate density|
|Male size range||17 - 50+mm||Male size at maturity|
|Female size range||Small-medium(3-10cm)||Female size at maturity|
|Growth form||Turbinate||Growth rate||See additional information|
|Body flexibility||None (less than 10 degrees)||Mobility|
|Characteristic feeding method||Predator|
|Typically feeds on||Barnacles and mussels (see Crothers, 1985).|
trematode parasites of sea birds, Parorchis acanthus and Lepocreadium sp.
|Is the species harmful?||No|
But not edible, being distasteful (Crothers, 1985).
The ecology, physiology and genetics of Nucella lapillus has been extensively studied. Therefore, the following review is based on more detailed reviews by Fretter & Graham (1994) and Crothers (1985), to which the user should refer for further detail. The original references are given where appropriate.
Growth rates vary depending on wave exposure, prey type and starvation. Sheltered shore populations grow faster than wave exposed shore populations, resulting in larger more elongate shells (Osborne, 1977; Crothers, 1985; Etter, 1989). Feare (1970b) reported that juveniles reached 10mm with a year, ca 15 mm at 2 years old and entered maturity at ca 20 mm at Robins Hood Bay in Yorkshire. Moore (1938a) reported that dog whelks reach 10-15 mm at I year, 21-26 at 2 years and 29.5 mm at maturity. Maturity was calculated to be reached at 2.5 years at which point shell growth stops (Fretter & Graham, 1994). However, Etter (1996) suggested that adults continued to grow but extremely slowly. Osborne (1977) noted that juveniles <12 mm grew at the same speed above which sheltered individuals grew faster than wave exposed individuals. Etter (1996) reported that juveniles grew 6 mm/150 days on wave exposed shores but 9 mm/150 days in sheltered conditions. Mussels supported the highest growth rates (Hughes & Drewett, 1985). Etter (1996) transplanted juveniles between shores of different wave exposure, and concluded that growth was determined by environmental factors and depressed by wave exposure since it reducing foraging or feeding time.
Crothers (1985) suggested that, although crabs select the largest first year class dog whelks, rapid growth may allow dog whelks to grow beyond the predators preferred size range and decrease their susceptibility to predation.
Nucella lapillus is an important intertidal predator and preys mainly on barnacles and mussels but may also prey on cockles, other bivalves and gastropods.
Factors affecting feeding
Shell shape, colour and sculpture variation
Nucella lapillus is highly variable in the appearance of its shell, depending on wave exposure and location (see Crothers, 1983; 1985 for review).
Shell shape variation
Variation in shell shape and length has been extensively studied (see Crothers, 1985 for a review). Key points follow.
In addition to the colour variation mentioned above, Nucella lapillus has been shown to demonstrate clines in allozyme (Day & Bayne, 1988; Day, 1990; Kirby, 1994a, b) and mitochondrial DNA polymorphisms (Kirby et al.,1997), Robertsonian translocation (Staiger, 1957; Bantock & Cockayne, 1975; Page 1988; Pascoe & Dixon, 1994; Pascoe et al., 1996), peri-and para-centric chromosomal inversions (Page 1988; Pascoe & Dixon, 1994; Pascoe et al., 1996; Pascoe, 2002). Variation in chromosome number was found to vary greatly between different populations, within some populations and even within some individuals (Pascoe, 2002).
|Physiographic preferences||Open coast, Strait / sound, Sea loch / Sea lough, Ria / Voe, Estuary, Enclosed coast / Embayment|
|Biological zone preferences||Lower eulittoral, Mid eulittoral, Sublittoral fringe|
|Substratum / habitat preferences||Artificial (man-made), Bedrock, Caves, Crevices / fissures, Large to very large boulders, Overhangs, Rockpools, Small boulders, Under boulders|
|Tidal strength preferences||Moderately Strong 1 to 3 knots (0.5-1.5 m/sec.), Strong 3 to 6 knots (1.5-3 m/sec.), Very Strong > 6 knots (>3 m/sec.), Weak < 1 knot (<0.5 m/sec.)|
|Wave exposure preferences||Exposed, Extremely exposed, Extremely sheltered, Moderately exposed, Sheltered, Very exposed, Very sheltered|
|Salinity preferences||Full (30-40 psu), Variable (18-40 psu)|
|Other preferences||No text entered|
|Migration Pattern||Non-migratory / resident|
|Reproductive type||Gonochoristic (dioecious)||Reproductive frequency||Annual protracted|
|Fecundity (number of eggs)||100-1,000||Generation time||2-5 years|
|Age at maturity||2.5 years||Season||Spring - Autumn|
|Life span||5-10 years|
|Larval/propagule type||-||Larval/juvenile development||Oviparous|
|Duration of larval stage||Not relevant||Larval dispersal potential||<10 m|
|Larval settlement period||Not relevant|
This MarLIN sensitivity assessment has been superseded by the MarESA approach to sensitivity assessment. MarLIN assessments used an approach that has now been modified to reflect the most recent conservation imperatives and terminology and are due to be updated by 2016/17.
|Removal of the substratum would cause removal of adult and juvenile dog whelks together with their egg capsules. Therefore, an intolerance of high has been recorded. Given their poor dispersal ability, recruitment from other populations is likely to be slow, therefore a recoverability of low has been recorded.|
|Little information on the effect of smothering was found. However, dog whelks are found at the mouths of highly turbid estuaries, such as the Severn Estuary where rock pools are often filled with silt. Dog whelks are therefore probably not adversely affected by temporary smothering. If smothering occurs, there will be an energetic expenditure involved in freeing itself from the smothering material. Hence, an intolerance of low has been recorded.|
|Nucella lapillus is found in turbid estuaries such as the Severn estuary, and is, therefore, unlikely to be adversely affected by an increase in suspended sediment concentration. However, the accumulation of silt or mud may restrict their distribution in silty estuaries such as the Severn. In addition, the abundance of their prey (barnacles and mussels) may be restricted by increased suspended sediment, reducing their food supply. Therefore, an intolerance of low has been recorded.|
|Tolerant||Not relevant||Not sensitive||High|
|Nucella lapillus is found on a variety of shores from wave exposed to sheltered and is, therefore, unlikely to be affected by a decrease in suspended sediment concentration. Hence, Nucella lapillus has been recorded as 'tolerant' to a decrease in suspended sediment.|
|Desiccation tolerance is dependant on the volume of water held inside the mantle cavity of the shell and hence the shell shape. Squat shells characteristic of some wave exposed shores have wider apertures and shorter spires which results in less water being retained within the shell when emersed and a greater rate of evaporation through the larger aperture.|
An increase in desiccation is likely to reduce the upper limit of adult dog whelks on the shore and an intolerance of intermediate has been recorded. Gibbs et al. (1999) reported that dog whelks surviving a mass-kill were able to re-establish the population within 2 years but where there were few survivors, many years may be required. Therefore, a recoverability of high, to previous population levels, has been recorded (see additional information). Dog whelks displaced to the top of the shore (e.g. by wave action) will probably succumb to desiccation unless they are able to migrate to the lower shore before emersion.
|The distribution of dog whelks on the shore is centred around the mid-tidal level and between 10-75% emersion (Fretter & Graham, 1994). Dog whelks extend higher upshore in Scotland or Norway than in south Britain (Dr John Crothers pers comm.), presumably because of the lower average air temperatures in more northern latitudes. In Norway, they can reach the uppermost Semibalanus and can eat-out their food supply. |
Increased emersion would expose the population to increased risk of desiccation and a wider range of temperatures. Coombs (1973b) reported that dog whelks were unlikely to experience more than 3 -4 hours of emersion at their preferred shore height, but also reported that dog whelks became comatose and reached critical water loss after 6 hours at 25 °C, a temperature that may be experienced during a hot summer. Comatose animals are likely to be dislodged to lower on the shore, where they would escape the effects of increased emmersion best, since they become relaxed, become more prone to desiccation. Therefore, some mortality of individuals at the upper limits of their range may occur as a result of an increase in emergence regime, and therefore an intolerance of intermediate has been recorded.
|Tolerant||Not relevant||Not sensitive||Moderate|
|The distribution of dog whelks on the shore is centred around the mid-tidal level between 10-75% emersion (Fretter & Graham, 1994). Decreased emergence would allow the population to follow their prey as they colonized further up the shore. However, it may also expose the individuals at the bottom of the shore to increased predation from crabs and starfish. It is likely that dogwhelks would migrate up the shore and the benefits of increased access to prey would balance out the possibility of increased predation, therefore an intolerance of tolerant has been recorded.|
|Low||Very high||Very Low||Moderate|
|Change to water flow rate mostly relevant to subtidal area. Etter (1988a) demonstrated that the tenacity of dog whelks to resist water flow was proportional to the pedal surface area. Tenacity of dog whelks from sheltered shores was lower than dog whelks form wave exposed shores. He also demonstrated that dog whelks from sheltered shores would develop a larger foot when transplanted to wave exposed shores. Therefore, Nucella lapillus exhibits considerable phenotypic plasticity in response to wave exposure and most likely current flow. Although, the most elongate specimens are probably highly intolerant of increases in water flow rates, hatchlings and juveniles, which are still growing, will probably adapt to the increase water flow regime. Therefore, an overall intolerance of low has been recorded. A recoverability of very high has been recorded to represent the time taken for juveniles to recolonize and adapt (see additional information below).|
|Tolerant||Not relevant||Not sensitive||Low|
|It is unlikely that a decrease in water flow rate will directly affect dog whelks even though the longer foot associated with strong flows becomes superfluous. However, the biotope may change and prey species, predominantly barnacles, become less abundant. Etter (1988a) demonstrated that the tenacity of dog whelks to resist water flow was proportional to the pedal surface area. A decrease in water flow may result in an increase in the mean shell length of the population (depending on wave exposure) but Nucella lapillus is otherwise probably tolerant of a decrease in water flow.|
|Largen (1967) reported that feeding rate was maximal between 20 -22 °C and fell steeply to zero at 25 °C whilst crawling reached zero at 27 °C. Sandison (1968); (reported unpublished in Lewis, 1964) noted that heat coma occurred in Nucella lapillus at 27 -28 °C, and death at 32 -33 °C. Largen (1967) noted that feeding rates were temperature dependant, dog whelks averaged consumption of 16 barnacles or 0.7 mussels per week at 20 °C but only 10.2 barnacles and 0.4 mussels per week at 15 °C. Newell (1979) noted that oxygen consumption (hence metabolic rate) fell with decreased temperature and starvation, being low in winter but high in summer. This resulted in a high scope for activity, and dog whelks responded rapidly to increases in temperature in the spring. Newell (1979) pointed out that dog whelks could adjust their metabolic rate with temperature and season. Stickle et al. (1985) also noted that feeding and ingestion rates decreased with decreasing temperature and salinity. Etter (1988b) noted that white shells reflected more light (reducing the rate of heating and the temperature reached within unit time) and that dog whelks were cooled by evaporation of the water retained within the shell during emersion. |
Increased temperatures also increase the risk of desiccation (see above), especially on sheltered shores. However, dog whelks demonstrate behavioural adaptations depending on the type of shore they inhabit, e.g. dog whelks from sheltered shores forage less in sunny, warm weather, whereas animals from wave exposed shores (higher humidity) favoured calm periods even when sunny (Burrows & Hughes, 1989; Fretter & Graham, 1994). In southern Britain mortality form high temperatures is probably more likely than from low temperatures (Dr John Crothers, pers comm.). Crothers (1985) suggested that the southern limit of dog whelk distribution was temperature dependant and noted that in Portugal dog whelks live inside mussels clumps and in Massachusetts, where water temperature may reach 25 °C, dog whelks may spend summer below the tide mark. Therefore, Nucella lapillus is probably relatively tolerant of temperature change within the normal range for the UK, and is probably tolerant to a change of 2 °C over a year. However, an acute temperature change (e.g. 5 °C) will probably interfere with feeding activity and in summer may result in direct mortality or indirect mortality due to heat coma and desiccation. Therefore an intolerance of intermediate has been recorded.
|Low||Very high||Very Low||Moderate|
|The northern geographical limit of Nucella lapillus is close to the 0 °C winter isotherm. Therefore, Crothers (1985) suggested that they were limited by ice, and that although dog whelks themselves could avoid ice in cracks and crevices, their prey (barnacles and mussels) could not avoid ice-scour. Cold torpor was apparent in dog whelks acclimated to 5 °C (Stickle et al., 1985). Speed of movement increases rapidly above 5 °C (Largen, 1967), and activity begins at 3 °C , however, Nucella lapillus is totally inactive at 0 °C and will fall off steep substrata (Largen, 1967; Crothers, 1985). Dog whelks crept into sheltered crevices in winter and probably effectively hibernate over winter (Moore, 1936; Largen, 1967). Cold torpor is likely, therefore, to increase this species risk of being washed offshore or of predation. Low temperatures make dog whelks less tolerant of low salinity (Dr John Crothers, pers comm.). Feeding and ingestion rates also decrease with temperature. Largen (1967) noted that spawning began once temperatures increased to 9-10 °C , and was interrupted by a fall in temperature. Largen (1967) reported that dog whelks averaged consumption of 16 barnacles or 0.7 mussels per week at 20 °C but only 10.2 barnacles and 0.4 mussels per week at 15 °C. Newell (1979) noted that oxygen consumption (hence metabolic rate) fell with temperature and starvation, being low in winter but high in summer. This resulted in a high scope for activity, and dog whelks responded rapidly to increases in temperature in the spring. Newell (1979) pointed out that dog whelks could adjust their metabolic rate with temperature and season. Stickle et al. (1985) also noted that feeding and ingestion rates decreased with decreasing temperature and salinity. During the severe winter of 1962/63, Nucella lapillus were reportedly unaffected in Anglesey, north Wales and the South Wales coast although many were reported killed in the Beaulieau River, Hampshire (Crisp ed., 1964). Overall, it appears that Nucella lapillus can survive temperatures as low as 3 °C and possibly 0 °C, although evidence for duration is lacking, the effects of low temperatures are sub-vital and an intolerance of low, at the level of the benchmark, has been recorded.|
|Tolerant||Not relevant||Not sensitive||High|
|Nucella lapillus is an active carnivore and is unlikely to be adversely affected by increases or decreases in light attenuation due to turbidity and has been recorded as 'tolerant' to this factor.|
|Tolerant||Not relevant||Not sensitive||High|
|Nucella lapillus is an active carnivore and is unlikely to be adversely affected by increases or decreases in light attenuation due to turbidity and has been recorded as 'tolerant' to this factor.|
|Dog whelks adapt to wave action through their shell shape and size of foot (Crothers, 1985). Etter (1988a) demonstrated that the tenacity of dog whelks to resist wave action was proportional to the pedal surface area. Tenacity of dog whelks from sheltered shores was lower than dog whelks from wave exposed shores. He also demonstrated that dog whelks from sheltered shores would develop a larger foot when transplanted to wave exposed shores. Therefore, Nucella lapillus exhibits considerable phenotypic plasticity in response to wave exposure and current flow. It is also found from very wave exposed to very sheltered shores. An increase in wave action, for example from sheltered to exposed (see benchmark) is likely to increase mortality due to dislodgement and result in loss of a proportion of the population. Very sheltered and sheltered shores are likely to be more intolerant of such an increase. Therefore, an intolerance of intermediate has been recorded. Recent juveniles colonizing the shore in autumn and winter in the UK, are likely to adapt their phenotype to the prevalent conditions. Therefore a recoverability of high (see additional information below) has been recorded.|
|Growth adaptations of the dog whelk to strong wave action result in a thinner shell and longer pedal opening. Therefore, although adhesion to the substrate will be more than adequate with an increase in shelter. However, wave exposed forms may be more liable to predation from crabs and to desiccation (see above). Therefore, an intolerance of intermediate has been recorded. Recent juveniles colonizing the shore in autumn and winter in the UK, are likely to adapt their phenotype to the prevalent conditions. Therefore a recoverability of high (see additional information below) has been recorded.|
|Tolerant||Not relevant||Not sensitive||High|
|While Nucella lapillus is probably sensitive to local vibration within its vicinity, possibly similar to that caused by a predator, it is unlikely to be adversely affected by noise of the type or levels addressed in the benchmark.|
|Tolerant||Not relevant||Not sensitive||High|
|Nucella lapillus bears light sensitive eyes on its tentacles. However, its visual acuity is probably low and it is unlikely to be adversely affected by movement or shading due to anthropogenic activities.|
|Shells of Nucella lapillus are likely to show signs of abrasion due to wave action or sediment scour. The flounces of Nucella lapillus var. imbricata may also be reduced due to abrasion. However, no information concerning the effect of abrasion such as trampling on dog whelks was found. It is likely that some individuals may be dislodged and some washed to deep water and lost as a result. The most adverse affect is likely to be indirect due to a loss of prey such as mussels or barnacles due to trampling or removal by an abrasive force. However, dog whelks are capable to switching to another prey source in the absence of their preferred prey, so an intolerance of low has been recorded.|
|Displaced and dislodged individuals may become subject to increased desiccation if up turned, or washed to deep water and lost. However, Bryan (1968) reported that adults, presumably narcotized by oil and dispersants and washed below low water recolonized the shore within about 6 months, suggesting that displaced individuals could return to the intertidal. However, Nucella lapillus does not readily crawl across sediment, therefore individuals displaced to unsuitable substrata may not be able to return. Therefore, a precautionary intolerance of intermediate has been recorded. Recruitment from surviving adults and recolonization by juveniles from below water may result in recovery within about two years and a recoverability of high has been recorded (see additional information below).|
|The effects of tributyl tin (TBT), used in anti-fouling paints, on Nucella lapillus have been extensively documented and represent one of the best known examples of the effects of chemical pollution. The following is based upon reviews by Hawkins et al. (1994) and Bryan & Gibbs (1991) to which the reader should refer for further detail.|
|Low||Very high||Very Low||Moderate|
|Bryan (1984) suggested that adult gastropod molluscs were relatively tolerant of heavy metal pollution. Bryan & Gibbs (1983) noted that Nucella lapillus accumulated Cu and Zn in the Fal estuary, but was excluded from the highly heavy metal contaminated Restronguet Creek. Food is the main route of uptake of iron (Fe) and zinc (Zn) in Nucella lapillus (Young, 1977). Nucella lapillus exhibits detoxification systems e.g. granules containing phosphate, calcium, zinc, magnesium (Mg) and copper occur in the digestive gland, which may explain their tolerance of high levels of Zn and copper (Cu), (Ireland, 1979; Bryan, 1984), Cadmium (Cd) is detoxified by storage as a metallothionien (Bryan, 1984). Therefore, an intolerance of low has been recorded.|
|No information||No information||No information||Not relevant|
|Gibbs et al. (1999) reported a massive kill of Nucella lapillus in Bude Bay, north Cornwall. Gibbs et al. (1999) suggested that the mass mortalities may have been caused by eutrophication and summer algal blooms due to a new sewage outfall in the area that received only primary treated sewage. Nucella lapillus has been shown to be severely affected by toxic algal blooms. For example, Robertson (1991) reported up to 98-99% mortality of dog whelks exposed to a toxic bloom of Chrysochromulina polylepis in Gullmar Fjord, west Sweden in June 1988. As a result, the distribution and abundance were reduced, 1-2 yr. olds (three years recruitment) suffered heavy mortality and subsequent reproductive capacity was reduced (Robertson, 1991). Similarly, Nucella lapillus was shown to be severely affected by a bloom of Gyrodinium aureolum in south west Ireland in 1979 (Cross & Southgate, 1980) and strongly affected by a bloom of Chrysochromulina polylepis in the Kattegat, Skagerrak and Norwegian coast of the North Sea, May -June, 1988 (Underdal et al., 1989). Therefore, an intolerance of high has been recorded. Given their poor dispersal and recruitment from other populations, recovery may take many years (see additional information below).|
|Low||Very high||Very Low||Moderate|
|Kirby et al. (1994b) simulated the effects of hyper-osmotic shock due to evaporation of mantle cavity retained seawater in Nucella lapillus. Exposure to 35, 45, 55, 65 and 75 psu over periods of 6, 12 and 24 hrs at 15 °C resulted in an increase in alanine production, with concomitant decrease in aerobic respiration and, on return to 35 psu, an increase in nitrogen excretion due to increased protein metabolism. However, no mortalities were observed during the experiment, although the dog whelks remained in their shells for the duration of the experiment (Kirby pers. comm.). Kirby et al. (1994b) noted that the wave exposed (short spired shell) form of Nucella lapillus suffered a greater decrease in aerobic respiration and increase in protein metabolism and hence greater stress than the sheltered site forms. Kirby et al. (1994b) also noted a correlation between the physiological effects of hyperosmotic shock and different alleles at the leucyl-amino peptidase (Lap) locus suggesting a genetic component to hyper-osmotic shock tolerance. Overall, it appears that Nucella lapillus would tolerate an acute, short term increase in salinity, albeit at metabolic cost, suggesting an intolerance of 'low'.|
|Nucella lapillus is unable to feed under brackish conditions and are likely to be absent from areas of fresh water influence on the shore (Crothers, 1985). Feare (1970b) noted that in rock pools at full salinity 100% of egg capsules hatched, whereas only 27% hatched in areas subject to fresh water runoff at low tide. Stickle & Bayne (1985) reported that, at between 5 -20 °C, dog whelks over 20 mm in length tolerated between 14.2 and 16.2 psu, whether exposed abruptly or after acclimation. In their experiments smaller dog whelks were able to tolerate salinities as low as 12.7 psu. Stickle et al., 1985 noted that reduced salinity and temperature reduced feeding rates in Nucella lapillus, e.g. only 10% fed at 25 psu and 5 °C or 15 psu and 8.5 °C. They reported that Nucella lapillus was a poor volume regulator and did not quantitatively regulate their free amino acid pool. Crothers (1985) noted that Nucella lapillus is usually absent from estuaries and although found in the Severn Estuary it is restricted to the lower shore up-channel from Minehead where they presumably avoid reduced salinities. Therefore, a reduction in salinity below 18 psu is likely to adversely affect reproduction and feeding. Hence, a reduction in salinity at the benchmark level is likely to reduce the extent or abundance of Nucella lapillus and an intolerance of intermediate has been recorded. Gibbs et al. (1999) reported that dog whelks surviving a mass kill were able to re-establish the population within 2 years, except where mortalities were extensive, and a recoverability of high has been recorded (see additional information below).|
|No information regarding tolerance to anoxic conditions was found. Nucella lapillus is able to maintain aerobic respiration when emmersed (Sandison, 1968; Houlihan et al., 1981; Innes & Houlihan, 1985) and unlikely to suffer anoxia at low tide. Nucella lapillus is reported to be capable of anaerobic respiration (Sandison, 1966 cited in Gibbs et al., 1999). Gibbs et al. (1999) suggested that its ability to respire aerobically at low tide would compensate for any anoxia experienced when immersed and that it is probably relatively tolerant of low oxygen conditions. Gelder-Ottaway (1976a) demonstrated mortalities (8-40%) in dog whelks held for 5 days in seawater under films of oil. Although the experiment was intended to demonstrate mortalities due to oil film, the death observed probably owed more to oxygen deficiency than the oil itself. Therefore, exposure to 2 mg/l O2 for one week is likely to result in some mortality in dog whelk populations, and an intolerance of intermediate is recorded, although the ability to respire during emersion will probably keep mortalities to a minimum. Gibbs et al. (1999) reported that dog whelks surviving a mass kill were able to re-establish the population within 2 years, except where mortalities were extensive, and a recoverability of high has been recorded (see additional information below).|
|Intertidal gastropods often act a secondary hosts for trematode parasites of sea birds. Nucella lapillus may be infected by cercaria larvae of the trematode Parorchis acanthus. Infestation causes castration and continued growth (Feare, 1970b; Kinne, 1980; Crothers, 1985). Infected individuals may exhibit a deformed and enlarged shell, additional rows of teeth in the aperture, and an additional seventh whorl (Feare, 1970b). Feare (1970b) reported 15% infestation in one sample, in which the shells showed 3-4 rows of teeth. In one population, however, Feare (1970b) reported an infestation rate of 69%. Kinne (1980) notes that Nucella lapillus may also be infested with larvae of Lepocreadium sp., which cause reduced or non-functional gonads and a reduction in penis size in males. Castration of a proportion of the population may result in a reduction in recruitment and a reduced decline in population size eventually. Therefore an intolerance of intermediate has been recorded. Recoverability is dependant on recruitment from within the population. Gibbs et al. (1995) noted that a small number of individuals surviving the effects of an algal bloom (see nutrients) in north Cornwall, were able to re-establish the population within two years but noted that it would probably take many years for the population to regain its former abundance. Therefore, a recoverability of high is reported.|
|No information||Not relevant||No information||Not relevant|
|The introduced American oyster drill Urosalpinx cinerea may feed on barnacles when not feeding on oyster spat and hence may compete with Nucella lapillus for either food or space. However, no further information was found.|
|Not relevant||Not relevant||Not relevant||Not relevant|
|Nucella lapillus is not subject to targeted extraction in the UK. However, whelks (including the dog whelk) were once collected for the production of Tyrian purple (see Baker, 1974 for review; Crothers, 1985).|
|Low||Very high||Very Low||High|
|Mussels are subject to extraction (see Mytilus edulis) and are a major food species for dog whelks where they occur. However, dog whelks are able to switch to a more abundant prey, such as barnacles (albeit slowly) if necessary and are therefore, likely to suffer a brief interruption in feeding and possibly temporary reduction in reproductive capacity. Therefore, an intolerance of low has been recorded.|
|OSPAR Annex V|
|Features of Conservation Importance (England & Wales)|
|National (GB) importance||Not rare/scarce||Global red list (IUCN) category||-|
|Origin||-||Date Arrived||Not relevant|
Anala, J., 1974. Foraging strategies of two marine invertebrates. , Ph.D. thesis, University of New Hampshire, Durham, USA.
Ankel, W.E., 1937. Die feinere Bau des Kokons der Purpurschnecke Nucella lapillus (L.) und seine Bedeutung fur der Laichleben. Verhandlungen Deutschen Zoologischen Gesellschaft, 39, 77-86.
Baker, J.M., 1976. Investigation of refinery effluent effects through field surveys. In Marine Ecology and Oil Pollution (ed. J.M. Baker), pp. 201-225. Barking: Applied Science Publishers Ltd.
Baker, J.T., 1974. Tyrian purple: an ancient dye, a modern problem. Endeavour, XXXIII, 11-17.
Bantock, C.R. & Cockayne, W.L., 1975. Chromosomal polymorphism in Nucella lapillus. Heredity, 34, 231-245.
Barnes, R.D., 1980. Invertebrate Zoology, 4th ed. Philadelphia: Holt-Saunders International Editions.
Bayne, B.L. & Scullard, C., 1978. Rates of feeding by Thais (Nucella) lapillus (L.). Journal of Experimental Marine Biology and Ecology, 32, 75-94.
Berry, R.J. & Crothers, J.H., 1968. Stabilizing selection in the dog-whelk (Nucella lapillus). Journal of Zoology, 155, 5-17.
Berry, R.J., 1983. Polymorphic shell banding in the dog whelk Nucella lapillus. Journal of Zoology (London), 200, 455-470.
Biodiversity Steering Group, 1995. Biodiversity: the UK Steering Group report, vol. 1 & 2. London: HMSO.
Blackman, R.A.A., Baker, J.M., Jelly, J. & Reynard, S., 1973. The Dona Marika oil spill. Marine Pollution Bulletin, 4, 181-182.
Boyle, P.R., Sillar, M.Y. & Bryceson, K., 1979. Water balance and mantle cavity fluid of Nucella lapillus (L.) (Mollusca: Prosobranchia). Journal of Experimental Marine Biology and Ecology, 40, 41-51.
Bryan, G.W. & Gibbs, P.E., 1983. Heavy metals from the Fal estuary, Cornwall: a study of long-term contamination by mining waste and its effects on estuarine organisms. Plymouth: Marine Biological Association of the United Kingdom. [Occasional Publication, no. 2.]
Bryan, G.W. & Gibbs, P.E., 1991. Impact of low concentrations of tributyltin (TBT) on marine organisms: a review. In: Metal ecotoxicology: concepts and applications (ed. M.C. Newman & A.W. McIntosh), pp. 323-361. Boston: Lewis Publishers Inc.
Bryan, G.W., 1968. The effect of oil-spill removers ('detergents') on the gastropod Nucella lapillus on a rocky shore and in the laboratory. Journal of the Marine Biological Association of the United Kingdom, 49, 1067-1092.
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Last Updated: 08/06/2007