The common whelk (Buccinum undatum L.): Life history traits and population structure

Abstract

The common whelk (Buccinum undatum L.) is a subtidal gastropod widely distributed in the North Atlantic Ocean. It is fished commercially in both Europe and Canada. The species is known for its variation; in size distribution, maturation size and morphology. From a data series of monthly samples collected from June 2007 to December 2008 the timing of copulation, size distribution and shell shape of the common whelk were studied at 10 stations across Breiðafjorður. Fragments of the mitochondrial genes 16S rRNA and COI were sequenced to study the population genetics of the common whelk in Breiðafjorður, Hunafloi and the Faeroe Islands. The genetic population structure of the common whelk in these areas was then compared with its morphological populations. The average size of whelks at the 10 sample locations in Breiðafjorður ranged from 49 – 57 mm. Size distribution, average size and maturation size were different between stations. Whelks became mature at a shell height of 45 – 70 mm and at 4.7 – 7.5 years of age. Monthly comparison of testis weight vs. eviscerated weight of the whelk indicates that copulation of whelks in W-Iceland takes place in the period from September to February. This is consistent with the time of mating in European populations. Morphological variability was high as 4 – 6 of the six shell ratios tested were significantly different between stations. Allele frequencies for both 16S rRNA and COI, were significantly different between Icelandic areas and between Iceland and the Faeroe Islands, but not inside Breiðafjorður. The morphology of whelk shells was significantly different between Breiðafjorður and the Faeroe Islands; whelks from Hunafloi and the Faeroe Islands seem to have similarly shaped shells. The common whelk is a variable species, especially within Breiðafjorður. This morphological variability does not seem to be reflected in the mitochondrial allele frequencies between areas, indicating that environmental factors could affect the shape of the shell of B. undatum.