|A physiological and biochemical approach to the taxonomy of Mytilus edulis L. and M. galloprovincialis LMK. from S.W. England|
Seed, R. (1971). A physiological and biochemical approach to the taxonomy of Mytilus edulis L. and M. galloprovincialis LMK. from S.W. England. Cah. Biol. Mar. 12(3): 291-322
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723, more
The reproductive cycles of coexisting populations of M. edulis and M. galloprovincialis in SW England were investigated between Jan 1968 and Sept 1969. The spawning period in galloprovincialis (July-Aug) was similar to 8 wk later than in edulis (May-June) and occurred only with the onset of maximum sea temps for this locality. The annual reproductive cycle was less pronounced in galloprovincialis, possibly indicating that in this region it is towards the northern limits of its breeding range. Cross fertilisation can be artificially induced in the laboratory but whether interbreeding would normally occur, in view of the different spawning periods, is questionable. Settlement of young mussels onto adult beds was monitored during 1968 but in view of the difficulties in identifying small individuals it was uncertain whether the peaks of settlement could be exclusively attributed to the different spawning periods of the 2 spp. Growth rates of groups of edulis and galloprovincialis of similar to similar initial size kept under identical laboratory conditions were recorded over the period of this investigation during which time edulis grew 4 times faster than galloprovincialis. Whether such differences would occur under natural conditions is again uncertain. The 2 spp at Rock (Nr. Padstow) showed marked and consistent differences in their infections with Pinnotheres pisum. The mean infection for edulis was 30.3% whi1st in galloprovincialis the mean was only 1.4% No marked seasonal differences in the infection in edulis were observed. Whilst the colour of the mantle edge in the 2 spp is generally a reliable taxonomic character, being purple-violet in galloprovincialis and yellow-brown in edulis, no marked biochemical differences in the pigments have so far been established. Carotenoids from the 2 spp appear to be identical but these alone are not responsible for colour variations. Posterior adductor muscle myogens have been separated electrophoretically using polyacrylamide gels and slight though consistent differences recorded. Thus in addition to the morphological and anatomical differences that are known to exist between these mussels in SW England there would not appear to be further points of difference which strengthen the case for considering these mussels as distinct spp.