The breeding of the scallop, Pecten maximus (L.), in Manx waters

Abstract

Marine Laboratory, Aberdeen MATERIAL AND METHODS An important fishery for the scallop, Pecten maximus (L.), is carried on during the winter months round the Isle of Man. A knowledge of the breeding of this lamellibranch would be useful should legislation become necessary with regard to the fishery.Regular samples of scallops were dredged, whenever possible, at roughly weekly or fortnightly intervals throughout the period October 195o-0ctober 1952, from a depth of 13-16 fm. off Bradda Head and Bay Fine, near Port Erin. Approximately 8000 scallops of all ages up to 13 years were examined, though very few young ones were caught. Scallops were aged by means of the growth-rings on the shell, of which one is laid down each spring (Mason, 1957)· The gonad of every scallop was examined macroscopically and classified as regards degree of development (see p. 656). Pecten maximus is a hermaphrodite, the gonad consisting of separate male and female parts.Several gonads in each stage of development were examined histologically by means of transverse sections, and serial sections were prepared of the whole of some small gonads. The material was always taken so as to include both ovarian and spermatic tissue. Three fixatives were used, Bouin, Heidenhain's Susa, and Zenker, of which Bouin proved the most satisfactory.There is always some loss of reproductive cells from the cut surface of the gonad, and so all pieces to be fixed were cut large enough to allow for this loss. Penetration of the fixative was facilitated by making needle-holes in the material, which was then placed in the fixative and left for several days. The material was then cut into halves, each half containing both ovary and testis, and replaced in the fixative. This second cutting involved no loss of reproductive cells. After dehydration with ethyl and n-butyl alcohols, clearing in cedarwood oil and embedding in paraffin wax, sections were cut parallel to the newly-cut face. Sections were cut between 5 and 8 Jk thick, and stained with Ehrlich's acid haematoxylin and eosin.Fixation always resulted in a slight contraction of the gonad, and so did handling.

Influence of the gametogenic cycle on the biochemical composition of the ovary of the great scallop

“…Several oocyte cohorts, at different stages of development, can be present in the gonad of an individual (Paulet and Boucher, 1991). Basically, the gametogenic cycle was similar to those of other European great scallop populations (Mason, 1958(Mason, , 1983Comely, 1974;Lubet et al, 1987;Wilson, 1987; the Brest population in Paulet et al, 1988;Strand and Nylund, 1991). Gonad maturation caused an increment in the content of all biochemical compounds (in absolute values), and a decrease of these coincided with spawning ( Table 2).…”

Population genetic differentiation of the great scallop Pecten maximus in western Britain investigated by randomly amplified polymorphic DNA

“…However, variation between beds in growth rate, size-and age-structure and year-class strength has been described, suggesting differences in recruitment (Brand 1991). Spawning of P. rnaximus in the Irish Sea occurs in 2 peaks, mainly in April-May and August-September (Mason 1958). The pelagic larval duration of P. maximus varies tvith water temperature, but is maximally over 6 wk (Beaumont & Barnes 1992).…”

Effects of pyrene exposure on immune response and oxidative stress in the pearl oyster, Pinctada martensii

“…Therefore only a few pearl oysters were dissected, and examined for spermatozoa and oocytes under the microscope. These specimens were verified to be of similar gonad maturation and at a pre-spawning stage of gametogenesis [51]. At the time of collection, ambient seawater temperature was 21 ± 1 C. Pearl oysters were acclimated to laboratory conditions for one week in static tanks containing recirculated and filtered seawater (32‰ salinity, 21 ± 1 C).…”