An experimental study of the combined effects of temperature and photoperiod on reproductive physiology of Pecten maximus from the Bay of Brest (France)

The influence of environmental factors on reproduction and energy partition ing was investigated in scallops (Pecten maximus) maintained in a hatchery under 'winter' and 'spring' conditions of changing temperature and day-leng th. Biometric measurements revealed that 'spring' conditions favoured gonad growth whereas 'winter' conditions were associated with somatic growth (ad ductor muscle and digestive gland). Biochemical analysis showed that in par allel with gonad growth, total proteins, carbohydrates and lipids accumulat ed in the female part of the gonad under 'spring' conditions. The lipid lev el of the digestive gland, which was more than 40% of the dry weight under both experimental conditions, emphasised the role of this organ in the stor age of reserves. Quantitative histological analysis of oogenesis establishe d that experimental conditions did not influence the total number of oocyte s in the gonad but affected the partitioning between previtellogenic and vi tellogenic oocytes. The contribution of vitellogenic oocytes was higher und er 'spring' conditions. Energy partitioning was strongly influenced by expe rimental conditions: 89% of the production was channelled into the gonad un der 'spring' conditions compared with 40% under 'winter' conditions. (C) 19 99 Elsevier Science B.V. All rights reserved.