Marker, T., P. Andreassen, E. Arashkewich & B.W. Hansen. (2003). Lipid deposition and sexual maturation in cohorts of Calanus finmarchicus (Gunnerus) originating from Bergen (60EN) and Tromso (69EN) reared in Tromso, Norway. Marine Biology 143(2):283-296. DOI 10.1007/s00227-003-1089-5. Published online: 14 May 2003.

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10.1007/s00227-003-1089-5 [view]

Marker, T., P. Andreassen, E. Arashkewich & B.W. Hansen

2003

143(2):283-296. Published online: 14 May 2003.

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Two cohorts of Calanus finmarchicus (Gunnerus), with habitats in Bergen (60°N) and Tromsø (69°N), were reared from copepodite stage III (CIII) in mesocosms in Tromsø from April 24 1998 to June 30 1998. The aim was to study whether the two cohorts diverged phenotypically with respect to indication of physiological preparation for diapause as opposed to initiating another generation. At the end of the experiment the fractions of the cohorts that had reached sexual maturation, based on observed stage shifts to adults, was $45% within the Bergen cohort and $35% for the Tromsø cohort, within which males appeared before females. Examination of the mandibular gnathobase of copepodites at stage V (CV) revealed that <10% of the Bergen cohort, but >40% of the Tromsø cohort were ready for ecdysis, eventually to become adults in the same year. The physiological expression of the range in individual maturity within the cohorts was revealed in individual carbon and nitrogen content. Both cohorts incorporated the storage lipids wax esters (WE) and triacylglycerols (TAG) rapidly, primarily during CV (0.16–0.21 lg total neutral lipid ind )1 day)1 ), with no significant difference. Lipid storage was incorporated from CIII and the maximum was reached at the CV stage. Presumably due to excess food, high WE, TAG and free fatty acid levels were observed in both cohorts. A relative decrease in neutral lipids was observed later in females from both cohorts. We suggest that part of the Bergen population, but also a fraction of the Tromsø population, prepared for diapause in CV. A possible reason for the sexual maturation among the rest of the CV copepodites could be a shift in life ‘‘strategy’’ caused by an unusually high rise in temperature in the mesocosms during the last 10 days of the experiment.

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