The scheduling of spawning with the moult cycle in Northern krill (Crustacea: Euphausiacea): a strategy for allocating lipids to reproduction
Euphausiids moult and grow throughout their life, which implies sharing of resources betweengrowth and reproduction for adult krill. In the Northern krill, Meganyctiphanes norvegica(M. Sars), female krill produce eggs cyclically. Spawning moult cycles alternate withvitellogenic moult cycles for lipi...
| Published in: | Invertebrate Reproduction & Development |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Int Science Services/Balaban Publishers
1999
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| Subjects: | |
| Online Access: | https://doi.org/10.1080/07924259.1999.9652694 http://ecite.utas.edu.au/90438 |
| Summary: | Euphausiids moult and grow throughout their life, which implies sharing of resources betweengrowth and reproduction for adult krill. In the Northern krill, Meganyctiphanes norvegica(M. Sars), female krill produce eggs cyclically. Spawning moult cycles alternate withvitellogenic moult cycles for lipid yolk accumulation. Histology shows that lipids are associatedwith the R cells of the digestive gland in both sexes, with the yolk platelets of mature oocytesand with the fat body cell membranes and blood lacunae in reproducing females. Mature femalekrill can have a total lipid content twice as high as males, mostly due to accumulation in theovary, the fat body and the haemolymph. In contrast, in males, as well as in non-reproducingfemales, the highest percentage of lipids is found in the digestive gland and the haemolymph. InMeganyctiphanes norvegica, the most abundant lipid fractions are polar lipids and triglycerides,the latter being relatively low in reproducing female gonad and fat body. Triglycerides arebelieved to be a pure energy source and polar lipids are essential for membrane development inembryos. The fatty acid content and composition of the triglyceride and polar lipid fractions infemales are different from males, related to both reproductive and dietary processes. Higherlevels of polyunsaturated fatty acids (PUFA) in the polar lipid fraction were found inreproductive females. During the non-reproductive season, the converse was found, indicatingthe specific role PUFA and other fatty acids play in growth and egg production. Adaptiveprocesses linked to reproduction were studied comparatively in three populations of theNorthern krill - Clyde Sea (W, Scotland), Kattegat (E, Denmark), Ligurian Sea (Mediterranean)- all differing considerably in climatic and trophic conditions. such adjustments inlipid synthesis and storage are viewed as reproductive strategies developed by the Northern krillin response to different environmental conditions |
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