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Laboratory experiments on the influence of environmental factors on the frequency of moulting and the increase in size at moulting of juvenile shore crabs, Carcinus maenas
Klein Breteler, W.C.M. (1975). Laboratory experiments on the influence of environmental factors on the frequency of moulting and the increase in size at moulting of juvenile shore crabs, Carcinus maenas, in: Klein Breteler, W.C.M. (1976). Oecologie van de strandkrab Carcinus maenas (L.) in de westelijke Waddenzee: een serie artikelen over de rol van strandkrabben in de voedselketens op het balgzand, met speciale aandacht voor de groei, produktie, migratie en bioënergetica tijdens het eerste levensjaar. : pp. 100-120
In: Klein Breteler, W.C.M. (1976). Oecologie van de strandkrab Carcinus maenas (L.) in de westelijke Waddenzee: een serie artikelen over de rol van strandkrabben in de voedselketens op het balgzand, met speciale aandacht voor de groei, produktie, migratie en bioënergetica tijdens het eerste levensjaar. PhD Thesis. Rijksuniversiteit te Leiden: Leiden. 376 pp., more

Also published as
  • Klein Breteler, W.C.M. (1975). Laboratory experiments on the influence of environmental factors on the frequency of moulting and the increase in size at moulting of juvenile shore crabs, Carcinus maenas. Neth. J. Sea Res. 9(1): 100-120, more

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  • Klein Breteler, W.C.M.

Abstract
    Motivated by field observations, the influence of some environmental factors on the growth of Carcinus maenas (L. ) has been studied in the laboratory. To this end 312 shore crabs were raised separately, from the first crab stage to a carapace width of about 10 mm, under different laboratory conditions, viz. 8 combinations of 2 different salinities, temperatures and amounts of food. Distinction was made between the influence of these factors on 2 growth characteristics, viz. the duration of the interval between 2 consecutive moults and the increment in carapace width during the moult. The trend observed was that the moulting interval lasted longer and the relative size increment decreased as the crabs grew older. The factor food influenced the 2 characteristics considerably. With restricted food crabs needed about 50% more time to complete the first 6 moults than with an excess of food, while at the same time they remained about 25% smaller. The influence of temperature on the length of the interval between moults was even larger than that of the factor food. However, no significant influence on the size increment per moult has been found, although at the end of the experiment the crabs kept at 15° C were found to be significantly heavier than those kept at 20° C. Salinity did not affect the total time of development, although the duration of certain stages was found to be influenced significantly. In the seventh stage crabs reared at 22‰ S were found to be significantly larger than those raised at 30‰ S. A significant interaction was observed between temperature and amount of food, from which it appeared that with restricted feeding growth was less retarded-both by way of duration of stages and by size increment-at a low temperature than at a high temperature. At the end of the experiments no difference has been found between the carapace width of males and females under the influence of the various factors. In another experiment crabs raised collectively were not found to be hampered in their growth by competition; it seemed rather that the time interval between moults was somewhat shortened. Mortality increased significantly in the course of the experiment. Presumably increasing cannibalism played a role, at first only on moulting animals which are still soft, later also on animals with a hard exoskeleton.An attempt to study the influence of these grown-up crabs on the growth of younger crabs was unsuccessful by heavy predation of the older ones. The experiments show that there are environmental factors which might account for the decrease in average carapace width per crab stage in the course of the season, as has been observed in the field.

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