Abstract
DR. GUNNAR THORSON accompanied the Danish Three-Year Expedition to East Greenland in 1931-34 under the leadership of Dr. Lange Koch, and made extensive and regular collections of plankton from the southern main station of Ella Island during the period from January until September 1932. Later, these samples were supplemented by others collected by a Greenlander, Benjamin Samuel-sen; thus giving a whole annual cycle of East Greenland plankton. In none of these samples and in none previously examined from these regions were there any prosobranchiate gastropods. This remarkable fact was partially explained by the large number of different prosobranchiate egg capsules with big embryos in the bottom samples and dredged material. In order to investigate further, Dr. Thorson continued the collecting of gastropod egg-masses in 1932 and during the cruise of the Godthaab in the summer of 1933, and in addition examined material from other expeditions. By carefully studying the species in their various habitats and their distribution, and by comparing the embryos with the adults a good knowledge of the prosobranchiate fauna was obtained, with their breeding, resulting in the discovery that not one species has a pelagic larva, but all pass directly into the free bottom stage after they have reached a considerable size in their capsules. Alone of the twenty-eight Greenland molluscs noted (in twenty of which the breeding is described for the first time) Acmaea rubella was found to be viviparous and hermaphrodite.
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Breeding of Arctic Marine Prosobranchs. Nature 138, 213–214 (1936). https://doi.org/10.1038/138213b0
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DOI: https://doi.org/10.1038/138213b0