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Embryology and foetal growth of the Grey seal, Halichoerus grypus
Author(s) -
Hewer H. R.,
Backhouse K. M.
Publication year - 1968
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1968.tb03066.x
Subject(s) - shetland , biology , embryo , seal (emblem) , anatomy , archaeology , fishery , geography , forestry
Descriptions of eight blastocysts, two embryos and 41 foetuses are given. Methods of estimating the age of these are discussed, and a modification of Huggett & Widdas's (1951) formulae used. The phenomenon of “delayed implantation” is discussed and a more realistic nomenclature is proposed. Both the method of comparison for blastocysts and embryos and the statistical treatment of the foetuses indicate that the recommencement of development occurs over a period of two months with a mean date at the end of the second week in February for the Orkney and Shetland group. There is a suspense of development for about 100 days. The specific foetal growth rate is shown to be similar to that of other mammals (apart from Cetacea and Primates). The significance of the 100 days suspense in interpreting the abnormal spring pupping in the Pembrokeshire group of Grey seals is discussed.