Abstract:
This work comprises three detailed studies of ontogeny and ecology. In the first chapter, four living species
of the ostracode genus Cyprideis were studied both morphologically and ecologically to determine whether
differences in age at maturity are correlated with heterochrony as expected; accelerated maturity should
yield generalized morphology and small size, while delayed maturity should produce specialized morphology
and large size. Two of the four species show the expected pattern, the other two do not. Cyprideis does not
support the generalization that life-history evolution causes heterochrony, and casts doubt on the inference
of life-history evolution from heterochrony where the data are drawn exclusively from extinct forms.
In the second chapter, populations of Globorotalia menardii and G. tumida were subjected to careful
morphological analysis; the stable-isotopic composition of the growth stages revealed that both species
inhabit the upper fifty meters of the ocean, descending to deeper water (75-l00m) for the emplacement of
an enveloping calcite crust.
The third chapter shows a simple relationship between proloculus size and rate of chamber expansion
in the polar planktonic foraminifer Neogloboquadrina pachyderma. The consequences for morphology of
variations in ontogeny can be used to suggest ways of selecting specimens that minimize ontogenetic variations
in shell chemistry.
