MEPS 247:103-122 (2003)  -  doi:10.3354/meps247103

Worldwide patterns in mode of development in calyptraeid gastropods

Rachel Collin1,2,3,*

1Committee on Evolutionary Biology, University of Chicago, Culver Hall, Room 402, 1025 E. 57th Street, Chicago, Illinois 60637, USA
2Department of Zoology, The Field Museum, 1400 South Lake Shore Drive, Chicago, Illinois 60605, USA
3Present address: Smithsonian Tropical Research Institute, Unit 0948, APO AA 34002, USA

ABSTRACT: The mode of development in marine invertebrates is believed to have consequences for dispersal, gene flow, geographic range, and speciation and extinction rates. The factors responsible for among-species differences in mode of development are not well understood and patterns of variation in mode of development have not been documented for many groups. I present a compiled data set of developmental characters for 78 species of calyptraeid gastropods: 53 Crepidula, 9 Calyptraea, 11 Crucibulum and 5 other species. Analysis of this data set shows that egg- and hatching-size distributions are strongly positively skewed. As expected, egg size correlates with hatching size and time to hatching in species without nurse eggs. Egg size is not significantly different between species with planktotrophic development and species with direct development with nurse eggs. Hatching size of direct developers with and without nurse eggs do not differ. Developmental characters do not vary with adult body size among species. There are strong latitudinal effects in mode of development, the frequency of planktotrophic species decreases with increasing latitude while the proportion of direct developers increases. There is also a striking latitudinal pattern in the occurrence of nurse eggs; almost all species with nurse eggs occur in the southern hemisphere. These latitudinal patterns do not appear to be explained by sea surface temperature. Comparisons with other gastropods for which similar compilations are available show a striking difference between heterobranchs (opisthobranchs and pulmonates) and caenogastropods in developmental characteristics.

KEY WORDS: Larvae · Invertebrate development · Crepidula · Crucibulum · Calyptraea

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