Patterns of development in nudibranch mollusks from the northeast Pacific Ocean, with regional comparisons
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Date
1992
Authors
Goddard, Jeffrey Harold Ryan, 1955-
Journal Title
Journal ISSN
Volume Title
Publisher
Thesis (Ph. D.)--University of Oregon, 1992.
Abstract
Biogeographic patterns of developmental mode in marine
invertebrates have been examined with respect to latitude,
depth, and general habitat type. Regional comparisons,
which might reveal the influence of specific ecological
mechanisms on mode of development, are few. The present
study was undertaken to: 1) characterize early development,
especially its mode, in nudibranch molluscs from the cold
temperate waters of the northeast Pacific Ocean: 2) compare
the development of these species to that of nudibranchs
from other geographic regions: and 3) attempt to explain
the observed patterns on the basis of regional differences
in hydrography, geology, and primary production.
Observations of egg size, embryonic development and hatching larvae were made for 30 species and were
supplemented with data from the literature. All data for
other regions were obtained from the literature.
Developmental mode was determined for 69 NE Pacific
species, over half the known fauna. sixty-seven (97%) have
planktotrophic development and two (Doto amyra and the
introduced Tenellia adspersa) produce short-term
lecithotrophic larvae. No evidence for nurse-eggs was
obtained in this study, and only the egg capsules of the
aeolid Cuthona lagunae were found to contain extra-zygotic
yolk reserves. These took the novel form of unusually
large, yolk-filled polar bodies that were ingested by the
embryonic veligers. Planktotrophic species with egg-shaped,
inflated larval shells develop from larger eggs than those
of species with typical spiral shells. The former, however,
have shorter embryonic periods, owing, in part, to their
smaller egg masses; many also hatch with eyespots.
World-wide I conclude that planktotrophy, at least among nudibranchs, is most common in regions with
relatively slow currents, high standing stocks of
phytoplankton, and large expanses of habitat suitable for the adults. This is documented by evidence from the NE Pacific, NE u.s., Britain, NW Red Sea, and NW Mediterranean. Nonfeeding modes of development tend to predominate in areas with fast boundary currents, oligotrophic waters, rapid changes in physical aspects of
the adult environment, or in areas formerly in contact with
polar waters (e.g., SE U.S., Marshall Is., New South
Wales). Latitude and its correlates do not sufficiently
account for the observed regional differences in mode of
development.
Description
Typescript.
Includes vita and abstract.
Bibliography: Includes bibliographical references.
Content: Patterns of development in nudibranch mollusks from the northeast Pacific Ocean, with regional comparisons. -- Lecithotrophic development in Doto amyra (Nudibranchia: dendronotacea), with a review of development in the genus. -- Unusually large polar bodies in an aeolid nudibranch, a novel mechanism for producing extra-embryonic yolk reserves.
xiv, 237 leaves : ill. ; 29 cm.
Keywords
Nudibranchia -- Development, Nudibranchia -- North Pacific Ocean, Doto amyra, Cuthona lagunae
Citation
Goddard, Jeffrey Harold Ryan. Patterns of Development in Nudibranch Mollusks from the Northeast Pacific Ocean, with Regional Comparisons. Thesis (Ph. D.)--University of Oregon, 1992.