The effect of a seasonal pulse of sinking phytodetritus on the reproduction of two benthic deposit-feeding species, yoldia hyperborea and ctenodiscus crispatus

Jaramillo, J. Roberto (2001) The effect of a seasonal pulse of sinking phytodetritus on the reproduction of two benthic deposit-feeding species, yoldia hyperborea and ctenodiscus crispatus. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (17MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Reproductive cycles of mollusc species have been extensively studied. Many of these studies demonstrated that fluctuating environmental factors affect the length of the spawning period and timing of reproduction. Since reproduction involves processes such as storage of energy and the production, accumulation and spawning of mature gametes, a close relationship has been proposed between the gametogenic cycle and food availability. -- Species inhabiting unstable environments generally have episodic reproductive cycles whereas species living in more stable environments generally reproduce continuously. Recent studies suggest that many stable environments, such as the deep sea, are not as stable as previously thought, since many sublittoral and deep sea areas experience seasonal phytodetritus sinking which may affect the reproductive activity of some species. -- In Conception Bay, Newfoundland, there is a deposition of phytodetritus which reaches the bottom at 240 m depth shortly after the spring and fall phytoplankton blooms. However, the reproductive response of the benthic community to this seasonal input is completely unknown. -- In order to examine the reproductive response to a seasonal input of food in the benthic community in Conception Bay, two common deposit feeders were selected, Yoldia hyperborea and Ctenodiscus crispatus . This study provides new data on the role of phytodetritus deposition in the reproduction of these species and on the ecological significance of a seasonally-pulsed food supply on the deposit feeding community inhabiting Conception Bay. -- Yoldia hyperborea had a mean egg diameter 120 μm, and a maximum apparent fecundity was of 8.5 × 10⁴ eggs per individual. Larval development occurred through a lecithotrophic pericalymma larva that is restricted to protobranch species. Spawning occurred during the winter-spring period coincident or following phytodetrital deposition. -- Laboratory feeding experiments showed that frequent addition of phytodetritus stimulates production of eggs, supporting field observations suggesting that gamete production of Y. hyperborea is dependent on food availability. Laboratory experiments using ¹⁴ C labelled Thalassiosira nordenskioldii demonstrated incorporation of cell contents into the gonad. -- Ctenodiscus crispatus eggs had a mean diameter of 450 μm. The maximum fecundity was 13.8 × 10⁶ eggs per individual. Eggs develop through a lecithotrophic larvae. Reproduction occurred continuously throughout the year, although fecundity was higher in spring due to seasonal phytodetritus sinking. -- The reproductive cycle of both deposit feeders was affected by fluctuations in food availability. Individual fecundity was maximal coincident with or just following the seasonal peak in phytodetritus deposition. Energy provided by resuspension events appeared to be utilized for gametogenesis both in Yoldia hyperborea and Ctenodiscus crispatus.

Actions (login required)

View Item