Gamete compatibility, gamete trait variation and their effect on fertilization success in northwest Atlantic blue mussel (Mytilus edulis l. and Mytilus trossulus gould) hybrid zone
Thesis (Ph.D.)--Memorial University of Newfoundland, 2009. Biology Includes bibliographical references (leaves 150-185) Mytilus edulis and M. trossulus coexist and form a natural hybrid zone along the Atlantic Canada coast, which provides an excellent model to study marine invertebrate evolution, sp...
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2009
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Online Access: | http://collections.mun.ca/cdm/ref/collection/theses4/id/130163 |
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ftmemorialunivdc:oai:collections.mun.ca:theses4/130163 |
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openpolar |
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Open Polar |
collection |
Memorial University of Newfoundland: Digital Archives Initiative (DAI) |
op_collection_id |
ftmemorialunivdc |
language |
English |
topic |
Gametogenesis Marine ecology--North Atlantic Ocean Mytilus edulis--Fertility--North Atlantic Ocean Mytilus trossulus--Fertility--North Atlantic Ocean |
spellingShingle |
Gametogenesis Marine ecology--North Atlantic Ocean Mytilus edulis--Fertility--North Atlantic Ocean Mytilus trossulus--Fertility--North Atlantic Ocean Liu, Guangxu, 1978- Gamete compatibility, gamete trait variation and their effect on fertilization success in northwest Atlantic blue mussel (Mytilus edulis l. and Mytilus trossulus gould) hybrid zone |
topic_facet |
Gametogenesis Marine ecology--North Atlantic Ocean Mytilus edulis--Fertility--North Atlantic Ocean Mytilus trossulus--Fertility--North Atlantic Ocean |
description |
Thesis (Ph.D.)--Memorial University of Newfoundland, 2009. Biology Includes bibliographical references (leaves 150-185) Mytilus edulis and M. trossulus coexist and form a natural hybrid zone along the Atlantic Canada coast, which provides an excellent model to study marine invertebrate evolution, speciation and especially reproductive isolation barriers that maintain species integrity. Gamete traits and their role in determining fertilization success among M. edulis, M. trossulus and their hybrids were investigated in the present study. Sperm of all three genotypes (the term genotypes was used throughout the thesis to include M. edulis, M. trossulus and their hybrids) conducted circular movement in a two dimensional plane, which may represent a trait that increases fertilization success under sperm limitation on a small spatial scale. Neither egg water nor egg presence elicited sperm chemotaxis in our experimental set-up, which suggests that sperm chemotaxis may not be necessary for successful fertilization of marine invertebrate species with dense aggregations, synchronized broadcast spawning and high gamete output. Although no significant difference in gamete output was detected among the different genotypes, sperm velocity differed among M. edulis, M. trossulus and their hybrids, F1 hybrids producing the slowest swimming sperm. Sperm of M. edulis had faster VAP (average path velocity) and angle change rate than those of M. trossulus . Most of the variation in sperm velocity was attributed to variation within individuals, which may be caused by differences in stage of maturity among individual sperm. Both sperm velocity and sperm half life (T50 ) decreased as temperature increased. F1 hybrids had the shortest sperm longevity and M. trossulus was least temperature sensitive, which may be an adaptation to a longer spawning period, resulting in exposure to higher temperature fluctuations. M. edulis produced larger eggs than M. trossulus and F1 hybrids, providing a larger target for sperm-egg interaction. Both homospecific and heterospecific fertilization success differed among parental combinations and may be due to the combined effects of gamete compatibility and gamete trait variation on fertilization success. Sperm velocity, egg size and especially the combination of these two gamete traits were positively correlated with fertilization success, supporting the hypothesis that fertilization success is partially determined by these gamete traits. The three parameters (β, β 0 and β/β 0 ) of the fertilization kinetics model differed significantly among the different crosses. The small β/β0 detected for the heterospecific crosses between M. edulis and M. trossulus suggests strong reproductive isolation between these species and can explain the rarity of F1 hybrids. In general, the poor gamete quality (small egg size, slow swimming speed and short life span of sperm) of F1 hybrids can lead to reduced fertilization success and may help to explain the genetic composition, especially the bimodal structure, of the blue mussel hybrid zone in Atlantic Canada. The present study shows that gamete trait variation (sperm velocity, sperm longevity and egg size) and gamete compatibility are crucial factors affecting both homospecific and heterospecific fertilization success, and provides a better understanding of prezygotic reproductive isolation between and among broadcast spawning species. |
author2 |
Memorial University of Newfoundland. Dept. of Biology |
format |
Text |
author |
Liu, Guangxu, 1978- |
author_facet |
Liu, Guangxu, 1978- |
author_sort |
Liu, Guangxu, 1978- |
title |
Gamete compatibility, gamete trait variation and their effect on fertilization success in northwest Atlantic blue mussel (Mytilus edulis l. and Mytilus trossulus gould) hybrid zone |
title_short |
Gamete compatibility, gamete trait variation and their effect on fertilization success in northwest Atlantic blue mussel (Mytilus edulis l. and Mytilus trossulus gould) hybrid zone |
title_full |
Gamete compatibility, gamete trait variation and their effect on fertilization success in northwest Atlantic blue mussel (Mytilus edulis l. and Mytilus trossulus gould) hybrid zone |
title_fullStr |
Gamete compatibility, gamete trait variation and their effect on fertilization success in northwest Atlantic blue mussel (Mytilus edulis l. and Mytilus trossulus gould) hybrid zone |
title_full_unstemmed |
Gamete compatibility, gamete trait variation and their effect on fertilization success in northwest Atlantic blue mussel (Mytilus edulis l. and Mytilus trossulus gould) hybrid zone |
title_sort |
gamete compatibility, gamete trait variation and their effect on fertilization success in northwest atlantic blue mussel (mytilus edulis l. and mytilus trossulus gould) hybrid zone |
publishDate |
2009 |
url |
http://collections.mun.ca/cdm/ref/collection/theses4/id/130163 |
op_coverage |
North Atlantic Ocean; |
geographic |
Canada |
geographic_facet |
Canada |
genre |
Newfoundland studies North Atlantic Northwest Atlantic University of Newfoundland |
genre_facet |
Newfoundland studies North Atlantic Northwest Atlantic University of Newfoundland |
op_source |
Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries |
op_relation |
http://collections.mun.ca/theses_extras/Liu_Guangxu.zip Electronic Theses and Dissertations (21.61 MB) -- http://collections.mun.ca/PDFs/theses/Liu_Guangxu.pdf a3241886 http://collections.mun.ca/cdm/ref/collection/theses4/id/130163 |
op_rights |
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. |
_version_ |
1766113451264966656 |
spelling |
ftmemorialunivdc:oai:collections.mun.ca:theses4/130163 2023-05-15T17:23:34+02:00 Gamete compatibility, gamete trait variation and their effect on fertilization success in northwest Atlantic blue mussel (Mytilus edulis l. and Mytilus trossulus gould) hybrid zone Liu, Guangxu, 1978- Memorial University of Newfoundland. Dept. of Biology North Atlantic Ocean; 2009 xx, 185 leaves : ill. (chiefly col.)+ 1 CD-ROM (4 3/4 in.) Image/jpeg; Application/pdf http://collections.mun.ca/cdm/ref/collection/theses4/id/130163 Eng eng http://collections.mun.ca/theses_extras/Liu_Guangxu.zip Electronic Theses and Dissertations (21.61 MB) -- http://collections.mun.ca/PDFs/theses/Liu_Guangxu.pdf a3241886 http://collections.mun.ca/cdm/ref/collection/theses4/id/130163 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. Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries Gametogenesis Marine ecology--North Atlantic Ocean Mytilus edulis--Fertility--North Atlantic Ocean Mytilus trossulus--Fertility--North Atlantic Ocean Text 2009 ftmemorialunivdc 2015-08-06T19:22:36Z Thesis (Ph.D.)--Memorial University of Newfoundland, 2009. Biology Includes bibliographical references (leaves 150-185) Mytilus edulis and M. trossulus coexist and form a natural hybrid zone along the Atlantic Canada coast, which provides an excellent model to study marine invertebrate evolution, speciation and especially reproductive isolation barriers that maintain species integrity. Gamete traits and their role in determining fertilization success among M. edulis, M. trossulus and their hybrids were investigated in the present study. Sperm of all three genotypes (the term genotypes was used throughout the thesis to include M. edulis, M. trossulus and their hybrids) conducted circular movement in a two dimensional plane, which may represent a trait that increases fertilization success under sperm limitation on a small spatial scale. Neither egg water nor egg presence elicited sperm chemotaxis in our experimental set-up, which suggests that sperm chemotaxis may not be necessary for successful fertilization of marine invertebrate species with dense aggregations, synchronized broadcast spawning and high gamete output. Although no significant difference in gamete output was detected among the different genotypes, sperm velocity differed among M. edulis, M. trossulus and their hybrids, F1 hybrids producing the slowest swimming sperm. Sperm of M. edulis had faster VAP (average path velocity) and angle change rate than those of M. trossulus . Most of the variation in sperm velocity was attributed to variation within individuals, which may be caused by differences in stage of maturity among individual sperm. Both sperm velocity and sperm half life (T50 ) decreased as temperature increased. F1 hybrids had the shortest sperm longevity and M. trossulus was least temperature sensitive, which may be an adaptation to a longer spawning period, resulting in exposure to higher temperature fluctuations. M. edulis produced larger eggs than M. trossulus and F1 hybrids, providing a larger target for sperm-egg interaction. Both homospecific and heterospecific fertilization success differed among parental combinations and may be due to the combined effects of gamete compatibility and gamete trait variation on fertilization success. Sperm velocity, egg size and especially the combination of these two gamete traits were positively correlated with fertilization success, supporting the hypothesis that fertilization success is partially determined by these gamete traits. The three parameters (β, β 0 and β/β 0 ) of the fertilization kinetics model differed significantly among the different crosses. The small β/β0 detected for the heterospecific crosses between M. edulis and M. trossulus suggests strong reproductive isolation between these species and can explain the rarity of F1 hybrids. In general, the poor gamete quality (small egg size, slow swimming speed and short life span of sperm) of F1 hybrids can lead to reduced fertilization success and may help to explain the genetic composition, especially the bimodal structure, of the blue mussel hybrid zone in Atlantic Canada. The present study shows that gamete trait variation (sperm velocity, sperm longevity and egg size) and gamete compatibility are crucial factors affecting both homospecific and heterospecific fertilization success, and provides a better understanding of prezygotic reproductive isolation between and among broadcast spawning species. Text Newfoundland studies North Atlantic Northwest Atlantic University of Newfoundland Memorial University of Newfoundland: Digital Archives Initiative (DAI) Canada |