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Seasonal and inter-species comparison of asymmetry in the genital system of some species of the oceanic copepod genus Metridia (Copepoda, Calanoida)
In: CrustaceanaThe seasonal and inter-annual changes in the asymmetry of female insemination and the male leg 5 of the planktonic calanoid copepods Metridia okhotensis and M. pacifica were investigated in the Okhotsk Sea. An inter-species comparison of both parameters was also carried out on seven Metridia species collected from oceans throughout the world. For M. okhotensis from the Okhotsk Sea, most of the females showed left-side insemination (annual average: 95.7%) and most of the males showed left-side asymmetry (99.7%) of the long inner process of the second exopodal segment in the fifth leg throughout the year. However, sympatric M. pacifica showed different ratios of asymmetry for female insemination and male morphotypes with a left : right = 1 : 2 ratio throughout the year. For the seven Metridia species from the global oceans treated in this study, ratios of asymmetry for female insemination and male morphotypes were correlated with each other. One-sided insemination (i.e., only left or only right insemination) was a common pattern for various Metridia species from global oceans, but their ratios varied by species. Previously, low hatching rates (29-68%) of eggs were reported for various Metridia spp. in laboratory experiments, but the reasons for these low rates were unclear. Because each spermatheca of Metridia spp. is connected to the oviduct on the same side, either left or right, this suggests that half of the eggs produced by unilaterally inseminated females remain unfertilized. The morphology of the genital structures and literature data of the egg hatching rates of Metridia spp. indicate that almost half of the eggs produced by females are not viable and are, thus, wasted.
Les changements saisonniers et interannuels de l’asymétrie de l’insémination de la femelle et de la patte 5 du mâle des copépodes calanoïdes planctoniques Metridia okhotensis et M. pacifica ont été étudiés dans la mer d’Okhotsk. Une comparaison des deux paramètres entre espèces a été menée également chez sept espèces de Metridia collectées dans les océans du monde entier. Chez M. okhotensis de la mer d’Okhotsk, la plupart des femelles ont montré une insémination du côté gauche (moyenne annuelle : 95,7%) et la plupart des mâles ont montré une asymétrie gauche (99,7%) du long processus interne du second segment de l’exopodite de la cinquième patte tout au long de l’année. Cependant, les M. pacifica sympatriques montraient des rapports différents sur l’année de l’asymétrie d’insémination des femelles et des morphotypes mâles avec un rapport gauche : droite = 1 : 2. Chez les sept espèces de Metridia des océans mondiaux traitées dans cette étude, les rapports d’asymétrie d’insémination des femelles et des morphotypes mâles était corrélés entre eux. L’insémination d’un seul côté (uniquement à gauche ou uniquement à droite) est un modèle commun pour diverses espèces de Metridia des océans, mais leurs rapports variaient suivant les espèces. Précédemment, des taux faibles d’éclosion des oeufs (29-68%) avaient été observés chez diverses espèces de Metridia spp. lors d’expériences en laboratoire, mais les raisons invoquées pour expliquer ces taux faibles étaient peu claires. Chaque spermathèque de Metridia spp. est reliée à l’oviducte du même côté, soit gauche, soit droit, et cela suggère que la moitié des œufs produits chez les femelles inséminées unilatéralement (d’un seul côté) restent non fécondés. La morphologie des structures génitales et les données de la littérature concernant les taux d’éclosion des oeufs de Metridia spp. indiquent que presque la moitié des œufs produits par les femelles ne sont pas viables et sont ainsi perdus.
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| All Time | Past Year | Past 30 Days | |
|---|---|---|---|
| Abstract Views | 251 | 27 | 4 |
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Seasonal and inter-species comparison of asymmetry in the genital system of some species of the oceanic copepod genus Metridia (Copepoda, Calanoida)
In: CrustaceanaThe seasonal and inter-annual changes in the asymmetry of female insemination and the male leg 5 of the planktonic calanoid copepods Metridia okhotensis and M. pacifica were investigated in the Okhotsk Sea. An inter-species comparison of both parameters was also carried out on seven Metridia species collected from oceans throughout the world. For M. okhotensis from the Okhotsk Sea, most of the females showed left-side insemination (annual average: 95.7%) and most of the males showed left-side asymmetry (99.7%) of the long inner process of the second exopodal segment in the fifth leg throughout the year. However, sympatric M. pacifica showed different ratios of asymmetry for female insemination and male morphotypes with a left : right = 1 : 2 ratio throughout the year. For the seven Metridia species from the global oceans treated in this study, ratios of asymmetry for female insemination and male morphotypes were correlated with each other. One-sided insemination (i.e., only left or only right insemination) was a common pattern for various Metridia species from global oceans, but their ratios varied by species. Previously, low hatching rates (29-68%) of eggs were reported for various Metridia spp. in laboratory experiments, but the reasons for these low rates were unclear. Because each spermatheca of Metridia spp. is connected to the oviduct on the same side, either left or right, this suggests that half of the eggs produced by unilaterally inseminated females remain unfertilized. The morphology of the genital structures and literature data of the egg hatching rates of Metridia spp. indicate that almost half of the eggs produced by females are not viable and are, thus, wasted.
| All Time | Past Year | Past 30 Days | |
|---|---|---|---|
| Abstract Views | 251 | 27 | 4 |
| Full Text Views | 203 | 2 | 0 |
| PDF Views & Downloads | 14 | 5 | 0 |