Sexual maturation in sea- and freshwater phases of Pacific salmonids and investigations of reproductive hormone involvement in osmoregulatory adaptation
Notice bibliographique
Résumé
The changes in reproductive parameters and hormones, and blood sodium during the final weeks of sexual maturation in wild coastal salmon, chinook, Oncorhynchus tshawytscha, and steelhead, O. mykiss, were documented for stocks spawning in two similar river systems on the west coast of Vancouver Island, British Columbia, Canada. Chinook were blood-sampled and sacrificed at intervals during migration from the ocean into brackish Nitinat Lake, through the completion of final maturation in Nitinat River, and at the post-spawning stage. Gonadosomatic index (GSI), hepatosomatic index (HSI), and oocyte germinal vesicle stage and hydration level were measured in sacrificed chinook and steelhead. Stamp River steelhead were serially sampled for blood during the month preceding and the month following final maturation. Blood samples were analysed by specific radioimmunoassay for gonadotropin (GtH), estradiol-17β (E₂), testosterone (T), 11-ketotestosterone (11-KT), and 17α,20β-dihydroxyprogesterone (17,20-P). Blood sodium was measured by flame photometry. GSI and hydration level of oocytes increased in females of both species between the earliest stages of maturation and ovulation. Patterns of hormone concentration were similar in chinook and steelhead, but the peaks in concentration of the steroids at each stage were much lower in steelhead. Concentrations of E₂ and T declined from initial levels to ovulation in females, while GtH and 17,20-P increased. In chinook males, T concentration peaked and declined before spermiation, while 11-KT was highest at spermiation, and declined thereafter. The concentration of 11-KT was higher than that of T in steelhead males at spermiation. Little change in GtH and 17,20-P concentration occurred in steelhead males, but these hormones increased in relation to onset of spermiation in chinook. Fertility was compared between chinook and chum salmon, O. keta, maturing in brackish and fresh water. Fertility was low in both brackish and freshwater chinook females at the beginning of the chinook migration, when salinity was high in Nitinat Lake. Blood sodium was higher in brackish water females, but there was no correlation between egg mortality and blood sodium at ovulation. Later in the season, as salinity in net pens decreased, chinook fertility increased. At the beginning of the chum migration season, when salinity was lowest, chinook fertility was equal to that of chum maturing at the same location. The relationship between plasma reproductive hormone concentration and the ability to osmoregulate in sea water was compared in post-spawning steelhead and coho salmon, O. kisutch, transferred from fresh water to brackish holding facilities. All hormones declined to low levels in steelhead while still in fresh water, within 3 weeks of spawning, but persisted at spawning levels for at least 6 weeks in coho. Steelhead blood sodium was stable in the range indicating osmoregulatory adaptation as salinity was increased to full sea water shortly after transfer. Coho blood sodium was higher in 2/3 sea water than that of steelhead in full sea water. High levels of reproductive hormones may interfere with the ability of salmonids to osmoregulate in sea water.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».