Two highly polymorphic microsatellite DNA loci were used to determine paternity of larvae of primiparous Chionoecetes opilio females. In addition, female spermathecal contents were genotyped at the two loci and histological analysis of the organs was carried out to elucidate patterns of sperm competition. Females carrying their first brood from controlled laboratory matings and from matings in the wild were examined. Spermathecal contents from wild-caught females were cut into several cross sections and each section genotyped individually. Both wild and laboratory females commonly mated with several males whose ejaculates were stored and stratified in the spermathecae. Genetic typing of the offspring of laboratory-mated females revealed single paternity and indicated that the last mate to inseminate a female before oviposition gained paternity of the clutch. The predominant mechanism ensuring single paternity appeared to be sperm stratification. In wild-caught females, the microsatellite typing of the offspring also revealed single paternity, but larvae appeared to be sired by males whose genotypes were found in the spermathecal cross sections towards the dorsal end (blind end) of the spermathecae. This suggested that they were the first males to mate with females that they guarded until oviposition, and females remated with other males thereafter.Résumé : Deux loci d'ADN microsatellite hautement variables ont été utilisés pour déterminer la paternité des larves de femelles primipares de Chionoecetes opilio. De plus, la détermination des génotypes du contenu des spermathèques des femelles a été faite à partir de ces deux loci et l'analyse de coupes histologiques des organes a été réalisée dans le but d'élucider les modalités de compétition du sperme. Des femelles avec leur premières portées d'oeufs obtenues à partir d'accouplements contrôlés en laboratoire et d'accouplements en nature ont été examinées. Les spermathèques des femelles sauvages ont été coupées en plusieurs sections transversales et le génotype de chacune des sections a été déterminé. Les femelles sauvages ainsi que celles de laboratoire se sont accouplées avec plusieurs mâles dont le sperme était accumulé de façon stratifiée dans les spermathèques. La détermination du génotype de la progéniture des femelles accouplées en laboratoire a révélé qu'il y avait paternité unique et que le dernier mâle à inséminer une femelle avant la ponte des oeufs était le père. Le mécanisme prédominant assurant la paternité unique semble être la stratification des éjaculats. Chez les femelles sauvages, la détermination du génotype des larves a également démontré qu'il y avait paternité unique. Cependant, les oeufs semblaient avoir été fécondés par les mâles dont les génotypes se trouvaient dans les sections des spermathèques les plus éloignées de l'ouverture des organes. Ceci suggère qu'ils étaient les premiers à s'accoupler avec les femelles et qu'ils les auraient ensuite protégées jusqu'à ce qu'elles pondent. Les femelles se seraient donc ré-accouplées avec d'autres ...
Crab p a r s , consisting of a male grasping another crab (the graspee), were collected by divers during the first breeding season of female snow crab Chionoecetes opllio Different types of graspees were found and were ranked according to their reproductive value to the male. High-value graspees were pubescent females (close to their terminal matunty molt) and nulliparous females ljust molted and close to oviposition). Postn~olt prirmparous females (clean-soft shell and carrying eggs) also mated and were inseminated by males, but they were of less value than pubescent or nulliparous females as there was only a remote chance that the males' stored sperm would be used to fertilize the next egg clutch. Females copulated with up to 6 different males dunng their first breeding season. Another category of graspees including males and juvenile females provided the grasping male with no fecundity benefit. Pubescent females paired with males u p to 13 d before molting. Males grasping the high-value pubescent and nulliparous females were larger, had a harder shell, and were missing fewer limbs than the males grasping low-value primiparous females, other males or juvenile females and than the overall population of adult males on the mating grounds assessed by trawl. Size-assortative mating by male chela size and female carapace width occurred in the predominant pubescent pairs. Moreover, males with larger chelae were associated with pubescent females missing fewer limbs or having relatively narrower abdomens. Both traits may influence female survivorship and lifetime fecundity. The complex assortative mating pattern of snow crabs apparently denves from mate choice and male sexual competition in the context of prolonged attractiveness of pubescent females to males
No abstract
Summary The identification of genes affecting disease resistance in domestic fowl has challenged research workers in various countries, in the study of their effects and in the evaluation of their potential for commercial poultry breeding. This study concerns endogenous viral genes (ev genes), which can play an important role in the response to avian leukosis virus infection. The incidence of ev genes was determined in three experimental White Leghorn strains of different origin, each consisting of two sublines genotypically either susceptible or resistant to infection from avian leukosis virus (ALV) of the subgroups A and B. The three pairs of sublines had been used extensively for investigations of the effects of leukosis infections in laying hens. Among the 11 ev genes found, only three were present in all three strains – ev1 and ev3, which appear to be very common in White Leghorn, and ev6, which has been associated with reduced immune response to ALV infection. Five of the 11 ev genes found occurred only in one of the three strains, while the number of different ev genes in each of the strains amounted to either six or seven. The frequency of each ev gene present in a strain was surprisingly similar in the genotypically resistant and susceptible subline. With the exception of ev1 and ev3, which were present in all three strains at a relatively high frequency, there were striking differences between the strains in the level of frequencies of the additional ev genes. In one of the strains, which originated from a commercial hybrid, this level was exceptionally low, while the additional ev genes had much higher frequencies in the other two strains. The information about the incidence of ev genes, and specifically that about ev6, suggested a plausible explanation for the striking difference observed between the three Leghorn strains in their respect to ALV infection and, in particular, the rate of congenital ALV infection. Zusammenfassung Vorkommen von endogenen Virus‐Genen in Leghorn‐Linien verschiedenen Ursprungs, jeweils mit Sublinien interschiedlichen Genotyps für Infektionsresistenz gegen Geflügelleukose Die Identifizierung von Einzelgenen, von denen Einflüsse auf die Widerstandsfähigkeit gegen Krankheiten beim Hausgeflügel ausgehen, haben in mehreren Ländern intensive Forschungsaktivitäten zur Untersuchung der von ihnen ausgehenden Wirkungen ausgelöst, um ihrem möglichen Nutzen für die kommerzielle Geflügelzüchtung besser bewerten zu können. Dieser Beitrag betrifft endogene Virusgene (ev Gene), die einen wesentlichen Einfluß auf die Auswirkung einer Infektion durch Geflügelleukoseviren ausüben können. Das Vorkommen endogener Virusgene wurde in drei experimentellen Linien von weißen Leghorn unterschiedlichen Ursprungs untersucht, von denen jede aus zwei Sublinien bestand, die genotypisch entweder empfänglich oder resistant gegen Infektion durch Geflügelleukoseviren (ALV) der Untergruppen A und B waren. Mit diesen drei Paaren von Sublinien waren bereits umfangreiche Untersuchungen über die Auswirkung von Leu...
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