Species-Specific Functional Regions of the Green Alga Gamete Fusion Protein HAP2 Revealed by Structural Studies

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Nocturnal swimming, aggregation at light traps, and mass spawning of scissurellid gastropods (Mollusca: Vetigastropoda)

Abstract. Thousands of minute scissurellid gastropods (Vetigastropoda: Scissurellidae) were observed and collected at floating light traps in Moorea, French Polynesia, where a mass spawning event occurred on November 11, 2002. More than 20,000 live snails were recovered from the traps, and epidemic spawning continued in the laboratory, where clouds of white sperm and red-orange eggs were broadcast into the water. No aggregations of this magnitude have been reported previously in vetigastropods, nor is the capacity for sustained swimming known from other vetigastropod taxa. Snails had emerged from a local benthic habitat of coral sand and swum through ≥2 m of water to reach the traps. Scanning electron micrographs of the ornate shells confirm the identity of the most abundant species as Scissurella spinosa , with lesser numbers of Sinezona plicata . Our observations indicate that scissurellids are not exclusively benthic and that they are not rare, even though they have seldom been collected and studied alive. Because little is known about the basic biology and anatomy of scissurellids and because their position within the basal Gastropoda is poorly resolved, we include information on the design and construction of inexpensive light traps to promote comparative investigation of other poorly known species.     

On the Adaptive Value of Some Mate Selection Strategies

Results of an agent-based computer simulation of the evolution of diploid sexual organisms showed that several mate selection strategies confer much higher average fitness to the simulated populations, and higher evolutionary stability to the alleles coding for these strategies, than random mating. Strategies which select for 'good genes' were very successful, and so were strategies based on assortative mating. The results support the hypothesis that mating is not likely to be random in nature and that the most successful mate selection strategies are those based on assortative mating or on advantageous genes.     

Parental tracking in the postfire wood decay ascomycete Daldinia loculata using highly variable nuclear gene loci

The origin of the male and female gametes involved in fertilization events within a local population of the postfire wood decay ascomycete Daldinia loculata was investigated by genotyping the mycelia growing in the wood and the sexual ascospores, using three highly variable nuclear gene loci. The study was conducted in a geographically isolated burned forest site in southern Sweden. An intensive sampling was performed by collecting stromata containing ascospores and wood samples containing mycelia. In total, from 32 mapped burned birches, cultures of 22 haploid genets from decayed wood and six ascospores from each of 19 stromata were isolated and analysed. In 80% of the investigated burned branches, only one genet was found. From the analysis of the ascospore genotypes, we detected 30 fertilization events and 60% of them were the result of mating between conidia (clonal propagules) acting as male gametes and the genets in the branches representing the female gametes. The male parents producing the conidia were detected within the same local population as the female parents in 27% of the fertilization events and originated either from the same branch or from different trees located at 0.5-36 m away from the female parents. In 33% of the fertilization events, conidia originated from three male parents that were not found within the local population sampled. These parents could be anywhere inside or outside the sampled area. For the remaining fertilization events, we could not rule out the ascospores or the conidia as fertilizing propagules. No strong evidence for fertilization by recombinant propagules (ascospores) was detected in this study. The pyrophilous insect species associated with conidia of D. loculata are suggested to be essential vectors for the realization of the sexual cycle of this fungal species. By feeding on the conidia and flying between nearby trees inhabiting wood decay mycelia, these insects allow the transfer of conidia and therefore the opposite mating types to meet within a localized burned forest site.     

Male age and its association with reproductive traits in captive and wild house sparrows

Evolutionary theory predicts that females seek extra‐pair fertilizations from high‐quality males. In socially monogamous bird species, it is often old males that are most successful in extra‐pair fertilizations. Adaptive models of female extra‐pair mate choice suggest that old males may produce offspring of higher genetic quality than young males because they have proven their survivability. However, old males are also more likely to show signs of reproductive senescence, such as reduced sperm quality. To better understand why old males account for a disproportionally large number of extra‐pair offspring and what the consequences of mating with old males are, we compared several sperm traits of both captive and wild house sparrows, Passer domesticus. Sperm morphological traits and cloacal protuberance volume (a proxy for sperm load) of old and young males did not differ substantially. However, old males delivered almost three times more sperm to the female's egg than young males. We discuss the possibility of a post‐copulatory advantage for old over young males and the consequences for females mated with old males.     

Association of female aging with decreased parthenogenetic activation, raised MPF, and MAPKs activities and reduced levels of glutathione S-transferases activity and thiols in mouse oocytes

This study aims to determine in the mouse whether oocytes from reproductively old females exhibit a different susceptibility to be parthenogenetically activated when compared to oocytes from young females. At the age of 10-12 (young-female group) or 60-62 (old-female group) weeks, hybrid female mice were superovulated using pregnant mare's serum gonadotropin (PMSG) followed by human chorionic gonadotropin (hCG) 48 hr later. After removing the cumulus cells, oocytes were exposed to any of two different activating protocols: (a) 6-min exposure to 8% ethanol; and (b) treatment with 200 microM thimerosal for 15 min followed by 8 mM dithiothreitol (DTT) for 30 min. Oocytes from old female mice displayed (1) lower total percentage of parthenogenetic activation and extrusion of the second polar body after treatment with either thimerosal + DTT or ethanol; (2) higher M-phase-promoting factor (MPF) and mitogen-activated protein kinases (MAPKs) activities; and (3) lower intracytoplasmic levels of glutathione S-transferases (GSTs) activity and thiols than oocytes from young females. These data show that female aging is associated with higher resistance of oocytes to be parthenogenetically activated, higher MPF and MAPKs activities and lower intracytoplasmic levels of GSTs activity and thiols.     

Genetic studies of anther culture ability in rice (Oryza sativa)

Inheritance of three anther and culture characters, callus induction, green plant regeneration and culture efficiency was studied using incomplete diallel crosses with a gamete model. It was suggested that callus induction was mainly controlled by gametic additive effects and with less effect of the maternal effects. Green plant regeneration was mainly determined by maternal effects with less influence of gametic additive effects. Culture efficiency was controlled by gametic additive, maternal and cytoplasmic effects. Cultivar Lunhui 422 showed positive genetic effects for all three traits and was a very good parent for rice anther culture breeding. Significant positive heterosis was observed for callus induction. Both gametic additive and maternal correlations contributed to the significant genotypic and phenotypic correlations between callus induction and green plant regeneration suggesting these two traits to be linked.Abbreviations 2,4-d 2,4-dichlorphenoxyacetic acid - NAA -napthaleneacetic acid     

Different genomic combinations in inter-section hybrids obtained from the crosses between Primulasieboldii (Section Cortusoides) and P. obconica (Section Obconicolisteri) by the embryo rescue technique

Inter-section hybrids were successfully obtained by rescuing the immature embryos produced in the cross between Primula sieboldii of Sect. Cortusoides and P. obconica of Sect. Obconicolisteri. In these hybrid plants two types of triploids with different genome combinations were found in addition to the normal diploid hybrids which each had one genome of the parents. Among the five triploids obtained, four had two genomes of P. sieboldii and one genome of P. obconica, whereas the remaining one had one genome of P. sieboldii and two genomes of P. obconica. The possibilities of diploid female gamete formation in P. sieboldii and diploid pollen formation in P. obconica as the causal factors for these triploid formations were discussed. Received: 22 August 2000 / Accepted: 22 September 2000