Cost of sexually embracing a large female offset by the number of eggs fertilized for small male Bufo bufo L.

When pairing with high quality females, a male increases its fitness through an increased number and/or quality of sired offsprings. In anurans, size has often been used as a measure of female quality. In the present study, we examined the effects of pairing with large females for small males in the common toad, Bufo bufo . For the first time in anurans, we show a fitness cost for males to maintain amplexus with a large female. Indeed, although we did not detect any effect of male size on male pairing success in a first breeding event in the presence of other competing males, when males that were successful in the first breeding event were tested for a second time, male pairing success strongly decreased when they had been first paired with a large female. However, the higher fecundity of large females (1.52-fold more than that of small females) may override this pairing cost, especially because high fertilization rate was not linked to male/female body size ratio. Indeed, we did not detect any difference in egg fertilization success between small males paired with large and small females. Our results suggest that predictable cues of female reproductive value exist in common toads, thus meeting a prerequisite of the occurrence of male mate choice. Male mate choice, probably underestimated in anurans, may be particularly important in species where the breeding season is short and the number of mating events for a male is limited. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 755–762.     

EVOLUTION OF MULTIPLE KINDS OF FEMALE SPERM-STORAGE ORGANS IN DROSOPHILA

Females of all species belonging to the family Drosophilidae have two kinds of sperm-storage organs: paired spherical spermathecae and a single elongate tubular seminal receptacle. We examined 113 species belonging to the genus Drosophila and closely allied genera and describe variation in female sperm-storage organ use and morphology. The macroevolutionary pattern of organ dysfunction and morphological divergence suggests that ancestrally both kinds of organs stored sperm. Loss of use of the spermathecae has evolved at least 13 times; evolutionary regain of spermathecal function has rarely if ever occurred. Loss of use of the seminal receptacle has likely occurred only once; in this case, all descendant species possess unusually elaborate spermathecae. Data further indicate that the seminal receptacle is the primary sperm-storage organ in Drosophila. This organ exhibits a pattern of strong correlated evolution with the length of sperm. The evolution of multiple kinds of female sperm-storage organs and the rapidly divergent and correlated evolution of sperm and female reproductive tract morphology are discussed.     

Review of the planthopper genus Neodurium Fennah, 1956 (Hemiptera,Fulgoromorpha, Issidae)

The planthopper genus Neodurium Fennah is reviewed and Neodurium fennahi Chang & Chen, sp. n. (Hemiptera: Fulgoromorpha: Issidae) from China (Yunnan), is described and illustrated. A checklist of the species of Neodurium is given and a key provided for their separation. The female genitalia of Neodurium species are described for the first time.     

Paternity in mallards: effects of sperm quality and female sperm selection for inbreeding avoidance

Postcopulatory processes might play an important role in sexualselection. In theory, fertilization success could be controlledby females via selection of particular sperm within their reproductivetract, or it could be determined by sperm competition per se.In practice, these two mechanisms are difficult to disentangle.To assess the relative importance of both mechanisms we usedartificial insemination in combination with measurements ofsperm quality (swimming speed and motility) in mallards. Inthis species, females often lack behavioral control over copulationsand hence may use postcopulatory mechanisms to optimize theirreproductive output. One important factor affecting female fitnessmay be selection of genetically compatible males. To investigatethe influence of sperm quality and parental relatedness on paternitywe inseminated 12 groups of related females with a sperm mixturecontaining equal numbers of sperm from a brother and from anunrelated male. Paternity was independent of the relatednessof the siring male to the female but was significantly affectedby long-term sperm swimming speed and motility. No interactionbetween relatedness and sperm quality on paternity was observed.These results suggest that female mallards are not able to selectsperm on a purely genetic basis and emphasize the importanceof sperm quality in gaining paternity.     

Meiosis and the Neo- XY system of Dichroplus vittatus (Melanoplinae, Acrididae): a comparison between sexes

The origin of neo-XY sex systems in Acrididae is usually explained through an X-autosome centric fusion, and the behaviour of the neo-sex chromosomes has been solely studied in males. In this paper we analysed male and female Dichroplus vittatus. The karyotype comprises 2n = 20 chromosomes including 9 pairs of autosomes and a sex chromosome pair that includes a large metacentric neo-X and a small telocentric neo-Y. We compared the meiotic behaviour of the sex bivalent between both sexes. Mean cell autosomal chiasma frequency was low in both sexes and slightly but significantly higher in males than in females. Chiasma frequency of females increased significantly when the sex-bivalent was included. Chiasma distribution was basically distal in both sexes. Behaviour of the neo-XY pair is complex as a priori suggested by its structure, which was analysed in mitosis and meiosis of diploid and polyploid cells. During meiosis, orientation of the neo-XY is highly irregular; only 21% of the metaphase I spermatocytes show standard orientation. In the rest of cells, the alternate or simultaneous activity of an extra kinetochore in the distal end of the short arm (XL) of the neo-X, determined unusual MI orientations and a high frequency of non-disjunction and lagging of the sex-chromosomes. In females, the neo-XX bivalent had a more regular behaviour but showed 17% asynapsis in the XL arm which, in those cases orientated its distal ends towards opposite spindle poles suggesting, again, the activity of a second kinetochore. The dicentric nature and the unstable meiotic behaviour of the sex neo-chromosomes of D. vittatus suggest a recent origin of the sex determination mechanism, with presumable adaptive advantages which could compensate their potential negative heterosis. Our observations suggest that the origin of the neo-sex system was a tandem fusion of two original telocentric X-chromosomes followed by another tandem fusion with the small megameric bivalent and a further pericentric inversion of the neo-X. The remaining autosomal homolog resulted in the neo-Y chromosome. This revised version was published online in July 2006 with corrections to the Cover Date.     

杉木雌配子体与后胚发育过程中核酸、蛋白质和类脂的消长

在杉木胚胎分化期至成熟期,每个雌配子体总核酸和DNA,RNA含量在初期增加,后期则随着胚的分化发育逐渐下降,而蛋白质和类脂则一直上升。每胚总核酸、DNA,RNA则相应增加,而蛋白质、类脂的含量和干重亦逐渐增加。在胚分化早期RNA的迅速合成与细胞的分化及器官形成有关。但以胚干重为单位的DNA、RNA含量却随着胚的发育而有所减少;蛋白质含量先增加,至成熟后才下降。授粉前的胚珠,以及雌配子体、胚中都发现有凝集素存在。     

Reproductive characters in a gynodioecious species, Silene italica (Caryophyllaceae), with attention to the gynomonoecious phenotype

Gynodioecious populations (i.e. populations with female and hermaphrodite individuals) often contain a third phenotype with an intermediate sex expression. In Silene italica , this phenotype is characterized by a mixture of pistillate and perfect flowers and is thus gynomonoecious. To characterize sexual functions of these gynomonoecious individuals and their potential influence in the maintenance of gynodioecy, reproductive characters of the three sexual phenotypes were compared over 2 years in several families of S. italica produced by crossing. We found that gynomonoecious individuals were intermediate for flower production and female fertility characters, although they did not always significantly differ from female individuals. Perfect flowers of gynomonoecious and hermaphrodite plants were similar in size and pollen production. Gynomonoecious individuals were thus intermediate in female and in male functions. Family effects were found for most of the characters. The female advantage (i.e. the fertility of females compared to the female fertility of pollen producing plants) was not dramatically different when gynomonoecious plants were taken into account.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 583–591.     

Polyandry reduces sperm length variation in social insects

Postcopulatory sexual selection, either in the form of sperm competition or cryptic female choice, is an important selective force that is thought to have generated the enormous variation in sperm morphology observed interspecifically. However, the evolutionary significance of intraspecific variation in sperm morphology, and the role that postcopulatory sexual selection plays in influencing this variation, remains poorly investigated in invertebrates. Here, we tested the hypothesis that postcopulatory sexual selection reduces variation in sperm morphology, both between and within males, in 27 species of eusocial ants and bees. These eusocial species offer an unusual opportunity to assess how selection acts on variance in sperm morphology, as haploid males produce clonal, haploid sperm that does not experience haploid-diploid conflict. We provide solid evidence that males of polyandrous ant and bee species indeed produce less-variable sperm, indicating that sperm competition selected for sperm of superior quality. Our results offer a mechanistic explanation for the evolution of high-quality sperm and provide comprehensive evidence that sperm morphology of social insects is influenced by sexual selection.     

Host species diversity and post-blood feeding carbohydrate availability enhance survival of females and fecundity in Aedes albopictus (Diptera: Culicidae)

Aedes albopictus mosquito is an opportunistic blood feeder and has a broad host range. The feeding behavior and habits of this mosquito are liable to increase the transmission potential of arboviruses. The survival and fecundity in A. albopictus fed on different hosts and post-blood meal provision of sugar were investigated in a laboratory-reared colony. Adult survival of caged female A. albopictus that were fed on blood of two different hosts (double meal) was higher than the females fed only on one host (single meal) (mean survival: 70.2 ± 9.6 vs. 55.5 ± 5.5%, respectively) when held in the laboratory for 72 h after blood feeding. Mean survival of females provided 10% sucrose solution (in water) after a single or double blood meal was higher (90.5 ± 6.4% and 89.3 ± 6.5%, respectively) than in the respective groups receiving water only following blood feeding (double meal: 49.0 ± 9.6%; single meal: 45.3 ± 10.9%). Females receiving a double meal were more fecund on average (89.0 ± 6.6 eggs) than females provided a single meal (82.3 ± 8.2 eggs).     

An enigmatic lineage of mites from Baltic amber shows a unique,possibly female‐controlled,mating

It is generally assumed that male control over mating and a lack of precopulatory female choice are prevalent in many animals and in astigmatan mites in particular. We show that several morphological structures of females of some astigmatan mites are indicative of precopulatory female choice: (1) copulatory tubes acting like intromittent organs; (2) specialized structures assisting male–female attachment and possibly allowing indirect mate selection in immature females; and (3) a unique, pad‐like terminal opisthosomal organ used to cling to the male during copulation in Glaesacarus rhombeus (= Acarus rhombeus Koch et Berendt, 1854) belonging to an extinct family, Glaesacaridae, from the Upper Eocene Baltic amber. An exceptionally well‐preserved copulating pair from amber provides insight into the function of this organ and reproductive behaviour in this mite. Female control over mating may reduce the timing of insemination, harassment by males, and damage caused by copulation. As a consequence, this can lessen male–male aggression, select against precopulatory guarding, and reduce the risk of predation. By contrast to extant taxa, males of G. rhombeus do not have any apparent specialized structures aiding clinging to the female during copulation, suggesting that this mating system is either an earlier step in the evolution of the female‐dominated mating system and/or a remarkable example of imbalanced female counteradaptations against the male's reproductive interest that may occur during an arms race between the two sexes. We offer an approach that can falsify the hypothesis assuming precopulatory female choice and discuss an alternative hypothesis suggesting that these female structures evolved in response to the need to reduce damage associated with mating or precopulatory guarding. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 661–668.