Temporal variation in sex allocation in the mealybug <em>Planococcus citri</em>:Adaptation, constraint, or both?

Sex ratio theory has been very successful in predicting under which circumstances parents should bias their investment towards a particular offspring sex. However, most examples of adaptive sex ratio bias come from species with well-defined mating systems and sex determining mechanisms, while in many other groups there is still an on-going debate about the adaptive nature of sex allocation. Here we study the sex allocation in the mealybug Planococcus citri, a species in which it is currently unclear how females adjust their sex ratio, even though experiments have shown support for facultative sex ratio adjustment. Previous work has shown that the sex ratio females produce changes over the oviposition period, with males being overproduced early and late in the laying sequence. Here we investigate this complex pattern further, examining both the robustness of the pattern and possible explanations for it. We first show that this sex allocation behaviour is indeed consistent across lines from three geographical regions. Second, we test whether females produce sons first in order to synchronize reproductive maturation of her offspring, although our data provide little evidence for this adaptive explanation. Finally we test the age at which females are able to mate successfully and show that females are able to mate and store sperm before adult eclosion. Whilst early-male production may still function in promoting protandry in mealybugs, we discuss whether mechanistic constraints limit how female allocate sex across their lifetime

Intermediates for incorporation of tetrahydroxypipecolic acid analogues of alpha- and beta-D-mannopyranose into combinatorial libraries: unexpected nanomolar-range hexosaminidase inhibitors. Synthesis of alpha- and beta-homomannojirimycin

Homoazasugars have the distinction as a class of natural products in that most of them have been synthesised before they were isolated. Syntheses of α-1 and β-homomannojirimycin 2 rely on the stereoselective and chemoselective sodium cyanoborohydride reduction of a [2.2.2] bicyclic imino lactone (6) to give a single [2.2.2] bicyclic amino-lactone (7). Methanolysis of 7 under basic conditions is accompanied by efficient epimerisation of the first formed α-amino-ester (8) to the more stable β-amino-ester (9) in which the 2,6-substitutents are equatorial. Both 7 and 9 are suitable intermediates for the incorporation of tetrahydroxypipecolic acid derivatives into combinatorial libraries containing α- and β-C-glycosyl analogues of aza-D-mannopyranose, respectively. Methylamides derived from 7 and 9 are shown to be specific and potent inhibitors of two β-N-acetylglucosaminidases but have no effect on an α-N-acetylgalactosaminidase. The synthesis of α- 14 and β-17 manno-pipecolic acids is also reported