Diet affects both lifespan and reproduction [1-9], leading to the prediction that the contrasting reproductive strategies of the sexes should result in sex-specific effects of nutrition on fitness and longevity [6, 10] and favor different patterns of nutrient intake in males and females. However, males and females share most of their genome and intralocus sexual conflict may prevent sex-specific diet optimization. We show that both male and female longevity were maximized on a high-carbohydrate low-protein diet in field crickets Teleogryllus commodus, but male and female lifetime reproductive performances were maximized in markedly different parts of the nutrient intake landscape. Given a choice, crickets exhibited sex-specific dietary preference in the direction that increases reproductive performance, but this sexual dimorphism in preference was incomplete, with both sexes displaced from the optimum diet for lifetime reproduction. Sexes are, therefore, constrained in their ability to reach their sex-specific dietary optima by the shared biology of diet choice. Our data suggest that sex-specific selection has thus far failed fully to resolve intralocus sexual conflict over diet optimization. Such conflict may be an important factor linking nutrition and reproduction to lifespan and aging.

Phenol oxidase (PO) was isolated as a proenzyme (pro-phenol oxidase, pro-PO) from the hemolymph of Manduca sexta larvae and purified to homogeneity. Pro-PO exhibits a Mr of 130,000 on gel filtration and two bands with an apparent Mr of -100,000 on SDS/PAGE, as well as sizeexclusion HPLC. Activation of pro-PO was achieved either by specific proteolysis by a cuticular protease or by the detergent cetylpyridinium chloride at a concentration below the critical micellar concentration. A cDNA clone for M. sexta pro-PO was obtained from a larval hemocyte cDNA library. The clone encodes a polypeptide of -80,000 Da that contains two copper-binding sites and shows high sequence similarity to POs, hemocyanins, and storage proteins of arthropods. The M. sexta pro-PO, together with other arthropod pro-POs, contains a short stretch of amino acids with sequence similarity to the thiol ester region of a-macroglobulins and complement proteins C3 and C4.Melanin biosynthesis occurs widely, not only in animals but also in plants and fungi (1). Phenol oxidase (PO), which possesses both tyrosinase activity (monophenol monooxygenase; monophenol, L-dopa:oxygen oxidoreductase; EC 1.14.18.1), as well as o-diphenol oxidase (1,2-benzenediol:oxygen oxidoreductase; EC 1.10.3.1), is responsible for initiating the biosynthesis of melanin (2, 3). In arthropods and especially in insects, PO is uniquely involved in another important biochemical process-cuticular sclerotization (hardening). Sclerotization is vital for the survival of all insects, as it affords protection to the soft invertebrate body (3-8). During sclerotization, PO-generated quinones participate in the quinone tanning process or serve as substrates for quinone isomerases that convert quinones to quinone methides for quinone methide sclerotization (9-13). Certain quinone methides are converted by another cuticular enzyme, quinone methide isomerase, to 1,2-dehydro-N-acyldopamine derivatives (14). These compounds are further oxidized by PO to reactive quinone methide imine amides (15, 16), which serve as the reactive intermediates of a,f3-sclerotization. Quinones, quinone methides, and quinone methide imine amides react with cuticular proteins and chitin, forming eventually cross-linked cuticle.Apart from participating in sclerotization and melanization of cuticle, POs are also known to be involved in two other physiologically important processes-defense reactions (arthropod immunity) and wound healing. During invasion by a foreign organism, pro-phenol oxidase (pro-PO) present in the hemocytes is released and activated to produce melanin pigments for deposition on the intruder (17)(18)(19). The damage that can be caused by the foreign organisms is thus limited by encapsulation and melanization. Similarly during wounding of insect cuticle, PO causes massive deposition of melanin pigment at the wound site to prevent hemolymph loss and to block the entry of opportunistically invading microorganisms (20).Given such important functions, it could be expected that PO would be one o...

Coagulation in crayfish blood is based on the transglutaminase-mediated crosslinking of a specific plasma clotting protein. Here we report the cloning of the subunit of this clotting protein from a crayfish hepatopancreas cDNA library. The ORF encodes a protein of 1,721 amino acids, including a signal peptide of 15 amino acids. Sequence analysis reveals that the clotting protein is homologous to vitellogenins, which are proteins found in vitellogenic females of egg-laying animals. The clotting protein and vitellogenins are all lipoproteins and share a limited sequence similarity to certain other lipoproteins (e.g., mammalian apolipoprotein B and microsomal triglyceride transfer protein) and contain a stretch with similarity to the D domain of mammalian von Willebrand factor. The crayfish clotting protein is present in both sexes, unlike the female-specific vitellogenins. Electron microscopy was used to visualize individual clotting protein molecules and to study the transglutaminase-mediated clotting reaction. In the presence of an endogenous transglutaminase, the purified clotting protein molecules rapidly assemble into long, f lexible chains that occasionally branch.