Egg-laying in response to prostaglandin injections in the Australian field cricket, Teleogryllus commodus

ABSTRACT. We report the effects of prostaglandin (PG) injection on egg-laying by sexually mature virgin crickets, Teleogryllus commodus Walker. High egg-laying activity is associated with PGE₁ PGE₂, 6-keto-PGE₁ and 15-keto-PGE₂, compounds that share the basic prostanoid backbone (C20 substituted fatty acid, 5 membered ring, a 7- and an 8-carbon aliphatic chain), and 9-keto, 11-hydroxyl ring substitutions. PGs without these ring features and other compounds that lack the prostanoid backbone have no or only intermediate egg-laying effects. Adding oxygen functionalities or an aliphatic double bond tends to increase egg-laying activity. Hence, 15-keto-PGF₂ and TxB₂, both of which have an additional backbone oxygen compared with their less active analogues, are highly active compounds. Two of the most active PGs, 15-keto-PGE₂ and 15-keto-PGE_2α, are the products of inactivating metabolism in mammalian systems, describing a fundamental difference in PG biochemistry with respect to mammals and insects.     

The Biological Significance of Prostaglandins and Related Eicosanoids in Invertebrates

SYNOPSIS. Prostaglandins and related eicosanoids are oxygenatedmetabolites of C20 polyunsaturated fatty acids. These compoundshave been detected in many vertebrate and invertebrate speciesthat represent all major phyla. The significance of eicosanoidsrelates to two broad areas of animal biology, one as mediatorsof crucial cellular events and another in mediation of certainecological interactions. Eicosanoids exert physiological actionsin reproduction, including release of egg-laying behavior insome insects, hatching in barnacles, egg-production in snails,spawning in bivalves, oocyte maturation in sea stars, and preventionof polyspermic fertilizations in sea urchin eggs. Eicosanoidsare also involved in salt and water transport physiology (insectsand bivalves), neurophysiology (mollusks) and cellular immunedefenses (insects). I propose that some eicosanoid actions arefundamental to animal physiology. Eicosanoids also mediate certainhost-parasite and predator-prey interactions. These includeskin penetration by blood fluke larvae, blood feeding by ticksand predator avoidance by certain octocoral and nudibranchs.Research in eicosanoids yields insights that help explain detailsof physiological and ecological phenomena in vertebrates andinvertebrates. Although we have seen considerable progress inour appreciation of eicosanoids in invertebrates, we are sorelylacking in our understanding of the biochemical mechanisms ofeicosanoid actions in invertebrates. I suggest that researchin this area will yield meaningful insights into the physiologyand ecology of invertebrates.     

Sexual transfer of prostaglandin precursor in the field cricket, Teleogryllus commodus

ABSTRACT. When injected into the haemolymph of newly emerged adult males of the field cricket, Teleogryllus commodus (Walker), [³H]arachidonic acid is incorporated into tissue phospholipids. Two reproductive tissues, testes and accessory glands, incorporate and preserve the labelled arachidonic acid for at least 49 days. With onset of circadian rhythm-controlled spermatophore production, radioactive arachidonic acid is incorporated into spermatophore phospholipids. After mating with untreated females, radioactivity was detected in spermathecae and in haemolymph from females. Some of the transferred radioactive arachidonic acid is subsequently converted into prostaglandins. Hence, males of T. commodus transfer prostaglandin synthetase activity and substrate by way of spermatophores during mating