Werner Loher

THE EFFECT OF MATING ON EGG PRODUCTION AND RELEASE IN THE CRICKET TELEOGRYLLUS COMMODUS

The female Teleogryllus commodus Walker is sexually receptive throughout the adult life. Mated females lay on an average four to six times more eggs than virgin females owing to higher total egg production and the retention of fewer eggs in the oviducts. Early mating does not result in earlier oviposition, but causes, when it occurs at a later date, the release of stored eggs. The mating‐factor originates in the testes and is transferred to the female via the spermatophore.

The influence of Prostaglandin E2 on oviposition in Teleogryllus commodus

Mating as a prerequisite for oviposition has been documented in many insects (Engelmann, 1970; Labeyrie, 1970; Leopold, 1976). In orthoptera, secretions originating from the accessory glands have a stimulatory effect upon egg-release and fecundity in the acridids Melanoplus sanguinipes (Pickford et al., 1969) and Schistocerca gregaria (Leahy, 1973). On the other hand, in the cricket Teleogryllus commodus, a chemically unidentified mating factor from the testes, transferred with the spermatophore during the mating act, causes oviposition within 24 hr and has a stimulatory long-term effect upon oocyte growth (Loher & Edson, 1973). Recently, prostaglandin synthetase has been found in the testes of the house cricket, Acheta domesticus (Destephano et al., 1974, 1976). During mating, it is transferred with the spermatophore to the female, which lacks the enzyme, where it apparently converts arachidonic acid into prostaglandins, which in turn cause egg release (Destephano & Brady, 1977). Prostaglandins are well-known for their multiple regulatory effects in mammalian reproduction (Badr, 1975; Embrey, 1975). The discovery that prostaglandins occur in the gonads of the male housecricket and, in the female, stimulate egg deposition offers the interesting possibility that the mating factor of T. commodus might be an identical or similar compound, perhaps providing the basis not only for egg release as shown in the housecricket, but also for the increased fecundity observed in T. commodus.

Rôle of eyes, optic lobes, and pars intercerebralis in locomotory and stridulatory circadian rhythms of Teleogryllus commodus

Abstract Locomotory and stridulatory activity rhythms of male crickets ( Teleogryllus commodus ) were assayed simultaneously following various experimental procedures. These included (a) severing the pathways between the ocelli and the brain, between the ommatidia and the optic lobes, or between the optic lobes and the brain, and (b) RF cauterization of the pars intercerebralis. The results indicate that (1) light-dark cycles which entrain both rhythms are perceived by the compound eyes and not by the ocelli; (2) loss of connexion between the brain and the optic lobes leads to arrhythmicity in both behaviours, but a single optic lobe can maintain rhythmicity; (3) absence of neurosecretory cells in the pars intercerebralis is correlated with loss of stridulatory activity and arrhythmicity in locomotory behaviour. It is suggested that the pars intercerebralis serves as a site of coupling between a circadian pacemaker and various overt behaviours. However, intermediate control by the pars intercerebralis is assumed to be exerted via channels that can be either hormonal or purely neuronal in nature.

Arachidonic and other long-chain polyunsaturated fatty acids in spermatophores and spermathecae of Teleogryllus commodus: Significance in prostaglandin-mediated reproductive behaviour

Abstract Estimates of weights of fatty acids, especially arachidonic acid, in spermathecae from virgin and mated T. commodus indicate substantial elevation in all fatty acids and particularly arachidonic acid following mating. Analysis of spermatophore lipids suggests that this can be in part accounted for by the contents of one or several spermatophores. Fractionation of total lipids from spermatophores showed that arachidonic acid comprised 24% of phosphotidylcholine and 4% of phosphotidylethanolamine, but was not detected in neutral lipids whereas it was approximately equally distributed over phosphotidylcholine and phosphotidylethanolamine in lipids from spermathecae. These data indicate that in addition to prostaglandin synthetase, the spermatophore contains a physiologically significant quantity of prostaglandin precursor, arachidonic acid, esterified to phospholipid and presumably unavailable for enzymatic action during mating transfer. We also note that proportions of arachidonic acid in the phosphotidylcholine of spermatophores are the highest recorded for this fatty acid in the insect literature, which in conjunction with recent work emphasizes the likely physiological significance of long-chain polyunsaturated fatty acids in insects generally.

Circadian control of spermatophore formation in the cricket Teleogryllus commodus Walker

Abstract The cricket Teleogryllus commodus has a circadian rhythm in spermatophore formation. A spermatophore is present 1–5 hr before the onset of stridulation under LL, DD and LD 12 : 12; it is retained during the whole stridulatory phase and disposed of within a variable time after termination of singing. Overwhelmingly one spermatophore is produced during a 24 hr-period. Severance of the abdominal nerve cord or removal of the accessory glands prevent spermatophore formation, but does not inhibit periodical stridulation; when a spermatophore is removed from a singing male, stridulation continues after a short time. Coagulation of the pars intercerebralis stops spermatophore production and singing; severance of the optic lobes rends both processes arhythmical. The role of the pars intercerebralis as an intermediary link between the timing-device and the effector organs is discussed.

IDENTIFICATION OF THE JUVENILE HORMONE FROM THE CRICKET, TELEOGRYLLUS COMMODUS, AND JUVENILE HORMONE TITRE CHANGES

Abstract In the cricket, Teleogryllus commodus , eggs, haemolymph of 7th and 8th (last)-larval instars, and haemolymph of adults of both sexes contain only juvenile hormone III. While in the male the hormone titre is independent of previous mating experience, juvenile hormone concentration in haemolymph taken from females 36–38 hr after mating (an event which is followed by oviposition) is at a level 5 times higher than that of virgin females. Based on data gleaned from several research groups the identification of juvenile hormone III as the exclusive juvenile hormone in the Order Orthopteroidea is discussed.

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‐PGE2α, are the products of inactivating metabolism in mammalian systems, describing a fundamental difference in PG biochemistry with respect to mammals and insects.

Biosynthesis of polyunsaturated fatty acids by the australian field cricket, Teleogryllus commodus

Abstract Aspects of testicular fatty acid biochemistry from the Australian field cricket, Teleogryllus commodus, are reported. Over 10% of the phospholipid fatty acids were C20 polyunsaturated fatty acids (PUFAs), with nearly 6% arachidonic acid (20:4). The testes and ovaries accumulated a large proportion of label from radioactive arachidonic acid that was injected into the hemocoel (about 30%). Specificity in the uptake was shown by comparison to a similar study with labelled stearic acid, in which only 1.5% of the radioactivity was taken up by testes. Sixty percent of the radioactivity taken up by testes from [3H]20:4 was incorporated into phospholipids and 30% into triacylglycerols. Fat body of males and females incorporated 27% of the [3H]20:4 into phospholipids and 68% (males) or 55% (females) into triacylglcyerols. Radioactivity from [1-14C]acetate was incorporated into testicular linoleic acid and eicosatrienoic acid, but not eicosatetraenoic acid, suggesting the de novo biosynthesis of both 18:2 and a C20 PUFA by this species. Label from injected [U-14C]linoleic acid was recovered mostly as linoleic acid, with a small portion of the recovered radioactivity in eicosatrienoic acid, but not eicosatetraenoic acid. Very little label from injected linoleic acid occurred as monounsaturated or saturated fatty acids, indicating only slight, if any, β-oxidation of 18:2 to acetate and subsequent lipid synthesis.

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

Circadian control of singing in crickets: two different pacemakers for early-evening and before-dawn activity

Abstract (1) Under LD 12:12 and constant temperature, calling song patterns of the Australian Field Cricket Teleogryllus commodus were frequently divided into two more or less distinct activity components. The first began 1–3 h before the L D -transition and ended with the sudden lights-off, whereas the second was restricted mainly to the second half of the night. In subsequent continuous light (LL) the circadian activity pattern was usually a unimodal band. Its onset slope was always a continuation of the first onsets in the preceding LD-cycle. In those cases where shortly after the LD LL transition the rhythm split into two components, both corresponded to those in LD. (2) In “atypical” LD-aatterns only the second component appeared during the late night. In such cases, the onset slope of the subsequent free-running rhythm did not start at the preceding LD-entrained onsets, but was advanced by several hours. (3) In free-running rhythms the mean value of the onset slopes ( τ o = 25.1 ± 0.07 h ) did not differ significantly from that of the end slopes ( τ e = 25.0 ± 0.07 h ). However, in individual activity patterns, simultaneous differences in onset and end slopes of up to 0.7 h were found. τo- and τe-values recorded directly after the LD LL -transition did not correlate with the preceding phase angle difference between the entrained activity and the zeitgeber. (4) Under constant conditions after-effects such as spontaneous period changes and phase shifts in the slopes of activity onset and/or end occurred mainly between five and 20 days after the LD LL -transition . (5) Period changes and phase delays in the onset and end slopes were also found when crickets were exposed to low temperature pulses (2 ± 2°C, 2h duration). Following the cold treatment both period changes and phase shifts in the onset slope frequently differed from those in the end slope. (6) The results are consistent with a concept of two activity components controlled by weakly coupled circadian pacemakers. This is clearly evident in split rhythms but is also true for unimodal patterns. Normally the two components partly overlap and their existence is concealed in the undivided activity band. They are only revealed in unimodal patterns if individual oscillatory properties such as different period lengths or phase shifts appear in the onset or the end slope.