Sexual signaling and immune function in the black field cricket Teleogryllus commodus

The immunocompetence handicap hypothesis predicts that male sexual trait expression should be positively correlated with immunocompetence. Here we investigate if immune function in the cricket, Teleogryllus commodus, is related to specific individual components of male sexual signals, as well as to certain multivariate combinations of these components that females most strongly prefer. Male T. commodus produce both advertisement and courtship calls prior to mating. We measured fine-scale structural parameters of both call types and also recorded nightly advertisement calling effort. We then measured two standard indices of immune function: lysozyme-like activity of the haemolymph and haemocyte counts. We found a weak, positive relationship between advertisement calling effort and lysozyme-like activity. There was, however, little evidence that individual structural call components or the net multivariate attractiveness of either call type signalled immune function. The relationships between immunity and sexual signaling did not differ between inbred and outbred males. Our data suggest that it is unlikely that females assess overall male immune function using male calls.     

Sexual conflict and cryptic female choice in the black field cricket, Teleogryllus commodus

The prevalence and evolutionary consequences of cryptic female choice (CFC) remain highly controversial, not least because the processes underlying its expression are often concealed within the female reproductive tract. However, even when female discrimination is relatively easy to observe, as in numerous insect species with externally attached spermatophores, it is often difficult to demonstrate directional CFC for certain male phenotypes over others. Using a biological assay to separate male crickets into attractive or unattractive categories, we demonstrate that females strongly discriminate against unattractive males by removing their spermatophores before insemination can be completed. This results in significantly more sperm being transferred by attractive males than unattractive males. Males respond to CFC by mate guarding females after copulation, which increases the spermatophore retention of both attractive and unattractive males. Interestingly, unattractive males who suffered earlier interruption of sperm transfer benefited more from mate guarding, and they guarded females more vigilantly than attractive males. Our results suggest that postcopulatory mate guarding has evolved via sexual conflict over insemination times rather than through genetic benefits of biasing paternity toward vigorous males, as has been previously suggested.     

Effects of protease inhibitors and dietary protein level on the black field cricket Teleogryllus commodus

Growth and survival responses were determined for black field crickets Teleogryllus commodus (Walker) (Orthoptera: Gryllidae) on artificial diets containing a range of levels of dietary protein, and protease inhibitors (PI's) at 0.33% (weight volume, w:v). The effect on cricket gut enzyme activities of adding PI's to a high protein diet was measured. All PI's which had in vitro binding activity against either trypsin or elastase (the two major cricket gut endopeptidases) reduced growth, but those which bound to both enzymes had the greatest effect. None of the PI's acted as a source of nutritional protein. Cricket growth rate increased with the addition of casein up to 3% w:v, but not with a similar addition of wheatgerm. The impact of PI's on growth was greatest on a 1.5% casein diet. On a high protein (3% casein) diet, the gut activity of trypsin was increased by potato proteinase inhibitors 1 and 2 while the activity of elastase and leucine amino peptidase were increased by soybean trypsin inhibitor and potato proteinase inhibitor 2. Increasing dietary casein up to 3.3% improved cricket survival. The potential of PI's as plant resistance factors against crickets was confirmed.     

Contact chemoreceptive sex recognition in the male cricket, Teleogryllus commodus

ABSTRACT. A behavioural continuum ranging from extreme aggression to overt sexual behaviour was used to measure male crickets' reactions to being touched in a standardized manner on their antennae with freshly severed antennae of male and female conspecifics. Sexually receptive males responded primarily with the aggressive song to male antennae and with the courtship song to female antennae. The ontogeny of the antennal effectiveness and the males' reaction was also determined. Because the ability of the antennae to elicit a reaction could be eliminated by treating them with chloroform, and since there were no morphological differences between male and female antennae, separate male and female sex recognition pheromones must be implicated. The chemo-tactile nature of these substances is indicated by the inability to obtain either behavioural or EAG responses to air carrying the odour of males or females.     

No evidence for inbreeding avoidance through postcopulatory mechanisms in the black field cricket, Teleogryllus commodus

Several studies suggest that females mate multiply so that they can preferentially fertilize eggs with the sperm of genetically more compatible males. Unrelated males are expected to be genetically more compatible with a female than her close relatives. We tested whether black field crickets, Teleogryllus commodus, can bias sperm usage toward unrelated males by comparing egg hatching success of females mated to two of their siblings (SS), two sibling males unrelated to the female (NN) or to one unrelated male and a sibling male (NS or SN). Egg hatching success was highly repeatable. Hatching success varied significantly among females of the three mating types (P = 0.011, n = 245 females). The estimated mean hatching success of 36.8% for SS females was significantly less that the 43.4% of NN females, indicating an effect of inbreeding on hatching success. If females preferentially use the sperm of a less closely related male, the hatching success of NS/SN females should be closer to 43.4% than 36.8%. It was, in fact, only 34.9%. This does not differ significantly from the value expected if the two males contributed an equal amount of sperm that was then used randomly. Although polyandry may confer indirect genetic benefits, our results provide no evidence that female T. commodus gain these benefits by biasing paternity toward genetically more compatible males through postcopulatory mechanisms.     

Limited plasticity in the phenotypic variance‐covariance matrix for male advertisement calls in the black field cricket,Teleogryllus commodus

Phenotypic integration and plasticity are central to our understanding of how complex phenotypic traits evolve. Evolutionary change in complex quantitative traits can be predicted using the multivariate breeders’ equation, but such predictions are only accurate if the matrices involved are stable over evolutionary time. Recent study, however, suggests that these matrices are temporally plastic, spatially variable and themselves evolvable. The data available on phenotypic variance‐covariance matrix ( P ) stability are sparse, and largely focused on morphological traits. Here, we compared P for the structure of the complex sexual advertisement call of six divergent allopatric populations of the Australian black field cricket, Teleogryllus commodus. We measured a subset of calls from wild‐caught crickets from each of the populations and then a second subset after rearing crickets under common‐garden conditions for three generations. In a second experiment, crickets from each population were reared in the laboratory on high‐ and low‐nutrient diets and their calls recorded. In both experiments, we estimated P for call traits and used multiple methods to compare them statistically (Flury hierarchy, geometric subspace comparisons and random skewers). Despite considerable variation in means and variances of individual call traits, the structure of P was largely conserved among populations, across generations and between our rearing diets. Our finding that P remains largely stable, among populations and between environmental conditions, suggests that selection has preserved the structure of call traits in order that they can function as an integrated unit.     

Esterases in relation to embryonic diapause in the field cricket,Teleogryllus commodus

Fourteen esterase isozymes were detected by polyacrylamide gel electrophoresis in homogenates of eggs of the field cricket Teleogryllus commodus, at various stages of development. One esterase isozyme appeared during embryonic diapause termination effected by prolonged chilling of the eggs.Esterase activity towards methyl butyrate in T. commodus egg homogenates increased with time. Sonication generated the maximum levels of esterase activity observed. Methyl butyrate esterase activity in T. commodus eggs was high during the first few days of embryogenesis; fell markedly during the period of rapid water uptake, and then remained fairly constant during diapause, diapause development, and during resumed embryogenesis.     

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     

Inbreeding and courtship calling in the cricket Teleogryllus commodus

Male field crickets produce two acoustic signals for mating: advertisement calls and courtship calls. While the importance of advertisement calling in mate attraction is well understood, the function of courtship calling is less clear. Here, we tested if the courtship call of male crickets Teleogryllus commodus signals aspects of male quality by comparing the calls of inbred and outbred males. We examined the effect of one generation of full sibling mating on fine‐scale call structure, along with several life history traits. Inbreeding reduced nymph survival but had no significant effect on weight or development time. Inbreeding resulted in a small but significant change in two of the six call parameters measured. We then tested if inbreeding affects call trait combinations that are important to females by using the results of a previous selection analysis to compare the multivariate attractiveness of the calls of inbred and outbred males. There was no difference. We conclude that the courtship call of T. commodus is not a reliable signal of aspects of male quality that are affected by inbreeding (which generally reduces fitness‐enhancing traits). It might, however, signal components of male fitness that are not affected by changes in heterozygosity.     

Dim artificial light at night reduces the cellular immune response of the black field cricket,Teleogryllus commodus

A functioning immune system is crucial for protection against disease and illness, yet increasing evidence suggests that species living in urban areas could be suffering from immune suppression, due to the presence of artificial light at night (ALAN). This study examined the effects of ecologically relevant levels of ALAN on three key measures of immune function (haemocyte concentration, lytic activity, and phenoloxidase activity) using a model invertebrate species, the Australian black field cricket, Teleogryllus commodus. We reared crickets under an ecologically relevant daily light‐cycle consisting of 12 hr bright daylight (2600 lx) followed by either 12 h darkness (0 lx) or dim environmentally relevant ALAN (1, 10, 100 lx), and then assessed immune function at multiple time points throughout adult life using haemolymph samples. We found that the presence of ALAN had a clear negative effect on haemocytes, while the effects on lytic activity and phenoloxidase activity were more complex or largely unaffected by ALAN. Furthermore, the effects of lifelong exposure to ALAN of 1 lx were comparable to those of 10 and 100 lx. Our data suggest that the effects of ALAN could be large and widespread, and such reductions in the core immune response of individuals will likely have greater consequences for fitness and survival under more malign conditions, such as those of the natural environment.     

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.     

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

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.     

De novo biosynthesis of prostaglandins by the Australian field cricket, Teleogryllus commodus

The accumulation and metabolism of certain polyunsaturated fatty acids by testes from the Australian field cricket, Teleogryllus commodus, are described. Testes accumulated a substantial proportion (about 16%) of label from radioactive C20:3n6 that was injected into the haemocoel. Fifty percent of the label accumulated by testes was associated with the phospholipid fraction, whereas in the remainder of the body 30% was incorporated into the phospholipid fraction. Prostaglandins (PG) E1, E2 and F2 alpha were quantified in extracts of the testes of adult insects by radioimmunoassay. Label from injected radioactive C18:2n6, C20:3n6 and C20:4n6 was recovered as prostaglandins PGE and PGF. The radioactivity from C18:2n6 that was recovered as PGE1 and PGF1 alpha indicated elongation/desaturation to C20:3n6 followed by conversion to PG. Since C18:2n6 is readily formed from acetate in T. commodus, these findings indicate the de novo biosynthesis of C20 polyunsaturated fatty acids and prostaglandins by this species.     

Microsatellite loci for the Australian field cricket Teleogryllus oceanicus and their cross‐utility in Teleogryllus commodus

Microsatellite loci were isolated from the Australian field cricket Teleogryllus oceanicus. Seven polymorphic loci were found with an observed number of alleles ranging from eight to 17 and observed heterozygosities between 0.26 and 0.94. One locus was found to be X‐linked. These seven loci were also tested for amplification and polymorphism in the congeneric species Teleogryllus commodus. The loci will be used for paternity studies in these species.     

Circadian control of spermatophore formation in the cricket Teleogryllus commodus Walker

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 rôle of the pars intercerebralis as an intermediary link between the timing-device and the effector organs is discussed.     

Ultrastructural changes to the midgut of the black field cricket (Teleogryllus commodus) following ingestion of potato protease inhibitor II

Ultrastructural changes to the midgut epithelium of nymphs of the black field cricket (Teleogryllus commodus) after ingestion of potato protease inhibitor II (PPI-II) (0.6% (w/v) in artificial diet) were determined by light and electron microscopy. Crickets fed diet containing PPI-II grew more slowly than those fed control diet and changes observed to the PPI-II-fed nymphs included reduction of midgut wall depth, vacuolisation of the epithelial cells, swelling of the microvilli, cellular protrusions into the midgut and eventual rupture of individual or small groups of epithelial cells. These changes were first seen 2 days after PPI-II ingestion. Complete disintegration of the midgut to the basement membrane was not seen during the 27-day observation period and repair and regeneration of pockets of epithelial cells was observed. Immunocytochemistry revealed that PPI-II was localised within the ectoperitrophic matrix space of the gut. The location of the peritrophic matrix was determined by labelling with wheat germ agglutinin (WGA), but no rupture of this structure was observed in PPI-II-fed nymphs.     

温度对蟋蟀若虫生长发育的影响

澳洲黑蟋蟀Teleogryllus commodusWalker若虫在22℃下,有9个龄期,在28℃下,只有8个龄期。若虫在22℃和28℃的平均历期分别是159d和79d,并且若虫胸部和腹部相对于头部的生长速率在低温条件下均小于高温条件下的若虫。     

Sexual selection on cuticular hydrocarbons in the Australian field cricket, Teleogryllus oceanicus

Background  

Females in a wide range of taxa have been shown to base their choice of mates on pheromone signals. However, little research has focussed specifically on the form and intensity of selection that mate choice imposes on the pheromone signal. Using multivariate selection analysis, we characterise directly the form and intensity of sexual selection acting on cuticular hydrocarbons, chemical compounds widely used in the selection of mates in insects. Using the Australian field cricket Teleogryllus oceanicus as a model organism, we use three measures of male attractiveness to estimate fitness; mating success, the duration of courtship required to elicit copulation, and subsequent spermatophore attachment duration.