Crickets in space

"Crickets in Space" (CRISP) was a Neurolab experiment by which the balance between genetic programs and the gravitational environment for the development of a gravity sensitive neuronal system was studied. The model character of crickets was justified by their external gravity receptors, identified position-sensitive interneurons (PSI) and gravity-related compensatory head response, and by the specific relation of this behavior to neuronal activation systems. These advantages allowed us to study the impact of modified gravity on cellular processes in a complex organism. Eggs, 1st, 4th and 6th stage larvae of Acheta domesticus were used. Post-flight experiments revealed a low susceptibility of the behavior to microgravity and hypergravity (hg) while the physiology of the PSI was significantly affected. Immunocytological investigations revealed a stage-dependent sensitivity of thoracic GABAergic motoneurons to 3g-conditions concerning their soma sizes but not their topographical arrangement. Peptidergic neurons from cerebral sensorimotor centers revealed no significant modifications by microgravity. The contrary physiological and behavioral results indicate a facilitation of 1g-readaptation by accessory gravity. proprioceptive and visual sense organs. Absence of anatomical modifications point to an effective time window of microgravity or hg-exposure related to the period of neuronal proliferation. Grant numbers: 50WB9553-7.

Effect of a single cold stress exposure on the reproductive behavior of male crickets

Cold stress is an important abiotic factor that can impact insect physiology, behavior, and overall fitness. Upon exposure to cold temperature, many insects enter a reversible state of immobility called chill coma. If the cold stress is brief and mild enough, insects can recover and regain full mobility upon return to warmer temperatures. However, the long-term impact of sublethal cold stress on insect behavior has been understudied. Here, sexually naïve adult male Acheta domesticus crickets were exposed to a single 0 °C cold stress for 6 h. One week later, the ability of these males to mate with a female was examined. For mating trials, a cold stressed male cricket was paired with a non-cold stressed, control female. Control pairs were comprised of a non-cold stressed control male and control female. Cold exposed males were less successful at mating than control males because most did not carry a spermatophore at the time of their mating trials. However, when these cold stressed males were allowed 1 h of chemosensory contact with a female, most produced a spermatophore. Males that produced spermatophores were given the opportunity to mate once with a female, and stressed males that successfully mated sired as many offspring as did control males. However, our results support that a single cold stress exposure can negatively impact the reproductive fitness of male crickets since it reduced their capacity to carry spermatophores and, as a consequence, to attract females.

Lipogenesis in a wing-polymorphic cricket: Canalization versus morph-specific plasticity as a function of nutritional heterogeneity

The influence of variable nutritional input on life history adaptation is a central, but incompletely understood aspect of life history physiology. The wing-polymorphic cricket, Gryllus firmus, has been extensively studied with respect to the biochemical basis of life history adaptation, in particular, modification of lipid metabolism that underlies the enhanced accumulation of lipid flight fuel in the dispersing morph [LW(f)=long wings with functional flight muscles] relative to the flightless (SW=short-winged) morph. To date, biochemical studies have been undertaken almost exclusively using a single laboratory diet. Thus, the extent to which nutritional heterogeneity, likely experienced in the field, influences this key morph adaptation is unknown. We used the experimental approach of the Geometric Framework for Nutrition and employed 13 diets that differed in the amounts and ratios of protein and carbohydrate to assess how nutrient amount and balance affects morph-specific lipid biosynthesis. Greater lipid biosynthesis and allocation to the soma in the LW(f) compared with the SW morph (1) occurred across the entire protein-carbohydrate landscape and (2) is likely an important contributor to elevated somatic lipid in the LW(f) morph across the entire protein-carbohydrate landscape. Nevertheless, dietary carbohydrate strongly affected lipid biosynthesis in a morph-specific manner (to a greater degree in the LW(f) morph). Lipogenesis in the SW morph may be constrained due to its more limited lipid storage capacity compared to the LW(f) morph. Elevated activity of NADP⁺-isocitrate dehydrogenase (NADP⁺-IDH), an enzyme that produces reducing equivalents for lipid biosynthesis, was correlated with and may be an important cause of the increased lipogenesis in the LW(f) morph across most, but not all regions of the protein-carbohydrate landscape. By contrast, ATP-citrate lyase (ACL), an enzyme that catalyzes the first step in the pathway of fatty acid biosynthesis, showed complex morph-specific patterns of activity that were strongly contingent upon diet. Morph-specific patterns of NADP⁺-IDH and ACL activities across the nutrient landscape were much more complex than expected from previous studies on a single diet. Collectively, our results indicate that the biochemical basis of an important life history adaptation, morph-specific lipogenesis, can be canalized in the face of substantial nutritional heterogeneity. However, in some regions of the protein-carbohydrate landscape, it is strongly modulated in a morph-specific manner.

Pyrethroid residue dynamics in insects depends on the circadian clock

Many factors may affect pesticide effectiveness against pests. One of the factors that should be considered is circadian rhythmicity. In this study, we evaluated daily variations in pyrethroid susceptibility in the house cricket, Acheta domesticus L. Crickets were exposed to a standard dose of ß-cyfluthrin at different times of a day, and pesticide residue levels were evaluated using gas chromatography. Results demonstrate that the time of pyrethroid disappearance is correlated with the circadian clock, with the highest decomposition rate at night. Furthermore, crickets also showed the highest resistance to the insecticide at night, expressed as a high survival rate. Moreover, ß-cyfluthrin induced significant changes in thermal preferences of intoxicated crickets. This is the first report showing that pyrethroid residue levels in the crickets' body depend on its circadian clock.

Measuring the Efficiency of Sound Production

Sound production efficiency is a complex phenotypic trait that incorporates biochemical and mechanical events beginning with substrate oxidation and ending with the radiation of sound. Its accurate measurement is significant in understanding the mechanisms and energetics underlying acoustic signaling and sexual selection. I show that in the short-tailed cricket Anurogryllus arboreus Walker, acoustic performance is apparently the same in acoustic free fields and in the reverberant conditions of a respirometry chamber. I present three methods for simultaneous and nearly simultaneous determination of calling metabolic rate and acoustic power output. The new methods yielded metabolic rates 3%-6% lower than matched controls using traditional flow-through respirometry (mean=8.1 mW); however, none of theses differences were statistically significant. I also evaluate four methods for determining the efficiency of sound production. The means of an individual's efficiencies calculated using these methods vary between 0.50% and 0.60%, with no statistically significant differences between the methods. I conclude with a critical evaluation of these techniques.

Biologically inspired coupled antenna beampattern design

We propose to design a small-size transmission-coupled antenna array, and corresponding radiation pattern, having high performance inspired by the female Ormia ochracea's coupled ears. For reproduction purposes, the female Ormia is able to locate male crickets' call accurately despite the small distance between its ears compared with the incoming wavelength. This phenomenon has been explained by the mechanical coupling between the Ormia's ears, which has been modeled by a pair of differential equations. In this paper, we first solve these differential equations governing the Ormia ochracea's ear response, and convert the response to the pre-specified radio frequencies. We then apply the converted response of the biological coupling in the array factor of a uniform linear array composed of finite-length dipole antennas, and also include the undesired electromagnetic coupling due to the proximity of the elements. Moreover, we propose an algorithm to optimally choose the biologically inspired coupling for maximum array performance. In our numerical examples, we compute the radiation intensity of the designed system for binomial and uniform ordinary end-fire arrays, and demonstrate the improvement in the half-power beamwidth, sidelobe suppression and directivity of the radiation pattern due to the biologically inspired coupling.

Sex-specific interactions of microbial symbioses on cricket dietary selection

The nutrients found in prey and nonprey foods, and relative digestibility of these foods, has a major influence on diet selection by omnivorous insects. Many insects have developed symbiotic relationships with gut bacteria to help with extracting nutrition from nonprey diets. Gryllus pennsylvanicus (Burmeister) (Orthoptera: Gryllidae) was assigned to one of two treatment groups, antibiotic-treated and nonantibiotic-treated, and consumption of seeds (nonprey) and eggs (prey) were measured. Male crickets administered antibiotics consumed more seeds and greater seed weight, while antibiotic-fed female crickets consumed fewer seeds and less seed weight, relative to the untreated male and female crickets, respectively. Both male and female antibiotic-treated crickets consumed similar weight of eggs as nonantibiotic-treated male and female crickets, respectively. These results provide evidence that gut symbionts influence diet selection of male and female G. pennsylvanicus differently. This sex-specific dietary selection may be because of the fact that male and female crickets have different nutritional requirements.

Comparative Analyses of Phenotypic Sequences Using Phylogenetic Trees

Phenotypic sequences are a type of multivariate trait organized structurally, such as teeth distributed along the dental arch, or temporally, such as the stages of an ontogenetic series. Unlike other multivariate traits, the elements of a phenotypic sequence are distributed along an ordered set, which allows for distinct evolutionary patterns between neighboring and distant positions. In fact, sequence traits share many characteristics with molecular sequences, although important distinctions pose challenges to current comparative methods. We implement an approach to estimate rates of trait evolution that explicitly incorporates the sequence organization of traits. We apply models to study the temporal pattern evolution of cricket calling songs. We test whether neighboring positions along a phenotypic sequence have correlated rates of evolution or whether rate variation is independent of sequence position. Our results show that cricket song evolution is strongly autocorrelated and that models perform well when used with sequence phenotypes even under small sample sizes. Our approach is flexible and can be applied to any multivariate trait with discrete units organized in a sequence-like structure.

Condition-Dependent Mutual Mate Preference and Intersexual Genetic Correlations for Mating Activity

Although mating represents a mutual interaction, the study of mate preferences has long focused on choice in one sex and preferred traits in the other. This has certainly been the case in the study of the costs and condition-dependent expression of mating preferences, with the majority of studies concerning female preference. The condition dependence and genetic architecture of mutual mate preferences remain largely unstudied, despite their likely relevance for the evolution of preferences and of mating behavior more generally. Here we measured (a) male and female mate preferences and (b) intersexual genetic correlations for the mating activity in pedigreed populations of southern field crickets (Gryllus bimaculatus) raised on a favorable (free-choice) or a stressful (protein-deprived) diet. In the favorable dietary environment, mutual mate preferences were strong, and the intersexual genetic covariance for mating activity was not different from one. However, in the stressful dietary environment, mutual mate preferences were weak, and the intersexual genetic covariance for mating activity was significantly smaller than one. Altogether, our results show that diet environments affect the expression of genetic variation in mating behaviors: when the environment is stressful, both (a) the strength of mutual mate preference and (b) intersexual genetic covariance for mating activity tend to be weaker. This implies that mating dynamics strongly vary across environments.

Chronic immune challenge is detrimental to female survival, feeding behavior, and reproduction in the field cricket Gryllus assimilis (Fabricius, 1775)

Physiological trade-offs among expensive fitness-related traits, such as reproduction and immunity, are common in life histories of animals. An immune challenge can have different effects on female reproduction mediated by resource allocation and acquisition. In this study, employing a widely used method to challenge the insect immune system (nylon implant), we assessed the effects of mounting a chronic immune response simulating three successive immune assaults on survival and reproduction of mated females of Gryllus assimilis. We also verified feeding behavior following an implantation, which can be important in explaining trade-off dynamics in terms of energy acquisition. For this, three experimental groups were designed (Control, Sham, and Implant) with oviposition rates, egg morphometry, and nymph vigour observed over 3 weeks, at which ovarian mass and unlaid eggs were quantified from remaining individuals. The results showed that chronic implants were detrimental to female survival and reproduction throughout the experiments; Surgical Sham had no effect on survival compared to the control, but did on reproductive aspects such as oviposition rates and hatchling vigour. These negative effects on reproduction in Sham disappeared in the last experimental week, but still strong in the implanted females. Such immune challenge affected the feeding behavior of implanted females by reducing food consumption compared to control after infection, which is probably explained by illness-induced anorexia that takes place to maximize the immune system performance as a part of sickness behavior, exacerbating the adverse effects observed on reproduction (i.e., fewer and smaller eggs, and low vigour of nymphs) and survival.

Response properties of wind-sensitive giant interneurons in the fourth-instar nymphs of the cricket, Gryllus bimaculatus

The response properties of four wind-sensitive giant interneurons (GIs) 8-1, 9-1, 9-2 and 9-3 in the fourth-instar nymphs of the cricket Gryllus bimaculatus were investigated to clarify the differences and/or similarities of the escape eliciting neural system between nymphs and adults. Air current was presented to the animal from 12 different directions in the horizontal plane, and the intensity-response curves for each GI were obtained at each stimulus direction. The intensity-response curves showed that the response magnitudes of GI 8-1 in the fourth-instar crickets increased with stimulus velocity up to 300 mm/s regardless of the stimulus direction. The response magnitudes of GI 9-1 in the nymphs reached a plateau at a stimulus velocity of 30 mm/s in most stimulus directions. The response magnitudes of GIs 9-2 and 9-3 increased with stimulus velocity up to 300 mm/s regardless of the stimulus direction. The directional sensitivity curves plotted on the basis of threshold velocities revealed that the preferential directions of the GIs were the ipsilateral-side in GI 8-1, the ipsilateral-front and contralateral-rear in GI 9-1, the ipsilateral-rear in GI 9-2 and the ipsilateral-front in GI 9-3, designated with respect to the side of the ventral nerve cord containing the axons. Although the GIs in nymphs occasionally showed higher threshold velocities and larger response magnitudes, the directional sensitivities, i.e., the preferred directions, of the GIs were basically the same with those of adults.

Immune Priming, Fat Reserves, Muscle Mass and Body Weight of the House Cricket is Affected by Diet Composition

Some insect species are capable of producing an enhanced immune response after a first pathogenic encounter, a process called immune priming. However, whether and how such ability is driven by particular diet components (protein/carbohydrate) have not been explored. Such questions are sound given that, in general, immune response is dietary dependent. We have used adults of the house cricket Acheta domesticus L. (Orthoptera: Gryllidae) and exposed them to the bacteria Serratia marcescens. We first addressed whether survival rate after priming and nonpriming treatments is dietary dependent based on access/no access to proteins and carbohydrates. Second, we investigated how these dietary components affected fat reserves, muscle mass, and body weight, three key traits in insect fitness. Thus, we exposed adult house crickets to either a protein or a carbohydrate diet and measured the three traits. After being provided with protein, primed animals survived longer compared to the other diet treatments. Interestingly, this effect was also sex dependent with primed males having a higher survival than primed females when protein was supplemented. For the second experiment, protein-fed animals had more fat, muscle mass, and body weight than carbohydrate-fed animals. Although we are not aware of the immune component underlying immune priming, our results suggest that its energetic demand for its functioning and/or consequent survival requires a higher demand of protein with respect to carbohydrate. Thus, protein shortage can impair key survival-related traits related to immune and energetic condition. Further studies varying nutrient ratios should verify our results.

Comparison of the physiology of the auditory receptor organs in Gryllus bimaculatus and Ephippiger ephippiger: CSD recordings within the auditory neuropiles

The syllables of the song of the tettigoniid Ephippiger ephippiger consist of a series of short sound impulses with a broad-banded frequency spectrum. Syllables of the song of the gryllid species Gryllus bimaculatus are nearly pure tones with sharply tuned frequency maxima. A comparison of the physiology of the auditory receptor organs of both species was carried out by using acoustical stimuli with different carrier frequencies and time-amplitude patterns. The neuronal ensemble activity of receptor cell groups of the tympanal organ was measured within the prothoracic ganglion using the CSD technique. In E. ephippiger, response maxima were found at carrier frequencies mirroring the broad frequency content of the conspecific song. The receptor cells of E. ephippiger are highly sensitive to transient sound impulses. In G. bimaculatus, the receptor cell population is more sharply tuned to the basic frequencies of the natural songs; pure tones represent more effective stimuli than transient sound signals. The causes for these species-specific differences are discussed with regard to probable adaptations of the receptor organs to the parameters of the conspecific songs.

Effects of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) metabolites on cricket (Acheta domesticus) survival and reproductive success

The effect of two major hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) metabolites, hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX), on cricket (Acheta domesticus) survival and reproduction was studied. RDX metabolites did not have adverse effects on cricket survival, growth, and egg production. However, MNX and TNX did affect egg hatching. MNX and TNX were more toxic in spiked-sand than in topical tests. TNX was more toxic to egg than MNX. Developmental stage and exposure time affected hatching. After 30 days exposure to MNX or TNX, the EC20, EC50, and EC95 were 47, 128, and 247 microg/g for TNX, and 65, 140, and 253 microg/g for MNX in topical tests. The ECs for 20, 50, and 95 were 21, 52, and 99 microg/g for MNX, and 12, 48, and 97 microg/g for TNX in sand. No gross abnormalities in cricket nypmhs were observed in all experiments indicating that neither TNX or MNX is teratogenic in this assay.

Roles of neural communication between the brain and thoracic ganglia in the selection and regulation of the cricket escape behavior

To survive a predator's attack, prey animals must exhibit escape responses that are appropriately regulated in terms of their moving speed, distance, and direction. Insect locomotion is considered to be controlled by an interaction between the brain, which is involved in behavioral decision-making, and the thoracic ganglia (TG), which are primary motor centers. However, it remains unknown which descending and ascending signals between these neural centers are involved in the regulation of the escape behavior. We addressed the distinct roles of the brain and TG in the wind-elicited escape behavior of crickets by assessing the effects of partial ablation of the intersegmental communications on escape responses. We unilaterally cut the ventral nerve cord (VNC) at different locations, between the brain and TG, or between the TG and terminal abdominal ganglion (TAG), a primary sensory center of the cercal system. The partial ablation of ascending signals to the brain greatly reduced the jumping response rather than running, indicating that sensory information processing in the brain is essential for the choice of escape responses. The ablation of descending signals from the brain to the TG impaired locomotor performance and directional control of the escape responses, suggesting that locomotion in the escape behavior largely depends on the descending signals from the brain. Finally, the extracellular recording from the cervical VNC indicated a difference in the descending activities preceding the escape responses between running and jumping. Our results demonstrated that the brain sends the descending signals encoding the behavioral choice and locomotor regulation to the TG, while the TG seem to have other specific roles, such as in the preparation of escape movement.

Impacts of ionization radiation on the cuticular hydrocarbon profile and mating success of male house crickets (Acheta domesticus)

PURPOSE

Ionizing radiation is well known to have drastic impacts on major life history features including survivorship, growth, fertility, and longevity. What is much less appreciated is how radiation stress can cause changes to more subtle traits, such as those associated with sexual signaling, an underappreciated but vital aspect of insect reproduction. In the House Cricket (Acheta domesticus) cuticular hydrocarbons are vital for sex and species recognition, as well as a possible indicator of stress, making them crucial for successful mating and reproduction.

MATERIALS AND METHODS

Here, we analyze the impacts of ionizing radiation on the cuticular hydrocarbons of male crickets and its subsequent impacts on mating success. We exposed juvenile (14-day, 4th instar) male crickets to a broad range of radiation doses (2 Gy - 2 Gy).

RESULTS

We detected significant changes in individual cuticular hydrocarbons across a broad range of doses in mature male crickets using gas-liquid chromatography. Specifically, dose was identified as a significant contributing factor to hydrocarbon increases p < .0001. Mating success was significantly reduced in 12 Gy (p < .0001), 10 Gy (0.0001), and 7 Gy (0.0060) groups compared to non-irradiated controls.

CONCLUSION

Insect chemical communication can be species specific, and functionally specialized. Here, we show that radiation can alter the chemical signals used to attract mates in a large bodied insect and this may be a contributing factor to the described reduction in male mating success. Further research should be conducted to further analyze the various modes of communication employed by male crickets to attract mates i.e. acoustic signaling, and how this may also contribute to the reduction in mating success seen in irradiated males.

Estimating the effect of tracking tag weight on insect movement using video analysis: A case study with a flightless orthopteran

In this study, we describe an inexpensive and rapid method of using video analysis and identity tracking to measure the effects of tag weight on insect movement. In a laboratory experiment, we assessed the tag weight and associated context-dependent effects on movement, choosing temperature as a factor known to affect insect movement and behavior. We recorded the movements of groups of flightless adult crickets Gryllus locorojo (Orthoptera:Gryllidae) as affected by no tag (control); by light, medium, or heavy tags (198.7, 549.2, and 758.6 mg, respectively); and by low, intermediate, or high temperatures (19.5, 24.0, and 28.3°C, respectively). Each individual in each group was weighed before recording and was recorded for 3 consecutive days. The mean (± SD) tag mass expressed as a percentage of body mass before the first recording was 26.8 ± 3.7% with light tags, 72 ± 11.2% with medium tags, and 101.9 ± 13.5% with heavy tags. We found that the influence of tag weight strongly depended on temperature, and that the negative effects on movement generally increased with tag weight. At the low temperature, nearly all movement properties were negatively influenced. At the intermediate and high temperatures, the light and medium tags did not affect any of the movement properties. The continuous 3-day tag load reduced the average movement speed only for crickets with heavy tags. Based on our results, we recommend that researchers consider or investigate the possible effects of tags before conducting any experiment with tags in order to avoid obtaining biased results.

Evolution: lending a helping hand in sperm competition?

Most females mate with many males. This can be costly, but the benefits to females are often unclear. A new study raises the possibility that females could benefit through an unconventional genetic pathway, while also showing that males can inadvertently increase rival males' fitness in surprising ways.

Tolerant pattern recognition: evidence from phonotactic responses in the cricket Gryllus bimaculatus (de Geer)

When the amplitude modulation of species-specific acoustic signals is distorted in the transmission channel, signals become difficult to recognize by the receiver. Tolerant auditory pattern recognition systems, which after having perceived the correct species-specific signal transiently broaden their acceptance of signals, would be advantageous for animals as an adaptation to the constraints of the environment. Using a well-studied cricket species, Gryllus bimaculatus, we analysed tolerance in auditory steering responses to 'Odd' chirps, mimicking a signal distorted by the transmission channel, and control 'Silent' chirps by employing a fine-scale open-loop trackball system. Odd chirps on their own did not elicit a phonotactic response. However, when inserted into a calling song pattern with attractive Normal chirps, the females' phonotactic response toward these patterns was significantly larger than to patterns with Silent chirps. Moreover, females actively steered toward Odd chirps when these were presented within a sequence of attractive chirps. Our results suggest that crickets employ a tolerant pattern recognition system that, once activated, transiently allows responses to distorted sound patterns, as long as sufficient natural chirps are present. As pattern recognition modulates how crickets process non-attractive acoustic signals, the finding is also relevant for the interpretation of two-choice behavioural experiments.

Wing movements underlying sound production in calling, rivalry, and courtship songs of the cricket Gryllus bimaculatus (DeGeer)

We recorded the wing movements and sound signals during the production of calling, rivalry, and courtship song in the bispotted field cricket Gryllus bimaculatus. Recordings confirm that salient sound pulses during calling and rivalry song are generated during the closing movements of the wings. Wing movements for calling and rivalry song start from an elevated wing position and are performed with a very similar opening-closing movement, indicating that both types of songs may be generated by the same neuronal network. Wing movements for courtship song start from a low wing position; rapid closing movements generate high-frequency ticks and low-amplitude wing oscillations lead to low-amplitude pulses, generated during the opening and closing movements with a carrier frequency corresponding to the calling song. The two types of wing movements underlying courtship song indicate a different motor control as compared to calling song and may represent an early evolutionary phenotype.

Variations in fuel use in the flight muscles of wing-dimorphic Gryllus firmus and implications for morph-specific dispersal

Although a considerable amount of information is available on tradeoffs in wing-polymorphic insects, only limited data are available on the relationship between flight and biochemical variation within species. In the current study, we compared the biochemical basis in the dorsolongitudinal flight muscle of the wing-dimorphic sand cricket, Gryllus firmus Scudder, with respect to tradeoffs in energy resources related to morph-specific flight, including glycogen, trehalose, and triglycerides. Our results show that levels of glycogen and trehalose in long-winged adults (LW[f]) were significantly higher before dispersal, on days 5 and 7. Considering that this is the period during which long-winged adults are flight-capable, these results suggest that both glycogen and trehalose are important to flight. However, levels of triglycerides in short-winged crickets (SW) were higher than in long-winged crickets, suggesting that triglycerides are not directly related to initial flight. In SW adults, triglyceride content on days 5 and 7 was significantly higher just before lights off than at the same time on day 1 or at any other time after lights on all other days. This suggests that triglycerides are probably related to reproductive behaviors, such as mating and oviposition, in the SW morph. In addition, flight muscle water content was significantly lower in the LW(f) morph than in the SW morph.

Fourier and electrophysiological analyses of acoustic communication in Acheta domesticus

Waveform and spectral analysis were made on the call song of the cricket, Acheta domesticus.Sounds produced by unrestrained male crickets were led directly to a computer where discrete Fourier transforms were performed on selected segments of the call song. The findings revealed essentially pure tone carrier frequencies which result from the rate at which the individual teeth of the pars stridens are struck by the plectrum. An electrophysiologically determined audiogram showed good agreement with the dominant frequency of the call song, but was less sensitive and more broadly tuned than hearing curves of most field-crickets.

Fluid-phase endocytosis does not contribute to rapid fluid secretion in the malpighian tubules of the house cricket, Acheta domesticus

When the Malpighian tubules (Mt) of the house cricket (Acheta domesticus) are treated with dibutyryl adenosine 3', 5'-cyclic monophosphate (db-cAMP; 1 mM), which causes a doubling in secretion rate, more than 50% of the cell volume is occupied by vesicles within 420 sec of exposure. In view of the fact that the increase in vesiculation occurs concomitantly with stimulated fluid transport, we set out to determine whether the vesicles are formed as a result of fluid-phase endocytosis (pinocytosis) and subsequently used to transport fluid to the lumen as one means of increasing transport rate. We used fluorescent fluid-phase markers (Lucifer Yellow Carbohydrazide [LYCH] and Alexa 488 hydrazide) and an electron dense marker (cationized ferritin) to elucidate the degree of endocytosis that occurred with db-cAMP stimulation. We found that, although some fluid is taken into the cells of the mid-tubule via endocytosis, it does not coincide with the level of vacuolation present in stimulated tubules. The amount of LYCH transported into the primary urine by the db-cAMP-stimulated Mt decreased by 40% as compared to the unstimulated transport, and the rate of transport of LYCH was only 30% of the unstimulated tubules. In summary, our findings do not support the theory that the majority of the vesicles or vacuoles comprise intracellular, endocytotic compartments formed via a basolateral endocytotic pathway. We also found no evidence to support the functioning of vesicles or vacuoles as transcellular "shuttling" mechanisms to move fluid from the basal region to the apical membrane and into the lumen.