Relation of blood composition to age in the larval female house cricket, Acheta domesticus

The blood volume, osmolality, and sugar concentration increase; the blood protein and lipid concentration decrease; and the blood ions and NPS concentration do not change during apolysis from the 7th to 8th instar of larval Acheta domesticus. The patterns of change in all blood constituents are basically identical in both of the last two larval instars. Blood volume increase is directly related to growth, but not directly to total body water. Blood protein concentration increases in exact relation to growth, resulting in a doubling of concentration by midinstar and a small decrease over the last 2 to 3 days. The concentration of clottable protein remains constant; the soluble protein concentration increase probably providing cuticular proteins prior to and following ecdysis. Blood lipid concentration increases steadily throughout both instars, even during the non-feeding phase. Total blood carbohydrate concentration decreases greatly in the first 2 days of an instar, then remains relatively constant for the remainder of the instar. Blood trehalose concentration is 85% of the total carbohydrate concentration throughout the instar, but drops to 65% with a corresponding increase in ‘other sugars’ with the onset of apolysis on the last day. Growth demands probably exceed dietary supply of amino acids resulting in a 50% decrease in NPS concentration in the first half of the instar, then NPS concentration increases in spite of a declining feeding rate because growth demands cease. Within the normal blood ion lability range, the principle blood ions, sodium and chloride, vary in an inverse proportion to NPS and sugar concentration at least in the first two-thirds of the instar. Thus blood osmolality is constant except for an unexplained drop in the last 2 days of an instar.     

Immune investment impairs growth, female reproduction and survival in the house cricket, Acheta domesticus

We investigated whether an immune response is associated with growth, female reproduction and survival costs in the house cricket. Using different intensities of challenge immune (implantation of one piece of nylon (1N) and two nylons (2N), with their respective sham-challenge and control groups) with body size and exoskeleton thickness as response variables, growth costs were determined for both sexes. A similar methodology was followed for reproduction costs, in which egg number and size, and female survival were measured as response variables. It was also determined whether mated and virgin females showed different immune responses. Body size decreased with immune challenge but only in the 2N treatment. Exoskeleton thickness increased in both sham-challenge groups and the 1N group but decreased in the 2N group. Egg number decreased more in the sham-challenge groups followed by the 1N and 2N groups. The 2N group showed the largest egg size at the end of the experiment. In these females, 2N group died first followed by the 1N, two nylon sham and one nylon sham groups. Finally, mated females showed a lower immune response than virgin females. These results are consistent with ecological immunity theory. The discovery of exoskeleton-related costs of immunity and injury may have important implications for experimental design in studies of the cost of immunity.     

Serotonin has kinin-like activity in stimulating secretion by Malpighian tubules of the house cricket Acheta domesticus

Serotonin stimulates secretion by Malpighian tubules (MT) of a number of insects, and functions as a diuretic hormone in Rhodnius prolixus and in larval Aedes aegypti. Serotonin is here shown to be a potent stimulant of secretion by MT of the house cricket, Acheta domesticus, with an apparent EC₅₀ of 9.4 nmol L⁻¹, although its diuretic activity is just 25% of the maximum achievable with either the native CRF-related peptide, Achdo-DH, or a crude extract of the corpora cardiaca. In this respect, the diuretic activity of serotonin is similar to that of the cricket kinin Achdo-KI, and when tested together their actions are not additive, which suggests they target the same transport process. Consistent with this suggestion, the activity of serotonin is chloride-dependent and is associated with a non-selective stimulation of NaCl and KCl transport. In common with Achdo-KI, serotonin has no effect on cAMP production by isolated MT, and both act synergistically with exogenous 8bromo-cAMP in stimulating fluid secretion, most likely by promoting the release of Ca²⁺ from intracellular stores. A number of serotonin agonists and antagonists were tested to determine the pharmacological profile of receptors on cricket MT. The results are consistent with the diuretic activity of serotonin being mediated through a 5-HT₂-like receptor.     

Isolation of the abdomen releases oviposition behaviour in females of the cricket, Acheta domesticus

Upon isolation, abdomens of adult female house crickets (Acheta domesticus) produced abdominal and ovipositor movements characteristic of normal oviposition. Oviposition behaviour was thus released even in reproductively mature or immature virgins where under normal conditions it was never observed. Decapitation was not sufficient to release oviposition behaviour but transection of the ventral nerve cord between the thorax and the abdomen of immobilized females evoked the response. These observations indicate that the motor programmes for certain components of the oviposition sequence reside in the abdominal ganglia. Moreover, the prerequisite circuitry for ovipositional posturing of the abdomen and ovipositor appears to be functional prior to sexual maturity and insemination, primed by mating, and subject to inhibition by the thoracic ganglia.     

The effect of temperature on feeding,growth, and metabolism during the last larval stadium of the female house cricket, Acheta domesticus

Eighth instar female house crickets at 35°C developed faster, gained slightly more wet weight, and consumed less food, water, and oxygen than at 25°C. The duration of the 8th stadium at 25°C was 13 days (undisturbed), but was 14 days when disturbed by daily weighing. The duration of the 8th stadium at 30°C was 8 days and at 35°C was 6 days. During the first half of the 8th stadium at 25, 30, and 35°C, there was a high rate of food and water consumption resulting in statistically equal maximum dry weight achievement (124 mg). Respiratory quotients greater than one during this time indicated the conversion of ingested carbohydrate to fat. During the latter half of the 8th stadium, food and water consumption declined and the crickets lost weight. The period of weight loss was proportionally much longer at 25°C than at 30 or 35°C. Respiratory quotients lower than 1.0 during the latter half of the 8th stadium at 30 and 35°C indicated the metabolism of stored lipids. The respiratory quotient at 25°C never fell below 1.0, possibly because some food remained in the gut. The absorption efficiency was not influenced by temperature (25–35°C). Though the caloric content of the faeces was lower at 25°C than at 30 or 35°C, which correlated to the much longer time for food passage at 25°C than at 35°C, the difference in total calories egested was insufficient to alter the absorption efficiency. A longer period of reduced feeding and greater dry weight loss during the latter half of the 8th stadium at 25°C resulted in a lower metabolic efficiency at 25°C than at 30 or 35°C. Eighth instar crickets in response to a step-function transfer from 30°C–25 or 35°C showed an immediate (<1 hr) and complete metabolic adjustment which was not affected by the temperature history during the 7th stadium. House crickets did not exhibit temperature acclimation in the range 20–40°C, the metabolic rate being determined by ambient temperature. The Q₁₀ for oxygen consumption in the range 20–40°C was about 2.     

Growth and moulting in nematodes: Changes in the dimensions and morphology of Rotylenchulus reniformis from start to finish of moulting

At a temperature of 24°C, freshly hatched second stage larvae (L₂) of Rotylenchulus reniformis take 2 weeks to complete moulting and become either adult males or immature females. Measurements of different nematode stages were made using a computer-interfaced digitizer (CID). This proved to be more rapid and reproducible than conventional techniques.Moulting and development were followed in individual living specimens viewed under Nomarski optics and oil immersion. The mean loss in body volume of these specimens from L₂ to immature female is about 17% compared with about 19% for the mean loss in body volume from L₂ to male. The mean volumes for a total of 70 randomly selected living specimens measured are 95·6 pi for L₂s, 72·9 pl for immature females and 74·2 pl for males. Mean losses in body volume during moulting calculated from these randomly selected stages were slightly higher than those observed for individuals, being about 24% for the immature female and about 22% for the male.     

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 fiels crickets.     

Circadian locomotory rhythm and the influence of moulting in Australian field cricket nymphs

ABSTRACT. Evidence is presented for a circadian control of locomotory activity in the larval stadia of the cricket, Teleogryllus commodus Walker. Under light—dark cycles (LD), maximal activity occurs around the L/D transition and/or in the hours preceding it. Free-running rhythm patterns longer than 24 h are observed in constant light. Re-entrainment to phase advances in the LD cycle is also accompanied by several transient cycles. However, free-running rhythms under constant darkness or transients when exposed to LD cycle delays were not found. LD cycles during the eighth stadium set the phase of a free-running rhythm in the adult, even if the nymph does not show a rhythm. Nymphal activity is often erratic and is disrupted periodically by the moulting cycle, but moulting does not interrupt the operation of the circadian system. The daily timing of the moult itself is not under circadian control.     

Synthesis of prostaglandin by reproductive tissue of the male house cricket, acheta domesticus

Whole reproductive tracts of male house crickets, Acheta domesticus, incubated with arachidonic acid and glutathione yielded an average of 17 ug of prostaglandin (PG) E₂/g of tissue. Biosynthesized PGE₂ was identified by mass spectroscopy. A compound with thin layer and gas chromatographic properties identical to PGE₁ was isolated from spermatophores of house crickets. This appears to be the first report of the occurrence of a PG in an insect species. The possible role of PG in insect reproduction is discussed.     

Studies on the group effect in Acheta domesticus (L.) using artificial diets

Larvae of Acheta domesticus were reared on artificial diets both singly and in groups of six. The growth of group-reared larvae was significantly faster, and survival of singly reared larvae was greatly reduced. Survival of singly reared larvae was raised to that of grouped larvae when 1% wheat-germ oil was added to the diet. Wheat-germ oil also improved the growth of grouped larvae and of singly reared female larvae. The fatty acid composition of body lipid was similar, except for linolenic acid, whether the larvae were singly or group-reared, or whether wheat-germ oil was fed or not. These results are discussed from the point of view of the mechanism of the group effect.     

The effect of rutin on growth,fecundity and food utilization in Acheta domesticus (L.)

Growth of larvae of Acheta domesticus to the adult stage on an artificial diet was improved significantly by the addition of 0.1% rutin to the diet. Fecundity was also increased. These results cannot be explained by a stimulation of feeding by rutin. They appear to be due to an effect on the utilization of the food, brought about possibly by an action on gut movement, on gut transport or on the microbiol flora.     

Influence of sex and dietary fat on the group effect in larvae of Acheta domesticus (L.)

Larvae of Acheta domesticus show the group effect when reared in pairs on an artificial diet with the opposite sex, but not when reared with the same sex. When wheat-germ oil is added to the artificial diet, all paired larvae exhibit the group effect, regardless of sex. Dietary fat also improves survival and growth, but the identity of the component(s) producing these results has not been determined. The possible roles of linolenic acid and linolenic acid synthesis in this insect are discussed.     

Temporal variation in the availability of an ecdysial motor programme during the last instar and early adult stages of the cricket Teleogryllus oceanicus

Abdominal peristalsis is a highly sterotyped motor programme which is normally performed only during ecdysis in the cricket. Peristaltic abdominal waves can be released in non-ecdysing crickets by providing them with sensory feedback similar to that which they would normally experience only during ecdysis, and transecting the ventral nerve cord between suboesophageal and prothoracic ganglia. The intensity of the behaviour released by these treatments increases significantly just before the expected time of the imaginal ecdysis, and decreases greatly afterwards.     

Effects of resource distribution on activity and territory defence in house mice, Mus domesticus

How much an animal invests in defending a territory depends, in part, on the quality, quantity and distribution of resources, but do animals target their investment in defence within the territory according to the location of different resources? We examined whether wild-caught male and female house mice increased aggression towards intruders of the same or opposite sex when in areas containing their food/water or nest site. Pairs of resident mice were established in enclosures consisting of two areas. In split enclosures, food and water were in one area and a nest site in the other, while in clumped enclosures all resources were in one area with no resources in the other. Residents of both sexes were quicker to attack intruders, and were more aggressive, in areas containing resources than in an area containing no resources. There was no difference in aggression between areas containing food/water, a nest site or both. The effect of resources on territorial defence was due largely to changes in aggression against intruders of the opposite sex. Residents, especially males, attacked intruders of their own sex more than those of the opposite sex. This bias was much stronger when no resources were present, owing to low aggression against opposite-sex intruders in the absence of resources. There were no differences in intruder aggression, and the relative size of the intruder (heavier or lighter than the resident) had no effect on resident aggression. Residents also spent less time out of their nest in clumped enclosures owing to low activity in the nonresource area.     

Azadirachtin affects growth and endocrine events in larvae of the tobacco hornworm, Manduca sexta

Injection of azadirachtin in freshly emerged last-instar larvae of Manduca sexta elicited different reactions according to the dose administered. At low doses, pupation occurred in most of the cases, but the resulting pupae were defective for the most part. Individuals treated with higher doses usually did not fully complete development, moulting to supernumerary larvae or dying as larvae (sometimes at the wandering stage) after varying periods of survival. The haemolymph ecdysteroid titre of individuals treated with 2 μg azadirachtin/g bodyweight showed characteristic changes which are presumed to cause the disorders in the last stages that normally lead to pupation. Injection of moulting hormone in azadirachtin-treated individuals at certain times during the penultimate stage elicited no reduction of the azadirachtin-induced effects. It is shown that azadirachtin is able to inhibit development even when individuals performed a complete moult after the treatment.