C.W. Clifford

Food utilization and metabolic efficiency in larval and adult house crickets

Abstract The most rapid growth of the fat body, ovaries and residual body occurred only at the time of maximal feeding, which was the time of highest metabolic rate. Larvae ceased feeding before the next moult and lost weight. Adult females did not cease feeding and never lost weight. Mated females maintained a high feeding rate that corresponded to a constant oviposition rate with no gonotrophic cycles. Virgin females maintained a lower feeding rate and maintained fully mature eggs in a viable state for life. Growth during the last larval stadium was entirely somatic and characterized by a great accumulation of a lipid rich (65%) fat body. Net growth during the first 10 days of adult life was entirely gonodal, because the small amount of residual body growth was matched by the amount of fat body loss. However, since the residual body was 60% protein and the fat body was 60% lipid, some of the somatic protein growth had to come from the diet and some of the fat body lipid went for ovarial growth. The 20% dietary protein was more than sufficient for all somatic and ovarial growth, and some protein was catabolized for energy. The amount of uric acid in larval faeces accounted for almost all protein catabolism, but in adult females half of the catabolized protein nitrogen did not appear in the faeces. With only 5% dietary lipid both larvae and adults had to synthesize additional lipids from carbohydrates to supplement absorbed lipids for growth demands. Almost all absorbed and synthesized lipids were used for somatic growth in the larvae and for ovarial growth in the adults, because the per cent of food calories used for growth greatly exceeded the per cent dry weight of food used for growth. Based on the calories and dry weight of available fuel, almost all energy production was based on carbohydrate oxidation. Some carbohydrate was used for lipid synthesis but very little was used for growth. Probably the absorption efficiency (72%) and growth efficiency (28%) was the same for both the last instar larvae and virgin females because they ate exactly the same food. However, the larval metabolic efficiency (42%) was higher than that of females (37%), which indicated that more of the absorbed food was converted to tissue during larval growth (somatic) than during adult growth (ovarial). Of the dry weight of food eaten during the last larval stadium, 30% was egested, 32% was oxidized, 28% appeared as growth, and 10% was condensed to lipid and became part of the 28% growth. Of the dry weight of food eaten during the first 10 days of adult life, 27% was egested, 41% was oxidized, 25% appeared as growth, and 6% was condensed to lipid.

Relation of feeding, growth, and metabolism to age in the larval, female house cricket.

Abstract The maximum growth rate occurs in the first half of the 7th and 8th larval instars of the house cricket, at which time food and water consumption is maximal. Growth ceases in the last 2 to 3 days of each instar when food consumption is almost nil. The metabolic rate is twice, and the locomotory activity is four times, higher in the first 2 to 3 days than in the last 2 to 3 days of each instar. The %-gain in dry wt is 120% for the 7th and 139% for the 8th instar. The average digestive coefficient (AD) for the 8th instar is 67% and the average efficiency of food conversion to tissue (dry wt ECI) is 27%. The average daily food consumption for 8th instar larvae is 31.4 mg, and, therefore, we calculate that an average of 12 mg food is burnt per day for energy which is confirmed by the observed average V O 2 of 1.2 ml O 2 /g-cricket/hr. Total lipids as %-total wt (239% mg-gain) increases in the first 4 days then remains constant in spite of cessation of feeding in the last 2 days. The RQ confirms the conversion of carbohydrates to lipids in the first half of each instar. In the moulting cycle carbohydrates are used for maintenance (when not feeding), but lipids are used at apolysis.

Effects of CO2 and anoxia on feeding, growth, metabolism, water balance, and blood composition in larval female house crickets, Acheta domesticus

Abstract A single 5 min exposure of larval house crickets to CO2 or N2 caused a 12 hr feeding inhibition and a 24 hr drinking inhibition. Daily 1–5 min gas exposure throughout the last instar caused a minimal 1 3 reduction in total food consumption and 1 3 reduction in weight gain. The crickets were most sensitive to feeding-growth retardation in the first half of the instar, when almost all feeding normally occurs. Gas treatment also lowered the efficiency of food conversion to body weight. The mortality threshold, measured by survival to the final ecdysis, for daily exposures was about 5 min, but for a single exposure the threshold was about 30 min. The metabolic rate was very slightly depressed by 5 min of anoxia, but was depressed for over 2 days following 15 min of anoxia. Single 1–5 min gas treatments of 3 and 5 day old larvae led to an average 20 mg diuretic water loss over the following 2–3 hr. Blood pH was lowered by CO2 (carbonic acid) and by N2 (lactic acid). A brief 1–5 min of anoxia caused a blood lipid increase within 3 hr with recovery to normal in 24 hr; blood NPS decreased within 3 hr and returned to normal in 24 hr; blood sugars increased within 3 hr, then decreased below controls before returing to normal in 24 hr. Blood lactate concentration indicated the extent of anoxia caused by CO2 and N2 exposure. Nitrogen caused asphyxiation with almost immediate anoxia. Carbon dioxide caused an immediate anesthesia which stopped breathing. Thus CO2 delayed the onset of anoxia but did not prevent it. Anesthesia resulted from the direct diffusion of CO2 from tracheae into neurones, and did not via the blood. Neither lowered blood pH or high lactate concentration directly caused immobilization, feeding-growth retardation, or any alteration in blood organic composition. We suggest that as little as 1–5 min of anoxia caused a long term disruption of certain neuroendocrine functions, which resulted in 3 hr of diuresis, 12 hr of feeding inhibition, and 12–24 hr of deviations in blood sugars, NPS, and lipids.

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

Abstract 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 (

Methods for rearing the house cricket, Acheta domesticus (L.), along with baseline values for feeding rates, growth rates, development times, and blood composition

The house cricket, Acheta domesticus, is an adaptable experimental animal, that can be inexpensively reared year round in a small temperature‐regulated room. Growth is rapid and development occurs without diapause at 30 °C. Different size glass aquaria or any convenient containers can be used to house the crickets as long as the relative humidity in the container can be regulated to be high for hatchlings and about 50 % for older crickets. Reusable cardboard gallon cartons with screen lids provide excellent containers for groups of up to 15 crickets each. Purina® Cricket Chow® provides all essential nutrients for continuous generations of large, healthy crickets. Specific information is provided for colony management, and isolation of known age individuals. Some basic developmental, metabolic and physiological values for the house cricket are provided.

The effect of temperature on energy distribution during the last-larval stadium of the female house cricket, Acheta domesticus

Abstract The distribution of energy during the last stadium of the house cricket at two temperatures was the main theme of this study. Food consumption, growth, and oxygen consumption were greater in the first half of the stadium at both 25 and 35°C. An RQ > 1 indicated the conversion of carbohydrates to lipids during the first half of the instar at both temperatures. The duration of the stadium increased from 6 days at 35°C to 14 days at 25°C. The same maximal weight, protein content and lipid content were attained at both 25 and 35°C. A weight loss (mostly in stored lipids) after the midstadium peak weight was greater at the lower temperature. The absorption efficiency and the production of metabolic wastes were not affected by temperature, but the metabolic efficiency was much higher at 35 than at 25°C during the first half as well as the latter half of the stadium. Although during the first half of the stadium more energy was ingested, absorbed, and made available for growth at 25 than at 35°C, only slightly more growth occurred at 25°C. During the last half of the stadium less energy was ingested at 25 than at 35°C, and much more growth occurred at 35°C because of the even greater heat loss at 25 than at 35°C. Therefore at a lower temperature cricket larvae eat slightly more and reach the same maximal weight as at a higher temperature, but they end up smaller because they waste more energy during the extended duration of the stadium at the lower temperature.

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

Abstract 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.

The effects of virginity and ovariectomy on growth, food consumption, fat body mass and oxygen consumption in the house cricket, Acheta domesticus

Abstract Virgins have a low percentage blood volume and a small digestive tract containing almost no food. Still, the virgins are 150–200 mg heavier than mated females by day 18 because they retain all ovulated eggs while mated females quickly lay ovulated eggs. Food consumption in virgins decreases to very low levels because the mass of ovulated eggs compresses the gut. Virgins can remain in this state for months. Within 24 h of mating 75% of the eggs are fertilized and laid, oogenesis is resumed, the percentage blood volume increases, and food consumption triples. During oogenesis most of the fat body mass is used up, but the mass of eggs ovulated is about 5 times the fat body mass lost. Clearly eggs are primarily made from ingested material that is processed through the fat body. The availability of fat body reserves in young females allows maximized early high ovulation rates. Ovariectomized Acheta domesticus have a higher blood volume and a larger fat body mass than mated females, but by unknown mechanisms food consumption declines and the fat body mass and total body weight stabilize and remain unchanged. The pattern of oxygen consumption in adult females is determined by the number of eggs present in the oviducts. Unfertilized eggs consume negligible amounts of oxygen, therefore the total body oxygen consumption is depressed in direct proportion to the amount of contained eggs. By day 12 mated females have started laying eggs and retain few (consume 1.4 ml oxygen/g cricket/h), but virgins retain all ovulated eggs (consume 0.8 ml oxygen/g virgin/h).

Development and relationships of locomotor, feeding, and oxygen consumption rhythms in house crickets

ABSTRACT. Locomotor, feeding, drinking, and oxygen consumption rhythms in adult virgin Acheta domesticus L. all appear to peak in the first half of the scotophase, be entrained cophasically by a LD 14:10 h cycle, have a lights‐off Zeitgeber and persist in LL with a πc. 25 h for the locomotor rhythm and c. 23 h for the oxygen consumption rhythm. There is no evidence of these rhythms in last instar larvae. The onset of the locomotor rhythm requires 3 days at 30°C but 5–7 days at 25–28°C after the final ecdysis in virgins, indicating a temperature related development of the locomotor rhythm. Oxygen consumption rhythms are lacking in 2‐day‐old virgins but present in 8‐day‐old virgins. Feeding rhythms can be recorded in virgins as young as 2 days (before locomotor rhythm developed). Both oxygen consumption and locomotor rhythms persist during starvation. The results suggest that a central brain oscillator drives both feeding and locomotor rhythms independently, but that the oxygen consumption rhythm is derived from the metabolic demands associated with the other rhythms.