Richard M. Roe

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.

Purification and kinetics of juvenile hormone esterase from the cabbage looper, Trichoplusia ni (Hubner)

Abstract A method for purifying juvenile hormone esterase from the haemolymph of Trichopulsia ni (Hubner) was developed. The procedure resulted in a single protein band when electrophoresed on SDS-polyacrylamide gels. The enzyme consisted of a single polypeptide chain of mol. wt 48,000 as determined by gel electrophoresis and gel filtration chromatography. Enzyme activity was stable in 40% sucrose for more than 5 months, and unstable when exposed to charged environments at low enzyme concentration. The enzyme possessed apparent K m values of 1.13 × 10 −6 and 0.402 × 10 −6 M for JH I and JH III, respectively.

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.

Characterization of the plasma juvenile hormone esterase in synchronous last stadium female larvae of the sugar cane borer, Diatraea saccharalis (F.)

Abstract A peak in the plasma juvenile hormone esterase (JHE) activity occurred near the time when female last stadium sugar cane borers reached their maximum weight, and a second peak of plasma JHE activity and a peak in the plasma α-naphthyl acetate esterase (α-NAE) activity occurred at the prepupal stage. Two JHEs were resolved by high pressure liquid chromatography (HPLC), gel filtration, and isoelectric focusing. Their apparent mol. wts were 40,000 and 34,000 and their isoelectric points 6.9 and 6.3. Juvenile hormone I was metabolized by JHE at about twice the rate of JH III. The apparent K m of prepupal JHE and the V max were also greater for JH I (3.29 μM and 8.38 nM min−1 ml−1, respectively) than for JH III (3.04 μM and 3.75 nM min−1 ml−1, respectively). The last stadium JHE and α-NAE activity pattern, the inhibition profile, the enzyme thermal stability pattern, isoelectric focusing pattern, gel filtration profile, and HPLC analysis indicated that JH I and JH III were metabolized by the same JHEs, that were physiochemically distinct from general esterase activity (α-NAE activity). General esterase was relatively unimportant in the metabolism of unbound JH in the plasma of last stadium sugar cane borers.

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 (

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.

Photoperiodically induced delayed insect metamorphosis: a larval oligopause inDiatraea saccharalis

Sugarcane borers enter a state of delayed metamorphosis when exposed to a 12-h photophase at 21°C. Larval feeding, growth, and molting continues but pupation is suppressed under these conditions.