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Circadian rhythmicity and capacity for enforced activity in the cockroach, Blaberus discoidalis, after cardiacectomy-allatectomy
7. Insect Physiol., 1972, Vol. 18, pp. 595 to 601. Pergamon Press. Printed in G&at Britain
CIRCADIAN RHYTHMICITY AND CAPACITY FOR ENFORCED ACTIVITY IN THE COCKROACH, BLABERUS DISCOIDALIS, AFTER CARDIACECTOMYALLATECTOMY MERLE
SHEPARD
and LARRY
L. KEELEY
Department of Entomology, Texas A. & M. University, College Station, Texas 77843 (Received 6.541~ 1971)
Abstract-The capacity for enforced activity in response to electrical stimulus and circadian locomotor activity were recorded for adult male Bl&ms discoid&s after long-term cardiacectomy-allatectomy (CC-+ CA-). CC-+ CA- cockroaches showed longer periods of exhaustion during shock stimulated activity than either normal or CA- animals. However, actograph studies revealed no differences between normal and CC-+ CA- cockroaches in either circadian rhythmicity or the intensity of activities. These results suggest the cockroach corpora cardiaca do not influence normal activity patterns but maintain metabolic processes at levels sufhcient to meet emergency demands.
INTRODUCTION
EFFORTS to relate circadian locomotor activities of insects to endocrine functions have resulted in conflicting reports. HARKER (1960) reported the suboesophageal ganglion regulated the circadian rhythmicity of Periplaneta americana. She found that a neurosecretion inhibitory to the suboesophageal ganglion was passed from the corpora cardiaca (CC) to the ganglion via nerve connectives with the corpora allata (CA). Severance of the CA-suboesophageal connectives resulted in arrhythmic cockroaches after 1 week (HARKER, 1960). In contrast to Harker, ROBERTS (1966) and BRADY (1967) reported no effects on locomotor rhythmicity after allatectomy (CA-) or cardiacectomy-allatectomy (CC- + CA-) of P. americana. The issue was raised again by NISHIITSUTSUJI-UWO et al. (1967) when they found disruption of neurosecretory functions of the pars intercerebralis resulted in arrhythmicity of P. americana and Leucophaea maderae. Furthermore, they reported a greater degree of locomotor activity after the destruction of neurosecretory cells, again, suggesting the cells secrete an agent suppressive to locomotor functions. NISHIITSUTSUJI-UWO and PITTENDRIGH (1968) showed the optic lobes were the driving sites for the rhythmicity while the pars intercerebralis regulated the levels of locomotor activity. Studies on behavioural change after destruction of the neuroendocrine system are complicated by the fact that this same system regulates diverse physiological 20
59.5
596
MERLE
SHEPARD
AND LARRYL. KEELEY
and metabolic processes which may not be specifically associated with behaviour in a direct cause-effect relationship. Increasing evidence indicates the CC influence both metabolic processes and respond to external stresses. In Blabems craniife, decreased quantities of stainable material suggested increased secretion by the CC after administration of electrical shock (HODGSON and GELDIAY, 1959). Furthermore, the CC have been reported to stimulate increases in the heartbeat rate (DAVEY, 1963), gut peristalsis (DAVEY, 1962), central nervous system activity (MILBURN and ROEDER, 1962), and the levels of blood trehalose and lipids (STEELE, 1963; MAYER and CANDY, 1969). Few studies have attempted to correlate behaviour and metabolism after endocrine imbalance. In one such study, ODHIAMBO (1966) suggested the increase in lipid content of the fat body of CA- male Schistocerca gregaria was the result of lethargy after gland removal. In contrast, STRONG (1968) found lipid storage but no decrease in locomotor activity in CA-, male Locusta migratoria. The CC and CA are frequently suspected of influencing locomotor functions, and it is these glands that are now known to affect metabolism, particularly that of the fat body. The hyperglycemic effect of the CC (STEELE, 1963) and its adipokinetic effect (MAYER and CANDY, 1969) act on the fat body for the release of stored reserves. Furthermore, KEELEY and FRIEDMAN (1967, 1969) found long-term deficiency of the CC and CA of Blaberus discoidalis decreased fat body respiration at the level of the mitochondria suggesting a generalized decrease in fat body metabolism. Considering the effect of CC and CA removal on fat body metabolism and the importance of fat body functions in the insect’s total metabolic picture, changes in fat body metabolism following CC-+ CA- may be manifested in the animal’s locomotor activities. The following studies were undertaken to determine the effect of long-term CC- + CA- on locomotor rhythms and on the capacity for sustained evasion of stress in the cockroach, B. discoidalis.
MATERIALS
AND METHODS
used in these experiments were 24 to 28 day old, adult, male B. procedures and surgical methods were described by KEELEY and FRIEDMAN (1967). Controls were normal animals as sham surgery had no significant effect on basal metabolism (KEELEY and FRIEDMAN, 1967) or fat body mitochondrial respiration (KEELEY and FRIEDMAN, 1969; KEELEY, 1970). Daily locomotor activity was monitored by an ultrasonic actograph activated Transparent cellulose acetate sheets were by movements of the cockroaches. fashioned into a cylindrical arena 13 cm high and 16 cm in dia. The roof and sides were secured with glue. Cockroach activity was confined to the floor of the arena which was the lid from a 1 gal. cardboard container. An ultrasonic motion detector (Alton Electronics Co., Gainesville, Fla.) monitored the locomotor activity of the animals. This device emitted high frequency sound waves into the experimental enclosure. One motion detector head, consisting of a high frequency transmitter, was placed 3 cm from the bottom of the arena. As sound waves were directed into The
insects
discoidalis. Rearing
ENFORCED ACTIVITY IN THE COCKROACH
597
the enclosed arena, movement by the cockroach produced changes in the amplitude of the high frequency sound waves. A resonant ceramic transducer on the opposite side of the arena detected the deflected sound waves and recorded them on a chart recorder. The sensitivity of the motion detector was adjusted to register walking movements but not movements of the antennae. The arena, containing the motion detector heads, was placed inside a photoperiod box containing an incandescent bulb (15 W) as the source of light for the LD 12 : 12 light-dark regime. This light-dark cycle was synchronized with that of the cockroach rearing room by use of an automatic timing device. Locomotor activity measurements were made on each cockroach for a 24 hr period in the absence of food and water. No cockroach was measured twice and a different individual was placed in the arena at approximately the same time each day (1200 hr). Temperature in the test arena was 28 + 2°C. Stress response experiments were conducted with individual cockroaches in an electrically wired 6.5 x 6.5 x 8.5 cm chamber. The chamber was designed such that completion of the electrical current was made through the cockroach as long as its tarsi were in contact with any of the inner surfaces. Thus, the only time the cockroach could possibly avoid electrical stimulation was when lying on its back. Electrical stimulus was produced by a Model 54K Grass square wave stimulator which was wired to the activity chamber. The stimulator was set to deliver 100 V pulses of 100 msec duration at a rate of l/set. Cockroach activity was timed over a 1 hr test period. Analysis of the stress response data was carried out by the Student’s t-test. RESULTS
Locomotor activity Fig. 1 shows the 24 hr locomotor activity pattern of normal and CC-+ CAB. discoidalis. Tests were conducted on 24 to 28 day old animals because animals of this age were shown to have recovered from the surgical trauma and their metabolism is understood (KEELEY and FRIEDMAN,1967). Examination of these data reveal no obvious differences in either the periodicity or the intensity of the locomotor activity between normal and gland-deficient cockroaches. The entrainment of the daily activity pattern of B. discoidalis to an LD (lightdark) 12 : 12 photoperiod was accomplished by the normal rearing conditions. Two peaks of locomotor activity occurred during the 24 hr test period. The phase of activity always began at, or near the transition from light to dark (0700 and 1900 hr) and vice versa. The cockroaches usually displayed a period of activity immediately after placement into the test arena. This was due to excitement created during the transfer and not to rhythmicity of the activity pattern as this period of restlessness occurred regardless of the time of transfer. Although food and water were denied the cockroaches, during the test period, there was no apparent intensive searching response unless it was congruent with daily locomotor activity.
MERLE SHEPARDANDLARRY L. KEELEY
598
FIG. 1.
Actograph recordings of circadian locomotor activity of normal and cardiacectomized-allatectomized adult, male B. discoidalis.
Stress response
The data in Table 1 illustrate differences between the activity and recovery times of normal and CC-+ CA- B. discoidalis receiving electrical stimulation. Those animaIs without CA and CC were less active (P-C O-05) than normal controls. The time spent in the active state by normal cockroaches was 40 per cent more than that of the CC- + CA- group. Interestingly, the normal animals were active for about one-half of the 1 hr test period. CA- reduced the stress-induced activity to a time intermediate between normal and CC- + CA-. A great deal of variability was found in the CA- group with about half of the animals acting normally and the others appearing like CC-+ CA- animals. This variability in results after CATABLE I-COMPARISON OF PERIODSOF ACTIVITYANDRECOVERY OF GLANDDEFICIENT ANDNORMALB. discoid&is AFTERELECTRICAL STIMULATION
Experimental animals Normal Allatectomized Cardiacectomized-
Average activity time (Min) 28.9 23.9 20.7 *
S.E. + 2.41 + 7.63 f 2.08
Average recovery time (Min) 31-1 36.1 39.3 *
No. of animals tested 6 5 6
* Indicates significant difference from the normal controls at the 5 per cent level using the Student’s t-test.
ENFORCED ACTIVITY IN THECOCKROACH
599
has been reported previously (KEELN and FRIEDMAN,1969) and agrees with other studies that report CA- disrupts neuroendocrine functions (HIGHNAMet at., 1967; THOMSENand LEA, 1969). Inhibition of neurosecretory activity after CA- would produce an animal comparable to CC-+ CA- deficiency, although not all animals show the effect. Electrical pulses from the square wave stimulator imparted no apparent physical damage to the cockroaches. Voltages of a lesser magnitude (< 90 V) caused the cockroaches to acclimate rapidly and thereby reduce or cease activity after a few minutes. During 100 V stimulation excitatory movements were exhibited by the cockroaches over the entire test period. Attempts by individuals to climb the walls of the container resulted in their falling upon their backs which prompted violent wing and leg movements in efforts to right themselves. These movements ceased after a period of time and the animals remained quiescent, seemingly in a state of exhaustion. After such periods of inactivity, the animals had no difficulty in righting themselves. Thus, during the course of the 1 hr test period, several stops and starts were made. Stops ranged from 5 to 19 for normal cockroaches and 3 to 15 for CC-+ CA- animals. DISCUSSION Actograph measurements to determine the effects of CC- + CA- on B. discoid& show no differences from normal animals in locomotor rhythmicity or intensity. However, the capacity for stress-induced activity was significantly reduced by CC-+ CA-. Since the number of active and rest periods was quite variable for both normal and CC-+ CA- cockroaches, no correlation can be made between the groups for the frequency of resting. Rather, it would appear that glanddeficient animals take longer to recover during a rest period. These findings can be correlated to known relationships of the CC with cockroach metabolism. The CC facilitate the conversion of fat body glycogen to blood trehalose (STEELE, 1963; GOLDSWORTHY,1970). KEELEY (1966) found blood trehalose of CC-+ CA- B. discoid&s was 170 mg%, a value 80 per cent lower than normal. Similarly, the 30 to 40 per cent reduction in respiratory capacity of fat body mitochondria after CC-+CA(KEELEY and FRIEDMAN,1969; KRELEY, 1970) would reduce the rate of energy production in the fat body. Although the normal energy demands of the fat body may be met by the lower electron transport activity after CC-+ CA-, the fact that stressed CC-+ CA- animals required longer recovery times suggests that the higher demands of sustained, stressinduced activity cannot be met as promptly as normal. Energy-requiring metabolic processes of the fat body, such as the synthesis and release of mobile metabolites serving as replacement energy sources for muscular activity, are slowed. Furthermore, removal of the CC may reduce cardiaca-activated enzymes, such as phosphorylase, which would continue to remain at levels below the metabolic demands required by stress situations. If CC-+ CA- B. discoid&s are capable of normal activity or short-term stress enforced activity with 20 per cent of their haemolymph trehalose and are exhausted
600
MERLESHEPARD AND LARRY L. KEELEY
only after long-term stress, then it is reasonable to assume that the levels of mobile sugar found in normal cockroaches are well above those usually necessary for activity. WEIS-FOGH (1964) h as indicated that the large fibre diameter of insect muscles and the low turnover rate of the circulatory system necessitates high concentrations of mobile reserves. This is in contrast to vertebrates where the rapid circulatory rate permits a response within seconds to the stress-induced release of epinephrine. Consequently, from the data presented here and those of other workers (STEELE, 1963; KEELEY, 1966; KEELEY and FRIEDMAN,1969; MAYER and CANDY, 1969), the CC appear as the regulative sites for the maintenance of high levels of basal metabolism and mobile metabolites in insects. Although these levels surpass those necessary to meet normal demands, they ensure a reserve for emergency situations. If the insect counters such situations successfully, the stress responsive CC then have time to return the depleted metabolic levels to normal. REFERENCES BRADYJ. (1967) Control of the circadian rhythm of activity in the cockroach---I.
The role of the corpora cardiaca, brain and stress. _Y. exp. Biol. 47, 153-163. DAWY K. G. (1962) The mode of action of the corpus cardiacum on the hindgut in Periplaneta americana. J. exp. Biol. 39, 319-324. DAVEY K. G. (1963) The release by enforced activity of the cardiac accelerator from the corpus cardiacum of Periplaneta americana. J. Insect Physiol. 9, 375-381. GOLDSWORTHY G. J. (1970) The action of hyperglycaemic factors from the corpus cardiacum of Locusta migratoria on glycogen phosphorylase. Gen. contp. Endocr. 14, 78-85. HARKERJ. E. (1960) Endocrine and nervous factors in insect circadian rhythms. Cold Spr. Harb. Symp. Quant. Biol. 25, 279-290. HICHNAMK. C., LUSIS O., and HILL L. (1967) The role of the corpora allata during oocyte growth in the desert locust, Schistocerca gregaria Forsk. J. Insect Physiol. 9, 587-596. HODGSON E. S. and GELDIAY S. (1959) Experimentally induced release of neurosecretory material from roach corpora cardiaca. Biol. Bull., Woods Hole 117, 275-283. KEELEY L. L. (1966) The corpus cardiacum as a metabolic regulator in Blaberus discoidalis Serville (Blattidae). Unpublished thesis, Purdue University. KEELEY L. L. (1970) Insect fat body mitochondria: endocrine and age effects on respiratory and electron transport activities. Life Sci. 9, 1003-1011. KEELEY L. L. and FRIEDMANS. (1967) Corpus cardiacum as a metabolic regulator in Blaberus discoidalis Serville (Blattidae)-I. Long-term effects of cardiatectomy on whole body and tissue respiration and on trophic metabolism. Gen. camp. Endocr. 8,129-134. KEELEY L. L. and FRIEDMANS. (1969) Effects of long-term cardiatectomy-allatectomy on mitochondrial respiration in the cockroach, Blaberus discoidalis. J. Insect Physiol. 15, 509-518. MAYER R. J. and CANDY D. J. (1969) Control of haemolymph lipid concentration during locust flight: an adipokinetic hormone from the corpora cardiaca. J. Insect Physiol. 15, 611-620. MILBURN N. S. and ROEDERK. D. (1962) Control of efferent activity in the cockroach terminal abdominal ganglion by extracts of corpora cardiaca. Gen. camp. Endocr. 2, 70-76. NISHIITSUTSUJI-UWO J., PETROPULOSS. F., and PITTEZNDRICH C. S. (1967) Central nervous system control of circadian rhythmicity in the cockroach-I. Role of the pars intercerebralis. Biol. Bull., Woods Hole 133, 679-696.
ENFORCED ACTIVITYIN THE COCKROACH
601
NISHIITSUTSUJI-UWOJ. and PITTENDRIGHC. S. (1968) Central nervous system control of circadian rhythmicity in the cockroach-III. The optic Iobes, locus of the driving oscillation ? 2. oergl. Physiol. 58, 14-M. ODHIAMBOT. R. (1966) The metabolic effects of the corpus allatum hormone in the male desert locust-II. Spontaneous locomotor activity. J. exp. Biol. 45, 51-63. ROBERTSS. K. DE F. (1966) Circadian activity rhythms in cockroaches-III. The role of endocrine and neural factors. J. Cell Physiol. 67, 473-480. STEELE J. E. (1963) The site of action of the hyperglycemic hormone. Gen. camp. Endocr. 3, 46-52. STRONG L. (1968) Locomotor activity, sexual behaviour, and the corpus allatum hormone in males of Locusta. J. Insect Physiol, 14, 1685-1692. THOMSENE. and LEA A. 0. (1969) Control of the medial neurosecretory cells by the corpus allatum in Calliphora erythrocephala. Gen. camp. Endocr. 12, 51-57. WEIS-FOGH T. (1964) Diffusion in insect wing muscle, the most active tissue known. J. exp. Biol. 41, 229-256.
CIRCADIAN RHYTHMICITY AND CAPACITY FOR ENFORCED ACTIVITY IN THE COCKROACH, BLABERUS DISCOIDALIS, AFTER CARDIACECTOMYALLATECTOMY MERLE
SHEPARD
and LARRY
L. KEELEY
Department of Entomology, Texas A. & M. University, College Station, Texas 77843 (Received 6.541~ 1971)
Abstract-The capacity for enforced activity in response to electrical stimulus and circadian locomotor activity were recorded for adult male Bl&ms discoid&s after long-term cardiacectomy-allatectomy (CC-+ CA-). CC-+ CA- cockroaches showed longer periods of exhaustion during shock stimulated activity than either normal or CA- animals. However, actograph studies revealed no differences between normal and CC-+ CA- cockroaches in either circadian rhythmicity or the intensity of activities. These results suggest the cockroach corpora cardiaca do not influence normal activity patterns but maintain metabolic processes at levels sufhcient to meet emergency demands.
INTRODUCTION
EFFORTS to relate circadian locomotor activities of insects to endocrine functions have resulted in conflicting reports. HARKER (1960) reported the suboesophageal ganglion regulated the circadian rhythmicity of Periplaneta americana. She found that a neurosecretion inhibitory to the suboesophageal ganglion was passed from the corpora cardiaca (CC) to the ganglion via nerve connectives with the corpora allata (CA). Severance of the CA-suboesophageal connectives resulted in arrhythmic cockroaches after 1 week (HARKER, 1960). In contrast to Harker, ROBERTS (1966) and BRADY (1967) reported no effects on locomotor rhythmicity after allatectomy (CA-) or cardiacectomy-allatectomy (CC- + CA-) of P. americana. The issue was raised again by NISHIITSUTSUJI-UWO et al. (1967) when they found disruption of neurosecretory functions of the pars intercerebralis resulted in arrhythmicity of P. americana and Leucophaea maderae. Furthermore, they reported a greater degree of locomotor activity after the destruction of neurosecretory cells, again, suggesting the cells secrete an agent suppressive to locomotor functions. NISHIITSUTSUJI-UWO and PITTENDRIGH (1968) showed the optic lobes were the driving sites for the rhythmicity while the pars intercerebralis regulated the levels of locomotor activity. Studies on behavioural change after destruction of the neuroendocrine system are complicated by the fact that this same system regulates diverse physiological 20
59.5
596
MERLE
SHEPARD
AND LARRYL. KEELEY
and metabolic processes which may not be specifically associated with behaviour in a direct cause-effect relationship. Increasing evidence indicates the CC influence both metabolic processes and respond to external stresses. In Blabems craniife, decreased quantities of stainable material suggested increased secretion by the CC after administration of electrical shock (HODGSON and GELDIAY, 1959). Furthermore, the CC have been reported to stimulate increases in the heartbeat rate (DAVEY, 1963), gut peristalsis (DAVEY, 1962), central nervous system activity (MILBURN and ROEDER, 1962), and the levels of blood trehalose and lipids (STEELE, 1963; MAYER and CANDY, 1969). Few studies have attempted to correlate behaviour and metabolism after endocrine imbalance. In one such study, ODHIAMBO (1966) suggested the increase in lipid content of the fat body of CA- male Schistocerca gregaria was the result of lethargy after gland removal. In contrast, STRONG (1968) found lipid storage but no decrease in locomotor activity in CA-, male Locusta migratoria. The CC and CA are frequently suspected of influencing locomotor functions, and it is these glands that are now known to affect metabolism, particularly that of the fat body. The hyperglycemic effect of the CC (STEELE, 1963) and its adipokinetic effect (MAYER and CANDY, 1969) act on the fat body for the release of stored reserves. Furthermore, KEELEY and FRIEDMAN (1967, 1969) found long-term deficiency of the CC and CA of Blaberus discoidalis decreased fat body respiration at the level of the mitochondria suggesting a generalized decrease in fat body metabolism. Considering the effect of CC and CA removal on fat body metabolism and the importance of fat body functions in the insect’s total metabolic picture, changes in fat body metabolism following CC-+ CA- may be manifested in the animal’s locomotor activities. The following studies were undertaken to determine the effect of long-term CC- + CA- on locomotor rhythms and on the capacity for sustained evasion of stress in the cockroach, B. discoidalis.
MATERIALS
AND METHODS
used in these experiments were 24 to 28 day old, adult, male B. procedures and surgical methods were described by KEELEY and FRIEDMAN (1967). Controls were normal animals as sham surgery had no significant effect on basal metabolism (KEELEY and FRIEDMAN, 1967) or fat body mitochondrial respiration (KEELEY and FRIEDMAN, 1969; KEELEY, 1970). Daily locomotor activity was monitored by an ultrasonic actograph activated Transparent cellulose acetate sheets were by movements of the cockroaches. fashioned into a cylindrical arena 13 cm high and 16 cm in dia. The roof and sides were secured with glue. Cockroach activity was confined to the floor of the arena which was the lid from a 1 gal. cardboard container. An ultrasonic motion detector (Alton Electronics Co., Gainesville, Fla.) monitored the locomotor activity of the animals. This device emitted high frequency sound waves into the experimental enclosure. One motion detector head, consisting of a high frequency transmitter, was placed 3 cm from the bottom of the arena. As sound waves were directed into The
insects
discoidalis. Rearing
ENFORCED ACTIVITY IN THE COCKROACH
597
the enclosed arena, movement by the cockroach produced changes in the amplitude of the high frequency sound waves. A resonant ceramic transducer on the opposite side of the arena detected the deflected sound waves and recorded them on a chart recorder. The sensitivity of the motion detector was adjusted to register walking movements but not movements of the antennae. The arena, containing the motion detector heads, was placed inside a photoperiod box containing an incandescent bulb (15 W) as the source of light for the LD 12 : 12 light-dark regime. This light-dark cycle was synchronized with that of the cockroach rearing room by use of an automatic timing device. Locomotor activity measurements were made on each cockroach for a 24 hr period in the absence of food and water. No cockroach was measured twice and a different individual was placed in the arena at approximately the same time each day (1200 hr). Temperature in the test arena was 28 + 2°C. Stress response experiments were conducted with individual cockroaches in an electrically wired 6.5 x 6.5 x 8.5 cm chamber. The chamber was designed such that completion of the electrical current was made through the cockroach as long as its tarsi were in contact with any of the inner surfaces. Thus, the only time the cockroach could possibly avoid electrical stimulation was when lying on its back. Electrical stimulus was produced by a Model 54K Grass square wave stimulator which was wired to the activity chamber. The stimulator was set to deliver 100 V pulses of 100 msec duration at a rate of l/set. Cockroach activity was timed over a 1 hr test period. Analysis of the stress response data was carried out by the Student’s t-test. RESULTS
Locomotor activity Fig. 1 shows the 24 hr locomotor activity pattern of normal and CC-+ CAB. discoidalis. Tests were conducted on 24 to 28 day old animals because animals of this age were shown to have recovered from the surgical trauma and their metabolism is understood (KEELEY and FRIEDMAN,1967). Examination of these data reveal no obvious differences in either the periodicity or the intensity of the locomotor activity between normal and gland-deficient cockroaches. The entrainment of the daily activity pattern of B. discoidalis to an LD (lightdark) 12 : 12 photoperiod was accomplished by the normal rearing conditions. Two peaks of locomotor activity occurred during the 24 hr test period. The phase of activity always began at, or near the transition from light to dark (0700 and 1900 hr) and vice versa. The cockroaches usually displayed a period of activity immediately after placement into the test arena. This was due to excitement created during the transfer and not to rhythmicity of the activity pattern as this period of restlessness occurred regardless of the time of transfer. Although food and water were denied the cockroaches, during the test period, there was no apparent intensive searching response unless it was congruent with daily locomotor activity.
MERLE SHEPARDANDLARRY L. KEELEY
598
FIG. 1.
Actograph recordings of circadian locomotor activity of normal and cardiacectomized-allatectomized adult, male B. discoidalis.
Stress response
The data in Table 1 illustrate differences between the activity and recovery times of normal and CC-+ CA- B. discoidalis receiving electrical stimulation. Those animaIs without CA and CC were less active (P-C O-05) than normal controls. The time spent in the active state by normal cockroaches was 40 per cent more than that of the CC- + CA- group. Interestingly, the normal animals were active for about one-half of the 1 hr test period. CA- reduced the stress-induced activity to a time intermediate between normal and CC- + CA-. A great deal of variability was found in the CA- group with about half of the animals acting normally and the others appearing like CC-+ CA- animals. This variability in results after CATABLE I-COMPARISON OF PERIODSOF ACTIVITYANDRECOVERY OF GLANDDEFICIENT ANDNORMALB. discoid&is AFTERELECTRICAL STIMULATION
Experimental animals Normal Allatectomized Cardiacectomized-
Average activity time (Min) 28.9 23.9 20.7 *
S.E. + 2.41 + 7.63 f 2.08
Average recovery time (Min) 31-1 36.1 39.3 *
No. of animals tested 6 5 6
* Indicates significant difference from the normal controls at the 5 per cent level using the Student’s t-test.
ENFORCED ACTIVITY IN THECOCKROACH
599
has been reported previously (KEELN and FRIEDMAN,1969) and agrees with other studies that report CA- disrupts neuroendocrine functions (HIGHNAMet at., 1967; THOMSENand LEA, 1969). Inhibition of neurosecretory activity after CA- would produce an animal comparable to CC-+ CA- deficiency, although not all animals show the effect. Electrical pulses from the square wave stimulator imparted no apparent physical damage to the cockroaches. Voltages of a lesser magnitude (< 90 V) caused the cockroaches to acclimate rapidly and thereby reduce or cease activity after a few minutes. During 100 V stimulation excitatory movements were exhibited by the cockroaches over the entire test period. Attempts by individuals to climb the walls of the container resulted in their falling upon their backs which prompted violent wing and leg movements in efforts to right themselves. These movements ceased after a period of time and the animals remained quiescent, seemingly in a state of exhaustion. After such periods of inactivity, the animals had no difficulty in righting themselves. Thus, during the course of the 1 hr test period, several stops and starts were made. Stops ranged from 5 to 19 for normal cockroaches and 3 to 15 for CC-+ CA- animals. DISCUSSION Actograph measurements to determine the effects of CC- + CA- on B. discoid& show no differences from normal animals in locomotor rhythmicity or intensity. However, the capacity for stress-induced activity was significantly reduced by CC-+ CA-. Since the number of active and rest periods was quite variable for both normal and CC-+ CA- cockroaches, no correlation can be made between the groups for the frequency of resting. Rather, it would appear that glanddeficient animals take longer to recover during a rest period. These findings can be correlated to known relationships of the CC with cockroach metabolism. The CC facilitate the conversion of fat body glycogen to blood trehalose (STEELE, 1963; GOLDSWORTHY,1970). KEELEY (1966) found blood trehalose of CC-+ CA- B. discoid&s was 170 mg%, a value 80 per cent lower than normal. Similarly, the 30 to 40 per cent reduction in respiratory capacity of fat body mitochondria after CC-+CA(KEELEY and FRIEDMAN,1969; KRELEY, 1970) would reduce the rate of energy production in the fat body. Although the normal energy demands of the fat body may be met by the lower electron transport activity after CC-+ CA-, the fact that stressed CC-+ CA- animals required longer recovery times suggests that the higher demands of sustained, stressinduced activity cannot be met as promptly as normal. Energy-requiring metabolic processes of the fat body, such as the synthesis and release of mobile metabolites serving as replacement energy sources for muscular activity, are slowed. Furthermore, removal of the CC may reduce cardiaca-activated enzymes, such as phosphorylase, which would continue to remain at levels below the metabolic demands required by stress situations. If CC-+ CA- B. discoid&s are capable of normal activity or short-term stress enforced activity with 20 per cent of their haemolymph trehalose and are exhausted
600
MERLESHEPARD AND LARRY L. KEELEY
only after long-term stress, then it is reasonable to assume that the levels of mobile sugar found in normal cockroaches are well above those usually necessary for activity. WEIS-FOGH (1964) h as indicated that the large fibre diameter of insect muscles and the low turnover rate of the circulatory system necessitates high concentrations of mobile reserves. This is in contrast to vertebrates where the rapid circulatory rate permits a response within seconds to the stress-induced release of epinephrine. Consequently, from the data presented here and those of other workers (STEELE, 1963; KEELEY, 1966; KEELEY and FRIEDMAN,1969; MAYER and CANDY, 1969), the CC appear as the regulative sites for the maintenance of high levels of basal metabolism and mobile metabolites in insects. Although these levels surpass those necessary to meet normal demands, they ensure a reserve for emergency situations. If the insect counters such situations successfully, the stress responsive CC then have time to return the depleted metabolic levels to normal. REFERENCES BRADYJ. (1967) Control of the circadian rhythm of activity in the cockroach---I.
The role of the corpora cardiaca, brain and stress. _Y. exp. Biol. 47, 153-163. DAWY K. G. (1962) The mode of action of the corpus cardiacum on the hindgut in Periplaneta americana. J. exp. Biol. 39, 319-324. DAVEY K. G. (1963) The release by enforced activity of the cardiac accelerator from the corpus cardiacum of Periplaneta americana. J. Insect Physiol. 9, 375-381. GOLDSWORTHY G. J. (1970) The action of hyperglycaemic factors from the corpus cardiacum of Locusta migratoria on glycogen phosphorylase. Gen. contp. Endocr. 14, 78-85. HARKERJ. E. (1960) Endocrine and nervous factors in insect circadian rhythms. Cold Spr. Harb. Symp. Quant. Biol. 25, 279-290. HICHNAMK. C., LUSIS O., and HILL L. (1967) The role of the corpora allata during oocyte growth in the desert locust, Schistocerca gregaria Forsk. J. Insect Physiol. 9, 587-596. HODGSON E. S. and GELDIAY S. (1959) Experimentally induced release of neurosecretory material from roach corpora cardiaca. Biol. Bull., Woods Hole 117, 275-283. KEELEY L. L. (1966) The corpus cardiacum as a metabolic regulator in Blaberus discoidalis Serville (Blattidae). Unpublished thesis, Purdue University. KEELEY L. L. (1970) Insect fat body mitochondria: endocrine and age effects on respiratory and electron transport activities. Life Sci. 9, 1003-1011. KEELEY L. L. and FRIEDMANS. (1967) Corpus cardiacum as a metabolic regulator in Blaberus discoidalis Serville (Blattidae)-I. Long-term effects of cardiatectomy on whole body and tissue respiration and on trophic metabolism. Gen. camp. Endocr. 8,129-134. KEELEY L. L. and FRIEDMANS. (1969) Effects of long-term cardiatectomy-allatectomy on mitochondrial respiration in the cockroach, Blaberus discoidalis. J. Insect Physiol. 15, 509-518. MAYER R. J. and CANDY D. J. (1969) Control of haemolymph lipid concentration during locust flight: an adipokinetic hormone from the corpora cardiaca. J. Insect Physiol. 15, 611-620. MILBURN N. S. and ROEDERK. D. (1962) Control of efferent activity in the cockroach terminal abdominal ganglion by extracts of corpora cardiaca. Gen. camp. Endocr. 2, 70-76. NISHIITSUTSUJI-UWO J., PETROPULOSS. F., and PITTEZNDRICH C. S. (1967) Central nervous system control of circadian rhythmicity in the cockroach-I. Role of the pars intercerebralis. Biol. Bull., Woods Hole 133, 679-696.
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NISHIITSUTSUJI-UWOJ. and PITTENDRIGHC. S. (1968) Central nervous system control of circadian rhythmicity in the cockroach-III. The optic Iobes, locus of the driving oscillation ? 2. oergl. Physiol. 58, 14-M. ODHIAMBOT. R. (1966) The metabolic effects of the corpus allatum hormone in the male desert locust-II. Spontaneous locomotor activity. J. exp. Biol. 45, 51-63. ROBERTSS. K. DE F. (1966) Circadian activity rhythms in cockroaches-III. The role of endocrine and neural factors. J. Cell Physiol. 67, 473-480. STEELE J. E. (1963) The site of action of the hyperglycemic hormone. Gen. camp. Endocr. 3, 46-52. STRONG L. (1968) Locomotor activity, sexual behaviour, and the corpus allatum hormone in males of Locusta. J. Insect Physiol, 14, 1685-1692. THOMSENE. and LEA A. 0. (1969) Control of the medial neurosecretory cells by the corpus allatum in Calliphora erythrocephala. Gen. camp. Endocr. 12, 51-57. WEIS-FOGH T. (1964) Diffusion in insect wing muscle, the most active tissue known. J. exp. Biol. 41, 229-256.