Influence of neurosecretion and nutrition on O2-consumption in the bug, Oncopeltus fasciatus

7. Insect Phyriol., 1970, Vol. 16, pp. 471 to 482. Pergamm Press. Printed in Great Britain

INFLUENCE OF NEUROSECRETION AND NUTRITION ON O,-CONSUMPTION IN THE BUG,

ONCOPELTUS ELSE-MARGRETE Zoological Laboratory,

FASCIATUS CONRADI-LARSEN

University of Oslo, Blindem, Oslo 3, Norway (Received

22 August

1969)

Abstract-The OS-consumption (mm” O,,/mg per hr) of adult milkweed bug females decreases with increasing body weight. In adult females having a sufficient supply of milkweed seeds and water, the variation in OS-consumption follows the weight changes with approximately one day’s delay. In animals fed with 3% glucose solution, the average Oa-consumption decreases by 24 per cent of the normal. Removal of the neurosecretory cells of the brain led to a 20 per cent reduction of the normal Os-consumption and considerably reduced nutrition uptake. When normal adult females were fed with glucose for 6 days, and then with milkweed seeds, a considerable increase in the Or-consumption was observed, already after 1 day of resumed feeding with seeds. No corresponding effect was found in animals deprived of the neurosecretory cells. INTRODUCTION

IT HAS long been known from results of corpus aliatum implantation experiments and allatectomy that corpus allatum hormone stimulates metabolism, i.e. 1955; DE respiration, in insects. (THOMSEN,1949; THOMSENand HAMBURGER, WILDE and STEGWEE, 1958; S#GESSER, 1960; ROUSSEL, 1963). One of the problems has been to decide whether this effect on the metabolism is a direct one or an indirect one via the stimulation of other organs. SLAMA (1964a) and SLAMA and NOVAK (1962) suggest that the effect of corpus allatum is indirect and results from a stimulation of the ovaries. THOMSEN and HAMF~JRGER(1955) f ound, on the other hand, that the Or-consumption in ovariectomized Calliphom females was of the same degree as in normal females, whereas the respiration was lowered by 24 per cent after the removal of corpus allatum. It is possible that stimulation of the metabolism is an indirect effect of the corpus allatum hormone because there is evidence that corpus allatum acts via the neurosecretory material. Experiments with isolated mitochondria from flying musculature in Locusta (MINKS, 1966) sh owed that corpora allata added to the medium had no effect upon the respiration. L~SCHER (1965) measured respiration in isolated tissue from the fat body of Leucophaea. These experiments showed that the respiration in the fat body either 471

ELSE-MARGRJXE CONRADI-LARSEN

472

remained unchanged or increased slightly when corpora allata were added. When corpora cardiaca were added, the oxygen consumption increased up to 180 per cent. A comparable but lower effect was attained when brains were added. After experiments in aiwo with CulZiphoru, THOMSEN (1961) found it probable that corpus allatum stimulates metabolism by way of neurosecretion. In insects the activity of both the corpus allatum and the neuroaecretory cells is influenced by feeding. Thus in Oncopeltus the growth and activity of corpus allatum was greatly reduced when the insects were fed with glucose or were starved (JOHANSSON,1958). Many authors have shown a relation between neurosecretory activity and nutrition in insects. DHANDA (1967) found an accumulation of material in the neurosecretory cells of Hyalomma dromedarii immediately before the animals were fed. When Leucophaea were starving the liberation of neurosecretory material was repressed, but a few hours after feeding was resumed the neurosecretory material was again liberated (HIGHNAM et al., 1965). An increased activity of both corpus allatum and the neurosecretory cells was observed in Culliphora when the animals were fed with meat (proteins) after a period of sugar-feeding (LEA and THOMSEN, 1962). The present paper presents a study of the effect of neurosecretion and nutrition in Oncopeltus fasciatus in vivo, and a possible relationship between these factors is discussed. MATERIALS AND METHODS Breeding

Adult females of the milkweed bug, Oncopeltus fasciutus (Dallas), were fed on seeds of milkweed (Asclepius sp.) by a method described earlier by BUTT (1949) and JOHANSSON(1958). The animals were kept at 30 + 1°C. Adult individuals used for experiments were isolated O-14 hr after emergence. The glucose-fed bugs were kept in clean jars after isolation, and their water supply was exchanged with 10% glucose solution. Measurement of respiration

Respiration exchange was measured with a respirometer constructed at the University of Oslo (SCHOLANDER and IVERSEN,1958). The technique was based on conventional manometric systems and 3% KOH-solution was used as CO,absorber. Eight individual respirometers could be used at the same time and they were kept at a constant temperature of 30 f O*l”C in a 100 1. water-bath with a thermomixer. Care was taken that the animals were not struggling while their Os-consumption was measured. The animals were fed ad Zib. before respiration was measured. The Os-consumption is given as mm3 O,/mg of the body weight per hr. For these calculations the body weights of the animals after the experiment were always used.

OI;-~~~~~~~~~~~ ANDNUTRITIONIN THE

MILKWEED

BUG

473

The body weight diagrams refer to daily weighings of the same individuals through the whole period covered by the diagram. Some of these animals were also used for respiration measurements. In these, animals were weighed both before and after the experiment, the first weight being used for the body weight diagram, the second for the calculation of the O,-consumption. The operation technique used is described by JOHANSSON (1958). RESULTS

O,-Consumption in relation to the body weight In Oncopeltus the O,-consumption decreases with increasing body weight (Table 1). Th e ex p eriments were therefore planned with about an equal number of animals in each weight group.

O,-Consumption after the use of ether as an anaesthetic In Oncopeltus the use of ether as an anaesthetic seemed to have no effect upon the O,-consumption (Table 2). Ether was therefore used for all operations.

and body weight of adult females fed with seeds

O&m.sumption

The body weight and O,-consumption of adult females during the first days after emergence is shown in Fig. 1. The results are based on respiration measurements of 97 adult females fed with seeds and water 1 to 11 days after emergence. Among these animals 5 were selected at random and their weight controlled each follow the weight changes, with day (Fig. 1). Th e variations in O,-consumption 1.7 -

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EMERGENCE

FIG. 1. O,-consumption and body weight of adult females fed with seeds. A. Average O,-consumption of 11 to 30 females. Vertical bars represent S.E. Horizontal dotted line represents the average O,-consumption for the whole period. B. Average body weight of 5 females.

34 39 42 42

39

1 2 3 4

Total f S.E.

Days after Average emergence wt. (mg)

20

4

5 z

No. of animals 0.06 0*05 0.09 0.09

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mm9 Os/mg per hr + S.E.

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Average wt. (mg)

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No. of animals

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64

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Average wt. (mg)

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mm8 Os/mg per hr f SE.

60 mg No. of animals

WEIGHTIN ADULTFEMALES

mm* O,/mg per hr f S.E.

SO-60 mg

TABLE l-On-CONSUMPTION IN RELATIONTO THEBODY

&-CONSUMPTION TABLE

2-THE

AND NUTRITION

IN THE MILKWEED BUG

475

EFFECT OF ETHER ANAESTHETIC ON THE 02-~~~~~~~~~~~ IN ADULT FEMALES

Days

after

nuns Oz/mg

emergence Ether

anaesthetic

for 45 set No

anaesthetic

per hr

No.

+ S.E.

of

animals

2

1.27 + 0.09

7

1.30 20.15

2

1.23 + 0.05

20

7

1.32 + 0.05

18

approximately 1 day’s delay. The average O,-consumption was 1.27 mm3 O,/mg per hr.

6 6

for the first 11 days

O,-Consumption and body weight of adult females fed with glucose solution The body weight and OS-consumption of adult females fed with glucose during the first 11 days after emergence is shown in Fig. 2. For this experiment 98 adult females, fed with 394 glucose solution from the first to the eleventh day

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EMERGENCE

FIG. 2. O,-consumption and body weight of adult females fed with glucose solution. A. Average O,-consumption of 6 to 18 females. Vertical bars represent S.E. Horizontal dotted line represents the average O,-consumption for the whole period. B. Average body weight of 5 females.

after emergence were used. The body weight diagram is based on weighings of 5 of these animals through the same period. The body weight of glucose-fed females decreases through the whole period, while the respiration decreases considerably the first 2 days of the period. From the third day of the period the O,-consumption is approximately stable. ‘5

ELSE-MARGRETECONRADI-LARSEN

476

The average Os-consumption of glucose-fed adult females, calculated over 10 days after emergence is 0.96 mm3 O,/mg per hr or 24 per cent lower than the corresponding average O,-consumption of normally fed females (Fig. 1). O,-Consumption of adult females deprived of the neurosecretory cells The neurosecretory cells were removed from 303 adult females 1 day after emergence. About 50 per cent of the operated animals died within 10 days after the operation. The Os-consumption of 87 operated animals that survived more than 10 days after the operation was measured, and 3 of these animals were used for the weight curve. The results are shown in Fig. 3.

1.7 1.6

490

1

2

3

4

5

DAYS

AFTER

6

7

8

9

10

11

EMERGENCE

FIG. 3. O,-consumption and body weight of adult females deprived of the neurosecretory cells and fed with seeds. Arrow marks the time of the operation. A. Average O,-consumption of 6 to 18 females. Vertical bars represent SE. Horizontal dotted line represents the average O,-consumption through the whole period. B. Average body weight of 3 females.

As controls 39 adult females were operated. The head capsule was opened, but the neurosecretory cells were not damaged. Of these animals eleven died. The Os-consumption of the remaining 28 individuals was measured, and 4 of these animals were used for the control-weight diagram. The results are shown in Fig. 4. The body weight of adult females deprived of the neurosecretory cells appeared to decrease in a corresponding way to that of glucose-fed females (Fig. 3, cf. Fig. 2). The body weight of controls decreased 5 days after the operation, then increased through the rest of the period. Thus removal of the neurosecretory cells of adult females seems to result in decreased metabolism and cessation of nutrition uptake.

O+ZONSUMPTION

AND NUTRITION IN THE MILKWEED BUG

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FIG. 4.

5

DAYS

AFTER

6

7

8

9

10

11

EMERGENCE

of controls, fed with seeds. A. Average B. Average body weight of 4 females. For of 7 to 13 females. further references, see Fig. 3.

O,-consumption

Oa-consumption

4

and body weight

O,-Consumption and body weight of adult females fed with glucose solution for 6 days and then with seeds The body weight and Oz-consumption of adult females fed with glucose solution for 6 days and then with seeds and water, is shown in Fig. 5. The results are based on respiration measurements of 18 adult females 1 to 10 days after emergence and daily weighing of 4 of these animals in the same period. ~ ~~__~ ~~~ _~_~_ _._.._~ _ ~--. --, 17 16

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FIG. 5. O,-consumption and body weight of adult female, fed with glucose solution from first to seventh day after emergence, and then with seeds. Arrow marks resumed seed-feeding. A. Average 01-consumption of 6 to 11 females. Vertical bars represent S.E. B. Average body weight of 4 females.

ELSE-MARCRETECONRADI-LARSEN

478

When adult females were again fed with seeds after glucose feeding for 6 days, they would start to feed at an extraordinarily high rate and recover the normal weight for females of the same age within 2 days (Fig. 5, cf. Fig. 1). The respiration of the animals increased correspondingly when the diet was changed from glucose to seeds, and within 2 days the O,-consumption was even higher than that of normally fed females of the same age (Fig. 5, cf. Fig. 1).

O,-Consumption and body weight of adult females deprived of the neurosecretory and fed with glucose solution for 6 days and then with seeds

cells

In 76 adult females the neurosecretory cells were removed 1 day after emergence. Of the operated animals 29 died within 10 days after the operation. The O,consumption of 45 surviving animals was measured 2 to 11 days after emergence. The results are shown in Fig. 6.

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FIG. 6. O,-consumption and body weight in adult females deprived of the neurosecretory cells and fed with glucose solution from first to seventh day after emergence and then with seeds. Arrow a marks the time of operation. Arrow b marks the time of resumed seed-feeding. A. Average Or-consumption of 6 to 10 females. Vertical bars represent S.E. B. Average body weight of 4 females.

As controls the head capsules of 28 females were opened without damaging the neurosecretory cells. The controls were fed with glucose and seeds as described above. Nine of the controls died within 10 days after the operation. The O,consumption of the surviving females was measured, and 4 of these were used for the control body weight diagram (Fig. 7). The results are shown in Fig. 7. In females deprived of the neurosecretory cells no increase in O,-consumption, and only a slight increase in body weight was observed when the diet was changed from glucose to seeds (Fig. 6). In controls the OS-consumption increased 24 per

OS-CONSUMPTION

AND

NUTRITION

IN

THE

MILKWEED

cent within two days after resumed seed feeding, weight increase of 16 mg within 4 days (Fig. 7).

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FIG. 7. O+onsumption and body weight of controls fed with glucose from first to seventh days after emergence and then with seeds. A. Average O,-consumption of 6 to 10 females. B. Average body weight of 4 females. For further references, see Fig. 6.

DISCUSSION

When adult Oncopeltus females are fed ad lib. they do not seem to eat at a constant rate but in periods of 2 to 3 days followed by corresponding resting periods (Fig. 1). A n increase of O,-consumption with increased feeding was always observed 1 day after the body weight maxima. When adult females are fed for a period with only glucose solution, the body weight decreases through the whole period, while the OS-consumption decreases to a minimum within 2 days and then remains approximately constant for the rest of the period (Fig. 2). After emergence the animals have a well-developed fat body that should be able to support a normal metabolism for several days. The animals seem to be able to lower their metabolic level momentarily when their natural supply of food is removed. JOHANSSON (1958) showed that adult Oncopeltus females cease egg-laying when they are fed only with glucose solution. The animals again start to produce eggs after implantation of active corpora allata. Thus egg-laying controlled by corpus allatum ceases where the natural food is lacking, though the animals have a storage of nutrients sufficient to make egglaying possible. The results described above (Fig. 2) indicate endocrine control of the metabolism. It has been stated that removal of the neurosecretory cells results in decreased metabolism and cessation of nutrition uptake (Fig. 3). It is not possible here to

480

ELSE-MARGRETE CONRADI-LARSEN

ascertain whether this effect is a primary one or a secondary consequence of the removal of the neurosecretory cells. In Locusta and Leucophaea an increase of the respiration in isolated fat body mitochondria was observed when homogenized brains were added. (L~~SCHER,1965; MINKS, 1966). On that account it is likely that hormone from the neurosecretory cells directly stimulates the metabolism. The lowered nutrition uptake (Fig. 3) may be the consequence of the reduced metabolism. It might also be possible that the neurosecretory cells control the nutrition uptake. When this eventual control is blocked, the animals might starve, even if the supply of food is sufficient. THOMSEN and MILLER (1962) assert that the presence of the neurosecretory cells is necessary for the protease activity in the gut of Calliphora. STRANGWAYSound that Calliphora deprived of the neurosecretory cells were DIXON (1961) f unable to digest proteins, although the animals were forcibly fed with proteins. The present study shows that the loss of body weight in glucose-fed Oncopeltus females and in females deprived of the neurosecretory cells is of about the same degree (Figs. 2, 3). These facts suggest that the operated animals are unable to digest proteins. The considerable increase in respiration of Oncopeltus females when they are fed after a period of starvation does not take place when the neurosecretory cells of the animals are removed (Figs. 5, 6). The neurosecretory cells seem to control the metabolism in proportion to the food supply. It would be of interest to investigate whether the neurosecretory cells react generally upon the reduced food supply or upon the absence of one or more special factors of the food. I find the latter suggestion probable, as the animals do not utilize the available glucose and the fat body supply to maintain a normal metabolism. Thus, in the absence of this eventual special factor, the animals will adjust to a starvation situation by an adequately slow consumption of the stored nutrients. As numerous investigations have shown that hormone from the neurosecretory cells influences several physiological functions, the hormone has recently been called ‘activation hormone’ (AH). When the influence of AH on the metabolism is investigated by means of respiration measurements, it is necessary to recall that some of the functions controlled by AH might have a secondary influence upon the total O,-consumption. SLAMA (1964b) asserts that AH controls the digestion metabolism in Pyrrhochoris. THOMSENand MILLER (1959) found a considerably reduced protease activity in the gut of Calliphora when the neurosecretory cells were removed and conclude that AH controls the protein synthesis. A reduced or blocked protein synthesis after removal of the neurosecretory cells may lead to a lowered O,-consumption. If the animals are not able to digest protein it is probable that the conditions in the gut after a short time will be abnormal and thus the overall digestion repressed. A lowered nutrition uptake from the gut after removal of the neurosecretory cells might then influence the Os-consumption in a corresponding way, e.g. when the animals are glucose-fed. However, it is likely that the eventual effect upon the Os-consumption would work more gradually

02-~~~~~~~~~~~ ANDNUTRITION IN THE MILKWEED BUG

481

than the effect that is here observed after removal of the neurosecretory cells (Fig. 3). THO~~SEN (1952) found that the fat content in the fat body decreased when AH was not present while the glycogen content increased. A stimulating effect upon the fat metabolism is later asserted (L~~SCHER,1965). A reduced fat metabolism after removal of the neurosecretory celIs will probably also be observable as a reduction of the total O,-consumption. It also ought to be mentioned that NAYAR (1957) showed that AH seemed to influence the water balance in Iphita limbata.

It is evident that when AH is not present, several changes take place in the insect that might influence the total O,-consumption. Probably the reduced O,-consumption observed in the present study after removal of the neurosecretoq cells is partly a consequence of the repression of several oxygen-consuming functions in the insect. However, animals deprived of the neurosecretory cells are no longer able to respond to repeated seed feeding after a period of glucose feeding. In addition, the reduction of the O,-consumption when the diet is changed from seeds to glucose is momentary. These facts indicate a hormonal control of the metabolism in relation to the food supply. As the neurosecretor) cells are observed to influence the O,-consumption, and the control of the O,-consumption in relation to the nutrition, it is probable that AH is the hormone which controls metabolism. REFERENCES BUTT F. H. (1949)

Embryology of the milkweed bug, Oncopeltus fusciutus (Hemiptera). Mem. Cornell Exp. St. 283, l-43. DHANDAV. (1967) Changes in neurosecretory activity at different stages in the adult Hyalomma dromedarii Koch, 1844. Nature, Lond. 214, 508-509. HIGHNAM K. C., HILL L., and MORDUE W. (1965) The effects of starvation and removal OP the frontal ganglion upon the endocrine control of oocyte development in the desert locust. Abstr. pap. 3rd Conf. Europ. Comp. Endocr., Copenhagen, p. 24. JOHANSSON A. S. (1958) Relation of nutrition to endocrine reproductive functions in the milkweed bug, OncopeZtus fascia&s (Dallas) (Heteroptera: Lygaeidae). Nytt. Mug.

Zool. 7, 1-132. LE.* A. 0. and THOMSEN E. (1962) Cycles in the synthetic activity of the medial neuro-. secretory cells of Calliphora erythrocephafa and their regulation. _%fem. Sot. Endocr. 12.

345-347. LOSCHER M. (1965)

The influence of hormones on tissue respiration in the insect, Leucophaea Abs. pap. 3rd Conf. Europ. Comp. Endocr., Copenhagen, p. 38. MIPZKS A. K. (1966) Effects in vitro of the corpus allatum hormone on respiratory metabolism in the African migratory locust. r. Endocrinol. 37, xx. NAYAR K. K. (1957) Water content and release of neurosecretory products in Iphita limbata. Cur. Sci. 26, 25.

madrae.

RO~SSEL J. P. (1963) Consommation d’oxygene apr&s ablation des corpora allata chez des femelles adultes de Locusta migratoria L. J. Insect Physiol. 9, 721-725. SKGESSER H. (1960) Uber die Wirkung der corpora allata auf den Sauerstoffverbrauch bei der Schabe Laucophae madrae (F.). J. Insect Physiol. 5, 264-285. Sand. SCHOLANDER P. F. and IVER~EN 0. (1958) N ew design of volumetric respirometer.

J. Ctin. W Lab. Invest. 10, 429-431.

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ELSE-MARGRETECONRADI-LARSEN

SLAMAK. (1964a) Hormonal control of respiratory metabolism during growth, reproduction, and diapause in male adults of Pyrrochoris apterus L. (Hemiptera). B&l. Bull., Woods Hole 127, 499-510. SLAMA K. (1964b) Hormonal control of haemolymph protein concentration in the adults of Pyrrochoris apterus L. (Hemiptera). J. Insect Physiol. 10,773-782. SL~MA K. and NOVAKV. J. A. (1962) The influence of the juvenile hormone on the oxygen consumption in Pyrrochoris apterus. Acta Symp. Evol. Ins., Prague, pp. 147-151. STRANGWAYS-DIXON J. (1961) Th e relationship between nutrition, hormones and reproduction in the blowfly Calliphora erythrocephala (Meig.)-II. The effect of removing the ovaries, the corpus allatum and the median neurosecretory cells upon selective feeding, and the demonstration of the corpus allatum cycle. J. exp. Biol. 38, 637-646. THOMSEN E. (1949) Influence of the corpus allatum on oxygen consumption of adult Calliphora erythrocephala Meig. J. exp. Biol. 26, 137-149. THOMSEN E. (1952) Functional significance of the neurosecretory brain cells and the corpus cardiacum in the female blowfly Calliphora erythrocephala. J. exp. Biol. 29, 137-172. THOMSENE. (1961) Quotation from Ltischer, M. 1965 : The influence of hormones on tissue respiration in the insect, Leucophae madrae. Abs. pap. 3rd Conf. Europ. Camp. Endocr., Copenhagen, p. 345. THOMSENE. and HAMBURGERK. (1955) Oxygen consumption of castrated females of the blowfly, Calliphora erythrocephala Meig. J. exp. Biol. 32, 692-699. THOMSENE. and MBLLER I. (1959) Neurosecretion and intestinal proteinase activity in an insect, Calliphora erythrocephala. Nature, Lund. 183, 1401-1402. THOMSENE. and MP~LLERI. (1962) Influence of neurosecretory cells and of corpus allatum on intestinal protease activity in the adult Calliphora erythrocephala Meig. J. exp. Biol. 40, 301-321. WILDE J. DE and STEGWEED. (1958) Two major effects of the corpus allatum in the adult Colorado beetle (Leptinotarsa decemlineata Say). Archs. neerl. Zool. (Suppl.) 13, 277289.