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Regulation of larval diapause by juvenile hormone in the European corn borer, Ostrinia nubilalis
J. Insect Physiol., 1976, Vol. 22, pp. 389 to 392. Pergamon Press. Printed in Great Britain.
REGULATION HORMONE
OF LARVAL DIAPAUSE BY JUVENILE IN THE EUROPEAN CORN BORER,
OSTRINIA
NUBILALIP
SHIGEMI YAGI and NOBUSUKEAKAIKE Laboratory of Applied Zoology, Faculty of Agriculture, Tokyo University of Education, Komaba, Meguro-ku, Tokyo 153, Japan (Received 18 August 1975) Abstract-The effects of juvenile hormone (JH) on the larval diapause of the European corn borer, Ostrinia nubilalis, were investigated. The larval period was prolonged and the development of gonads was retarded if non-diapause larvae were treated with JH. Pupation of diapausing larvae was accelerated by allatectomy. It was concluded that the diapause of this borer is largely regulated by JH. INTRODUCTION IT IS well established that the larval diapause of the European corn borer, Ostrinia nutn’lalis, is induced by a short-day photoperiod of 10 to 14hr/day at 3O”C, whereas non-diapause larvae are obtained by a long-day photoperiod or continuous dark or continuous light. Furthermore, the insects do not need a low temperature for breaking diapause but the diapause is terminated by exposing them to a long-day photoperiod for about 2 weeks (BECK, 1962). BECK and ALEXANDER(1964a, b) reported that the termination of diapause in this borer resulted from the activation of the brain which had been stimulated by a hormone ‘proctodone’ which originated in the epithelial cells of the hindgut. Later, from histological studies on the anterior portion of the hindgut, it was suggested that the ileal epithelial cells have a secretory function, and that the granules which were observed in the cells contained an endocrine substance, proctodone (BECK et al., 1965; HA~~EMERand BECK, 1968). However, few studies have been made to support this hypothesis except in the greater wax moth, Gal&a mellonella (BECK and ALEXANDER,1964a; BECK, 1968). On the other hand, from a series of experiments, FUKAYA and MITSUHASHI (1957, 1958, 1961) claimed that the larval diapause of the rice stem borer, Chile suppressalis, is induced and maintained by a hormone secreted from the corpus allatum, and recently this was proved by YACI and FUKAYA (1974); namely, juvenile hormone (JH) is a key factor which regulates the larval diapause of this borer and, further, the induction of diapause is * Muruua~ and MUNROE (1970) stated that the European corn borer distributed in Japan should be Ostrinia furnacalis. 12
closely related with the high JH titre in the haemolymph during the early stage of the last larval instar. Moreover, it has been postulated that JH regulates the larval diapause of the southwestern corn borer, Diatraea grartdiosella (CHIPPENDALB and YIN, 1973; YIN and CHIPPENDALE,1973,1974), and the khapra beetle, Trogoderma granarium (NAIR, 1974). In the present paper we describe the r61e of JH on the larval diapause of the European corn borer, 0. nubilalis. MATERIALS
AND METHODS
Insects The progeny of insects collected from the fields of Tohoku Agricultural Experiment Station in Iwate Prefecture was used in the present experiments. Larvae were reared on the flesh leaves or stalks of maize, Zea mays, or of sorrel, Rumex japonicus. An artificial diet (BECK et al., 1968) was also used in some experiments. Plastic cups (200 ml) were used as rearing containers. In order to avoid cannibalism of the larvae, they were reared individually in glass vials (1.5 x 10.5 cm) after the fourth instar, and were kept at 25°C under a long-day photoperiod of 16L : 8D (LD) or a short-day photoperiod of 12L : 12D (SD) which resulted in non-diapause or diapause, respectively. Juvenile hormone According to the procedures employed for the experiments in the rice stem borer (YAGI and FUKAYA, 1974), either 1-(3,4-methylenedioxyphenyl)-7-epoxy-4,8-dimethyl-nona-1,3-dine (JHA) or C-18 Cecreia JH (C-18JH) was used. Larvae were reared on the artificial diet containing various concentrations of JHA under the LD condition.
389
390
SHIGEMI
YAGI AND NOBUSUKEAICAIKE
The developmental stages of the insects were continuously examined for 70 days after hatching as in the case of the rice stem borer. On the other hand, daily topical applications of C-ISJH to the fourth instar larvae destined to become non-diapause were made for 20 days. Allatectomy Diapause larvae of the last instar reared under the SD condition were used. The corpus cardiacumallatum complexes were removed with sharpened forceps under a dissecting microscope. Shamoperated controls were also done. After the operation the photoperiod was changed from SD to LD to accelerate the termination of diapause.
the controls, almost all of the larvae pupated during the acetone treatment. An interesting fact is that in the case of the application of 2 pg of C-18JH five larvae survived more than 20 days even under the LD non-diapause condition, and later they normally pupated. In this case the average number of days required for pupation after onset of the hormone treatment was 29.0 days, which was longer than both controls 1 and 2. In the larvae treated with 2 pg of the hormone, however, about one-sixth of the larvae ecdysed to larval-pupal intermediates, whereas only one intermediate was obtained from treatment with 0.2 pg of the hormone (Table 2). The gonads of the larvae treated with 2 pugC-ISJH were less developed than those of non-diapause larvae, and their development was retarded like diapause ones (CLOUTIERand BECK, 1963).
RESULTS
Effects of allatectomy
Effects of JH on non-diapause larvae When the larvae were continuously reared on an artificial diet containing various concentrations of JHA, the larval period was prolonged with an increase of the hormone concentration; some larvae survived more than 50 days in the JHA-treated plot, whereas in control cultures all larvae pupated within 41 days after hatching (Table 1). Among the larvae treated with 130 ppm of JHA one larval-pupal intermediate was obtained; moreover, two larvae survived more than 70 days. These larvae, however, did not pupate and died later (Table 1). Table 1.
Effects of JHA on development of nondiapause larvae of 0. nubilalis
on diapause larvae
A pair or a half of the corpora allata was extirpated from 3 to 4-day-old diapause larvae of the last instar. After operation the larvae were kept under LD conditions. The results are shown in Table 3. Pupation occurred in both allatectomized and shamoperated larvae. However, termination of diapause occurred sooner in the larvae from which a pair of corpora allata had been removed than in those from which only one was extirpated or the shamoperated ones. The average number of days required for pupation in a ‘half-allatectomized larvae’ was almost equal to that of the shamoperated controls. DISCUSSION
The present experiments show that larval diapause of the European corn borer, 0. nubilalis, is pupationafter hatching largely regulated by JH. This was proved by the 1XTae pxpae cont. following results: (1) prolongation of the larval obtnined’) used (PPd Max. AVW. Iii::. period occurred when JH was applied, (2) the gonads of non-diapause larvae treated with JH were Irl 33.6 0 33 (0) 35 13 retarded like those of diapause ones, and (3) pupaJ,l.h 53 21, (16) :5 26 WJ tion was accelerated by allatectomy in diapause :i6. ; 1’3 (33)j) 3: jr 73 130 larvae although both allatectomized and sham58 55.2 operated larvae pupated by the change of photo$2 22 5 (17) 650 period from SD to LD just after operation. As indicated in Tables 1 and 2 we could not a) Figures ii-psrentheses shoa the nun'oerof deadla%-vae obtain larvae which showed the same or a greater duringthe trentxe.,t. intensity of diapause as those of SD-induced diapause larvae, although the dosage of JH used for Ostrinia was almost equal to that used for CMo In the next series of experiments, the effects of (YAGI and FUKAYA, 1974). This seems to suggest C-18JH on non-diapause larvae were examined. that Ostrinia is more sensitive to the photoperiod. The hormone was topically applied daily for 20 days In this regard BECK and APPLE (1961) have already to the l-day-old fourth instar larvae destined to reported that the diapause of this borer can be become non-diapause by the LD condition. As terminated rapidly by a change of photoperiod from indicated in Table 2, when the hormone was SD to LD in the early stage of diapause. Similar applied, some larvae survived until the end of the results were also obtained in our experiments treatment, but none pupated. On the contrary, in (Tables 2, 3). It is therefore suggested that, in
:iorKme
x0.
0:
:;o. Of
Days
required for
Regulation of larval diapause by juvenile hormone in the European corn borer
391
Table 2. Effects of C-18JH on non-diapause larvae of 0. nub&& Dose")
Eo. Of
Results 20 days after
(pg/0.5+)
larvae
oraet Of treatment
Aver. days requirsd for pupation after
used iio.of
1:o.Of
110.0:
lw_Ta?
internediates pupae
onset Of hormone treatmenY survivedb) o:,tziLeE") rurtro1-1 (3cetwe) 0.2 2
7
1 (0)
19
16 (2) 35 (27)
1.t:
CJ::trcl-2’!)
(LW
1”
0
'
SD)
obtained
0
6
1
0
2'1
0
0
(0)
15.4
(2?.o)e)
10.5
17
a) Zir::erC-133;;dissolved ir 0.5 pl of acetate or t'r.e acetone only I:J:iopicalll;applied daily to eacizl-day-old larva of the 4th inStaP for 20 Ck:/z. _) T_xres
in.parentheses show the nam~?erof dead larvae durin?:tale
trcat!xe:ll. c) Intenzediatecobtained were slightly progressive(intermediate +) or :?cavilJpro,rressiuc(internediate ++) larval-pupal interwdiates (Sac T&
ad
fi&,
1574).
u) Tllotape~io,. sas changed from SD to I>Dat the 1st da7 of tileL,t;: i:lstar. e) Fire lsrvae pupated after the 20th dar.
Table 3. Effects of allatectomy on diapause larvae of 0. nub&&s
Operztiol-~“) ::a.
or
Lo.
Ds:lcrequired for pupation
0.p
larva~~ pupae 33ec.
after operation
'3) ol-toir*,d IX_::.
k::.
LXX,
20
12.0
a pi;_
27
i, (23)
a Pall"
55
11 (27)
14
31
22.?
Lb'
12 (35:
iT
2: _',
73 --._
Si311
Ostrinia, unlike Chile, the photoperiodic stimuli of the LD condition may be stronger than those of applied JH. On the other hand, it was shown that the diapause intensity of this borer was greatIy affected by extirpation of a pair of corpora allata in diapause larvae (Table 3). A further notable fact is that one half of a pair of corpora allata could function in a manner which compensated for loss of the other (Table 3). Moreover, it was observed that when allatectomized diapause larvae continued to be reared under SD condition, one of the larvae
pupated 37 days after the operation although almost all of the larvae died within 40 days (YAGI,1975). BECK and SHANE (1969) observed that diapause larvae which had been injected with a relatively high dosage of a- or /?-ecdysone could not pupate but died during the apolysis to larval-pupal intermediates. In our experiments the ecdysis to these intermediates was also observed when JH was applied to non-diapause larvae (Tables 1, 2). From these results it was suggested that JH plays an important r6le for the induction and maintenance of
392
SHIGJIMI YAGI AND NOBUSUKEAKAIKE
diapause in this borer, and that the JH titre is rather high at an early stage during diapause. Further, this idea is supported by histological studies that the secretory activity of the corpora allata in 0. nub&zlis seems to be active during diapause (MITSUHASHI, 1963). As has already been suggested (FUKAYA and MITSUHASHI, 1961; MITSUHASHI, 1963), the Chiletype diapause, mediated intrinsically by JH, exists widely in other insect species which have a larval diapause (YAGI and FUKAYA, 1974). This is also supported in Diatraea grandiosella (CHIPPENDALE and YIN, 1973; YIN and CHIPPWDALE, 1973, 1974), Trogoderma granarium (NAIR, 1974). Moreover, in the cabbage armyworm, Mamestta brassicae, in which
pupal diapause is induced by a short-day photoperiod at 20°C during the larval period, it was revealed that in larvae destined to enter diapause the high JH titre at an early stage of the last larval instar caused the inhibition of spermatogenesis and prolongation of the last larval period as in the Chile-type diapause (MAGI, 1975). Further, a similar mechanism mellonella
has
been
demonstrated
in
Gall&a
in which active corpora allata cause considerable prolongation of the last larval instar (GRANGERand SEHNAL,1974; SEHNALand GRANCER, 1975). In Ostrinia, whether proctodone does or does not exist, and if it does, the relationship between JH and this hormone-these questions remain to be investigated. Acknowledgements-We wish to thank the late Professor M. FUKAYA of this laboratory for his suggestions and criticisms. Thanks are also due to Dr. T. KOBAYA~HIand Mr. 0. SAITO of Tohoku Agricultural Experiment Station for supplying the insects used in this study, to Dr. D. B. SIDDALLof Zoecon Corporation and Professor S. TAMURAof Tokyo University for supplying the hormones used in this study, and to Dr. J. MITSUHASHI of National Institute of Agricultural Sciences for his kindness in reading through this manuscript.
REFERENCES BECK S. D. (1962) Photoperiodic induction of diapause in an insect. Biol. Bull., Wooa’s Hole 122, i-12. BECK S. D. (1968) Insect Photoperiodism. Academic Press, New York. BECK S. D. and ALEXANDW N. (1964a) Hormonal activation of the insect brain. Science, Wash. 143,
478-479.
BECK S. D. and AL WANDERN. (1964b) Proctodone, an insect developmental hormone. Biol. Bull., Woods Hole 126,185-198. BECK S. D. and APPLE J. W. (1961) Effects of temperature and photoperiod on voltinism of geographical populations of the European corn borer, Py~austu nubilalis (Hbn.). J. econ. Ent. 54, 550-558.
BECK S. D., CHIPPENDALEG. M., and SWINSON D. E. (1968) Nutrition of the European corn borer, Ostrinia nubilalis-VI. A larval rearing medium without crude plant fraction. Ann. ent. Sot. Am. 61, 459-+62. BECK S. D. and SHANE J. L. (1969) Effects of ecdysones on diapause in the European corn borer, Ostriniu nubilalis. J. Insect Physiol. 15, 721-730. BECK S. D., SHANE J. L., and COLVIN I. B. (1965) Proctodone production in the European corn borer, Ostrinia nubilalis. J. Insect Physiol. 11, 297-303. CHIPPENDALEG. M. and YIN C.-M. (1973) Endocrine activity retained in diapause insect larvae. Nature, Lond. 246, 511-513. CLOUTIER E. J. and BECK S. D. (1963) Spermatogenesis and diapause in the European corn borer, Ostriniu nubilalis. Ann. ent. Sot. Am. 56, 253-255. FUKAYA M. and MITSUHASHIJ. (1957) The hormonal control of larval diapause in the rice stem borer, Chilo supptessalis--I. Some factors in the head maintaining larval diapause. Jap.._7. Appl. Ent. Zool. 1, 145-154. FUKAYA M. and MITSUHASHIJ. (1958) The hormonal control of larval diapause in the rice stem borer, Chilo suppressalis-II. The activity of the corpora allata during the diapausing period. Jap. J. Appl. Ent. Zool. 2, 223-226. FUKAYAM. and MITSUHASHIJ. (1961) Larval diapause in the rice stem borer with special reference to its hormonal mechanism. Bull. nut. Inst. Agr. Sci. (C) 13, l-32. GRANGERN. A. and SEHNAL F. (1974) Regulation of larval corpora allata in Gallaia mellonella. Nature, Land. 251,415-417. HA~SEMERS. M. and BECK S. D. (1968) Histochemistry of the ileum of the European corn borer, Ostrinia n&la&. 7. Insect Phvsiol. 14. 1233-1246. MITSUHASHI”J. (1963) Histological studies on the neurosecretory cells of the brain and on the corpus allatum during diapause in some lepidopterous insects. Bull. mat. Inst. Am. Sci. (Cj 16. 67-121. MUTUURA A. and MUNROE-E. (19iOj Taxonomy and distribution of the European corn borer and allied (Lepidoptera: Pyralidae). species : genus Ostriniu Mem. ent. Sot. Can. 71, 1-112. NAIR K. S. S. (1974) Studies on the diapause of Trogoderma grunatium: effects of juvenile hormone analogues on growth and metamorphosis. J. Insect Physiol. 20, 231-244. SEHNAL F. and GRANCER N. A. (1975) Control of corpora allata function in larvae of Galleria mellonella. Biol Bull.. Woods Hole 148. 106-l 16. YAGI S. (19j5) Endocrinological studies on diapause in some lepidopterous insects. Mem. Fat. Agric. Tokyo Uniw. Education 21, l-49. In Japanese with English summary. YAGI S. and FUKAYAM. (1974) Juvenile hormone as a key factor regulating larval diapause of the rice stem borer, Chilo su&ressal&. Appl. I&t. Zool. 9, 247-255. YIN C.-M. and CHIPPENDALE G. M. (1973) Juvenile hormone regulation of the larval diapau& of the southwestern corn borer, Diatraea grandiosella. J. Insect Phvsiol. 19. 2403-2420. YIN C.-M.- and C&PPENDALE G. M. (1974) Juvenile hormone and the induction of larval polymorphism and diapause of the southwestern corn borer, Diatraea grandiosella. J. Insect Physiol. 20, 1833-1848.
REGULATION HORMONE
OF LARVAL DIAPAUSE BY JUVENILE IN THE EUROPEAN CORN BORER,
OSTRINIA
NUBILALIP
SHIGEMI YAGI and NOBUSUKEAKAIKE Laboratory of Applied Zoology, Faculty of Agriculture, Tokyo University of Education, Komaba, Meguro-ku, Tokyo 153, Japan (Received 18 August 1975) Abstract-The effects of juvenile hormone (JH) on the larval diapause of the European corn borer, Ostrinia nubilalis, were investigated. The larval period was prolonged and the development of gonads was retarded if non-diapause larvae were treated with JH. Pupation of diapausing larvae was accelerated by allatectomy. It was concluded that the diapause of this borer is largely regulated by JH. INTRODUCTION IT IS well established that the larval diapause of the European corn borer, Ostrinia nutn’lalis, is induced by a short-day photoperiod of 10 to 14hr/day at 3O”C, whereas non-diapause larvae are obtained by a long-day photoperiod or continuous dark or continuous light. Furthermore, the insects do not need a low temperature for breaking diapause but the diapause is terminated by exposing them to a long-day photoperiod for about 2 weeks (BECK, 1962). BECK and ALEXANDER(1964a, b) reported that the termination of diapause in this borer resulted from the activation of the brain which had been stimulated by a hormone ‘proctodone’ which originated in the epithelial cells of the hindgut. Later, from histological studies on the anterior portion of the hindgut, it was suggested that the ileal epithelial cells have a secretory function, and that the granules which were observed in the cells contained an endocrine substance, proctodone (BECK et al., 1965; HA~~EMERand BECK, 1968). However, few studies have been made to support this hypothesis except in the greater wax moth, Gal&a mellonella (BECK and ALEXANDER,1964a; BECK, 1968). On the other hand, from a series of experiments, FUKAYA and MITSUHASHI (1957, 1958, 1961) claimed that the larval diapause of the rice stem borer, Chile suppressalis, is induced and maintained by a hormone secreted from the corpus allatum, and recently this was proved by YACI and FUKAYA (1974); namely, juvenile hormone (JH) is a key factor which regulates the larval diapause of this borer and, further, the induction of diapause is * Muruua~ and MUNROE (1970) stated that the European corn borer distributed in Japan should be Ostrinia furnacalis. 12
closely related with the high JH titre in the haemolymph during the early stage of the last larval instar. Moreover, it has been postulated that JH regulates the larval diapause of the southwestern corn borer, Diatraea grartdiosella (CHIPPENDALB and YIN, 1973; YIN and CHIPPENDALE,1973,1974), and the khapra beetle, Trogoderma granarium (NAIR, 1974). In the present paper we describe the r61e of JH on the larval diapause of the European corn borer, 0. nubilalis. MATERIALS
AND METHODS
Insects The progeny of insects collected from the fields of Tohoku Agricultural Experiment Station in Iwate Prefecture was used in the present experiments. Larvae were reared on the flesh leaves or stalks of maize, Zea mays, or of sorrel, Rumex japonicus. An artificial diet (BECK et al., 1968) was also used in some experiments. Plastic cups (200 ml) were used as rearing containers. In order to avoid cannibalism of the larvae, they were reared individually in glass vials (1.5 x 10.5 cm) after the fourth instar, and were kept at 25°C under a long-day photoperiod of 16L : 8D (LD) or a short-day photoperiod of 12L : 12D (SD) which resulted in non-diapause or diapause, respectively. Juvenile hormone According to the procedures employed for the experiments in the rice stem borer (YAGI and FUKAYA, 1974), either 1-(3,4-methylenedioxyphenyl)-7-epoxy-4,8-dimethyl-nona-1,3-dine (JHA) or C-18 Cecreia JH (C-18JH) was used. Larvae were reared on the artificial diet containing various concentrations of JHA under the LD condition.
389
390
SHIGEMI
YAGI AND NOBUSUKEAICAIKE
The developmental stages of the insects were continuously examined for 70 days after hatching as in the case of the rice stem borer. On the other hand, daily topical applications of C-ISJH to the fourth instar larvae destined to become non-diapause were made for 20 days. Allatectomy Diapause larvae of the last instar reared under the SD condition were used. The corpus cardiacumallatum complexes were removed with sharpened forceps under a dissecting microscope. Shamoperated controls were also done. After the operation the photoperiod was changed from SD to LD to accelerate the termination of diapause.
the controls, almost all of the larvae pupated during the acetone treatment. An interesting fact is that in the case of the application of 2 pg of C-18JH five larvae survived more than 20 days even under the LD non-diapause condition, and later they normally pupated. In this case the average number of days required for pupation after onset of the hormone treatment was 29.0 days, which was longer than both controls 1 and 2. In the larvae treated with 2 pg of the hormone, however, about one-sixth of the larvae ecdysed to larval-pupal intermediates, whereas only one intermediate was obtained from treatment with 0.2 pg of the hormone (Table 2). The gonads of the larvae treated with 2 pugC-ISJH were less developed than those of non-diapause larvae, and their development was retarded like diapause ones (CLOUTIERand BECK, 1963).
RESULTS
Effects of allatectomy
Effects of JH on non-diapause larvae When the larvae were continuously reared on an artificial diet containing various concentrations of JHA, the larval period was prolonged with an increase of the hormone concentration; some larvae survived more than 50 days in the JHA-treated plot, whereas in control cultures all larvae pupated within 41 days after hatching (Table 1). Among the larvae treated with 130 ppm of JHA one larval-pupal intermediate was obtained; moreover, two larvae survived more than 70 days. These larvae, however, did not pupate and died later (Table 1). Table 1.
Effects of JHA on development of nondiapause larvae of 0. nubilalis
on diapause larvae
A pair or a half of the corpora allata was extirpated from 3 to 4-day-old diapause larvae of the last instar. After operation the larvae were kept under LD conditions. The results are shown in Table 3. Pupation occurred in both allatectomized and shamoperated larvae. However, termination of diapause occurred sooner in the larvae from which a pair of corpora allata had been removed than in those from which only one was extirpated or the shamoperated ones. The average number of days required for pupation in a ‘half-allatectomized larvae’ was almost equal to that of the shamoperated controls. DISCUSSION
The present experiments show that larval diapause of the European corn borer, 0. nubilalis, is pupationafter hatching largely regulated by JH. This was proved by the 1XTae pxpae cont. following results: (1) prolongation of the larval obtnined’) used (PPd Max. AVW. Iii::. period occurred when JH was applied, (2) the gonads of non-diapause larvae treated with JH were Irl 33.6 0 33 (0) 35 13 retarded like those of diapause ones, and (3) pupaJ,l.h 53 21, (16) :5 26 WJ tion was accelerated by allatectomy in diapause :i6. ; 1’3 (33)j) 3: jr 73 130 larvae although both allatectomized and sham58 55.2 operated larvae pupated by the change of photo$2 22 5 (17) 650 period from SD to LD just after operation. As indicated in Tables 1 and 2 we could not a) Figures ii-psrentheses shoa the nun'oerof deadla%-vae obtain larvae which showed the same or a greater duringthe trentxe.,t. intensity of diapause as those of SD-induced diapause larvae, although the dosage of JH used for Ostrinia was almost equal to that used for CMo In the next series of experiments, the effects of (YAGI and FUKAYA, 1974). This seems to suggest C-18JH on non-diapause larvae were examined. that Ostrinia is more sensitive to the photoperiod. The hormone was topically applied daily for 20 days In this regard BECK and APPLE (1961) have already to the l-day-old fourth instar larvae destined to reported that the diapause of this borer can be become non-diapause by the LD condition. As terminated rapidly by a change of photoperiod from indicated in Table 2, when the hormone was SD to LD in the early stage of diapause. Similar applied, some larvae survived until the end of the results were also obtained in our experiments treatment, but none pupated. On the contrary, in (Tables 2, 3). It is therefore suggested that, in
:iorKme
x0.
0:
:;o. Of
Days
required for
Regulation of larval diapause by juvenile hormone in the European corn borer
391
Table 2. Effects of C-18JH on non-diapause larvae of 0. nub&& Dose")
Eo. Of
Results 20 days after
(pg/0.5+)
larvae
oraet Of treatment
Aver. days requirsd for pupation after
used iio.of
1:o.Of
110.0:
lw_Ta?
internediates pupae
onset Of hormone treatmenY survivedb) o:,tziLeE") rurtro1-1 (3cetwe) 0.2 2
7
1 (0)
19
16 (2) 35 (27)
1.t:
CJ::trcl-2’!)
(LW
1”
0
'
SD)
obtained
0
6
1
0
2'1
0
0
(0)
15.4
(2?.o)e)
10.5
17
a) Zir::erC-133;;dissolved ir 0.5 pl of acetate or t'r.e acetone only I:J:iopicalll;applied daily to eacizl-day-old larva of the 4th inStaP for 20 Ck:/z. _) T_xres
in.parentheses show the nam~?erof dead larvae durin?:tale
trcat!xe:ll. c) Intenzediatecobtained were slightly progressive(intermediate +) or :?cavilJpro,rressiuc(internediate ++) larval-pupal interwdiates (Sac T&
ad
fi&,
1574).
u) Tllotape~io,. sas changed from SD to I>Dat the 1st da7 of tileL,t;: i:lstar. e) Fire lsrvae pupated after the 20th dar.
Table 3. Effects of allatectomy on diapause larvae of 0. nub&&s
Operztiol-~“) ::a.
or
Lo.
Ds:lcrequired for pupation
0.p
larva~~ pupae 33ec.
after operation
'3) ol-toir*,d IX_::.
k::.
LXX,
20
12.0
a pi;_
27
i, (23)
a Pall"
55
11 (27)
14
31
22.?
Lb'
12 (35:
iT
2: _',
73 --._
Si311
Ostrinia, unlike Chile, the photoperiodic stimuli of the LD condition may be stronger than those of applied JH. On the other hand, it was shown that the diapause intensity of this borer was greatIy affected by extirpation of a pair of corpora allata in diapause larvae (Table 3). A further notable fact is that one half of a pair of corpora allata could function in a manner which compensated for loss of the other (Table 3). Moreover, it was observed that when allatectomized diapause larvae continued to be reared under SD condition, one of the larvae
pupated 37 days after the operation although almost all of the larvae died within 40 days (YAGI,1975). BECK and SHANE (1969) observed that diapause larvae which had been injected with a relatively high dosage of a- or /?-ecdysone could not pupate but died during the apolysis to larval-pupal intermediates. In our experiments the ecdysis to these intermediates was also observed when JH was applied to non-diapause larvae (Tables 1, 2). From these results it was suggested that JH plays an important r6le for the induction and maintenance of
392
SHIGJIMI YAGI AND NOBUSUKEAKAIKE
diapause in this borer, and that the JH titre is rather high at an early stage during diapause. Further, this idea is supported by histological studies that the secretory activity of the corpora allata in 0. nub&zlis seems to be active during diapause (MITSUHASHI, 1963). As has already been suggested (FUKAYA and MITSUHASHI, 1961; MITSUHASHI, 1963), the Chiletype diapause, mediated intrinsically by JH, exists widely in other insect species which have a larval diapause (YAGI and FUKAYA, 1974). This is also supported in Diatraea grandiosella (CHIPPENDALE and YIN, 1973; YIN and CHIPPWDALE, 1973, 1974), Trogoderma granarium (NAIR, 1974). Moreover, in the cabbage armyworm, Mamestta brassicae, in which
pupal diapause is induced by a short-day photoperiod at 20°C during the larval period, it was revealed that in larvae destined to enter diapause the high JH titre at an early stage of the last larval instar caused the inhibition of spermatogenesis and prolongation of the last larval period as in the Chile-type diapause (MAGI, 1975). Further, a similar mechanism mellonella
has
been
demonstrated
in
Gall&a
in which active corpora allata cause considerable prolongation of the last larval instar (GRANGERand SEHNAL,1974; SEHNALand GRANCER, 1975). In Ostrinia, whether proctodone does or does not exist, and if it does, the relationship between JH and this hormone-these questions remain to be investigated. Acknowledgements-We wish to thank the late Professor M. FUKAYA of this laboratory for his suggestions and criticisms. Thanks are also due to Dr. T. KOBAYA~HIand Mr. 0. SAITO of Tohoku Agricultural Experiment Station for supplying the insects used in this study, to Dr. D. B. SIDDALLof Zoecon Corporation and Professor S. TAMURAof Tokyo University for supplying the hormones used in this study, and to Dr. J. MITSUHASHI of National Institute of Agricultural Sciences for his kindness in reading through this manuscript.
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BECK S. D., CHIPPENDALEG. M., and SWINSON D. E. (1968) Nutrition of the European corn borer, Ostrinia nubilalis-VI. A larval rearing medium without crude plant fraction. Ann. ent. Sot. Am. 61, 459-+62. BECK S. D. and SHANE J. L. (1969) Effects of ecdysones on diapause in the European corn borer, Ostriniu nubilalis. J. Insect Physiol. 15, 721-730. BECK S. D., SHANE J. L., and COLVIN I. B. (1965) Proctodone production in the European corn borer, Ostrinia nubilalis. J. Insect Physiol. 11, 297-303. CHIPPENDALEG. M. and YIN C.-M. (1973) Endocrine activity retained in diapause insect larvae. Nature, Lond. 246, 511-513. CLOUTIER E. J. and BECK S. D. (1963) Spermatogenesis and diapause in the European corn borer, Ostriniu nubilalis. Ann. ent. Sot. Am. 56, 253-255. FUKAYA M. and MITSUHASHIJ. (1957) The hormonal control of larval diapause in the rice stem borer, Chilo supptessalis--I. Some factors in the head maintaining larval diapause. Jap.._7. Appl. Ent. Zool. 1, 145-154. FUKAYA M. and MITSUHASHIJ. (1958) The hormonal control of larval diapause in the rice stem borer, Chilo suppressalis-II. The activity of the corpora allata during the diapausing period. Jap. J. Appl. Ent. Zool. 2, 223-226. FUKAYAM. and MITSUHASHIJ. (1961) Larval diapause in the rice stem borer with special reference to its hormonal mechanism. Bull. nut. Inst. Agr. Sci. (C) 13, l-32. GRANGERN. A. and SEHNAL F. (1974) Regulation of larval corpora allata in Gallaia mellonella. Nature, Land. 251,415-417. HA~SEMERS. M. and BECK S. D. (1968) Histochemistry of the ileum of the European corn borer, Ostrinia n&la&. 7. Insect Phvsiol. 14. 1233-1246. MITSUHASHI”J. (1963) Histological studies on the neurosecretory cells of the brain and on the corpus allatum during diapause in some lepidopterous insects. Bull. mat. Inst. Am. Sci. (Cj 16. 67-121. MUTUURA A. and MUNROE-E. (19iOj Taxonomy and distribution of the European corn borer and allied (Lepidoptera: Pyralidae). species : genus Ostriniu Mem. ent. Sot. Can. 71, 1-112. NAIR K. S. S. (1974) Studies on the diapause of Trogoderma grunatium: effects of juvenile hormone analogues on growth and metamorphosis. J. Insect Physiol. 20, 231-244. SEHNAL F. and GRANCER N. A. (1975) Control of corpora allata function in larvae of Galleria mellonella. Biol Bull.. Woods Hole 148. 106-l 16. YAGI S. (19j5) Endocrinological studies on diapause in some lepidopterous insects. Mem. Fat. Agric. Tokyo Uniw. Education 21, l-49. In Japanese with English summary. YAGI S. and FUKAYAM. (1974) Juvenile hormone as a key factor regulating larval diapause of the rice stem borer, Chilo su&ressal&. Appl. I&t. Zool. 9, 247-255. YIN C.-M. and CHIPPENDALE G. M. (1973) Juvenile hormone regulation of the larval diapau& of the southwestern corn borer, Diatraea grandiosella. J. Insect Phvsiol. 19. 2403-2420. YIN C.-M.- and C&PPENDALE G. M. (1974) Juvenile hormone and the induction of larval polymorphism and diapause of the southwestern corn borer, Diatraea grandiosella. J. Insect Physiol. 20, 1833-1848.