R e v i s t a d a S o c ie d a d e B r a s i l e i r a d e M e d ic in a T r o p ic a l 2 5 ( 4 ) : 2 3 1 - 2 3 3 , o u t- d e z , 1 9 9 2
IN FL U E N C E OF LIGHT CONDITIONS O N A D U L T
M ORTALITY A N D EGG-LAYING OF T R 1A T O M A B R A S IL 1 E N S 1 S
N E IV A , 1911 (HEMIPTERA: REDUVIIDAE: TR IATOM INAE)
Carlos Brisola M arcondes and João A gnaldo N ascim ento
W e c o m p a r e d , f o r T riatom a b r a silie n sis , th e e g g - la y in g p r o c e s s a n d th e m o r ta lity o f a d u lts u n d e r c o n d itio n s o f a lm o s t p e r m a n e n t d a r k n e s s a n d w ith n o r m a l la b o r a to r y lu m in o s ity . M o r ta lity d i d n o t d if f e r b e tw e e n g r o u p s . T h e e g g - la y in g p e r v ia l a n d p e r f e m a l e w a s s ig n if ic a n tly g r e a t e r in th e g r o u p o f n o r m a l lu m in o s ity . W e c o n s id e r th a t it is n o t r e c o m m e n d a b le to k e e p th e a d u lts o f th is s p e c i e s u n d e r c o m p le te d a r k n e s s . O th e r b io l o g ic a l a s p e c t s s h o u ld b e a n a ly s e d in r e la tio n to lu m in o s ity .
K e y - w o r d s : L ig h t- d a r k c y c le . Triatom a b ra silien sis. T ria to m in a e .
Due to the predominance o f feeding and ambulatory activity of triatomine bugs during the nocturnal period, under experimental condition25 and in nature8, these bugs have generally been bred, in thelaboratory, with little or no luminosity.
Based on reports of better performance in almost total darkness7 and better yield with light6, we decided to observe the effect of total darkness on egg-laying and mortality o f adults of T.
b r a s ilie n s is, to look for ways to improve the
productiveness o f breeding o f these insects and to obtain data on the effect of light deprivation on their biology.
MATERIAL AND METHODS
W e divided the adults of a colony of T.
b r a s i l i e n s i s , started four years before the
experiment, with insects of the municipalities of Aguiar and Boqueirão dos Cochos, in Paraíba, into two groups. Each group initially had 98 males and 7 3 females and was maintained in a transparent plastic cylinder. The cylinders had a volume of 4.71, contained a perforated light cardboard cylinder, absorbent paper in the bottom and were covered with white shirting. Both were kept in a
Núcleo de Medicina Tropical da Universidade Federal da Paraíba, João Pessoa, PB.
Apoio financeiro do CNPq (Proc. 40.3755/82-PIDE V). Endereço para correspondência: Prof. Carlos Brisola M arcondes. Depto. de Microbiologia e Parasitologia/CCB/ UFSC, 88040-900 Florianóplolis, SC.
Recebido para publicação em 13/09/91.
bookcase, three meters from a window, and near fluorescent lamps frequently used during the day, with a light-dark periodicity of ca. 13:1 lh . One of them was covered by a black cardboard cylinder, a little larger then the cylinder itself. The room temperature was held at 27 + /-1 °C and the relative humidity was 70-80%.
RESULTS
Mortality for the period o f 15 weeks was about 50%. The differences between groups, analysed by Chi-square, were not significant. The egg-laying per vial and per female per week (Table 1) was higher in the vial exposed to luminosity, analysed by Wilcoxon at 5 %. The general means o f egg/female week were 4 .6 + /-0.9 for the group in total darkness and 5 .9 + / -1.2 for the light/dark group. The eclosion percentage, for some weeks, also is shown in Table 1.
DISCUSSION
Wood13 emphasized the negative phototaxic responses, indicating preference for darkness, Dias4 did not refer to this factor, while Gomez-Nunez6 affirmed that light increased the production of
R h o d n iu s p r o lix u s . It was known that triatomine
bugs perceive light stimuli with the eyes, the ocelli and tegument12, the proportion of darkness: light hours influences the ry thm o f oviposition1, and bugs prefer to lay eggs between 6 and 8 p.m ., under laboratory conditions in Belo Horizonte, Minas Gerais, Brazil5. However, there was no conclusive data on the influence of light on mortality and
M a r c o n d e s C B , N a s c im e n to J A . I n f lu e n c e o f lig h t c o n d itio n s o n a d u lt m o r ta l it y a n d e g g - l a y in g o /T r i a t o m a b r a s ilie n s is N e iv a , 1 9 1 1 ( H e m ip te r a : R e d u v ii d a e : T r ia to m in a e ) . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c in a T r o p ic a l. 2 5 : 2 3 1 - 2 3 3 , o u t- d e z , 1 9 9 2 .
T a b le 1 - O v ip o s itio n o f T . b ra silien sis m a in ta n e d in d if fe r e n t lig h t c o n d itio n s .
W e e k s
D a rk n ess L ig h t/d a rk n ess
m ea n o f fe m a le s /
p erio d
e g g s / v ia l
e g g s / fem a le*
% o f e c lo sio n
m ean o f fe m a le s/ p erio d
e g g s / v ia l
e g g s / fem a le*
% o f , e c lo s io n
1 7 2 .0 4 8 2 6 .7 - 7 3 .0 6 1 3 8 .4
-2 6 9 .5 3 4 2 4 .9 - 7 1 .0 2 2 1 3 .1
-3 6 6 .5 3 6 5 5 .5 5 5 .1 6 8 .5 4 0 3 6 .0 6 9 .5
4 6 2 .5 2 1 5 3 .4 - 6 5 .5 3 8 0 5 .8
-5 5 8 .5 2 9 8 5 .1 5 5 .4 6 1 .5 4 5 8 7 .5 8 3 .8
6 5 6 .0 2 2 1 4 .0 4 8 .9 5 7 .2 3 1 3 5 .5 6 8 .7
7 5 4 .0 2 2 1 4 .1 4 8 .9 5 5 .8 3 1 2 5 .5 6 8 .6
8 5 0 .6 2 1 4 4 .2 5 0 .0 5 2 .5 2 5 2 4 .8 6 2 .3
9 4 6 .0 1 7 7 3 .8 - 5 0 .0 2 4 2 4 .8 6 2 .0
10 4 3 .5 2 4 2 5 .6 5 3 .7 4 8 .5 2 5 4 5 .2
-11 4 0 .0 175 4 .9 - 4 5 .0 2 9 5 6 .6
-12 3 6 .5 11 7 3 .2 - 4 2 .5 2 6 3 6 .2
-13 3 4 .0 1 8 2 5 .4 - 3 8 .5 2 6 4 6 .9
-14 3 2 .0 1 60 5 .0 - 3 3 .5 2 2 0 6 .6
-15 3 0 .0 1 37 4 .6 - 3 0 .0 1 9 0 6 .3
-* T h e ratio e g g s /f e m a le w a s ca lcu la ted takin g into a cco u n t th e e g g s la y e d du rin g th e w e e k and th e m ea n o f fem a le s at th e b e g in n in g an d at th e en d o f th e sa m e p eriod .
laying.
Direct sunlight, with or without glass, can be harmful to some species of triatomine bugs10 u . In our study, this factor probably had no effect, due to distance from the window and the moderate temperature.
The insects exposed to light could hide temselves in the cylinder, therefore they were not forced to be exposed to strong light, implying that it was the availability of light which influenced egg-laying. Probably, a little light must have passed through the shirting, which was not covered. The significant differences in the egg-laying indicates that this light leakage was not enough to equate the results, but it could have influenced mortality.
We can conclude that it is advantageous to m aintain adults o f T. b r a s i l i e n s i s in normal luminosity conditions. The higher proportion of eclosion o f eggs from females in this condition is an additional factor indicating this condition as better for breeding.
Egg production per day per female and the proportion o f eclosion in light/dark and darkness
conditions was m uch low er than observed previously7 9. This could be an influence o f blood source3 and of age of females and of time colonies are maintained in the laboratory9. The colony used in this study, eight years after it started, had such a production decrease that it could not be used for xenodiagnosis.
RESUMO
C o m p a r a m o s , p a r a T . b r a silie n sis . a p o s t u r a e a m o r ta lid a d e d e a d u lto s e m c o n d iç õ e s d e e s c u r id ã o q u a s e p e r m a n e n te e d e lu m in o s id a d e n o r m a l d e la b o r a tó r io . O s g r u p o s n ã o d if e r ir a m s i g n if i c a ti v a m e n t e q u a n to à m o r ta lid a d e . A p o s t u r a p o r f r a s c o e p o r f ê m e a f o i s ig n ific a tiv a m e n te m a io r n o g r u p o d e lu m in o s id a d e n o rm a l. N ã o c o n s id e r a m o s r e c o m e n d á v e l m a n te r o s a d u lto s d e s t a e s p é c ie e m e s c u r id ã o c o m p le ta . O u tr o s a s p e c t o s b io l ó g ic o s d e v e m s e r a n a li s a d o s c o m r e l a ç ã o à lu m in o s id a d e .
P a la v r a s - c h a v e s : C ic lo c la r o - e s c u r o . T ria to m a b ra silien sis. T ria to m in a e .
M a rcon de s CB, N ascim en to JA. Influence o f ligh t con dition s on adu lt m orta lity an d egg-lay in g o f Triatoma brasiliensis N eiva, 1911 (H em iptera: R ed u viid ae: Triatom inae). R e vista d a S o cie d a d e B ra sile ir a d e M edicin a T ropical. 2 5 :2 3 1 -2 3 3 , ou t-de z, 1992.
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