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Irreversible malnutrition in Tribolium castaneum attributable to parasitization by Nosema whitei
J. stored Prod. Res., 1972,
Vol. 8, pp. 227-228. Pergamon Press. Printed in Great Britain.
SHORT
Irreversible Attributable
COMMUNICATION
Malnutrition
in Tribolium castaneum
to Parasitization
by
Nosema whitei
(First received 16 November 1971, and infinalform 27 February 1972)
INTRODUCTION
SOKOLOFF et al. (1966) h ave shown that the growth of larvae of Tribolium castaneum (Hb.) is accelerated by supplementation of diets of rice flour or soy flour with brewers yeast. GEORGE (1971) has further demonstrated that supplementation increases the number of larvae parasitized by Nosema whitei able to pupate on these diets and enables larvae that do not pupate to survive longer. There is at the moment no information about the influence of a change of diet on infected larvae at any intermediate stage between hatching and pupation. This work explores the results of changing from a deficient to an adequate diet during development. MATERIALS
AND
METHODS
In the present study, second-instar larval T. castaneum were retrieved from inadequate diets, infected with microsporidian spores, and returned to fresh portions of the same media for 15 days. After feeding for 15 days ad libitum on the inadequate diets, half of the larvae were removed and placed on nutritionally adequate regimens. The remaining larvae were allowed to continue feeding on the inadequate diets. At 15-day intervals, all larvae were observed, cadavers and pupae removed and the remaining larvae returned to their respective media. The inadequate diets employed were the flours of rice and soy. The two adequate diets were prepared by fortifying each of the above flours with brewers yeast to give a flour-yeast mixture of (19 : 1). All larvae were individually reared in one-dram glass vials and incubated at 30 + 1°C and 60 + 2% r.h. Two hundred and forty infected larvae, along with an equivalent number of uninfected ones, were reared on each diet. The data were statistically analyzed by a significance test designed to compare two percentages based on two large samples (BAILEY, 1961). RESULTS
All of the infected larvae died on the rice flour diets (Table l), whereas about a third of the uninfected larvae survived (pupated) on these diets. A small proportion of the infected larvae pupated on the soy diets and more of the uninfected larvae pupated on these diets than on the rice diets. Mortality was reduced by transferring to the yeast-supplemented diet only for uninfected larvae fed on soy-flour. 227
SHORTCOMMUNICATION
228 TABLE
1. THE
INFLUENCEON DEATHAND
PUPATION
OF LARVAE
OF
T. castaneum
PEDONRlCEORSOYFLOUROFINFECTINGSOMEOFTHEMINTHESECONDINSTARUiITH Nosema INFECTED
whitei AND THEN AND
15 DAYS LATER
UNINFECTED
LARVAE
OFTRANSFERRING
TO A SIMILARDIET
HALF
OF EACH
SUPPLEMENTED
OF THE
WITH
YEAST
Number of larvae Not infected
Dead
Infected
Pupated
Rice + yeast Rice
154 160
86 80
Soy
79 110
161 130
+
yeast Soy
SUMMARY
Dead
Pupated
240
0
240 234 229
0 6
11
AND CONCLUSION
Inasmuch as N. whitei parasitizes mainly the fat body of T. castaneum, infected larvae normally do not live beyond the pupal stage because stored nutrients which could be used to support the host during the pupal stage are consumed by the pathogen. Therefore, survivorship in this study was defined on the basis of whether or not the larvae pupated. If N. white&infected T. castaneum are supplied with adequate nutrients (e.g. proteins and vitamins of the B-complex group) they are capable of meeting their own metabolic needs, plus those of the parasite for a longer period. The host and the parasite appear to compete for stored nutrients in the former’s fat body (GEORGE, 1971). From the present study, I conclude that the parasite, during the first 15 days of infection, consumed such enormous quantities of host’s fat body that the nutrient reserve was not great enough to sustain the larvae until pupation. The depletion of nutrient reserve reached a point after 15 days, that supplemented diets failed to increase survivorship in infected larvae. CHARLES R. GEORGE
Department of Biology, North Carolina Central University, Durham, North Carolina 27707, U.S.A. REFERENCES
BAILEY, N. J. (1961) Statistical Methods in Biology. English Univ. Press, London. GEORGE, C. R. (1971) Interaction between malnutrition and infection in Nosema white&infected Tribolium castaneum. J. Invert. Pathol. 18, 383-388. SOKOLOFF, A., FRANKLIN, I. R., OVERTON, L. F. and Ho, F. (1966) Comparative studies with Tribolium (Coleoptera, Tenebrionidae)-I: Productivity of T. castaneum (Herbst) and T. con&sum PLIV. on several commercially-available diets. J. stored Prod. Res. 1,295-311.
Vol. 8, pp. 227-228. Pergamon Press. Printed in Great Britain.
SHORT
Irreversible Attributable
COMMUNICATION
Malnutrition
in Tribolium castaneum
to Parasitization
by
Nosema whitei
(First received 16 November 1971, and infinalform 27 February 1972)
INTRODUCTION
SOKOLOFF et al. (1966) h ave shown that the growth of larvae of Tribolium castaneum (Hb.) is accelerated by supplementation of diets of rice flour or soy flour with brewers yeast. GEORGE (1971) has further demonstrated that supplementation increases the number of larvae parasitized by Nosema whitei able to pupate on these diets and enables larvae that do not pupate to survive longer. There is at the moment no information about the influence of a change of diet on infected larvae at any intermediate stage between hatching and pupation. This work explores the results of changing from a deficient to an adequate diet during development. MATERIALS
AND
METHODS
In the present study, second-instar larval T. castaneum were retrieved from inadequate diets, infected with microsporidian spores, and returned to fresh portions of the same media for 15 days. After feeding for 15 days ad libitum on the inadequate diets, half of the larvae were removed and placed on nutritionally adequate regimens. The remaining larvae were allowed to continue feeding on the inadequate diets. At 15-day intervals, all larvae were observed, cadavers and pupae removed and the remaining larvae returned to their respective media. The inadequate diets employed were the flours of rice and soy. The two adequate diets were prepared by fortifying each of the above flours with brewers yeast to give a flour-yeast mixture of (19 : 1). All larvae were individually reared in one-dram glass vials and incubated at 30 + 1°C and 60 + 2% r.h. Two hundred and forty infected larvae, along with an equivalent number of uninfected ones, were reared on each diet. The data were statistically analyzed by a significance test designed to compare two percentages based on two large samples (BAILEY, 1961). RESULTS
All of the infected larvae died on the rice flour diets (Table l), whereas about a third of the uninfected larvae survived (pupated) on these diets. A small proportion of the infected larvae pupated on the soy diets and more of the uninfected larvae pupated on these diets than on the rice diets. Mortality was reduced by transferring to the yeast-supplemented diet only for uninfected larvae fed on soy-flour. 227
SHORTCOMMUNICATION
228 TABLE
1. THE
INFLUENCEON DEATHAND
PUPATION
OF LARVAE
OF
T. castaneum
PEDONRlCEORSOYFLOUROFINFECTINGSOMEOFTHEMINTHESECONDINSTARUiITH Nosema INFECTED
whitei AND THEN AND
15 DAYS LATER
UNINFECTED
LARVAE
OFTRANSFERRING
TO A SIMILARDIET
HALF
OF EACH
SUPPLEMENTED
OF THE
WITH
YEAST
Number of larvae Not infected
Dead
Infected
Pupated
Rice + yeast Rice
154 160
86 80
Soy
79 110
161 130
+
yeast Soy
SUMMARY
Dead
Pupated
240
0
240 234 229
0 6
11
AND CONCLUSION
Inasmuch as N. whitei parasitizes mainly the fat body of T. castaneum, infected larvae normally do not live beyond the pupal stage because stored nutrients which could be used to support the host during the pupal stage are consumed by the pathogen. Therefore, survivorship in this study was defined on the basis of whether or not the larvae pupated. If N. white&infected T. castaneum are supplied with adequate nutrients (e.g. proteins and vitamins of the B-complex group) they are capable of meeting their own metabolic needs, plus those of the parasite for a longer period. The host and the parasite appear to compete for stored nutrients in the former’s fat body (GEORGE, 1971). From the present study, I conclude that the parasite, during the first 15 days of infection, consumed such enormous quantities of host’s fat body that the nutrient reserve was not great enough to sustain the larvae until pupation. The depletion of nutrient reserve reached a point after 15 days, that supplemented diets failed to increase survivorship in infected larvae. CHARLES R. GEORGE
Department of Biology, North Carolina Central University, Durham, North Carolina 27707, U.S.A. REFERENCES
BAILEY, N. J. (1961) Statistical Methods in Biology. English Univ. Press, London. GEORGE, C. R. (1971) Interaction between malnutrition and infection in Nosema white&infected Tribolium castaneum. J. Invert. Pathol. 18, 383-388. SOKOLOFF, A., FRANKLIN, I. R., OVERTON, L. F. and Ho, F. (1966) Comparative studies with Tribolium (Coleoptera, Tenebrionidae)-I: Productivity of T. castaneum (Herbst) and T. con&sum PLIV. on several commercially-available diets. J. stored Prod. Res. 1,295-311.