Vairimorpha necatrix was detected among laboratory cultured and field collected Spodoptera frugiperda larvae. Weak infections were not always fatal. In the case of fatal infections among diseased larvae, white patches were formed by agglomerations of adipose tissue beneath the transparent integument. The mid-gut of S. frugiperda larvae presented the first site of histological alterations caused by V. necatrix. The migration of the pathogen, probably occured in the form of agglomerations, from the epithelial cells to the body cavity. Adipose tissue appears to be the principal site for the pathogen development. The nerve ganglia, muscle fibres and epidermis also presented histological alterations due to the pathogen propagation

Brooks W.M

Habib M.E.M

Kramer J.P

Maddox J.V

Mohamed E. M. Habib

Patel P.N

Pilley B.M

Prafulbala N. Patel

Steinhaus E.A

Tanada Y

Wigglesworth V.B

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Protozoosis caused by Vairimorpha necatrix (Microsporia, Nosematidae) in larvae of Spodoptera frugiperda (Lepidoptera, Noctuidae)

Patel,Prafulbala N.

Habib, Mohamed E. M.

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Vairimorpha necatrix was detected among laboratory cultured and field collected Spodoptera frugiperda larvae. Weak infections were not always fatal. In the case of fatal infections among diseased larvae, white patches were formed by agglomerations of adipose tissue beneath the transparent integument. The mid-gut of S. frugiperda larvae presented the first site of histological alterations caused by V. necatrix. The migration of the pathogen, probably occured in the form of agglomerations, from the epithelial cells to the body cavity. Adipose tissue appears to be the principal site for the pathogen development. The nerve ganglia, muscle fibres and epidermis also presented histological alterations due to the pathogen propagation.59359

Patel, Prafulbala N.

Repositorio da Producao Cientifica e Intelectual da Unicamp

REVISTA BRASILEIRA DE ZOOLOGIA 
Revta bras. Zoo!., 5 ( 4) : 5 9 3 - 5 9 8 30.XI.1988 
PROTOZOOSIS CAUSE O BY Vairimorpha necatrix 
(MICROSPORIDA, NOSEMATIDAE) lN LARVAE OF 
Spodoptera frugiperda (LEPIDOPTERA, NOCTUIDAE). 
ABSTRACT 
Prafulbala N. Patel1 
Mohamed E. M. Habib1 
Vairimorpha necatrix was detected among laboratory cultured and field 
collected Spodoptera frugiperda larvae. Weak infections were not always fatal. 
ln the case of fatal infections among diseased larvae, white patches were formed 
by agglomerations of adipose tissue beneath the transparent integument. 
The mid·gut of S. frugiperda larva e presented the first site of histological 
alterations caused by V. necatrix. The migration of the pathogen, prabably 
occured in the form of agglomerations, fram the epithelial cells to the body 
cavity. Adipose tissue appears to be the principal sUe for the pathogen 
development. The nerve ganglia, muscle fibres and epidermis also presented 
histological alterations due to the pathogen propagation. 
INTRODUCTION 
Nosema necatrix, like some other species of the genus, is basically 
pathogenic in relation to some lepidopterous larvae. Nosema and Thelohania 
were considered as responsible for a rnicrosporidiosis in larvae of the arrnyworm, 
Pseudaletia unipunctata (Haworth). Such a disease was previously recorded by 
Tanada and Chang (1962). Subsequently, Krarner (1965) narned the two 
pathogens as Nosema necatrix and Thelohania diazoma and described their life 
cycle, rnentioning that both of thern occurred in the sarne host organ. Madox 
(1968) suggested that these two agents represented a single dirnorphic species 
and that the dirnorphisrn depends upon the temperature conditions. Pilley 
(1976) investigating the !ife cycle of such a pathogen in another host,Spodoptera 
exempta, confirrned the existence of dirnorphism and placed this rnicroorganism 
in a new genus, Vairimorpha. 
The purpose of the present study is to dernonstrate sorne external 
syrnptorns and histopathological effects caused by V. necatrix in Spodoptera 
frugiperda larvae. The disease was initially detected under laboratory conditions 
and later in com fields (State of São Paulo). ln rnany cases, the larvae suffered 
rnixed infections caused by NPV (Nuclear Polyhedrosis Virus) and V. necatrix. 
1 Departamento de Zoologia, UNICAMP, 13.100, Campinas, SP. 
Revta bras. Zool. 
MATERIAL AND METHODS 
For the symptomatological descriptions, parameters indicated by 
Steinhaus (1963), Habib (1978a) and Patel (1981) were adopted. For the 
histopathological examinations, basic histological techniques and optical 
microscopy were utilized. Sections (6-8 microns thick) stained by haematoxylin 
and counter stained by eosin were examined. 
RESULTS AND DlSCUSSION 
1. Symptomatology: 
The diseased larvae during the initial phase of infection did not present 
any evident or clear symptoms. Light pink coloration on the ventral side of the 
body, specially between the sternites, lack of appetite and slight flaccidity were 
the first signs observed. The highly infected larvae almost stopped feeding and 
the light pink coloration became more pronounced. The flaccidity became more 
intensified leading to death. The dead larvae became black in color, revealing 
accelerated alterations of the body tissues, but always without emitting odour 
and the cuticle remained intact. 
Weak infections were not always fatal. ln the case of fatal infections, the 
larvae became turgid, the coloration continued to be lightly pink and white 
patches beneath the transparent integument began to appear. These patches are 
agglomerations of infected adipose tissue, and they were more evident on the 
ventral side of the body wall. Our observations coincide with the general 
symptomatological description given by Steinhaus (1963) for microsporidial 
infections. The surviving infected larvae were able to pupate normally but 
resulted in adults both smaller in size and with lower fecundity and longevity. 
During the subsequent generation, the disease manifested itself again, probably 
caused by means of transovogenic transmission, which is common in other 
species ofthe genus Vairimorpha (Steinhaus, 1963; Brooks, 1968). 
2. Histopathology: 
A.Mid~t: 
The mid~t of S. frugiperda larvae presented the first site of histological 
alterations caused by V. necatrix. During the initial stage of infection, the 
peritrophic membrane appeared to be partially ruptured. The invasion of the 
pathogen provoked certain characteristic abnormalities in the epithelial cells, 
including the grouping of these cells in variable numbers. Separation and 
FIGS. 1 - 7 - Histological alterations in tissues of S. frugiperda larvae: 1, Cross section 
showing a migration of V. necatrix from the mid-gu t to the body cavity; 2, Highly 
infected adipose tissue; 3, Adipose tissue (not infected) in diseased larvae; 4, Aggio· 
merations of V. necatrix spores in a smear of infected adipose tissues; 5. Cross sec-
tion of a nerve gangiion in diseased larvae; 6, Cross section of a muscle in diseased 
larvae; 7, Integument of a diseased larva. 
594 
VaI. 5(4), 1988 
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Revta bras. Zool. 
displacement of circular muscles (fig. 1) from the rest of the intestine wall, 
vacuolization and disintegration of the epithelial cytoplasm, and beginning of 
cromatin condensation in the nucleus were also observed. The lack of appetite 
ar the retention of food in the diseased larvae could be explained as a result of 
these histological alterations in the mid-gut epithelial layer. The intensity of 
these symptoms increased with time in diseased larvae. 
During late stages of infection, breakdown of epithelial boundaries and 
scattering of the cell contents in the lumen were observed. The migration of the 
pathogen probably occured in the form of agglomerations, fram the epithelial 
cells to the body cavity. Such agg1omerations were found to be enveloped by 
some host tissues (Fig. 1). Regenerative cells were not observed in infected 
intestine, indicating lack of regenerative capacity. 
B. Adipose tissue: 
According to Wigglesworth (1972) and Habib (1978b), the adipose tissue 
in lepidopterous larvae is composed of two types of cells. The first occupies the 
region between the integument and the longitudinal muscles, while the second 
surrounds the different organs and systems within the body cavity. The first 
type occurs in small numbers of adipose cells, while the second consists of 
agg1omerations in large numbers of these cells, forming fat bodies. 
ln the present work, various histological alterations caused by V. necatrix 
were observed in this tissue. Rupturing of connective membranes, disintegration 
of adipose cell boundaries and a presence of large quantities of the pathogen 
occupying the cytoplasm (Fig. 2) were the most important features. Sirnilarly, 
Kramer (1965) also observed disintegration among fat bodies of Pseudaletia 
unipuncta with a presence of microsporidian spores of Nosema necatrix. 
Nuclei and lipid capsules were completely destroyed in the infected fat 
tissue of S. frugiperda larvae. Non infected adipose tissue in the diseased larvae 
suffered only a reduction in volume and leaness (Fig. 3). Partial disintegration 
of its connective membrane and evident cromatin condensation were also 
observed. Smearing.of infected fat tissue revealed large quantities of spores 
(Fig. 4). Physiological disturbances are common in fat bodies not invaded by 
etiological agents, as an indirect effect of infection (patel, 1981; Habib, 1983). 
C.Muscles: 
Rupturing and disintegration of sarcolema, in addition to loosening of 
muscle fibrillae were detected in many sections. Spores of the pathogen were 
observed surrounding this type of fibrillae and, sometimes, separating it from 
the sarcolema (Fig. 5). These histological alterations in the musculature, 
principa1ly among the dorsal and ventral longitudinal muscles, explain the 
reason for the flaccidity observed in the diseased larvae. 
596 
VaI. 5(4), 1988 
p. Nerve ganglia: 
The histological alterations observed in the nervous system of S. frugiperda 
larvae infected by V. necatrix, probably developed as an indirect effect of the 
di:;ease, as a result of some physiochemical disturbances; since the pathogen was 
not observed invading the tissues of this system. 
Disintegration of neurolema, separation between the larval and imaginaI 
nerve cells, and condensation of cromatin were the most evident symptoms 
(Fig. 6). The neuropile masses presented only a weak dissociation. 
E. Epidermis: 
The integument epithelial cells suffered pronounced alterations, like 
reduction in cytoplasm volume, disintegration of cell boundaries and cromatin 
condensation (Fig. 7). These alterations could explain the transparency of the 
integument and the facility to visualize the agglomerated patches of the infected 
adipose tissue . The cuticular layers remained without any injury. 
REFERENCES 
Brooks, W.M. 1968. Transovarian transmission of Nosema heliothidis in the com earworm, 
Heliothis zea . J. Invertebr. PathoI., 11 :510-512. 
Habib , M.E.M . 1978a. A bacterial disease of the American cotton leafworm, Alabarna 
argillacea (Hübner, 1818) (Lepid., Noctuidae) , with notes on its histological effects. Z. 
ang. Ent., 85 :76~l. 
Habib, M .E.M . 1978b . Anatomy and histology of the mature larva of the American cotton 
leafworm, Alabarna argil/acea (Hübner, 1818). Anais da S.E.B., 7:7-14. 
Habib, M.E.M. 1983 . Potency of Bacil/us thuringiensis var o israelensis (H-l4) against some 
aquatic dipterous insects. Z. ang. Ent., 95:368-376 . 
Kramcr, J.P. 1965 . Nosema necatrix sp . n. and Thelohania diazoma sp.n. microsporidians 
from the armyworm Pseudaletia unipunctata (Haworth). J. Invertebr. Pathol., 7 :117-
12l. 
Maddox, LV. 1968. Generation time of the microsporidian, Noserna necatrix, in larvae of 
the armyworm, Pseudaletia unipunctata. J. Invertebr. Pathol., 11 :90-96. 
Patel, P.N. 1981. Estudos de fatores bióticos de controle natural em populações de Spo-
doptera frngiperda (Lepidoptera, Noctuidae). Campinas, 98pp. Tese de Mestrado, 
UNICAMP. 
Pilley , B.M . 1976 . A new genus, Vairimorpho (Protozoa: Microsporidae) for Noserna 
necatrix Kramer, 1965: Pa thogenicity and [ife cyc1e in Spodoptera exempta (Lepidopte-
ra : Noctuidae). J.lnvertebr. Pathol., 28:177-183. 
597 
Revta bras. Zoo!. 
Steinhaus, E.A. Insect Pathology. An advanced treatise. Vol. 1,661 pp; Vol. 2, 689pp. 
Academic Press, New Y ork & London. 
Tanada, Y. & C.Y. Chang. 1962. An epizootic resulting from microsporidian and two virus 
infections in the armyworm, Pseudaletia unipunctata (Haworth). J. Invertebr. Pathol., 
4:129-131. 
Wigglesworth, V.B. 1972. The principies of Insect Phrsiology. 7th edition, Chapman & 
Hall, London, 795 pp. 
598 


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Protozoosis caused by Vairimorpha necatrix (Microsporia, Nosematidae) in larvae of Spodoptera frugiperda (Lepidoptera, Noctuidae)

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