Fine-structural changes in the egg chorion of Bradinopyga geminata (Rambur) induced by paper mill effluent (Anisoptera: Libellulidae)

2006·0.9 MB·English

by  Andrew, R J

Odonatologica35(2):187-192 June I,2006
SHORTCOMMUNICATIONS
Fine-structural changesin theeggchorion
ofBradinopyga geminata(Rambur)
inducedby papermill effluent
(Anisoptera: Libellulidae)
R.J.Andrew¹*,L.Kodhe² andS.S.Kurup²
1DepartmentofZoology,HislopCollege,Civillines,Nagpur-440001 (MS),India
*[email protected]
2 DepartmentofZoology,SSESAs ScienceCollege,CongressNagar,Nagpur-440012 (MS),India
ReceivedMay2,2004 /RevisedandAcceptedNovember 1,2005
Theeggchorion ofthedragonflyB.geminataundergoesmajorstructuralchanges
when incubated in papermill effluent.Theexochorionbecomes blemished,marred
andperforated. Itbunches intoagranularcondition and loosesitsjelly-likeoriginal
identity.The endochorion developscracks and ispittedwith holes. The hexagonal
demarcations oftheendochorionplatesareobliterated andreplacedbyanetworkof
angularsurfacereticulations. Themicropylar stalk and thecircularbasal ridge dis-
solve anddistortthemicropylarapparatus.
INTRODUCTION
Theinsecteggchorionserves variousfunctionssuchas protectionfrompatho-
gens, predators andmechanical stressand fromenvironmentalhazards such as
desiccationandhydration. Itallowsspermentry andprovides elasticityforeasy
oviposition. Later, itprotects thegrowing embryo, ensuressufficientoxygenand
carbondioxideexchange andhelpsinliberationofthelarva.Theeggchorion, in
insects, is thereforeanextensively modifieddynamic structure withmajorfunc-
tionalsignificance (HINTON, 1981;MARGARITIS, 1985).
Theenvironmentalpollution dueto smallandmediumscale pulp andpaper
industriesismultidimensionalcausingseriousproblems,notonly tothelandmass
fertilitybutalsoto thenaturalflora,faunaaswellasaquaticbodies(KSIBI etah,
2003). Thisresults inserious threatstoaquatic organisms(GHOSE &KONAR,
1980;RAO&NAADHAKUMAR,1982;CHANDRASEKARAN etal„ 1989)
188 R.J.Andrew,L,Kodhe&S.S.Kurup
including dragonflies(SUBRAMAN1AN&VARADARAJ,1993;VARADARAJ
etal., 1993; SUBRAMANIAN & MURALIDHARAN, 1999).
A reviewofliteraturereveals thatvery fewattempts havebeen madeto study
theeffect of paper milleffluents(PME) on dragonflies and these reports are
mostly related to histopathological, histochemicalandbiochemicalparameters
(SUBRAMANIAN & VARADARAJ, 1993; VARADARAJ etal., 1993).Fur-
thermore, informationon the eggs of dragonflies has mostly beenundertaken
withrespect to theeffectof differentpH, temperatureandoxygen on hatching.
(PUNZO, 1988;SOEFFING, 1990;MILLER, 1992). Thefinestructureof the
©donatechorionhasbeeninvestigated mostly tounderstandthe“structure-func-
tion”relationship withrespect to theprocess offertilizationandoviposition [see
ANDREW(2002) fordetailreferences]. No majorattempts haveyetbeenmade
to study theeffectofPMEontheeggchorionofaquatic fauna.Thepresentin-
vestigation has thereforebeenundertakento studytheeffectofPMEonthefine
structureoftheeggchorionofthe dragonfly, Bradinopyga geminata.
MATERIALANDMETHODS
Theegg-layingfemaleswerecollectednearsmalllocalpondsatNagpur,duringthepost-monsoon
periods(September-November)of 1999-2000.Eggdumpingwasinitiated bypassingathin needle
throughthe thoraxorby holdingthe wingsflat and dippingthe abdominal tipinwatertubes and
petri-dishes(ANDREW&TEMBHARE, 1996;ANDREW,2002).
Theeggspassed outofthe genitalopeningand accumulatedonthe sub-genitalplate.Theeggs
weredivided intotwogroups. Thefirstgroupofeggswasplacedinpetri-dishescontainingpondwa-
terwhilethesecondgroupwasplacedinpaper mill effluent(PME)procuredformthelocalindustrial
area(MIDC,Hingna,NagpurDistrict). Afterfivedays,theeggsofboth thegroups wereprepared
forscanningelectronmicroscopy (SEM).Eggsweredehydratedinethanol,transferred toacetone,
air-dried,mountedonstubs,coatedinagold-coatingunit(E-5200)andexaminedunderastereoscan
250MK IICambridgeScanningElectron Microscope.
OBSERVATIONS
Theeggsincubatedinpondwaterhatchedin8-12daysandhadonly 8%mortal-
ity whereas 100%percent mortalitywas foundintheeggs incubatedinPME.
Various structural disintegration of theegg chorion with respect to the exo-
chorion, endochorionandmicropylarapparatuswas observedin thepapermill
effluenttreatedeggs(Figs 1-4).Theexochorionbecameblemished, marredand
perforated.Itbunchedintogranularconditionandlostitsjelly-likeoriginal iden-
tity. Theendochorion developed cracks and itwas pitted withholes.Thehexa-
gonal demarcationsoftheendochorionplates wereobliteratedandreplaced by
anetworkofangularsurfacereticulations. Themicropylarstalk andthecircular
basalridgedissolved anddistortedthemicropylar apparatus.
Acomparative account of this degeneration is given inTableI.
Fine-structure ofegg chorion in Bradinopygageminala 189
Table1
Fine-structural changesinthechorion componentsoftheeggsofBradinopygageminataincubated
inpaper mill effluent(PME)
Eggchorion Dry-egg* Wet-egg* PME-incubated egg
Components
Exochorion (EX) Thin,unsculptured, Thickunsculptured, Jelly-like,spongynature
uniformlayer jelly-like,spongy lost.Itbunchesintosmall
layer(Fig.1) lobules orgranules,be-
comesdissolvedinplaces,
detachesfromtheEN,
andexhibits agrainyor
sandytexture(Fig.2)
Endochorion (EN) Whitetopalecream; Dark brown,sculptured Thehexagonaldemarca-
composedofhexa- with regularhexagonal tionislost;thesurface
gonalplates plates(Fig. 1) developscracksandis
pittedwith tinycircular
holes(Fig.2); some
crackedpieces breakoff
fromthesurface
Micropylar Triangularwith a Asindrycondition TheMAsinks, and
Apparatus(MA) circularbase;stalk acquiresagranulartex-
possessesapairof ture; thestalk disintegra-
subapicalcircular tes,whilethecircular
micropylarorifices. ridgeisobliterated (Fig.4)
Differentiated from
theEXbyathincir-
cular ridge(Fig.3)
*ANDREW&TEMBHARE(1996)
DISCUSSION
Protection against environmental hazards during embryogenesis is the main
functionoftheeggchorionafteroviposition. Thisisfulfilledbythephysical-me-
chanicalproperties of theegg.Thisproperty isthe consequenceofthe chemical
stabilityofthechorion,which dependsuponthecross-linksexisting betweenthe
componentmolecules(MARGARITIS, 1985).
Theinsecteggchorionispredominantly composed ofprotein (>95%)(PETRI
etal., 1976)alongwithtracesoforganic(carbohydrates, lipids)andinorganic(Cal-
cium, Iron,Ca+2 Na+ K+) ions/atoms/molecules(REIGER etal., 1980, 1982).
, ,
Thecross-linksbetweenthechorionproteins aremainlydisulphide bridges, dity-
rosine-trityrosine bondsandsclerotization through quininetanning, whichmay
occur separatelyorincombination(KAWASAKIetal., 1972;PETRIetal., 1976).
190 R.J.Andrew,L.Kodhe&S.S.Kurup
Inthe dragonflychorion, disulphidebridgesare themajor cross-linkbetween
theprotein molecules(KAWASAKI etal., 1974).Thepresentinvestigation indi-
cates thatthepapermilleffluentcontainscompounds thatdenaturethechorion
protein, probablyby breaking these di-sulphide bridges. Thevariationin the in-
tensity of denaturationbetween theexochorionandendochorionindicates that
the exochorionproteins are mostly linkedwithdi-sulphide bridges, sincethe in-
tensityofproteindenaturationbythePMEismoresevereintheouterexochorion
Figs 1-4.Normal and papermill effluent(PME)treated eggs ofBradinopygageminata (Scalebar
=5pm): (1)SEMoffracturedchorion toshow thick exochorion (thickarrow)and endochorion
composed ofhexagonalplates(thinarrow); - (2)PMEtreated chorionshowsgranular(blackar-
rowhead)lobulated (whitethick arrow)exochorion,whiletheendochorioniscracked (whitearrow
head)and pittedwith circularholes(thinarrow); —(3)Normal micropylarapparatus; — (4)PME
treatedmicropylarapparatuswithdisintegratingstalkand orifice(arrow).
Fine-structure ofeggchorion in Bradinopygageminata 191
thentheinnerendochorion.Variationintheactionofdenaturationbetweenthese
two layersmayalsobebecauseofthedifferenceinthephysical nature ofthetwo
chorions, the outerexochorion being spongyand the innerendochorionbeing
composed ofcompacthexagonal plates (ANDREW & TEMBHARE, 1996).
ACKNOWLEDGEMENT
RJA wishes to thank the UGC for supportunder the minor research project, F. 23-382/99
(WRO).
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