Stomodeal cuticular structures in the dragonfly Brachythemis contaminata (Fabricius) (Anisoptera: Libellulidae)

8 Pages·2002·2.3 MB·English

by  Tembhare, D B

Odonatologica31(1):47-54 March I,2002
Stomodealcuticular structures in the
dragonflyBrachythemis contaminata(Fabricius)
(Anisoptera: Libellulidae)
D.B.Tembhare andS.M. Wazalwar
DepartmentofZoology,NagpurUniversityCampus,Nagpur-440010,India
ReceivedAugust28, 2000/Revised andAcceptedMay28, 2001
Lightand scanningelectronmicroscopicstudiesreveal variousstomodeal cuticular
structures. Inthelarvaeandadults,microspinesonthe surfaceofthelongitudinalfolds
of the pharynx, and dome-shaped, beaded structures on the inner surface ofthe
oesophagous areevident. Inthe larvae,the foldsofthe crop bearlong hairslaterally
andparallelrowsofmicrospinesmedially.In thelarvae,theproventriculusisprovided
with 4longitudinalplates;2largeplateswith teeth oneach lateralside and 2small
plateseach with4fineapical teeth,oneitherside. Scale-like acanthaeareobserved
nearthestomodealvalve. Awhorloflonghairsisevidentinthe stomodealvalve. Inthe
adultdragonfly,theacanthaeandcurvedspinesoccupytheanteriorandposteriorregions
oftheproventriculardentalplates,respectively.The functional significanceofvarious
stomodealcuticular structuresisdiscussed.
INTRODUCTION
Thepresenceofawell-definedstrong armature intheproventriculi of insects that
feedon solidfood materialhas beenknownforalong time(SNODGRASS, 1935;
DAY& WATERHOUSE, 1953;WATERHOUSE,1957;RICHARDS &DAVIES,
1984;CHAPMAN, 1985). SEMstudiesontheinternalsurfaceofproventriculihave
revealedfine spines ofvariablesize inorthopteroid insects (NOIROT& NOIROT-
-TIMOTHEE, 1969;MILLER&FISK, 1971)andColeoptera(BALFOUR-BROWNE,
1944;ZHAVORONKAVA, 1969). Microspines throughout the foregut have been
observed inBlattaorientalis(ELZINGA & HOPKINS, 1994), Locusta migratoria
(HOCHULI et al., 1992)and some orthopteroid insects (BOUDREAUX, 1980;
CHAPMAN, 1985).
InOdonata, strong armature intheproventriculus ofthelarvaandadegenerated
armature in the adult is reported (TILLYARD, 1917). There is, however, no
48 D.B.Tembhare&S.M. Wazalwar
informationonthecuticularprocesses ofotherregions oftheforegutand hindgut,
and noSEMstudieshavebeen carriedout till now.
The present work was, therefore, undertakento explore the various types of
cuticular processes ofthe stomodaeum in thelarva and adult ofthe dragonfly,
Brachythemis contaminata,withthehelpofmorphological, histologicalandscanning
electron microscopic methods.
MATERIALAND METHODS
Thepenultimatelarvaewerecollectedfrompondsduringtherainyseasonandbroughttothelaboratory.
Theywerereared in speciallydesignedtubs. Mosquitolarvaeweresuppliedtwiceadayandthewater
wasreneweddaily.Newlyemergedadultdragonfliesweretransferredtocagescoveredwithamosquito
net.The present study wascarried outwith the helpoffollowingmorphological,scanningelectron
microscopic andhistologicalstainingmethods.
MORPHOLOGICALMETHOD. — Last instarlarvae,aboutaweekold,weretakenoutfromatub
andanaesthesizedbyC02 afterkeepingtheminiceinarefrigeratorfor 15-20 minutes. The excessof
water wassoakedbywrappingcleanblottingpaperoverthebody.Theproventriculusfromthegutwas
removed,alongslitwasmadeinittoexposetheinternalsurface. Thetracheae,fatbodiesandmuscles
wereremoved andtheproventriculus waswashedthoroughlyin distilledwater. Itwasboiledfor 15
minutesin 10% aqueousKOH solution andrinsed thoroughlyindistilled water,dehydratedinethanol
and clearedinclove oil.The proventricularteethandother cuticularstructures werestudiedunderthe
binocular microscopeatvarious magnifications.
SCANNINGELECTRON MICROSCOPICMETHOD. —Thealimentarycanal was dissectedout
inRinger’ssaline,removedfromthebodyandthe foregutwasseparatedfromthealimentarycanal and
openedwithalongitudinalslitanteroposteriorly.Theforegutwasspreadoutandglued,withtheinternal
surfaceexposed,toapieceofcardboard usingacynoacrylateglue,fixedin 10%formaldehydefor24
hours,washedindistilledwateranddehydratedin ethanol.Specimensweredriedat roomtemperature,
mounted onastub,andcoated withgoldpalladiumalloyin aPoloronAutomaticUnit. AStereoscan
250MKIIICambridgescanningelectronmicroscopewasusedtoexaminethespecimensattheRegional
SophisticatedInstrumentationCentre (R.S.I.C.),NagpurUniversity Campus,Nagpur.
HISTOLOGICAL METHOD. — Alimentary canal ofboth, larvae and adults was dissected in
Ringer’ssolution.Theforegutwasseparatedfromthealimentarycanalandfixedimmediatelyinaqueous
Bouin’sfixativefor 24hours. The foregutwaswashed indistilled water, dehydratedin 30%to 100%
ethanol,clearedinxyleneandembedded inparaffinwaxat60“C,The 4-6 mmthicksectionswerecut,
dehydratedand stainedwith(i)EhrlichHaematoxylin-Eosin(HE),(ii)Heidenhain’sIron-Haematoxylin
(FeH)and (iii)Mallory’sTriple (MT).
OBSERVATIONS
Although the alimentary canalis secondarily modifiedinthelarvaandadult in
relationto the aquatic and terrestrial modeoflife respectively, the foregut is
commonly differentiatedinto the pharynx, oesophagus, crop and proventriculus
(Fig.l). The foregut is typically composed of outer circular muscle, middle
longitudinal muscleandinnerepitheliallayers. Theepitheliumiscomposedoftall
columnar cells. Itis folded and internally lined with the cuticularintimaequipped
withvariouscuticularstructures.
Stomodeal structures inBrachythemiscontaminata 49
The pharynx consistsoftheenormously
foldedepitheliumandthickchitinousintima,due
towhichthelumenis greately reduced inboth
the larva and adult. The cuticular intimais
differentiated into outer stained and inner
unstainedareas.Therowsoffinespines andthe
folds are clearin thehistological preparations
ofthepharynxofboth,thelarvaandadult(Figs
2-5).
The oesophagus resemblesthepharynx
in structuralorganisation but the internalfolds
occupy mostofthelumen.Thecuticularintima
is differentiatedinto outer stainedand inner
unstainedregions similartothatinthepharynx.
TheSEMreveals thattheentireinnersurfaceof
thecuticularintimaisrough duetothepresence
ofspherical, dome-shaped projections giving a
beadedappearance to the entiresurface ofthe
oesophagus (Figs 6, 7). Fig. I. Morphologyofthealimentary
canal of Brachythemis contaminata
The crop is greately enlarged, sac-like (diagrammatic):(A)thelast instarlarva;
structureinboththelarvaandtheadult,enclosing — (B) the adult. — [CR: crop, — IL;
alarge lumen.Inthelarva, thecuticularintima ileum,— IS:iliac sac, —MG: midgut,
is thin measuring 16.66+2.35pm in thickness — MX: malpighiantubules, — OE:
and withlong hairslaterally and some parallel oesophagus, — PH:pharynx, — PV;
rows of microspines medially along thefolds proventriculus, - RE: rectum, - VE:
vestibule].
(Figs8-10). Thelumenisextensive.Intheadult,
the cuticular intima is invaginated with a large numberof folds. Four large
diverticula-likefoldsofephithelium linedwiththincuticularintimaare developed
in thelumen.
The proventriculus is a prominent structure in the larvabut is ill-
-defined in the adult dragonfly. The wall of the proventriculus is commonly
composed of an outer muscle layer andaninner, thin, indistinct epithelium. The
cuticularintimais thickandconsistsofdentalarmature inthelumen.
Inthelarva,thecuticularintimaisdifferentiatedintofourdentalplates, twolarge
andtwo small (Fig. 11).Thelarge plates beartwo large teethon eachlateralside,
whilethe small plates bearfour fineteeth apically, of decreasing size, on either
side.Inaddition,thedentalplatesare providedwithscale-likemicrospines (acanthae)
intheposteriorregion(Figs 12-14). They are arrangedinalarge numberofparallel
rows all over the surface. The majority ofthem are uniramous but some are
multiramousstructures.
Intheadult,thecuticularintimaisdifferentiatedintofourelongated dentalplates.
Theplates posses small, very fineteeth alloverthe surface. The anteriorregion is
50 D.B.Tembhare&S.M.Wazalwar
occupied by alarge numberoffine,uniramousacanthaemeasuring 2.85±0.15pm
inlength whiletheposterior region is coveredby alarge numberoflarge, curved,
apically pointed andbasallybroad spines measuring 3.48±0.16pminlength (Figs
15-17).
DISCUSSION
Themorphologicalandstructuralorganisationofthealimentarycanalofthelarva
andadult ofBrachythemis contaminatarepresentsbasically theorthopteroidtype
ofgut,although itis extensively modifiedinthelarvaandtheadultinaccordance
with the aquatic and terrestrial modeofliferespectively (MARSHALL, 1914;
Figs2-7.Cuticularstructures ofpharynx andoesophagusshowingarowofspinesalonganepithelial
fold:(2)cross sectionofpharynxinthelarva, FeH; — (3)SEMofcuticular surface ofthepharynxin
thelarvashowingtypicalcuticular armature(->); — (4)SEM viewofpharyngealspinesin thelarva
(-»); — (5)crosssection ofpharynxofadultshowingrows ofspinesalongepithelilalfolds(—»),FeH;
— (6)SEMofcuticularsurfaceofoesophagusinthe larvashowingspherical,dome-shapedprojections;
— (7)SEMofinnersurface ofoesophagusintheadultshowingsphericaldome-shapedprojections.
Stomodeal structures inBrachythemiscontaminate 51
TILLYARD, 1917;SNODGRASS, 1954;RICHARDS &DAVIES, 1984).
The well developed larvalproventriculus contrasts withthatintheadultandthe
differencemight be due to varied nature offoodmaterialthey consume i.e. the
larvaefeed upon crustaceans andother hard-bodiedaquatic organisms, whereas
theadultsfeedselectively on soft-bodiedprey,suchas mosquitoes, midges, small
butterfliesandotherinsects.Adaptations inthealimentarycanalofinsectsinrelation
Figs 8-14.Cuticular structuresofcropandproventriculus:(8-10)SEM ofinner surfaceofwall ofcrop
inthelarvashowingrowsofhairs andspines; — (11)in-situpreparationofproventriculusinthe larva
showingpairedlarge and small dental plates with teeth[INC: incisor, - MD:minute denticles, -
LDP: largedental plate, — SDP: smalldental plate]; — (12-14)SEMoflargeproventriculardental
platesshowingspinesonsurfaceinthelarva.
52 D.B.Tembhare &S.M. Wazahvar
tothenatureoftheirfoodhasbeennoticedwidely (WATERHOUSE,1957;DADD,
1970;CHAPMAN, 1985).The thick cuticular surfacein the oesophagus and the
complex dentalapparatus intheproventriculus ofB. contaminataare presumably
associatedwiththestructuralmodificationsoftheforegutinrelationtoacarnivorous
feeding habit in both, the larva and adult (SNODGRASS, 1954; POPHAM &
BEVANS, 1979).Similarmodificationshave beennoticedintheforegut ofother
carnivorous insects (CHAPMAN, 1985).
Themicrospines inthe oesophagus, along withthe bundlesofhairs, has also
been reported in Blatta orientalis (MIALL & DENNY, 1886; ELZINGA &
HOPKINS, 1994), B. germanica (ELZINGA & HOPKINS, 1994),Periplaneta
americana (MURTHY, 1975; BRACKE et al., 1979) and other blattids (Me
KITTRICK, 1964).Themicrospinesoracanthaearefoundcommonly intheforegut
ofsomeorthopteroid insects (MURA-
LIRANGAN & ANANTHA-
KRISHNAN, 1974;BOUDREAUX,
1980; HOCHULI et al„ 1992;
BENTOS-PEREIRA & LOR1ER,
1992). The adaptive function of
microspines inthepharyngeal region
seems to be related to cutting and
driving the food material from the
buccal cavity to the oesophagus
(ELZINGA& HOPKINS, 1994).The
pharyngeal spines ofB. contaminata
are tannedandstiffenedlikethoseof
P. americana, andthey may actas a
naturalvalve,incolaborationwiththe
epithelial folds, to prevent
regurgitation andlossofingestedfood
(ELZINGA& HOPKINS. 1994).In
B. contaminata the pharyngeal
microspines and the oesophageal
cuticularbeaded surface may play a
vital role in chewing, cutting and
grinding the foodmaterialinrelation
tothecarnivoroushabit(CHAPMAN,
1985).
BOUDREAUX (1980) and
Figs 15-17. SEMofproventriculardentalplatesin CHAPMAN (1985) discussed the
the adult:(15)dentalplate,showinganteriorregion proventricular microspines oracanthae
(AR) andposteriorregion(PR) with fine spines; — in different insect orders, and
(16) spines in anterior region; — (17)spines in
suggested theirpossible utilizationin
posteriorregion.
Stomodealstructures in Brachythemiscontaminata 53
systematics. Themicrospines oracanthaearereported invariousorthopteroid and
other insects, adapted mostly to the phytophagous or carnivorous feeding habit
(MURALIRANGAN & ANANTHAKR1SHNAN, 1974; BOUDREAUX, 1980;
NATION,1983;HOCHULIet.ah, 1992;CHAPMAN, 1985).Theyarealsoreported
in adephagous Coleoptera (ZHAVORONKOVA, 1969), Mecoptera and
Siphonaptera (RICHARDS&RICHARDS, 1969),along withthehairs.Inblattids,
thereare, moreover, scale-likemicrospines atthetips ofblade-like,proventricular
teethinadditiontothemulti-andunispinose microspines (ELZINGA&HOPKINS,
1994).Thepresentstudy demonstratesclearly proventricular modificationsinthe
larvaandadultindependently, andrules out thegeneral statement madeby earlier
workers that,“inadultdragonflies thearmature is weakorabsent” (CHAPMAN,
1985).Similartootherinsects,themicrospines andacanthaein theproventriculus
mayperform thefunctionofgrindingthefoodmaterial,whilethewhorlofhairsof
thestomodealvalve mightbetopreventbackflowofenzymes fromthemidgut in
thelarvaandadultof Brachythemis contaminata.
REFERENCES
BALFOUR-BROWNE,F., 1944. TheproventriculusoftheColeoptera(Adephaga)andother insects
— astudy inevolution.R. microsc. Soc. 64:68-117.
BENTOS-PEREIRA, A. & E. LORIER, 1992. Cuticular structures ofthe stomodaeum iriPaulinia
acuminata(De Geer)and Marellia remipesUvarov (Orthoptera:Paulinidae).Int. J. Insect
Morphol.Embryol.21: 167-174.
BOUDREAUX, H.B., 1980. Proventricular acanthae and their phylogeneticimplications.Ann. ent.
Soc. Am.73(2): 189-196.
BRACKE,J.W.,D.L.GRUDEN&A.D.MARKOVETZ, 1979.Intestinalmicrobial floraoftheAmerican
cockroach,PeriplanetaamericanaL. Appl.environ. Microbiol. 38: 945-955.
CHAPMAN, R.F., 1985.Structure ofthe digestivesystem. In:G.A.Kerkut & L.I.Gilbert,[Eds],
Comparativeinsectphysiology,biochemistryandpharmacology 4:65-211,
DADD, R.H., 1970. Digestionin insects. In:H. Florkin & B.T.Scheer, [Eds],Chemical zoology5:
117-185.
DAY,M.F.&D.F. WATERHOUSE, 1953.The mechanism ofdigestion.In:K.D.Roeder[Ed.],Insect
physiology,pp. 311-330,NewYork.
ELZINGA,R.J.&T.L,HOPKINS, 1994.Foregutmicrospinesinfourfamiliesofcockroaches(Blattaria).
Int. J.InsectMorphol.Embryol.23: 253-260.
HOCHULI,D.F.,B.ROBERTS&G.D.SANSON, 1992.Anteriorlydirectedmicrospinesintheforegut
ofLocustamigratoria(Orthoptera:Acrididae).Int.J.InsectMorphol.Embryol.21: 95-107.
MARSHALL,W.M.S., 1914. On the anatomyofthe dragonfly,L. quadrimaculataLinn.Trans. Wis.
Acad.Sci. 17;755-790,
Mc KITTRICK,F,A., 1964. Evolutionarystudiesofcockroaches. Mem.Cornell Univ. agric.Exp.Stn
389: 1-197.
MIALL,L.C.&A.DENNY, 1886.Thestructureandlife-historyofcockroach,Periplanetaamericana.
Lovell Reeve,London.
MILLER, H.K.& F.W. FISK, 1971.Taxonomic implicationsofthe comparativemorphologyof
cockroachproventriculi.Ann.ent.Soc.Am.64: 671-687.
MURALIRANGAM, M.C.& T.N. ANANTHAKRISHNAN, 1974. Taxonomic significance ofthe
foregutarmaturein someIndianAcridoidea (Orthoptera).Oriental Insects8: 119-145.
54 D.B.Tembhare&S.M.Wazalwar
MURTHY, R.C., 1975. StructureoftheforegutcuticleofPeriplanetaamericana. Experienlia32;316-
-317.
NATION, J.L., 1983. Specialization in thealimentary canal ofsome mole crickets (Orthoptera:
Gryllotalpidae).Int. J.InsectMorphol.Embryol. 12:201-210.
NOIROT, C.H.&C.NOIROT-TIMOTHEE, 1969.Lacuticleproctodéaledesinsectes. 1.Ultrastructure
comparée.Z.Zellf. 101: 477-509.
POPHAM,E.J. &E. BEVANS, 1979.Functional morphologyofthe feedingapparatus in larvaland
adultAeshnajuncea(L.).Odonatologica8:301-318.
RICHARDS, P.A.& A.G. RICHARDS, 1969. Acanthae: a newtype ofcuticular process in the
proventriculusofMecopteraandSiphonaptera.Zoo/. Anat. 86: 158-176.
RICHARDS,O.W.&R.G. DAVIES, 1984.Immsgeneraltextbookofentomology,IOthedn,Champman
& Hill, London.
SNODGRASS, R.E., 1935. Principlesofinsect morphology.McGraw-Hill,New York.
SNODGRASS, R.E., 1954.Thedragonflylarva. Smithson, misc. Colins 123: 1-38.
TILLYARD. R.J.. 1917. Biologyofdragonflies.CambridgeUniv. Press, London.
WATERHOUSE, D.F., 1957. Digestionininsects.A. Rev.Ent. 2: 271-277.
ZHAVORONKOVA,T.N.,1969.CertainstructuralpeculiaritiesoftheCarabidae(Coleoptera)inrelation
totheir feedinghabits.Ent. Rev. 48: 462-471.