Description of the last larval instar of Acanthagrion ablutum Calvert (Zygoptera: Coenagrionidae)

2005·0.77 MB·English

by  Pessacq, P

Odonatologica34(1):73-76 March 1,2005
Descriptionof thelast larvalinstar
ofAcanthagrionablutumCalvert
(Zygoptera: Coenagrionidae)
P.Pessacq¹,J.Muzón¹ andN.VonEllenrieder 2
1InstitutedeLimnologfa“Dr. R.A.Ringuelet”,C.C.712,1900LaPlata,Argentina
e-mail: [email protected]
2AquaticBioassessment Laboratory,2005NimbusRoad,RanchoCordova,
CA95670,UnitedStates
e-mail:[email protected]
Received September23, 2003/RevisedandAcceptedMay8,2004
Thefinallarvalinstar isheredescribedforthefirsttimeanditiscomparedwiththeother
knownAcanthagrionlarvae. Itdiffersfrom themmainlyinthenumberofpalpalandpre-
mentalsetaeandshapeofheadposterolateralmargin.
INTRODUCTION
Acanthagrion isa widespread neotropicalgenus,composed ofalmostfourtyknown
species, from which eight have been recorded inArgentina (MUZON & VON EL-
LENRIEDER,1998;MUZONetal.,2001).Thelastlarvalinstarsofonlythefollowing
six species havebeendescribed;A.adustumWilliamson, A.fluviatile DeMarmels, A.
hildegardaGloger, A.indefensum Williamson,A.ascendensCalvertandA.quadratum
Selys (GEIJSKES, 1941, 1943;DE MARMELS, 1984;MUZON, 1995;WESTFALL
& MAY, 1996;MUZ6Netal., 2001).
Acanthagrion ablutumCalvertis presently knownfromBolivia, Paraguay andAr-
gentina(LEONARD,1977;MUZ6N &VONELLENRIEDER, 1998). Inthepresent
studywe describethefinallarvalinstarofAcanthagrion ablutumbasedonrearedspec-
imensfromSaltaprovince, Argentina, andcompareitwiththe otherknownlarvaeof
thisgenus.
74 P.Pessacq,J.Muzdn&N.vonEllenrieder
ACANTHAGRIONABLUTUM CALVERT
Figures 1-12
Material.—Argentina,Saltaprovince:provincialRoute9,charca(pond)aprox. 5km.boundarywith
Jujuyprovince,3-FV-1997,N.vonEllenrieder&PerezGoodwynleg.,2 5lastinstarexuviae;—DiqueCam-
poAlegre,charcadesaguadero,9-1-1998,PerezGoodwyn&N.vonEllenriederleg.,1 9lastinstarexuviae;
- Lesser stream,24°40’57”S 65° 28'39” W, 1312 m, 11-1-1998, N.vonEllenrieder &Perez Goodwyn
leg.,3 9and2<J lastinstarexuviae. —Thespecimenswererearedinlaboratory;theresultingexuviaeand
adultswerefixed in70%alcohol.ThespecimensaredepositedintheCollectionofDepartamentoCientrfico
Entomologra,MuseodeLaPlata,Argentina.
DESCRIPTION. — Head (Fig. 1):Almosttwo timesas wideas long, posterolateral
margins slightlyconcave, notproduced orangulated,posterioranglewithseveralshort
spines.Posteriormargin
concave.Antennae(Fig.
2)7-segmented, the3th
antennomere thelong-
est. Labium(Figs 3-4)
reaching secondcoxa,
prementum almost 1.5
as long as wide, with
three or fourlong setae
and usually a smaller
inner one; lateral sides
with a row of spini-
formsetae.Palpal (Fig.
4) setae 5 to 6; mov-
ablehook slender and
sharp, about 1.4 times
as long as distal mar-
ginof palp. Outerhalf
ofdistalmarginofpalp
with4or5 smallteeth,
innerhalfwith 3 teeth
andthe typical curved
endhook;innermargin
of palp finely crenu-
lated. Mandibularfor-
Figs 1-11.AcanthagrionablutumCalvert:(1) antenna; — (2)head,dorsal mula(sensuWATSON,
view; —(3)prementum,dorsalview;—(4)labialpalp,dorsalview;—(5) 1956) as follows (Figs
rightmandible; — (6)left mandible;— (7)female gonapophyses;—(8) 5-6): L 1+23450ab;R
lateral caudallamellae;— (9)femalecercus, lateral view; — (10)female
1+2345ya
cerci,dorsalview; —(11)malecerci, dorsalview; —(12)malecercus,lat-
eral view.— [ScalesFigs2-3,7-8; 1mm.Figs 1,4-6,9-12:0.5mm] Thorax. — Wing
LarvaofAcanthagrionablutum 75
pads nearly parallel, theexternalonesreaching middleof4thabdominalsegment.
Abdomen. — Cylindrical. Femalegonapophyses as inFigure 7. Caudallamellae
lanceolated.Laterallamellae(Fig. 8)aboutfivetimesaslongas wide;noduslocatedat
0.52ofitslength, dorsalcarinawithapproximately24-26antenodalsetae,ventralcarina
withapproximately 45-50antenodalsetae,ventralsetae seriesabout 1.2 timeslonger
thandorsal series.Central lamellaaboutfourtimesas long as wide; noduslocated at
0.45ofits length, dorsalcarinawithapproximately 45-50antenodalsetae,ventralca-
rinawithapproximately 16antenodalsetae,dorsalsetae seriesabout 1.25timeslonger
thanventral series.Maleandfemalecercus asinFigures 9-12;malecercus presentsa
smallcentralconcavity onits innersurface.
Measurements (inmm,N=8). —Bodylength(withoutcaudal lamellae):approximately8.0;head
maximumwidth:2.85±0.1,headmaximumlength:1.54±0.14;prementummaximumlength:2.46±0.61,
prementummaximumwidth1.7±0.14;femurIlength: 1.5±0.1,femur H:1.8±0.1,femurEDI:2.57±0.11;
tibiaIlength:1.84±0.074,tibiaII:1.98±0.04,tibiaHI:2,57±0.09;externalwingpadslength:3.83±0.20,
internalwingpads length:3.98±0.1,cerci:0,3;caudallamellae5.85 ±0.4.
DISCUSSION
Theexternalmorphology oftheknownlastlarvalinstarsofAcanthagrioncanbechar-
acterizedby aslenderbody, posterolateral margin ofheadvariable:slraighttoconcave,
notproduced (i.e..A.ablutum,A. hildegarda, A.luteumandA. quadratum)ordistinctly
produced and angulated (i.e. A.adustum, A.fluviatileandA. indefensum); mandibles
with4-5incisorsand1-2molarteeth;distalmarginofprementumproduced, premental
setae 1-4,palpal setae 4-8;caudallamellaelanceolatedwithacuminatetips, as long as
abdomen,fivetosixtimesas long aswide,noduslocatedat0.45to0.75oftheirlength
andtracheationclosely branched.
ThelastinstarlarvaofA.ablutum(characters ofA.ablutuminparentheses), canbe
easily distinguished fromthose ofA. adustum, A.fluviatile andA. indefensum by the
concave posterolateral marginofhead(slightly concave), thepresenceofone pairof
long premental setae (3-4), fourpalpal setae (5-6) and conspicuous nodus on caudal
lamellae(inconspicuous). ItdiffersfromA. hildegarda by theabsenceofspines onthe
posterior angle ofhead(presence) andpresenceof4-5palpal setae(5-6), andfromA.
luteumandA.quadratumbythepresenceofshortspinesinthelastabdominalsegments
(absence)andfourpalpal setae(5-6).
ACKNOWLEDGMENTS
Thispaperisthescientificcontribution N°772ofthe ILPLA.This studywassupportedby theConsejo
Nacional deInvestigacionesCientfficas yTecnicasofArgentina(CONICET).
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