A description of the remarkable larva ofPseudolestes mirabilisKirby (Odonata: Pseudolestidae)

2011·0.2 MB·

by  Xin Yu

InternationalJournalofOdonatology
Vol.14,No.2,June2011,105–110
A description of the remarkable larva of Pseudolestes mirabilis
Kirby (Odonata: Pseudolestidae)
XinYu*andWenjunBu
InstituteofEntomology,CollegeofLifeSciences,NankaiUniversity,Tianjin,300071,PRChina
(Received3March2011;finalversionreceived26May2011)
ThelarvaoftheChineseendemicPseudolestesmirabilisisdescribedandfiguredforthefirsttime.Speci-
menswerecollectedfromHainan,theonlyknownlocalityforthisspecies.Thepresenceofventralpaired
gilltuftsonS10andsack-likecaudalgillsindicatethatamongotherzygopteranfamiliesthisspeciesmay
bemostcloselyrelatedtotheAmphipterygidae,butothercharacters,especiallythoseoftheadultsuggest
itmaybesufficientlyuniquetowarrantplacementinitsownfamily.
Keywords: Odonata;dragonfly;Zygoptera;Pseudolestidae;Pseudolestesmirabilis;larva
Introduction
Pseudolestesmirabilis,thewell-knownChineseendemicspecies,hasbeenthesubjectofconsid-
erablerecentspeculationwithregardtoitsphylogeneticposition.Basedonitsunusualandunique
adultcharactersthespecieswasoriginallyplacedinitsownsubfamilybyKirby(1900).Calvert
(1902)andTillyardandFraser(1938–1940)placeditinsubfamilyLestinae(nowLestidae).Fraser
(1957)thenestablishedthefamilyPseudolestidaetohousePseudolestesandseveralothergenera,
whichwasfollowedbyDaviesandTobin(1984)andvanTol(2006).Howeverrecentphyloge-
neticstudiesusingmoleculartechniques(Bybee,Ogden,Branham&Whiting,2008)suggestthis
speciesbelongsintheMegapodagrionidae.Thelarvaeofmegapodagrionidshavebeendivided
intofourgroupsbyKalkman,Choong,OrrandSchütte(2010):(1)specieswithinflatedsack-like
gillswithaterminalfilament;(2)specieswithflatverticalgills;(3)speciesinwhichtheoutergills
inlifeformatubefoldedaroundthemediangill;(4)specieswithflathorizontalgills.Kalkman
et al. (2010) discussed the likely characters of unknown larvae of supposed megapodagrionids
(includingP.mirabilis)andsuggestedthatthelarvaofP.mirabiliswouldfallintoabovegroup1,
i.e.havingsack-likegills.ThisstudyprovidesadetaileddescriptionofthelarvaofP.mirabilis
anddiscussesthephylogeneticimplicationsofitsunusualcharacters.
*Correspondingauthor.Email:[email protected]
ISSN1388-7890print/ISSN2159-6719online
©2011WorldwideDragonflyAssociation
DOI:10.1080/13887890.2011.592486
http://www.informaworld.com
106 X.YuandW.Bu
Areaandmethods
Larvaewerefoundinbothshadyandopenmontanestreamswithshallowwaterandstonysub-
stratesinDiaoluoshanandBaiwangling,Hainan,China.Adultswerepresentaroundthesiteand
atnearbystreamsinmoderatenumbers.Larvaewerecollectedusingadipnetwithremovalof
bigstonesbyhand.Thoughvegetationofthesurroundingareawasalsosearchedthoroughlytoa
heightof2m,exuviaewereonlyfoundonstonesextendingabovethestreamsurface.Attempts
weremadetorearcollectedlarvaeinthelaboratoryinplasticcontainersbutfailed.Livingphotos
were taken in the field before or just after collecting with a digital camera (Canon Power Shot
A710).CharacterphotosweretakeninthelaboratoryusingDiagnosticSpotCCDcameraadapted
tothestereomicroscopeNikonSMZ1000.Specimensexcepttheexuviaewerepreservedinabso-
lute ethanol and were examined and dissected under a stereo microscope Olympus C011. The
dorsalhabitusphotograph(Figure1a)wassuppliedbyHaomiaoZhang.
DescriptionofLarvae
Pseudolestesmirabilis(Figures1–3)
Materialexamined
1(cid:2)exuviae,Diaoluoshan,Hainan,China,1June2007,XinYuleg.;1(cid:3),Baishuiling,Diaoluoshan,
Hainan,China,29May2007,Ji-MengHualeg.;1(cid:2),Bawangling,Hainan,China,9June2007,
Ji-MengHualeg.
Diagnosis
Arobustzygopteranwithalargehead,shortlegsandsack-likegills.Atuftofabdominalgillsis
present ventrally on the final segment (Figure 1a). Ground colour of body dark brown, lacking
distinctbandsormarks.
Description
Head. Relatively broad, exceeding maximum breadth of mesothorax; in dorsal view general
shapeacompressedpentagon,withtheposteriorsidedeeplyexcavatedtoformaroundedmargin.
Postocularlobessomewhatswollen.Antennae7-segmented,moderatelylongandevenlytapered,
segmentsofequallengthexcepttheapicalone,whichisjusthalfthelengthofothersandincon-
spicuous.Labium(Figure2a)elongate;prementumabout1.7timesaslongasbroadandbasally
narrow. Distal lobe moderately convex with strong marginal crenulations; median cleft short.
Labialpalp(Figure2a,b)robust,lackingsetae;distallywithtwostrong,short,incurvedteethand
smallshortsecuriformprocessontheinnermarginjustbasadofinnertooth;movablehooklong
androbust.Maxilla(Figure2g–j)twiceaslongasbroad.Galeaandlaciniapartlyfused;lacinia
terminatinginfourlongsharpspines,formingacurved,inward-directed,pitchfork-likestructure;
galeawiththreeshorterspinesdirectedupward.Palpwithshortbasalsegmentandasinglelong
banana-shapedterminalsegment,reachingtobaseofmostdistalspinesongaleo-lacinia,covered
indenselongsetaeforthedistaltwo-thirdsofitslength.Rightmandible(Figure2c–d)withfour
welldevelopedincisorsandafifthinnermosttooth;outermost(ventral)toothwithsmallsecondary
toothwellbeforeitsapex;molarcrestproducedtoformawell-definedcurvedbifidspine(thus,in
theterminologyofM.C.Watson[1956],R12344’yab).Leftmandible(Figure2e–f)withsimilar
ThelarvaofPseudolestesmirabilis 107
Figure 1. (a)LarvalhabitusofPseudolestesmirabilis,finalstadiumfemale,photobyHaomiaoZhang;(b)finalstadium
male,ventralviewofendofabdomenshowinggilltufts;(c)F-1stadiumfemale,ventralviewofendofabdomenshowing
gilltufts.
incisors;molarcrestproducedstraight,withdistaledgeserratedwithsevenfinecusps(L12344’
ya(m1,2,3,4,5)b).
Thorax. Prothorax robust; anterior one quarter rather narrow but posterior to this strongly
expanded laterally with paired, solid, blunt processes around the midpoint of the margin.
Meso- and metathorax irregular, rounded, sub-rectangular in shape. Legs moderately short and
strong,bearingscatteredshortspinesandhairs,lackingbandsorothermarks;legsprogressively
slightly longer from pro- to metathorax. Wing pads moderately long, flat and narrow, almost
reachingtodistalmarginofS7inspecimenwithrelativelycontractedabdomen(Figure1a).
Abdomen. Robustandelongatewithpaired,possiblyretractable,gilltuftsontheventerofS10.
Gonapophyseswelldevelopedinmale,projectingfromanteriormarginofS9toalmosttheendof
thissegment(Figure1b).InfemaleoutergonapophysesprojectingfromanteriormarginofS9to
middleofS10;innergonapophysesreachingstillfurther(Figure1c).Cerciwhollyconcealedby
expandedgilltuftsinventralview(Figure1a,b).Inflatedsack-likecaudalgillscoveredinshort,
stoutsetae;football-likeinthefinallarva(Figure1)withbluntapicalprojections,slightlylonger
108 X.YuandW.Bu
Figure 2. LarvalcharactersofPseudolestesmirabilis:prementumandlabialpalps,(a)dorsalviewand(b)ventralview;
leftmandible,(c)dorsalviewand(d)ventralview;rightmandible,(e)dorsalviewand(f)ventralview;leftmaxilla,(g)
dorsalviewand(h)ventralview;rightmaxilla,(i)dorsalviewand(j)ventralview.
Figure 3. LeftlateralcaudalgillofF-1stadiumfemale.Left,outerview;right,innerview.
and finger-like in the earlier instar larva (Figure 3); each lateral gill c.1/5 of total body length
excludingantennaewiththemedianonedistinctlylonger;overallcolourratherdarkwithoutany
pattern.
ThelarvaofPseudolestesmirabilis 109
Microhabitatandbehaviour
Larvae were found in both shady and open montane streams with stony substrates. Some even
occurredinverysmall“puddles”coveredwithdensevegetationformedbydiscontinuousstreams.
Theyusuallywerefoundconcealedamongstonesorgravel.Adultscanbefoundinmostareasin
Hainan;however,aslarvaearelessconspicuousthanadultstheyareundoubtedlyunder-sampled.
Emergence is from late March to early May. The larvae creep onto the surface of stones just
10–20cmabovethewaterwheretheyemerge.
Discussion
LarvaofP.mirabilispossesspairedgilltuftswhichstronglyresemblethoseofamphipterygids
(Corbet, 1999; Novelo-Gutiérrez, 1995; J.A.L. Watson, 1966). It is not clear if the gills are
retractable, but it is very probable they are, as described in Devadatta argyoides (Orr, 2008).
If so, it would seem very probable that the organs are homologous autapomorphies. Elsewhere
in the Odonata abdominal gills occur only in larvae of Euphaeidae and Polythoridae (Corbet,
1999; Sisby, 2001). These are simple finger-like ventral-to-lateral projections along much of
the abdomen (not S10) and probably evolved independently. They are quite unrelated to the
gill tufts of Pseudolestes. If closer examination of these should prove them to be essentially
the same as the structures known from Amphipterygidae, it would be strong evidence for a
shared ancestry.Although the adult characters of P. mirabilis are quite different from those of
known amphipterygids, the species is so aberrant and has proved so difficult to place that its
adult characters may simply be the result of rapid evolution and adaptation associated with its
extraordinaryagonisticdisplays(Reels,2008).Inanycase,ithasprovenverydifficulttoplace
this species by analysis of adult characters, as evidenced by the variety of suggestions as to
itsrelationships(Lestinae[Tillyard&Fraser1938–1940];Pseudolestidae[Fraser,1957;Davies
&Tobin, 1984; vanTol, 2006]; and Megapodagrionidae [Kalkman et al., 2010]). However the
presence of gill tufts convincingly separates it from the Megapodagrionidae.Also, in view of
the new larval characters, the phylogenetic position of P. mirabilis close toAmphipterygidae,
recovered in one cladogram based on traditional characters by Rehn (2003), seems the most
convincing. Further studies, especially comprehensive molecular analysis, may recover a clear
relationship between Pseudolestidae and Amphipterygidae. Presently, we believe P. mirabilis
shouldremaininitsownfamily,Pseudolestidae.
Acknowledgements
WewouldliketothankDrDaweiHuangforprovidingthechanceforHainanexploration.WeacknowledgeDrMatti
HämäläinenandDrK.D.P.Wilsonforthevaluablediscussiononthislarva.WethankHaomiaoZhangforproviding
thevaluedphotoandinformationonthelarva.WearealsogratefulforDrA.G.Orrforreviewingthemanuscriptand
providingvaluablecommentsandsuggestions.ThisprojectwassupportedbytheNaturalScienceFoundationofChina
(No.J0930005andNo.30725005).
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