Diagnostic characters distinguishing the larvae of Ablabesmyia and Paramerina, and first record of Paramerina in Brazil (Insecta, Diptera, Chironomidae)

5 Pages·1997·1.7 MB·

by  E Stur

SPIXIANA
Fig.1. Pammerinasp.Larva, a. Antenna. b. Mandible. c. Maxillarypalp. d. Paraligula. e. Pectenhypopharyngis.
f. Clawsofposteriorparapode. Scale: 50pm.
Body. All claws ofposterior parapode simple; one dark claw (Fig. If).
mm
Pupa. Total length ca. 3.6
Thoracichörn. AsinFig. 2a;lengthc. 240pm;plastronplateoppositetheCorona;hörnsacwall,a
reticulate cuticular mesh opposite Corona.
Abdomen. SegmentsVIIandVIIIwithafineshagreenofisolatedspinulesonlyontheventralside;
patternofdorsalsetaeasinFig.2b.Anallobewithfineshagreendispersedontheanteriorhalf;genital-
sac ofmale projectingbeyond the end ofthe anal lobe (Fig. 2c).
Comments
Compared with the immature states of other Paramerina species, this Brazilian species seems to be
similartoP.fasciataSublette&Sasa,1994,fromGuatemala.Althoughthedimensionsofonlyonelarval
headofParamerinafasciatahavebeenpublished,thesizeofantennaandmandible,andtheratioofthe
two- segmented basal segment of the maxillar palp fall within the ranges ofthe Brazilian species. In
Sublette and Sasa's (1994) description, however, the larval antenna has a verv short antennal blade
(half size of second segment), whereas the Brazilian species has an antennal blade longer than the
second segment.
The Brazilian P(7ra;7!en»n-speciescanbedistinguished from otherParamerina-speciesfromCentral
and North America, by the following features:
P. niwiiialus Beck& Beck, 1966Larva: allclawsof posteriorparapodepale;ligula,innerteethand
middletoothpoints,pale. Pupa: length3mm,thereforesmaller;genital-sacshorterthaninP.sp.from
Rio Bento Gomes, Brazil.
P.sniitliae(Sublette), 1964Larva:posteriorparapode,twosmallerclawsbifidandonesmallerclaw
pectinate. Pupa: threespinessubapicallyoninnermarginofsegmentIX;thoracichörn, plastronplate
smaller and neck ofplastron plate thicker (Roback 1972).
OfP. testa Roback, 1971 (Florida) and P.fragilis (Walley), 1925 (SouthCaroHnaand probabelyalso
Florida) the immature stages are not known (Epler 1995).
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Fig.2. Paramerina sp. Pupa. a. Thoracichörn. b. SegmentsVIIand VIII. c. Partofanallobe.Scale: 50pm.
Ecological remarks
ThelarvaeofParamerinasp.arefoundinthemiddlereachesofthelüoBentoGomes(ca.56°35'W,15°
50'S).Thisintermittenttropicallowland riverflowsintothenorthernPantanalinMatoGrosso,Brazil.
During the period of sampling between May 1993 and June 1994, the mean water temperature was
25°C (ränge29°C-17°C), themean pH 7.2 (ränge8.0-6.0), and the mean conductivity 180pS (ränge
50pS-290]aS). Single specimens ofParamerina were collected during the dry and rainy seasons. The
larvae were more numerous at the end of the dry and beginning of the rainy seasons. The larvae
occured in leaflitter, which was either accumulated on thewater surface or the riverbottom.
Differentiation ofParamerina und Ablabesmyia in the larval stage
Larvae of Ablabesmyia have the basal segment of the maxillary palp subdivided into 2-6 Segments
(Roback1985,Fittkau&Roback1983).Normally,ifthebasalsegmentofmaxillarypalpisdevidedinto
twoparts,theyaresubequalinlength,ortheproximalislongerthanhalfofthedistalpart(Epler1995).
However,inParamerina theproximalsegmentisshorterthanhalfthelengthofthedistalsegment(see
alsoTab. 1).OneormoreclawsofposteriorparapodeinAblabesmyiaareusuallydark(Cranston1996,
Epler1995,Fittkau&Roback1983),withtheexeptionofA.philosphagnosBeck&Beck,1966,whichdoes
Tab.1. FirstsegmentmaxillarypalpofParamerina:ratioproximaltodistal(meshuredinthefiguresoftherespective
authors). NotethattheratioinAblabesmyiadiffersfromtheusual.
species
Fig.3. Parameriimsp.,Brazil,RioBentoGomes,withcephalicsetaeandsensorypores. a. Ventralview. b. Dorsal
view. Abbreviations: DP:dorsalpore;S4-S10: cephalicsetae;SSm:submentalsetae;VP: ventralpore.
not have dark claws on the posterior parapodes (Roback 1985). On the other hand, Paramerina is
supposed not to have these dark claws (Cranston 1996, Epler 1995, Fittkau & Roback 1983), but one
dark claw is present in the Brazilian Paramerina-larva.
InthesubfamilyTanypodinaetheanalysisofthesubmentalsetaeand sensoryporesofthelarval-
headsmakesitpossibletodistinguishthedifferentgenerainthelarvalstage(Kowalyk1985)(Figs3,4).
These setal pits and sensory pores result in a certain pattern which does not seem to vary within a
genus.Kowalyk(1985)comparedthepatternsofvariousspeciesofAblabesmyia-larvaeanddidnotfind
differences in the pit-patterns, and Cranston (1996) used these patterns to distinguish Australian
genera. A.minulata, which alsodiffers in othercharacters ofligula, procercusand posteriorparapode
fromtheremaining Ablabesmyia-species(Fittkau&Roback1983),showedanotherarrangementofthe
setae. AlthoughthepitpatternsofcephalicsetaeofAblabesmyia-speciesarereasonablewellknown,to
date the patterns only three Paramerina-species have been described. Kowalyk (1985) compared the
patterns ofthecephahcsetaeofParamerina fromP.fragilis (Walley), 1925, and P. sp. (Kowalyk 1985),
and Cranston (1996) investigated those ofP. parva (Freeman), 1961.
TheclearestfeaturestodifferenciateAblabesmyiafromParamerinaarethepositionof thesubmental
setaeS9,SlOandSSm,andtheventralporeVp(Figs3Aand4A).Thesepatternscorrespondwiththose
mentioned by Kowalyk (1985) and Cranston (1986) for the respective genera.
Resumo
EntreaslarvasdeTanypodinaedoRioBentoGomes(56°30'W16°S)MatoGrossofoiencontradoumtipodelarva
que näo pode ser diferenciada das do genero Ablabesmyia, pela chave de Tanypodinae holärticos (Fittkau &
Roback 1983). A forma docornotoräcicoindicoutratar-sedeumoutrogenero,eainda uma anälisedassetas
submentaispossibilitou sua inclusäonogenero Pammerina, segundo Kowalyk (1985).
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Fig.4. Ablabesmyiasp.,Brazil,RioBentoGomes,withceplialicsetaeandsensorypores. a. Ventralview. b. Dorsal
view.Abbreviations: DP: dorsalpore;S4-S0:cephalicsetae;SSm: submentalsetae;VP:ventralpore.
Acknowledgements
We would like to thankUlrike Nolte and Mirian A. Serrano forsupport in Brazil and Stephen Ridgway for
commentsonthedraft.E.SturreceivedfinancialsupportfromtheDeutscheForschungsgemeinschaft(DFG:Fi
99/11-1,2)granted toE.]. Fittkau.
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