The emergence of Halocladius variabilis (Staeger) (Diptera: Chironomidae) in the surroundings of the Tvärminne Biological Station in the northern Baltic Sea

2006·0.07 MB·

by  Mauri Hirvenoja

©EntomologicaFennica.16June2006
The emergence of Halocladius variabilis (Staeger)
(Diptera: Chironomidae) in the surroundings
of the Tvärminne Biological Station in the northern Baltic Sea
MauriHirvenoja,ErnstPalmén†&ElinaHirvenoja
Hirvenoja,M.,Palmén,E.&Hirvenoja,E.2006:TheemergenceofHalocladius
variabilis (Staeger) (Diptera: Chironomidae) in the surroundings of the Tvär-
minneBiologicalStationinthenorthernBalticSea.—Entomol.Fennica17:87–
89.
TheemergenceofthemarinespeciesHalocladiusvariabilis(Staeger)inthesur-
roundingsoftheTvärminneBiologicalStation(about6‰S)inthenorthernBal-
ticSeain1952–1953isoutlined. Mostindividualsemergedinthesubmerged
funneltrapsusedinthestudyfromthelasthalfofMaytotheendofJune.Thepo-
pulationdensityinthesitesstudiedvariedbetween0and328indiv./m2;widear-
eashadapopulationdensityofnearly10indiv./m2.Noemergencewasfoundin
thetrapsnearesttothebuildingsofthestation,butthehighestnumbersofthe
emergenceoccurredinthemostdistantsitesstudied.
M.Hirvenoja&E.Hirvenoja,Sotilaskorventie13,FI-01730Vantaa,Finland
Received26February2004,accepted8February2005
1.Introduction ish Museum of Natural History, Helsinki, in-
cludestheinformationgivenbelowaboutthema-
In1952thelateProf.E.Palménbegantocollect rine chironomid species Halocladius variabilis
aquaticemerginginsectswithsubmergedfunnel (Staeger),collectedin1952and1953,underthe
traps (Brundin 1949) in thesurroundings ofthe nameCricotopus(Trichocladius)vitripennisK.
Tvärminne Biological Station in the northern The main distribution areas of H. variabilis
Baltic Sea. A brief description of sites 1–29 aretheeasternandwesternshoresofthenorthern
(1952)and30–50(1953)isincludedinapaperby AtlanticOcean,theBalticSea,theMediterranean
Palmén(1962).Localities60–69and70–78stud- SeaandtheBlackSea(Hirvenoja1973).Itisone
ied later on are briefly described in a paper by ofthefewmarinespeciesinFinlandandtheonly
Palmén&Aho(1966).Becauseofhisotherdu- speciesofthisgenusintheBalticSea.Itoccurs
ties,Palménbecametotallyestrangedfromthese northwardsonthesouthernshoreoftheGulfof
studies.Thisiswhylargepartsofhismaterials, FinlandnearthetownofNarva,northernEstonia
especiallythoseconcerningtheoccurrenceofthe (Järvekülg1979:Fig.66,subTrichocladiusvitri-
fresh water species in the brackish water areas, pennisMeigen).Itsdistributionoutsidethebeta-
havestilltodaynotbeencharacterised.Someof mesohaline Tvärminne area in Finland is un-
hisdeterminedaswellasundeterminedmaterials known.Thematerialtreatedinthepresentpaper
preservedinalcoholareinthecollectionsofthe originates from the shallow littoral areas, but
FinnishMuseumofNaturalHistory,Helsinki. Palmén and Lindeberg (1959, under the names
Palmén’snotebook,whichisalsointheFinn- CluniomarinusHalidayandTrichocladiusvitri-
88 Hirvenojaetal. (cid:127) ENTOMOL.FENNICAVol.17
Fig.1.ThesumofthedailyemergenceofHalocladiusvariabilis(Staeger)inthe
Tvärminneseaareain1952and1953basedon29or30submerged0.25m2funnel
traps,respectively.Darkcolumns,females;whitecolumns,males.
pennis Meigen) reported that pupal exuviae of H.variabiliswereinthesurroundingsofthenear-
H.variabilisoccurveryregularlyinthesamesur- est islands Vikaskär and Jovskär opposite to
face samples, where Clunio balticus Heimbach Krogarviken Bay. At that time, the Biological
wasfoundinareasmorethan10mdeep.Incon- Stationhadnowastewaterpurifyingplant.This
trasttoH.variabilis,thelatterspeciesisveryrare situation may have had some influence on the
inshallowerareas. aquaticbiota.
H.variabilishasnotbeenfoundinfreshwater Unfortunately,noinformationisavailablefor
habitats,butSanthakumaranetal.(1984)report, thewaterchemistryintheTvärminnearea1952–
that the larvae were unaffected when placed in 1953. Traps were also set in summer 1953 in
distilled water and could withstand salinities as someofthesitesstudiedin1952(1–2,12–13a–b,
high as 70.5 ‰ when transferred directly from 27–29),butsites30–51werenew.Nosubsequent
distilledwaterand97.0‰afteracclimation.Ac- emergenceofH.variabiliswasobservedin1953
cordingtothoseauthorsthelarvaewerepresent in Krogarviken Bay or in traps 34–37 near the
inTrondheimsfjorden,Norway,amongavariety shoreofJovskärisland.
offoulingcommunitiesrangingfromathinfilm Thehighestpopulationdensityin1953wasat
ofalgaeandsilttoextremelyheavysettlementsof sites 45–47, at the eastern tip of Longholmen
coelenterates, serpulids, barnacles, bivalves, about700–800mfromthebuildingsoftheBio-
bryozoans, ascidians, or algae together with a logicalStation.Atsite45(depth6m)thedensity
thicklayerofsiltandfaecesofpolychaetes,as- can be converted from the emergence to 328
cidians,andwood-borers. indiv./m2.Thenearesttraps,46and47(depths12
and13m),producedsmallercatches.Thevertical
distributionofthelarvaeisnotknownintheBal-
2.PopulationdensityatTvärminne ticSea.Mostofthesitesstudiedin1953wereata
basedontheemergence greaterdistancefromtheBiologicalStationthan
those in 1952, and the mean catch in 1953 was
Therewereatotalof29funneltrapseach0.25m2 higher,being23.6indiv./m2.
inarea,usedin1952and30trapsin1953atthe
sitesneartheBiologicalStation.Theyarenum-
bered in the map given by Palmen (1962). The 3.PhenologyofH.variabilis
population density of H. variabilis was low in intheTvärminneseaarea
1952withamaximumof5indiv./0.25m2(=20
indiv./m2).Atthe15sites(=traps)whereemer- As mentioned above, the population density of
gencewasobserved,themeanpopulationdensity H. variabilis was very low in most of the sites
canbeconvertedto10.4indiv./m2. studied.Therefore,thedaily catchesofalltraps
Intraps1–6,8–12and27–28noindividuals arecombinedintothehistogramsinFig.1,where
emergedin1952.Sites1–6inKrogarvikenBay inbothyearsthetotalcatchoriginatedfrom29or
(depths 1–7 m) that has abundantly vascular 30(1953)traps(each0.25m2),i.e.thedailycol-
plantswerenearesttotheStationbuildings.The umnsarethesumsofcatchesfromtotalareasof
othersites8–12and27–28withoutemergenceof 7.25or7.50m2.Theseareasalsoincludethetraps
ENTOMOL.FENNICAVol.17 (cid:127) EmergenceofH.variabilisinBalticSea 89
(sites)wheretheemergenceofH.variabiliswas Kenntnis der Bodenfaunistischen Characterzüge
notobserved. schwedischeroligotropherSeen.[WithEnglishsum-
mary].—Inst.Freshw.Res.Drottningholm,Rep.30:
Theoccurrenceoftwoormoreemergencepe-
1–914.
riodsduringaseasonisaquitecommonphenom-
Hirvenoja,M.1973:RevisionderGattungCricotopusvan
enoninthelifecycleofthelittoralchironomids. derWulpundihrerVerwandten(Diptera,Chironomi-
Fig.1showsthatthepopulationofH.variabilis dae).—Ann.Zool.Fennici10:1–363.
in the Tvärminne sea area is univoltine. It Järvekülg,A.1979:Thebottomfaunaofeasternpartofthe
BalticSea.[InRussian].—382pp.Valgus,Tallinn,
emergesfromthelasthalfofMay totheendof
Estonia.
June,perhapswhenthebottomwatertemperature
Palmén,E.1962:Studiesontheecologyandphenologyof
isabove+4°Candthesurfacewatertemperature the Chironomids (Dipt.) of the Northern Baltic. 1.
exceeds about +8°C (see Fig. 13 in Palmén & Allochironomus crassiforceps K. — Ann. Entomol.
Aho1966:thedevelopmentofthetemperaturein Fennici28:137–168.
Palmén,E.&Aho,L.1966:Studiesontheecologyand
1960). There happened also occasional emer-
phenologyoftheChironomidae(Dipt.)oftheNorth-
gences in the Tvärminne population during the
ern Baltic. 2. Camptochironomus Kieff. and Chiro-
othersummermonths. nomusMeig.—Ann.Zool.Fennici3:217–244.
Palmén, E. & Lindeberg, B. 1959: The marine midge,
Acknowledgements.ThanksareduetoMr.DonaldSmart CluniomarinusHal.(Dipt.,Chironomidae),foundin
forrevisionofthelanguage. BrackishwaterinthenorthernBaltic.—Int.Rev.Ges.
Hydrobiologie44:383–394.
Santhakumaran,L.N.,Sneli,J.-A..&Sundnes,G.1984:
References The larvae of (Halocladius (Halocladius) variabilis
(Diptera: Chironomidae) from the fouling assem-
Brundin,L.1949:ChironomidenundandereBodentiere blages on wooden test panels submerged in Trond-
derSüdschwedischenUrgebirgseen.EinBeitragzur heimsfjorden.—Sarsia69:155–158.