Ecological Notes on the Adult Stage of Graphelmis shirahatai (NOMURA) (Coleoptera, Elmidae)

2007·6.2 MB·English

by  Hayashi, M

Elytra,Tokyo,35(1):102-107,May30,2007
EcologicalNotesontheAdultStageofGraphelmisshirahata1
(NoMURA) (Coleoptera,Elmidae)
Masakazu HAYAsHI
HoshizakiGreenFoundation,0kinoshima,Sone, Izumo,691-0076Japan
Abstract Arareelmidbeetle,Graphelmlsshlrahatai (NoMuRA),wasabun-
dant in thelower portionof the Hii-kawaRiver, ShimanePrefecture,Japan. Its
ecologyandhabitatarediscussedbasedonmyobservations.
Graphelmisshirahatai (NoMuRA) isoneof therarest speciesof theElmidae in
Japan(YOSHITOMI,2006). NoMURA(1958)describeditasStenelmisshirahataiandits
twotypespecimenswerecollectedfromYamagataPrefecturein1947and l954. A few
collectionshavebeenmadefromHonshu (Miyagi, Tokyo, Niigata,andHyogo),but
mostrecordsarefromthe1940'ste t970's(SATo,1985;TAKAHAsHI,1996). Inrecent
years, YosHIToMI (1996) foundnineadult G. shirahatctiondriftwoodin theRiver
Yahagi-gawa,AichiPrefecture. YosHIToMI (2006)statedthatG.shirahataishouldbe
designatedasanendangeredspecies,butdeterminingitsstatusisverydifficultbecause
littleisknownaboutitsecology.
In2005, I happened tocollect oneadult of thisspeciesin theHii-kawa,Shimane
Prefecture(HAYAsHI&SHIMADA,2006). IcollectedandobservedG.shirahataialong
theriverinthefollowingyear,fromJanuarytoOctober2006. Duringthisinvestigation,
Iobservedmanyadults.Here,I willdiscusstheecologyofG.shirahataiadultsbasedon
myobservations.
StudyArea
TheHii-kawaisarelativelylargeriver inShimanePrefecture, ChugokuDistrict,
Japan. Itsmouthislocatedonthewesterncoastofabrackishlake,Shinji-ko. Coarse
sandandgranulesoriginatingfromthegranitezoneoftheChugokuMountainRegion
characterize the fluvial sediments of the lower area. The river water level changes
frequentlydueto rainandsnowfall. Thewater level isusuallylow(0-100cmdeep)
fromlateMarch toOctober,except duringheavyrainsin lateJune. Thewidthofthe
mainchannel isabout120-200minthelowerportionof theriver.
I investigated fivesitesalongthelowerportionoftheHii-kawa(Fig. 1):
Site1: Shimamura-chinkabashi, Shimamura-cho, IzumoCity,ShimanePref: Ia,
mainchannel; lb,branch channel.
Site2:Shimamura-hi,Shimamura-cho,IzumoCity,ShimanePref:branchchannel.
EcologicalNotesonGraphelmisshirahatai 103
Fig.1. study area. Index map showing distribution of G. shira1tatai in Japan (modified afto「
YosHIToMI et al., lg99). - 1,Shimamura-chinkabashi,IzumoCity;2,Shimamura-hi, IZumo
city;3, Mizuho_ohashi,Hikawa-cho. Legendsofmap:closedcircle,G.shirahataiWasfound;
opencjrcle,(J.shirahataiwasnot found;crossedhatch,hillsandmountainregion;da「kColo「,
riverandlake;white, flat (Izumo-heiya).
sjte3:Mizuho_ohashi,Nakanoshima,Hikawa-cho,ShimanePref:3a,mainchan-
nel (Figs 2-4);3b,branchchannel (Fig 5).
104 Masakazu HAYAsH]
Methods
I surveyed thefivesitesa total of 34 times fromJune toOctober 2006. Elmjd
beetleswerecollectedbysweepingaroundtherootsofplants(e.g.,willows,reeds)usjng
anet andexaminingdriftwood. Alladultswerecollectedand thespecimenswere
deposited in theHoshizaki InstituteforWildlifeProtection. Izumo.
Results
Recordsfromthesites
A totalof219adultG.shirahata1werecollectedfromthefoursites(Tablet):4
eXS・,Site ta,20-VIII-2006,M.HAYAsHI leg;8exs.,ditto,7-IX-2006;1ex.,Sjte lb,
30-VII-2006,M.HAYASHI leg;49exs.,Site3a, l7-VIII-2006,M.HAYAsHI leg;26
exs.,ditto,19-VIII-2006;18exs.,ditto,26-VIII-2006;34exs.,ditto,3-IX-2006;9exs.,
ditto,12-IX-2006;2exs.,Site3b,14-VII-2006,M.HAYAsHIleg;1ex.,ditto, l5-VII-
2006;22exs.,ditto,3-VIII-2006;15exs.,ditto,6-VIII-2006;23exs.,ditto,10-vIII-
2006;4exs.,ditto,11-VIII-2006;3exs.,ditto,3-IX-2006.
Thefollowingdatashowitsnon-collectingrecordsfromthefivesites:Site3b,9-I-
2006;Sitelb,21-II-2006;Site2,7-V-2006;Site3b,4-VI-2006;Site3b,13-vI-2006;
Table t・ Co1lCetionrecordsofG.shirclhataiinlowerportionoftheHii-kawa.SeetextandFjg.1for
site numbers.
JAN FEB MAY JUN JUL
Day
9 21 7 4 13 16 21 24 25 7 8 14 15 30
S.1te
la
lb 0 0
2
3a
3b 0 0 0 0 2 1
Total 0 0 0 0 0 0 0 0 0 0 0 2 1 1
AUG SEP COT
Day
1 3 6 8 10 11 17 19 20 26 3 7 12 24 29 14
S.Ite
la
1b
2
3a 49 26 18 34
3b 22 15 23 4 3
Total 0 22 15 0 23 4 49 26 4 18 37 8 g 0 0 0
EcologicalNotesonGraphe1,nlsshirahatai 105
、・ '
一 ' 、 1 . ,
= -・
一 -
, ,1S、-1
登f' -,
- -
装' 1、1.1..
- - .
i f
、,
Fjgs 2-7. photographsof G. shirahata1and its habitat. - 2-4, Site3a (2, sandy bed of the
Hii_kawa;3,deepoftheriver;4,driftwood);5,Site3b;6-7,G.s11tra11atai on the driftwood.
Site3b, l6-VI-2006;Site3b,21-VI-2006;Sitelb,21-VI-2006;Sitelb,24-VI-2006;
site2,25-VI-2006;Site3b,7-VII-2006;Sitelb,8-VII-2006;Sitelb,1-VIII-2006;Site
lb,8-vIII-2006;Site3a,24-IX-2006;Site3b,24-IX-2006;Siteta,29-IX-2006;Site
3a 14-X-2006;Site3b, 14-X-2006.
106 Masakazu HAYAsHI
Coexistingaquaticbeetles
I found l3speciesofaquaticbeetlesfromthestudysites,asfollows: [Hydrophili-
dae] Laccobius fragilisNAKANE; [Elmidae] Stenelmisnipponica NoMuRA,Stenelmis
、'ulga「Si NOMURA,Stenelmismiyamoto1NoMURAetNAKANE, 0rdobre・via fo(veico111s
SCHONFELDT, Leptelmis gracilis SHARP, Leptelmispara11ela NoMURA, 0ptioservus
nitidus NOMURA, Pseudamophilus Japonicus NoMURA, Grouve11inus marginatus
(KONo),Zaitzevlariabrevis(NoMURA),Zaltzeviaawana(KONo); [Dryopidae]Elmo-
morphusbrevicornisbrevicornlsSHARP. Amongthem,twoelmidbeetlesS.vulgarisand
S miyamoto1arethecommonestspeciesinthestudiedsites.
Distribution in the Hii-kawa
Acontinuoussandybedoccursalongtheriverformorethan20kmfromthemouth
oftheriver. ThissandybedisthehabitatofG.shirahatai (YosHIToMI,1996). I found
G.shit''ahataiatninesites,includingthefivesitessurveyedhere,but foundnonefrom
sitesfurtheruptheriver. Intheupperriverarea,thesurfaceofthesandybediscovered
withathinlayerofmudandalgae.
Discussion
AdultG.shirahataiwerefoundfrommid-Julytomid-Septemberatthesurveysites.
Ididnotobserveanymissingappendagesormudcoatingthebody,indicatingthat the
adultshadec1osedduringthecurrentseason. Nocopulatingpairswereobserved. Itis
possiblethat copulationoccursat night.
Mostadultswerefoundindepressionson thesurfaceofdriftwoodandin roots
withinthecurrent. TheadultspreferarelativelystrongcurrentbecauseG.shirahata1
hasthelargestclawintheJapaneseElmidae; Ihavenot foundanyindividualsinstill
water. Thewoodwasusuallyofwillow(Sailx:;spp),whichisacommontreealongthe
river,anditsrootswereexposeddeepwithintheriver. Sail)cisrecognizedasthefood
ofG.shirahata1adults. However,YosHIToMI (1996) reportedthatadriftwoodfound
intheYahagi-gawaisofcherry,Prunussp.
Thehabitat ofGI. shirahatai isariver withasandy bed and riparian willow
vegetation. Therivercurrentcarriesdriftwoodfromtheforestandwashesthesandbed.
In theHii-kawa, fluctuation in theriverwater levelplaysan important rolein the
formation ofhabitat forG. shirahata1.
Acknowledgements
I thankDr.HiroyukiYosHIToMIandDr.TeijiSoTAfortheirhelpinpreparing
thismanuscript. Idedicatethispapertothememoryof thelateDr.MasatakaSAT0,
whowasawell-knownspecialistofaquaticColeopterainJapan.
EcologicalNotesonGraphelmisshirahatai 107
要 約
林 成多: ァヤスジミソ'ドロムシ(甲虫目ヒメドロムシ科)の生態学的知見. - アヤスジミ
ノドロムシは日本産ヒメドロムシ科のうちでももっともまれな種の一つであり, 1940-1970年代
の数例の記録があるほか,近年では愛知県矢作川での記録があるに過ぎない. 2005年になって島
根県の斐伊川下流域から1個体が採集された.そこで, この地域において,2006年1月から10月
まで本種の生息状況について調査を行った. その結果, 斐伊川下流域には多数の個体が生息して
いることが判明した. 成虫は7月中旬から9月中旬に出現し, 流れのある淵に沈んでいるヤナギ
の流木や根にみられた. 斐伊川では, マサ土(花崗岩由来の土砂)からなる砂質の河床が, 河口
から20km以上にわたって分布しているが,山間部では泥や藻類が砂の表面を覆っていることが
多く,本種を確認できなかった. 今回の観察結果から, 本種の生息環境は, ヤナギなどの河畔林
を伴った粗粒砂~細礫を主体とする砂質河床の河川で, 本種の餌である木質物の供給が現地また
は上流からあり, 流水によって砂が移動して底質に泥や藻類が付着しにくい場所であると考えら
れる. このような生息環境を形成するうえで, 斐伊川の顕著な水位変動が重要な役割を果たして
いるとみられる.
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