Mashiko Kikuya

益子 帰来也

Kanazawa University Repository for Academic Resources

The Science Reports of the Kanazawa University， Vol. l. No. 2， PP. 35← 41 M，arch 195壬-3o -， On the Geographical Distribution of Some Brackish-and I，'resh-water Copepods in and around Japan Kikuya MASHIKぴCReceived ](). Jan. 1Ho4) In troducti on Cosmopolitanism is One of the well.known fεatures of the fresh-wat巴rplankton. So立lecopepods such as Calanoida of inland waters， however， are taken a日 a consplcuoUS exception， each species of them having more or le雪sits own limlted distribution. This characteristic feature of the geographical distribution of such copepods may be explained from the f3ct that the adaptation or migration of th巴sespecies from sea to inland waters has taken place in an age comparatively recent. From this point of view， our attention may be drawn to the brackish.water copepods， because they may be regarded as the important links connecting those in the fresh-waters with those in the sea. In Japan， there are many brackish-water .lakes or lagoons which are situated along the coast of the Pacific Ocean as well as the Sea of Japan ancl are connected with the sea by rivers or canals. These lakes are suppos巴dto offer more or less convenience for the plankton animals to migrate from sea to inlancl waters (or 'l，ice ver8u). From a ョimilarpoint of view， the Yangtse.kiang in Central China and many lalces connected with it may also be a matter of our great interest. Thus， the geographic乱1distribution of a number of copepocls found in these brackish-and fresh田watersin Japan and the adjacent territories arouses our special inten治仁Remarks on the Principal Species Gen. Sinocalanus. Two closely related species which belong to this genus are known at presnt. One of them is S. mystrophoru8 BURCKHARDT which is endemic to the Yangtse-kiang region of Central China， and the other is S tenell'l8 (KIKUCHD WhlCh is found in vanous brackish-wate1's in the territories surrounding the Sea of Japan. S. mystro ph07 U8 was first found by BURCKHARDT (1913) in the lowermost reaches of the Yangtse-kiang， the Riye' Sutschau勾'hoand 1，a1ωTai-hu， and was a180 recorded later by TUGE and others (19409) from several 8tョtionsof the lower reach巴Sof the Yangtse-kiang (Wusung， Kian宮町in，Chinkiang and Nanldng). The prε'seロtwriter 0%1) {ound this species even in sllch a remote inland region as Hankow (the Yangtse-kiang and four lakelets in the suburbs of the city) as well as Lake Tungting-hu which is situated about 1，000 km away f1'o11 the river mouth. * Zoological Institute， Faculty of Science， l.Jniver"，ity of Kanazaw早- 36 - K. MASHIKO s. tenellu・8，on the other hand， is one of most typical brackish個watercopepods abundantly found in most brackishァwaterlakes in ]apan. According to the writer's studies (1952) on the brackish明 aterlakes in the HokuriI王uDistr記t，"Japan， this species is commonly found in the waters of which the chlorinity ranges fromabout 500 to 5，000 mg/L， but rarely met with in waters less than 200 or more than 8，000 mg/L in chlorinitj人 Thisspecies， however， was reported to be commonly found in Lake Kasumi句ga.urawhich is situated near the Pacific coast 0でlbarakiPrefecture and is generally recognized as a fresh.water lake. s. tenellU8 has also been reported frorn Siberia (SMIRt司OV，1929)， Sachalin (RYLOV， 1932; UENO， 1936) and the Kurile Islands CKJKUCHI， 193;ヲ).In 1932， SMIRNOV divided this species into two subspedes， in8ulαntl8 and coniULentαlis. The former is the form found in the Japanese Islands an社 thelatter is that in the Suifun River. Gel1， 1n 1913， BURCKHARDT described two closely a1lied species of this genus， sincnui3 and E. as occurn口gin Central China and in Japan， The fonner， E. was first found in the material from the River Sutschau.ho near Shanghai by BURCKHARDT， and later TUGE others (1939) found it in thcir collections from the Yangtse.kiang， from W usung to Nanking曲 Andrecently， the writer also reported the. occu:rrence of this sp邑cicsIn his ιol1ections from the Yangt間崎kiangat Hankow and Kiukiang， and that from Lake Tungting.hu (MASHIKO， 19δ1) .1udging trom these records， E. sinensis seems to be distributed in the Yangtse開kiang and its tributaries， ranging from the lowermost part to such an inland. region as Tungting田hu.E. on the other hand， was first described by BURCKHARDT from Lake Biw呂田 MiddleJapan， and afterwards it was folind in various fresh.water as well as brackish.water lakes in Japan such as L. Biwa司ko，1. Suigetsu.ko， L. 1¥1ikata.ko， L. Suga主o (KIKUCHI， 1929， 1936)， L. Kasumi.ga旬ura (BREHM， 1925)， 1. Otsi-gata (MASHIKO et INOUE， 1952)， L. Abura句ga.huchi(MS) and in smaIl ponds in the vicimty of Otsu， Kyoto， Osaka， Akashi and Takamatsu (KIKUCHI， 1928， 1936). Judging from these facts， E. sinensis may be presumed to be almost entirely a freshwater form， while E. though 10t乱 typicalbrackish目waterform， is found in fresh. as welI as brackish勘waters.Gen. Pseudodiaptomus. Among many species hitherto known， most of the spedes are fou.l1d in brackish.waters; and a small number of them 1S lmown to occur in bracl王ish.water，and fresh-water or fresh.water only. 1n Easiern Asia， three spedes of this ge11us have been recorded， 1，iz吋 PS.inopinus POPPE et RICHARD， PS. BURCKHARDT and PS. ja ponic附 KJKUCHI.PS匂・besiwas first described by BURCKHARDT (1913) as occur:ring in the Yangtse-ldang. According to lateγstudies， this species is fouQd iQ thii;l ;river， ranging from the υn thθ (}regr(t ph(:cra lJz:8tribllliOIる ofSome B;-，t('ki8/，ト (!.IulF'1'Cul-7{Jl.dc'/・()o}jf'pods ln ci1Icl lti・0111)，(..Tu'JPf，lI '_'I <)1 一一lower part to comparatively upper reaches. 1n H12お， KIKUCHI rでportedan OCCLlrrence of this species in Lake Sllibayama-J史ata，1shikawa Prefecture， Japan. This is the only ぜecord of this species' being found in any other locality than the Yangtse-kiang 'region. 1n his case， however， the identification seems to have bcen madεby fernale spccimens only. In spite oE many collections macle ovcr thc past sevcral years， none ot this species has been found by the present writcr， though PS. inopinus was often met with (MASHJKO et 1NOU長， 1952). PS. 'ino pin1l8 is widely clistributed .in Central China， Sibeτia ancl the Japanese Is1ands. This species is one of the commouest ones in the brackish-waters in ]apan， but it seems to be found sometimes even in the fresh.waters which lie near the sea coast. 1n the Yangtse-kiang， Central China， this species is found only in the lowerrnost 1'eaches of the τiver， but， so far as known at present， is never Eound in the inland reglOn， Ps. ja.POIιiCU8 was tirst described by KIKUCHJ (1928) and it is a species closely related to Ps. inopim18， but according to the write1"s study (MASHJKO et INOUE， 1952)， itseems very difficult to distinguish these two species from each other， because the thickness of the furcaI spines of these species a1'e sometimes very variable and the differences in other characte1's are a1so often ve1'y indistinct. Pm'acyclopina llana SMIRl'可OV.Besides such Calanoida as stated above， there are some other copepods which are found 1n b1'ackish-waters in Eastern Asia， BURCKHARDT (1913) described two C ycIopoid copヨpods，Cyclops (II，) 叩 tor'eus (= FIl.tHcyclo ps s'Inensお KIEFER)and Ouh(l1凶 (L) s印ensか(=L1:mnoithona sincMis (BURCKHARDTj KIEFER)， as occurring at the lowe1'most part of the Yangtse.kiang. In recent yea1's， Pαωl'αωcyclμopコ{如7ηl.a 1托αωn附αwask王nownt匂ooccαu1' ve白Z了.3γyc∞orm往加n削10】工nl辻yin孔1va副riぬousb1'acki王dsh(lH3 ら) fro可刀羽ω〕丸m the Su叫Ufll旧nRi討ver人.コ， Siぬb】enaてJ. So fa1' as k王nov旬1九有呼てη叩?戸n at p似rでesel此1詑t，this 呂p(ε三cie印siおS fOllnd only in the b1'喝a拭ck王i治sh恥wa計te匂rs1n the peripheral 1'egion of the S 巴回a0ぱf]apar民1丸 ψn匂Za ， many b1'a拭iばωck王ish]apan (MASHIKO et INOUt;， 1H52). Sllch a geographical distribution of th Discu自siOl1In regard to the p1'oblem of the migration of animals fro111 sea to inland wate1's， the f臼o刈泊Ilowingc∞on:凶1羽sid仁e町1'a叫tiぬ01凶lSmay possibly be g副iv刊en工わ)The brackish Oぱ[la1'ge r1vers 01' lakes n悶ea訂rthe sea coast may be one 0ぱfthe most possible p阿as鉛sa昭ge王吉古through which the ma1'ine animals mig1'ate 01' adapt themselves to the inland waters. i) When a species which has o1'iginally inhabited the sea migrates into inland w旦ters，the physlo1ogical adaptatioD may bring with it more or less morphological chang倍。K. MASH:rKu And if the migration of the same species had taken place at diHer官 1tplaces， the morphological differentiations which occurred at respective places would be similar to each other， but not quite the same. Then， itwill necessarily follow that closely allied races， varieties or species are found to be endemic in the su，rrounding district of the respective estuaries or places of that sort. ii) A form which is met with in a narrowly limited area near an estuary may be considered to be that which adapted itself to the iuland waterin a more recent age than those which are found in a large inland area extending far from the sea. The present geographical distribution of the principal copepods mentioned before in Eastern Asia and the division of the waters in which they occur are as seen in Table 1. has i).; -?????? ? 。 ? ??????。??〕????? ?。???。? ?????????????? ? ? ? 〉?。G 。@ 一「十一「S. tenelus @ 十十十十十Eo. s';nensis T O 。←L Eo. japonicus 。O ? 十十十-r Ps. inopinns 。O 斗(Ps. ，iα抑制cus)? 。? + 十十十Ps. foγbesi O @ O 十十Pα?・α.'/:国nαIn the Yangtse町kiangregion of Central China， Ps. ino pinu8 is found on1y in the lowermost region， and PS. forbesi， S.叫jstrophOr附 andEo. sinensis are found in a wider area extending from Wusung to，L. Tungting.hu. And， S. mystroplwrtts and Eo. sinensis (and probably Ps. forbesi too) are endemic to the Yangt配地kiangValley. According to TUGE and others (1939)， the chlorimty of the river water at the time when their collections were made is as shown in Table 2. Thus， judging from the present geographical distribution， the order of the landward extension of these copepods from the sea may bεarranged as follows: Lirnnoithonαsinensis， Halicyclops sinensis→ Ps. ino }Jimt8→ P久 forbe.si→ Eo.sinensぬL Table 一歩 β mystro phorlls In the territories surrounding the Sea of ]apan， on the other hand， we may see a closely related and parallel but different series of copepods. Namely， there occur S. 。1the Geogrαphical DistT'Ibution 0 f Somc E'Iαclc'isZト側d -39-F1・l!sh-1仰 '，terθopepods in and aTouncl Jωpω1 tenellu.s instead of S. mystrophorus， Eo. jαJlonicus instead of Eo. sinensis and， though a very questionable species， PS. japonicu8 instead o[ Ps. forbe8i. And it may be possible to correlate Hal~cyclop8 sinensis with P附 αcyclopin(t nal凶. The Sea of Japan， therefore， seems to have played in this case the same role as the Yangtse-kiang in Central China園 Thisfact may be explained by the assumption that the Sea of ]apan musthave remained in a brackish-water condition for a considerably long period in the o S. mystropborus 。s.tenellus o Eo. sinensis 日iEo. japonicus a Ps. forbesi A. Ps. inopinus Ps. japonicus )( Par. nana G 。a . 〆@ . Pacific 持 Ocean -40 - K. MASHIJ{O S匂tiondep，th W usung Nanking Wuhu Om 4.31 3.81 4.20mgjL 10 m 3.99 3.56 4:.48mgjL Table 2. The chlorinity of the Yangtse-kiang (TUGE ，KOKUBO and IMAI， 1939) early stage of its formatien， offering a convenient environment to the migration of animals. P8. inopinu8， however， iswidely found in the areas near the sea coast in both regions. 1n regard to ihis fact， a further discussion wi1l be given later. Conclusion 1n Easiern Asia， a number of copepods are found in the brackish-waters which have connections with the sea directly or indirectIy， having more or less its own Iimited geographical distribution. From the view point of the migration of animals from sea to inland watet;s， these copepods may be considered aS the important links connecting those of the fr田h-waterwith their felJows in the sea. Two series of such copepods are observed in主asternAsia，. one in the Yangtse-kiang Valley， Central China， and th~ other in the territ.ories surrounding the Sea of Japan. In this case， the Sea of. Japan， in the early stage of.，its formation， seems to have played the samerδle as the estuary of the Yangtse-kial1g in Central China. These two series show an obvious parallelism， consisting of closely reJated species r田pectively.The order of the adClptation from sea to inland waters in these two series may presumably be as follows: Ya暗 tse-kia暗 L.Bin仰 8i8，H. 8inen8i8→P8. i仰 pinU8→P8.forbe8i→Eo. 8inen8is→ S. mystro phor・usS田 ofJapan: P. nαna→S. tenellu8→ P8. ino pinu8 (P8. japonicu8)→Eo. jαponiCU8 Among these copepods， P8. ino pinus only is widely found in the two regions of Central China and the surrounding territories of the Sea of Japan， but it occurs only in the zones near theとsea，showing no wide landward extension of its distributon. BREHM (1930) is of the opinion that this species may have been. widely distributed before the Japanese Is1ands were separated from the Asiatic Continent by the formation of the Sea of Japan. If it is true， P8. ino pi仰 8must be considered to have adapted itself to the brackish-water in a very early age， and to have remained there for a long time， attempting litle landward migtation. On t!te OeoglωpM仰 1Di・stTibuuollof Some Br凶ckおhαndJi'J'C"/z-Wi.tUぅγ(プopepocls in an d arollud .rαpun References BREHM， V. 1930・Uberasiatische Diaptomiden. Arch. f. Hydrobiol.， 22; 140-161. 41 RURCKHARD'I， G.， 191:l;九司Tiss令n8chaftlicheErgebnisse einer Reise um die Erd邑 vunPernorc1 und Schroter. I1l Zooplankton aus 08t-und Suc1-asiatischen Binnengewasser. Zool. Jahrb. (Systふ 34;:;41-472 KIKUCHI， K.. 1928; Fresh-water Calanoida of Middle and Southwestern Japan. M告m. Coll. Sci Kyoto Imp. Univ.くB)，4; 6.5-77. 一品巴四一.'HJ:J6: Fresh-water anc1 Br司ckish-waterCalanoid Copepoc1s of J日panwith Notes on 守、heieら札Geographical Distribution. Bull. Biogeogr. Soc. Japヨn，6: 2，~7 -284. 〆MASHIKO， K.， 1951: Stuc1ies of th白 Fresh-waterPJankton of Cent四 JChina， 1， I.Sci. Rep. Kana-zawa Univ.， 1: 17-m， 137-154. MASHIKO， K. et A. INouf:， H152: LimnologcaJ Studies of the Brackish-water Lakes in the Hokuri・1m District， Japan. Special Publ. Japan Sea Regional Fisheries Research Lab.on the 3rd Anniv. of its Founding， 17.5-191. SMIRNOV， S.， llJ:l9; Beitrage zur Copepodenbuna Ostasiens. Zool. Anz.， 81: 317-329. 一一・ 1935:Zur Syst白matikder Copepoden-Famili白 CyclopinidaeG.O.Sars. Zool. Anz.， 109: 203同210.TUGE， H.; S. KOKUBO and T. IMA r， 1939: On the Plankton of Yangtse-Idang. Journ⑨ Shanghai Sci.lnst.， IV， 4; 65-8B. ゆ

On the Geographical Distribution of Some Brackish and Fresh-Water Copeppods in and around Japan.

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On the Geographical Distribution of Some Brackish and Fresh-Water Copeppods in and around Japan.

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