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Species Diversity, 2009, 14, 307-322

Freshwater Planarians (Platyhelminthes: Tricladida:

Planariidae) from the and Kamchatka

Ronald Sluysi, Irene Smoldersi, Masaharu Kawakatsu2, Theodore W. Pietsch3 and Ryoichi B. Kuranishi`

iinstitutefor Biodiversdy and Eeosystem Dynamics & Zootogical MLtseum, Uhiversity of Amsterdam, P. O. Box 9476a 1090 GTAmsterdam, The IVethertands E-mail: R.Slays@･uva.nl 2 9j6 9 ch6me 1-6, Shinkotoni, 1fita-icu, Sopporo, OOI-C19(19 .ltxpan S V}ziversi(v of Wtishington, Seattte, wn, UIS,A.; School ofAquatic and Ftshei:y Sciences and Barhe Mttseum ofAigtural Histoily and Culture, U)ziversi(y qf'IVtishiizgton, Seattle, i-X 98J95-5C12a [LS.A. `IVtitural History Museum and institute, (]hiba, 955-2 Aoba, Chuo-hu, Chiba, 260-8682 Jttpan

(Received 26 June 2009; Accepted 4 November 2009)

Collectiens of fireshwater planarians made by two expeditions to the KuTil Islands and Kamchatka are described, thus providing the first comprehen- sive account of the occurrence of this group of animals in the Kuril Arehipel- ago. The samples contained three specles: Seidlta schmidti (Zabusov, 1916), S. elongata (Zabosova, 1929), and Plzagocata sp. The new reeords for S. schmidti and S, elongata include asexual specimens that were identified on the basls

of their eye arrangement. This study shows that freshwater planarian

species that were already known to occur in Karnchatka and have also

colonized the Kuril Islands. Possible scenarios for dispersal into the Kuril Is-

lands from two mainland source areas during the Last Glacial Maximum are discussed.

Key Words: Platyhelminthes, Tricladida, Kuril Islands, Kamchatka, taxon-

omy, biogeography.

Introduction

The Kuril Islands are an archipelago of more than 56 islands in the northwest- ern Pacific Ocean between the Kamchatka Peninsula and . The biodiver- sity of the Kuril Archipelago has been the subject of a recent (1994-2000) biotic sur- vey of the terrestrial and freshwater plants and animals by the International Kuril Island Project (IKIP), The results of this survey have been published in numerous publications and are also available from a website maintained at the University of Washington (cf, www,okhotskia,org; see also Pietsch et al, 2003 and references therein), The freshwater planarians, collected during one of the seven IKIP expedi- tions, remained to be examined. A second, briefer biotic survey of only the North Kuril Islands as well as Kam- chatka, was carried out by joint expeditions of Japanese and Russian scientists in 1996 and 1997 (ctL Komai 2000). A preliminary repert on the freshwater planarians collected during this survey was published by Kawakatsu and Kuranishi (2000). Earlier flrom the Kurils, only Miyadi (1937) had reported any find of fireshwater pla-

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308 Ronald Sluys et aL

narians, namely the two species PolyceZis schmidti? and Bdellocephala? sp., on Island. Freshwater planarians from the Kamchatka Peninsula were first reported by Zabusova (1929), who mentioned the finding of Seidlia schmidti (Zabusov, 1916) and described as new the species Seidlia elongata (Zabusova, l929). A mere recent sum- mary of freshwater planarian records from Kamchatka was provided by Dyganeva and Porfiejeva (1990). The present paper details the collections of fireshwater planarians made by the IKIIP and Japanese-Russian expeditions on the Kuril Islands and Kamchatka and thus provides the first eomprehensive account on the occurrence of this group of animals in the Kuril Archipelago.

Material and Methods

Specimens were preserved in 7e% alcohol, sectioned at intervals of 8pm, and stained with Mallory-Cason. All of the material examined has been deposited in the Zoological Museum of the University of Amsterdam, The Netherlands (ZMA) and the Natural History Museum and Institute, Chiba, Japan (CBM). Microscopi- cal reconstructions of the eopulatory apparatus of the animals were made with the help of a camera lucida. Abbreviations used in the figures are as fbllows: bc, bursal canal; bca, bulbar cavity; ca, common atrium; cb, copulatory bursa; cod, common oviduct; ed, ejacu- latory duct; ex, expansion; go, gonopore; ia, intestinal anastomosis; ma, male atrium; mo, mouth; od, oviduct; pg, penis glands; ph, pharynx; pp, penis papilla; vd, vas defer- ens,

Taxonomy

Genus Seidlia Zabusov, 1911 Seidlia schmidti (Zabusov, 1916) (Figs IA, 2)

Material examined (for locations of listed islands, see Fig. 8). : ZMA V.Pl. 6828.1, sagittal sections on 7 slides, V.Pl, 6828.2, sagittal sections on 7

slides, and V.Pl. 6828.3, horizontal sections on 2 slides, all frem Utyosnaya River c,

1,5km inland from ocean, 50037.72'N, 156007,29'E, 1 August 1996. 0nekotan: ZMA

V,Pl, 6829.1, sagittal sections on 7 slides, V,Pl. 6829.2, sagittal sections on 7 slides,

V,Pl. 6829,3, sagittal sections on 4 slides, V,Pl. 6829.4, sagittal sections on 3 slides,

V,Pl. 6829.5, horizontal sections en 1 slide, V.Pl. 6829.6, horizontal sections on.3 slldes, V.Pl. 6829.7, horizontal sections on 2 slides, and V.Pl. 6829.8, transverse sec-

tions on 9 slides, all flrom inland firom Nemo Bay, 49036,43'N, 154048.88'E, 4 August

1996; ZMA V.Pl, 6830.1, sagittal sections on 5 slides, V,Pl. 6830,2, sagittal seetions on

6 slides, V.PI. 6830,3, horizontal sectiens on 4 slides, and V.Pl. 6830.4, transverse

sections on 9 slides, all from river flowing into Nemo Bay, 100m from mouth of river, 49e36.61'N, 154049.51'E, 4 August 1996; ZMA V,Pl, 6831, 17 preserved, asexual specimens, stream 1km S of Cape Subbotna, 49023.84'N, 154038.67'E, 5 August 1996;

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ZMA V.Pl. 6832.1, sagittal sections on 7 slides and V,Pl. 6832,2, sagittal sectiens on 4

slides, both from Trudny River about 2km from mouth, 49016.76'N, 154045.02'E, 9 August 1996; ZMA V,Pl. 6833.1, sagittal sections on 4 slides, V.Pl. 6833.2, sagittal sec-

tions on 5 slides, V.Pl, 6833.3, horizontal sections on 3 slides, V,Pl, 6833.4, horizon-

tal sections on 2 slides and V,Pl. 6833.5, transverse sections on 3 slides, all from river fiowing into Mussel Bay, 49023.56'N, 154e49.08'E, 7 August 1996, Kharimkotan: ZMA V.Pl. 6834, 51 preserved, asexual specimens, waterfa11/stream near northern end of Severgina Bay, 49009,69'N, 154e30.39'E, 8 August 1996, Shi- askotan: ZMA V,Pl, 6835, 17 preserved, asexual specimens, waterfall flowing into Zakatnaya Bay, 48046.96'N, 154002,66'E, 11 August 1996. : ZMA V.Pl. 6836.1, sagittal sections on 7 slides and V,Pl. 6836.2, horizontal sections on 3 slides, both

frem small lake about 500m inland firom Aynu Bay, 48003,39'N, 153014.38'E, 14 Au- gust 1996; ZMA V.Pl. 6837.1, sagittal sections on 6 slides, V,PI, 6837,2, sagittal sec- tions on 5 slides, and V.Pl. 6837.3, horizontal sections on 3 slides, all from stream

tlewing into lake about 500m inland from Aynu Bay, 48003.39'N, 153014.38'E, 14 Au- gust 1996. : ZMA V.Pl. 6838.1, sagittal seetions on 11 slides, V.Pl. 6838.2, sagit- tal sections on 7 slides, and V.Pl. 6838.3, horizontal sections on 5 slides, all from

stream fiowing into Ukromnaya Bay, 45C34,90'N, 149031.85'E, 20 August 1996, Shumshu: ZMA V.Pl. 6839.1, sagittal sections on 5 slides and V.Pl. 6839.2, sagittal sections on 5 slides, both from Lake Bol'shoye, 50046'N, 156015'E, alt. 15m, 3 July

1996-5 August 1997, Kamchatka: ZMA V.Pl. 6840.1, sagittal sections on 5 slides, V,Pl. 684e.2, sagittal sections on 5 slides, and V.Pl. 6840,3, horizontal sections on 5 slides, all from upper part of Pravaya River 23km S of Pushchino, 54000'N, 157051'E, alt. 540m, 3 July 1996-5 Augtist 1997; CBM-ZX 11, sagitta} sections on 4

slides, Poperechnaya River, Bystraya River basin, 53022'N, 157e41'E, alt. 400m, 3 July 1996-5 August 1997; Z]v{[A V.Pl. 6841.1, sagittal sections on 6 slides, basin of Bystraya River 10 km SE of Anavgay, 56002'N, 159004'E, alt, 310 m, 3 July 1996-5 Au- gust 1997; CBM-ZX 1, 1 preserved, asexual specimen, stream 5km W of Mount Vil- nyuehinsky, 52042'N, 158nlO'E, alt. 150m, 3 July 1996-5 August 1997; ZMA V.Pl. 6842, 1 preserved, asexual specimen, stream 5km W of Mount Vilnyuchinsky, 52e42'N, 158olO'E, alt. 150m, 3 July 1996-5 August 1997; ZMA V.Pl, 6843, 3 preserved, asexual specimens, upper part of Poperchnaya River 25km from Malki village, alt. 450m, 53o05'N, 157052'E, 3 July 1996-5 August 1997; ZMA V,Pl. 6844, 34 preserved, asexual specirnens, Athal stream, near Lake Azhabach'ye, 56011'N, 161041'E, alt, 20m, 3

July 1996-5 August 1997. Comparative discussion. The dorsal and ventral surfaces of the speeimens are beige and the animals are provided with small auricles and 30-40 eyes along the anterior body margin (Fig. IA). Their size varies from 5 to 17mm in length, with a width of about 2 mm. The pharynx lies in the posterior half of the body and measures about 1/4 of the body length. The prepharyngeal testes are situated ventrally. The relatively large male atrium houses a relatively small penis papilla and is surrounded by a very thick layer of circu}ar muscles, bounded by a thin layer of longitudinal muscles. The copu-

]atory bursa is smal1, communicating with a long bursal canal that is successively surrounded by subepithelial circular muscles and a layer of longitudinal fibres. That the animals belong to Seidlia schmidti js apparent from the presence of a muscularized intestinal anastomosis connecting the two posterior gut branches at the level of the male atrium (Fig. 2). The musculature around the anastomesis con-

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A B c

t-

1mm- dmm, .L[.!u].m

Fig. 1. Seidlia schmidti (Zabusov, 1916), external features of preserved specimen (A), Seidlia elon.crata (Zabusova, 1929), external features of preserved specimen (B), and Phagocata sp., ex- ternal features of preserved specimen (C).

m pp

Fig. 2. Seidlia schmidti (Zabusov, 1916), ZMA V.PL 6836.1, sagittal reconstruction of copula-

tory apparatus. For abbreviations, see Material and Methods.

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Far Eastern freshwater planarians 311

sists of intermingled layers of circular and longitudinal muscle fibres, The degree

to which this musculature is developed varies between specimens but it never reaches the thickness described by Kawakatsu (1964) and Kawakatsu and Yamada (1966) for specimens from Japan. This difference between our specimens and those from Japan may be due to the Japanese animals being older and more developed. This is suggested by the generally greater size of the Japanese animals (15-20mm in length) than our animals, which on average are 8mm in length. There is one other species with a muscular intestinal anastomosis, Seidlia re- mota (Smith, 1988) from Nerth America. In contrast to S, schmtdti, in the North American species the posterior end of the male atrium is developed into a broad papilla that projects into the common atrium (cf, Kawakatsu and Mitchell 1998). Such a distinct nozzle is not present in our specimens from Kamchatka and the Kuril Islands. Generally, this nozzle on the male atrium is much smaller in S. schmidti (cf. Zabusov 1916; Kawakatsu 1964; Kawakatsu and Yamada 1966). It is pos- sible that the degree of development of this nozzle differs among specimens and that, consequently, S. remota is a junior synonym of S. schneidti, Ecological data support this inasmuch as S. schmidti is a stenothermic species (Zabusova- Zdhanova 1956; Kawakatsu 1974) and S. remota was collected from a spring in which the water temperature varies only between 8,50 and 9,OeC (Smith 1988). Seidlia auriculata (Ijima and Kaburaki, 1916) also shows an anastomosis be- tween the two posterior gut trunks, but unlike S. schmidti, it concerns a normal, non-muscular connection between the gut branches (cf. Kawakatsu et al, 198e and

references therein).

Seidlia elongata (Zabusova, 1929) (Figs IB, 3-5)

Material examined. : ZMA V,Pl. 6845.1, sagittal sectiens on 4 slides, V.Pl. 6845.2, sagittal sections on 4 slides, and V.Pl. 6845.3, horizontal sections on 4 slides, all from stream 1km S of Cape Subbotna, 49023.84'N, 154038.67'E, 5 Au- gust 1996; ZMA V.Pl, 6846.1, sagittal sections on 3 slides, V.PI. 6846.2, sagittal sec- tions on 5 slides, and V.Pl. 6846.3, sagittal sections on 5 slides, a]1 from c. 1km S of Cape Subbotna, 49024.06'N, 154038.65'E; ZMA V,Pl, 6847.1, sagittal sections on 6

slides, V,Pl. 6847,2, transverse sections on 15 slides, V.Pl, 6847,3, sagittal sections on 7 slides, and V,Pl, 6847,4, horizontal sections on 3 slides, all from waterEall/stream c. 1 km S of Cape Subbotna, 49D24.33'N, 154038.88'E, 5 August 1996; Zmo V.Pl, 6848, 12 preserved, asexual specimens, river N of Lake Chyornoye, fiowing into Nemo Bay c, 100m from mouth of river, 49036.61'N, 154049.51'E, 4 August 1996; ZMA V.Pl. 6849, 20 preserved, asexual specimens, river just N of Resvyi River, flowing into Mussel Bay, 49e23.56'N, 154049.08'E, 7 August 1996, Kharimkotan: ZMA V.Pl. 6850.1, sagittal sections of anterior end on 2 slides, V,Pl. 6850,2.a, sagittal sections of anterior end on 2 slides, V,Pl, 6850.2.p, sagittal sections of posterior end on 2 slides, and V.Pl. 6850,3, sagittal sections on 3 slides, all from watembIYstream at northern end of Severgina Bay, 49009,69'N, 154030.39'E, 8 August 1996. Shumshu: CBM-ZX 4, sagittal sections on 3 slides, Lake Bol'shoye, 5ee46'N, 1560!5'E, alt, 15m, 3 July 1996-5 August 1997, Paramushir: ZMA V.Pl, 6851, 23 preserved, asexual specimens, Utyosnaya River c. 1.5km inland firom ocean, 50037.72'N, 156007.29'E, 1

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August 1996, Kamchatka: CBM-ZX 3, 5 preserved, asexual animals, basin of Bystraya River 10km SE ef Anavgay, 56002'N, 159004'E, alt, 31em, 3 July 1996-5 Au- gust 1997; ZMA V.Pl. 6854,1, sagittal sections on 6 slides, upper part of Poperech- naya River 25km from Malki village, 53005'N, 157052'E, alt. 450m, 3 July 1996-5 Au- gust 1997, Comparative discussion. The animals are about 4-10mm in length (mean: 7mm) and 2mm in width, with the dorsal and ventral body surfaces beige. The eyes are arranged in two clusters, with about 20 eyes in each cluster (Fig, IB). The pharynx lies in the posterior half of the body and measures between lf4 and 1/3 of the body Iength, The prepharyngeal testes are located ventrally. The ovaries are lo- cated at about 1/5 of the distance between the brain and the root of the pharynx. The copulatory apparatus (Fig. 3A, B) of most of the animals examined is not yet fully developed in that the musculature around the bursal canal is not very thick (Fig. 3B), and oniy two specimens showed the distinct posterior expansion of the common atrium, which is characteristic for the species (cf. Zabusova 1929; Zabusova-Zdhanova 1956). This expansion is only present in the specimens ZMA V.Pl. 6847.3 and V.Pl. 6854,1 (Figs 4A, B, 5A, B). Notably, the last-mentioned speci- men appears to be much more fully developed than any of the other specimens ex- amined, with the musculature of the male atrium and the bursal canal approach- ing the situation described by Zabusova-Zdhanova (1956). The last-mentioned au- thor described the musculature around the bursal canal as consisting of a thick, subepithelial layer of circular muscles, surrounded by a thin layer of longitudinal muscles. In specimen ZMA V.Pl, 6854.1, the zone of circular muscles around the bursal canal is highly develeped, but the few longitudinal muscles are somewhat intermingled with the circular layers (Fig. 5B). Other examined specimens do not show the posterior expanslon of the bursal canal and thus resemble PolyceZis eudendrocoeloides (Zabusova, 1929), and Polycelis polyopsis Zabusova, 1936 from Kamchatka, Several of these specimens have a rather large common atrium (Fig. 3B), perhaps an artefact ot' preservation. That these worms show charaeteristics of P, eudendrocoeloides, P, polyapsis, and S. elon- gata is consistent with Kawakatsu and Mitche!1's (1998> view that the forrner two nominal species are synonyms of S. elougata, Polycelis smpporo (Ijima and Kaburaki, 1916) from Hokkaido and southern (cf. Kawakatsu and Timoshkin 1998, fig. 1) dilfers from our specimens in the presence of a long cemmon oviduct, a highly developed penis bulb, and a very large copulatory bursa. Furthermore, P. sqpporo is a milky-white species, in con-

trast to our specimens, which are beige.

Genus Phagocata Leidy, 1847 Phagocata sp. (Figs IC, 6, 7)

Material examined. : ZMA V.Pl, 6852.1, sagittal sections on 7 slides, V.Pl. 6852.2, sagittal seetions on 5 slides, V.Pl. 6852.3, sagittal sections on 3 slides,

and V.Pl. 6852.4, hortzontal sections on 3 slides, all from stream flowing into Koservnaya Bay, 45019.79'N, 147059.75'E, 19 August 1996, Urup: ZMA V. Pl. 6853.1, sagittal sections on 5 slides, V.Pl. 6853.2, sagittal sections on 6 slides, and V.Pl.

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Far Eastern freshwater planarians 313

pp

i--i-,ii-iM-,N-,iir ma bca A vd

ca b[

cod B mo

Fig. 3. Seidlia elongata (Zabusova, 1929), ZMA V.Pl. 6845.1. A, Sagittal reconstruetion of

male copulatory apparatus; B, sagittal reconstmction ot' female copulatory apparatus. For ab-

breviations, see Material and Methods.

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314 Ronald Sluys et al,

-200m

A

go BFig.

4. Seidlia etongata (Zabusova, 1929), ZMA V.Pl. 6847,3, A, Sagitta1 reconstruction of the male eopulatory apparatus; B, sagittal reconstruction of the female copu!atory apparatus.

For abbreviations, see Material and Metheds.

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Far Eastern freshwater planarians 315

b[a Pgp

ri.QQ-,tiiL

ex A ca

go BFig.

5. Seidlia elongata (Zabusova, 1929), ZMA V.Pl. 6854.1. A, Sagittal reconstruction of male copulatory apparatus; B, sagittal reconstruction of female copulatory apparatus. For ab- breviations, see Material and Methods.

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200 -m [b - - -- -

Fig. 6. Phagocata sp., ZMA V.Pl. 6852.3, sagittal reconstruction of copulatory apparatus, For

abbreviations, see Material and Methods.

6853.3, horizontal sections on 5 slides, all from stream 3km N of Kama River in

Tetyaeva Bay, 45e39.66'N, 149:28,60'E, 21 August 1996. Description. The dorsal surface shows a unifbrm beige ground colour with numerous minuscule darker speeks. The animals are about 7-10mm long and 2mm wide. The anterior margin of the body is slightly cenvex and is provided with two small auricular projections (Fig. IC), At the level of the eyes the body shows "neck". some incurving of the lateral margins, thus suggesting the presence of a The pharynx lies in the posterior half ofthe body. In sample ZMA V. Pl. 6852 there are a few specimens with multiple (6-8) pharynges; unfortunately those animals are asexual. Testes are located ventrally throughout the body and are also present between the two posterior gut branches in the htnd end of the body, The penis papilla is a blunt cone, provided with an aeentrally located, ventrally displaced ejaculatory duct, thus resulting in an asymmetrical penis papilla (Figs 6, 7). The bulbar cavity or intrabulbar seminal vesicle is only slightly wider than the ajaculatory duct. Un- fortunately, the precise openings of the vasa deferentia into the bulbar cavity could not be traced in the specimens examined. The oviducts unite to form a common oviduct that opens into the common atrium or into the most posterior section of the male atrium. The bursal canal is surrounded by a subepithelial layer of circular muscles, covered externally by a layer of longitudinal muscles (Figs 6, 7). Comparative discussion. The animals described above resemble several

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Far Eastern freshwater planarians 317

cod

Fig, 7, Phagocata sp., ZMA V.PI. 6853.2, sagittal reconstruction of copulatory apparatus. For

abbreviations, see Material and Methods.

species of Phagocata; combined with the limited amount of reasonably geod mate- rial available, this has made us refrain from assigning the specimens te any partic- ular species. The animals resemble Phagocata sibirica (Zabusov, 1903) in the pres- ence of an asymmetrical penis papilla with a ventrally displaced ejaculatory duct and in the absence of a well developed bulbar cavity (cL SIuys et al. 2001) such as is present in Phagocata vivida (Ijima and Kaburaki, 1916), The last-mentioned species possesses a symmetrical penis papilla, in contrast to our specimens and P. sibirica (cE Kawakatsu et al, 1994). Ph(rgocata tenella Ichikawa and Kawakatsu, 1963 is an unpigmented species from Hokkaido that lacks a well developed bulbar cavity, as do eur animals. This species does not have an asymmetrical penis papilla, though, while it has a very large cepulatory bursa that fi11s up a considerable space between the pharynx and the copulatory apparatus. This situation differs very much from that in our speci- mens, in which the bursa is much smaller and located antero-dorsally to the penis bulb, Furthermore, in P. tenella the epithelium ef the most ventral part of the bursa is expanded to a very tall lining, a feature that is absent in our specimens. Other species of Phagocata that occur in adjacent geographical regions and more or less resemble Phagocata sp. are P. albata Ichikawa and Kawakatsu, 1962 and P.

iwamai Ichikawa and Kawakatsu, 1962 frem Hokkaido; however, both species have a symmetrical penis papilla, in contrast to Phagocata sp.

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318 Renald Sluys et al.

Biogeography

The distributional records of the material examined are summarized in Fig. 8, These records include asexual specimens that were identified on the basis of their eye arrangement as presumably belonging to one of the three species described - T't l R)SllX s. ? RUSSIAe ' . L1/re 7[P1

' , t ,

RUSSIA

+ ' '

@ SEA OF OKHorslc 4

'o

- A- Onekotan.,Lg ! A# Kha[imkotan-v A Shiashkota"n? :/MatuaA# 48 ' L , n

" XRasshua

msf < 46 to 2lll %Hekknlde 44 +

1 ' A#eSeidilaschmidti Seidllaelongala s,"vli Phago[atespe[. 141 144 147 ISO IS3

Flg. 8. Distributional records of Seidlia schmidti, S. elongata, and Phagocata sp. based on

material examined in this study, including anatomically identified spectmens as well as asex-

ual animals identified on the basis of external appearanee.

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Far Eastern fireshwater planarians 319

"Material above (see examined" sections). Our study shows that freshwater planarians that were already known to occur in Kamchatka and Japan have also colonized the Kuril Islands, In this respect S. schmidti has the widest distribution, occurring in Kamchatka, Shumshu, Para- mushir, Onekotan, Kharimkotan (asexual specimens), (asexual speci- mens), Matua, and Urup (Fig, 9), This species has otherwise been reported llrom

A'E."'fl 5 ger･'

SSIA ,xzsg

.

. 4 ZI + sskx-[s6Y 'Hrr14 +KamchatkeA#

t

54

,

SEA OF oKtvorsk S2 : ' , h

para:`il' ll;Yi.,, to . Onekotanxdi Kharimkotan-b

shiashkotae.;I7 :/Mntue 4S ' . o + / e XRasshua

% cel/mushir ･ -,46 .fX . . .e a,1,% "

i Seldliaschrnidti %kkaido 4 # Seidliaelongata t - Phegocetn elbete " Phagocnra renella + Phagoceta iwama[

X PhagocaLayivida

O Phagocata sibirica

,ki 144 147 1SO 153

Fig. 9. Previously reported distributional records of Seidlia schmidti, S. elongata, Phago-

cata sibirica,P vivida,P, iwanzai, P. albata, and P. tenelga,

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320 Ronald Sluys et al.

Kunashir, Hokkaido, Sakhalin, and various loealities on the mainland of (Fig. 9; see also Dyganova and Porfirjeva 1990), The currently known distribution of S. etongata is somewhat narrower than that of S. schrnidti: Kamchatka, Sakhalin, Kunashir, Shumshu, Oneketan, Kharimkotan, Matua (only asexual specimens), and Paramushir (only asexual specimens) (Figs 8, 9; see also Dyganova and Porfirieva 1990). We found specimens of Phagocata sp. only on the southern Kuril Islands of Uturup and Urup, This is consistent with the sltuation that species of Phagocata thus fatr have not been reported from either the northern Kuril Islands or Kam- chatka, but several species are known from Sakhalin and Hokkaido (Fig, 9).

Discussion

In view of its currently known distribution (Figs 8, 9), it is remarkable that Seid- lia elongata does not occur on islands such as , Urup, and Iturup. In a similar vein, it is remarkable that S. schmidti dees net occur on islands such as

Simushir and Itump. In other words, it is noteworthy that these two species have not yet colonized the entire chain of the Kuril Islands. This distributional pattern may certainly be due, at least in part, to uneven collecting elfort. On the other hand, the current distribution may reflect the geographic history of the region. The assumption that these species must have colonized the chain by dispersal from mainland source areas is based on the facts that (1) freshwater planarians cannot cross sea straits by their own effbrts but can only disperse through contigu- ous fireshwater bodies; (2) all of the Kuril Islands are volcanic in origin; and (3) during sea-level regressions in the Last G!acial Maximum (c, 18,OOO-15,OOO years BP), several islands of the chain were connected and united with the adjacent mainland, With respect to the palaeogeography, it has been established that during the Last Glacial Maximum, Sakhalin, Hokkaido, , Kunashir, and probably Iturup were united into a single mountainous region that at the same time was connected to the Russian mainland (cf. Pietseh et al, 20e3 and references therein). During this period Kamchatka was connected to Shumshu and Paramushir. These sea-level regressions may have facilitated the colonization of the north- ern and southern Kuril Islands by Seidlia schmidti and S. elongata by dispersal from northern and southern source areas, respectively. In other words, two path- ways of immigration (c£ Pietsch et al. 2003, fig. 1) may have facilitated the eurrent distribution of these planarians in the Kuril Archipelago. However, islands such as Onekotan, Kharimkotan, Matua, Simushir, and Urup never formed a single, interconnected mountain chain during any sea-level regression, even though Onekotan, Kharimkotan, and Shiashkotan were once

united into a single island and the same holds true for Urup and a few adjacent small islands. But these two aggregations of islands were still separated by sea

straits, even during the sea-level regressions, In the absence of contiguous fresh- water streams between these islands, this should have prevented their coloniza- tion by freshwater planarians. Nevertheless, Seidlia schmidti occurs on Onekotan, Kharimkotan, and Shiashkotan (which were interconnected at one time), Matua, and Urup; S. elongata is found on the same islands, except Shiashkotan and Urup

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Far Eastern fireshwater planarians 321

(Figs 8, 9). The only connection that ever existed between these three groups of is- lands, more or less in the middle of the chain, was sea ice that covered the during the Last Glacial Maximum (Bezverkhniy et al. 2002), Whether these conditions were favorable for the dispersal of freshwater planarians is debat- able. Furtheumore, the , south of Simushir (Figs 8, 9), was never cov- ered by ice (Bogatov 2002), so even connection by sea ice cannot explain the occur- rence of S. schmidti on Urup. The Bussol Strait has recently been shown to fbrm one of the most important biogeographic boundaries within the Kuril Archipelago (Pietsch et al. 2003). Evi- dently, Seidlia schmidti and S. elongata do not obey this boundary, which may per- haps result from colonization of the Kuril Archipelago from both the northern and southern mainland source areas, Ieaving aside the distributional records that are difficult to explain under a dispersal scenario during the Last Glacial Maximum (see above). It is only Phagocata sp. and the genus Phctgocata in general (cf, Sluys et al. 2001, fig. 1) that do not extend their distributional range beyond the Bussol Strait.

Acknowledgements

Biodiversity studies in the Kuril Islands were supported by the Biological Sci- ences Directorate

References

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