Checklist of tapeworms (Platyhelminthes, Cestoda) of vertebrates in Finland

Abstract A checklist of tapeworms (Cestoda) of vertebrates (fishes, birds and mammals) in Finland is presented, based on published observations, specimens deposited in the collections of the Finnish Museum of Natural History (Helsinki) and the Zoological Museum of the University of Turku, and additional specimens identified by the present author. The checklist includes 170 tapeworm species from 151 host species, comprising 447 parasite species/host species combinations. Thirty of the tapeworm species and 96 of the parasite/host species combinations have not been previously reported from Finland. The total number of tapeworm species in Finland (170 spp.) is significantly lower than the corresponding figure for the Iberian Peninsula (257 spp.), Slovakia (225 spp.) and Poland (279 spp.). The difference between Finland and the other three regions is particularly pronounced for anseriform, podicipediform, charadriiform and passeriform birds, reflecting inadequate and/or biased sampling of these birds in Finland. It is predicted that there are actually ca. 270 species of tapeworms in Finland, assuming that true number of bird tapeworms in Finland corresponds to that in other European countries with more comprehensive knowledge of the local tapeworm fauna. The other main pattern emerging from the present data is the seemingly unexplained absence in (northern) Fennoscandia of several mammalian tapeworms that otherwise have extensive distributions in the Holarctic region or in Eurasia, including the northern regions. Previously unknown type specimens, that is, the holotype of Bothrimonus nylandicus Schneider, 1902 (a junior synonym of Diplocotyle olrikii Krabbe, 1874) (MZH 127096) and the syntypes of Caryophyllaeides fennica (Schneider, 1902) (MZH 127097) were located in the collections of the Finnish Museum of Natural History.


Introduction
There are no comprehensive checklists or other faunistic reviews of tapeworms (Cestoda) of vertebrates in northern Europe, although the cestodes of fishes have been recently reviewed in Latvia (Kirjušina and Vismanis 2007) and Finland (Pulkkinen and Valtonen 2012). Among other host groups, the cestode fauna of rodents and shrews has been intensively studied in northern Europe (see, for example, Haukisalmi 1986, 1989, Bugmyrin et al. 2003, Anikanova et al. 2007). However, the cestode fauna of birds and large mammals in northern Europe has received surpirisingly little attention, with the exception of a recent series of studies on taeniid cestodes of carnivores in Finland and Sweden (Lavikainen et al. 2006, Haukisalmi et al. 2011. Comprehensive checklists of cestodes covering all vertebrate groups have, however, been published at least for France (Joyeux and Baer 1936), Spain and Portugal (Cordero del Campillo et al. 1994), Slovakia (Synopsis of cestodes in Slovakia I-V: Macko et al. 1993, Hanzelová et al. 1995, Hanzelová and Ryšavý 1996, 1999, Poland (Pojmańska et al. 2007) and Belarus (Merkusheva and Bobkova 1981). Because of recent developments in tapeworm taxonomy, the older checklists, such as those of Joyeux and Baer (1936), are naturally somewhat outdated. Tapeworm taxonomy has long flourished in Russia and the former USSR, resulting in major faunistical and systematical reviews of cestodes of all vertebrate groups. The most appropriate example is the "Essentials (or Fundamentals) of Cestodology" -series, started in 1951, and now including 14 volumes. However, there are evidently no proper checklists or faunistic reviews summarizing information on tapeworms of all vertebrate classes in the European part of Russia.
The main purpose of the present study is to provide a comprehensive list of tapeworm species reported or found from Finland, including two of the former Finnish territories lost as a consequence of the Second World War (Karelia and Petsamo regions). The study concerns all vertebrate groups present in Finland, but no tapeworms are known from Finnish elasmobranchs, amphibians and reptiles. Besides published reports, specimens deposited in the collections of the two major Finnish natural history museums were examined for the presence of otherwise unknown species. The present checklist also includes as yet undescribed, more or less cryptic mammalian tapeworms identified by molecular methods (for example, Haukisalmi et al. 2008, 2009a, Lavikainen et al. 2013.
The present faunistic data from Finland are compared with the existing checklists from Europe, particularly the most recent ones from the Iberian Peninsula, Slovakia and Poland. These comparisons allow the identification of host and cestode groups that need to be examined more comprehensively to obtain a better idea of the overall cestode diversity in Finland and northern Europe in general.

Materials and methods
The list of tapeworm species of Finland, including the former territories in northern and south-eastern parts of the country, is based on published observations, speci-mens deposited in the collections of the Finnish Museum of Natural History, Helsinki (MZH) and the Zoological Museum of the University of Turku, Finland (ZMUT), as well as additional specimens identified by the present author. For each cestode species, all known definitive and intermediate host species are listed with references for published records. The checklist does not, however, provide a complete list of references. Instead, the first known reference and, if available, one or more recent ones with additional information on the particular cestode species, such as DNA sequence data, distribution and biology, is given for each cestode species/host species combination. The checklist does not include regions or localities for the cestode records, except for the former Finnish territories.
When specimens of a particular cestode species have been deposited in museum collections (in Finland or elsewhere), this has been indicated in the list, separately for each host species. However, collection/accession numbers are still unavailable for most of the specimens deposited in the Finnish museums (Helsinki and Turku). The specimens in the collections of both Finnish museums are generally old, commonly from the early 20 th century. Most of the specimens in the Finnish Museum of Natural History are stored in 80% ethanol (originally usually in formaldehyde), whereas the entire material in the Turku museum consists of specimens on slides.
Three workers stand out as collectors of older museum specimens of Finnish cestodes. Kaarlo M. Levander (1867-1943) and Guido Schneider (1867-1948 collected cestodes and other helminths of marine and freshwater fishes from Finland. The latter also published several faunistic and taxonomic papers on fish tapeworms, including descriptions of new taxa (e.g. Schneider 1902b(e.g. Schneider , 1904(e.g. Schneider , 1905. Knowledge of the tapeworm fauna of Finnish birds is based largely on the collections and original identifications of Väinö H. Pekkola . Pekkola never published any data on tapeworms he collected, but fortunately a major part of his extensive collections is deposited in MZH and ZMUT. Tapeworms available for study (other than museum specimens) originate from three main sources. Practically all the existing knowledge of the Finnish tapeworm fauna of rodents and shrews is based on specimens collected in connection with research projects led by Heikki Henttonen (Natural Resources Institute Finland Luke, previously Finnish Forest Research Institute) from the late 1970's until the present. Several tapeworm species and tapeworm/host species combinations new to Finland were identified among the tapeworms collected by specialists at the Finnish Safety Authority Evira (Marja Isomursu, Antti Oksanen). In addition, Antti Lavikainen (Haartman Institute, University of Helsinki) has recently collected and identified (by molecular methods) several taeniid species and taeniid/host species combinations new to Finland.
The geographical distribution of tapeworms of the field vole Microtus agrestis in Fennoscandia (Fig. 2) is based partly on published sources (Haukisalmi 1986, 2009a and partly on the tapeworm collections of H. Henttonen, V. Haukisalmi and coworkers from Finland, northern Norway and Denmark, and on the field vole material collected by Maarit Jaarola from Sweden (Jaarola and Tegelström 1995, 1996, Jaarola et al. 1997.
The identifications of vouchers and other specimens deposited in museum collections were checked, except when the specimens were in poor condition or when the rostellar hooks were lacking. The original identifications of cestodes without existing voucher specimens were accepted as such, the names modified to follow current taxonomy. The latter was derived from several sources, the seminal book "Keys to the cestode parasites of vertebrates" (Khalil et al. 1994) forming the backbone of the genus-level classification. However, the genus name Passerilepis Spasskii & Spasskaya, 1954 has been used for Microsomacanthus Lopez-Neyra, 1942 -like cestodes parasitizing passerine birds, instead of merging them with the latter genus. Other major deviations from the classification scheme of Khalil et al. (1994) concern the Anoplocephaloides Baer, 1923 and Paranoplocephala Lühe, 1910 -like species (Anoplocephalidae) of rodents and Taenia Linnaeus, 1758 -like species (Taeniidae) of carnivores, recently revised by Haukisalmi (2009) and Haukisalmi et al. (2014), and Nakao et al. (2013, respectively. Species-level taxonomy and identification are based on publications too numerous to be listed here, but the following books and papers may be mentioned as particularly important sources: Joyeux and Baer 1936 (all tapeworms), Scholz et al. 2007 (Proteocephalus), Spasskaya 1966 (hymenolepidids of birds), Spasskaya and Spasskii 1977, 1978(dilepidids of birds), Matevosyan 1969(paruterinids of birds), Spasskii 1951, Beveridge 1978, Vaucher 1971 (tapeworms of shrews) and Abuladze 1964 (taeniids). However, recent changes in species names have also been considered.
Tapeworms that could not be identified to species were included in the list if they were morphologically clearly different from other (congeneric) species. The checklist includes only those synonyms and misidentifications that have been used in publications concerning the Finnish cestode fauna or in museum specimens.

Results
The present checklist of tapeworms of Finland includes 170 parasite species from 151 host species, comprising 447 parasite species/host species combinations (see Appendix).
Fishes, birds and mammals have 31, 80 and 67 tapeworm species, respectively. There is a slight overlap in the tapeworm faunas of the three main host groups, because the life-cycles of diphyllobothriids (eight species) and Cladotaenia globifera (Batsch, 1786) (Paruterinidae) include hosts representing two different vertebrate classes (birds and fishes, mammals and fishes, and birds and mammals). Among birds, the highest tapeworm diversity is found in anseriforms (34 spp.), charadriiforms (18 spp.) and passeriforms (14 spp.) ( Table 1).
The checklist includes 30 tapeworm species and 96 parasite species/host species combinations (including the 30 "new" species) that have not been previously reported from Finland, marked as "Present study" in the references/source column. Four of the Finnish tapeworm species are sporadic imported parasites of humans and domestic animals not exhibiting natural transmission in Finland (see Discussion). Eight of the tapeworm species in the present checklist have been recorded only from the former territories of Finland, either from the Petsamo (Pechenga) region at the coast of the Arctic Ocean or from Karelia in the south-east of Finland.
The Finnish tapeworms represent seven orders and 18 families. As expected, the order Cyclophyllidea is the most diverse element of the Finnish cestode fauna (134 species or 80% of the total diversity), Hymenolepididae (61 spp.) being the most species-rich family.
The total number of tapeworm species in Finland (170 spp.) is lower than the corresponding figure for the Iberian Peninsula (257 spp.), Slovakia (225 spp.) and Poland (279 spp.) (Fig. 1). The difference between Finland and the other three regions is particularly pronounced for birds, the Finnish species diversity being only 46-70% of the corresponding diversity in the other regions. Among birds, the tapeworm fauna of anseriforms, podicipediforms, charadriiforms and passeriforms is usually significantly lower in Finland than in the other parts of Europe (Table 1). The species diversity of tapeworms in galliform birds in Finland is also unexpectedly low, partly because no cestodes have been reported from Finnish chickens (Gallus gallus domesticus).
In addition, there is low tapeworm diversity in mammals in Finland (67 spp.) compared with that in the Iberian Peninsula (106 spp.). The latter difference is partly due to the presence of tapeworms of marine mammals in Spain and Portugal (12 spp.); such tapeworms are not known from Finland, because the only regularly occurring and breeding marine mammals in Finland are seals (Halichoerus grypus and Pusa hispida), which do not carry host-specific tapeworms. However, Finnish seals accidentally carry fish-transmitted tapeworms of water birds and predatory fishes.
The holotypes of five species of tapeworms originate from Finland: Schistocephalus cotti, Paranoplocephala jarrelli Haukisalmi, Henttonen & Hardman, 2006, P. kalelai (Tenora, Haukisalmi & Henttonen, 1985, Catenotaenia henttoneni Tenora, 1993 andTaenia arctos Haukisalmi, Lavikainen, Laaksonen &Meri, 2011 (see Checklist for collection numbers). The MZH collection also includes a slide of Bothrimonus nylandicus Schneider, 1902 from Finland that is marked by Guido Schneider as "typ-ex", although he did not designate a type specimen in his publication (Schneider 1902a). The date and locality of the specimen match with those given in the original description. Thefore, this specimen is identified as the holotype of B. ny- Table 1. The number of tapeworm species in various bird orders in the Iberian Peninsula (Spain and Portugal), Slovakia, Poland and Finland. For source references, see Materials and methods. If a tapeworm species occurs in more than one bird order, it has been exluded from the data.

General characteristics of the tapeworm fauna of mammals in Finland
This section describes various features of the tapeworm fauna of shrews, rodents (particularly voles and lemmings) and carnivores in Finland. The mammalian tapeworms are among the most extensively studied parasites in Finland, and practically all of them have been subject to molecular systematic analysis of some form. By contrast, evidently no published DNA sequence data exist for tapeworms of fishes and birds from Finland, with the exception of Caryophyllaeides fennica (see Brabec et al. 2012, Scholz et al. 2014, Diphyllobothrium ditremum and D. latum (see Wicht et al. 2010).
One of the main patterns emerging from the present data is the seemingly unexplained absence in (northern) Fennoscandia of several mammalian tapeworms that have extensive distributions in the Holarctic region or in Eurasia.

Shrews
There are six species of shrews (Soricidae) in Finland, five species of Sorex and the water shrew Neomys fodiens. According to the present checklist, Sorex shrews have 15 species of tapeworms, most of them hymenolepidids, parasitizing shrews in the adult stage [this figure excludes Dilepis undula (Schrank, 1788) and Polycercus sp., parasites of birds that do not reach full size and maturity in shrews]. The smaller and scarcer species of Sorex shrews (S. minutus with 6 species, S. caecutiens with 12 species) have more depauperate tapeworm assemblages than the larger ones, particularly when compared with the numerically dominant S. araneus (with 15 species) (see also Haukisalmi 1989). However, their faunas are overlapping in the sense that all the tapeworms of the smaller shrews also parasitize the larger ones. The only (partial) deviation to this pattern may be Staphylocystoides stefanskii (Żarnowski, 1954), which has been found most frequently from the pygmy shrew S. minutus in Finland (one record from S. araneus). On the other hand, S. stefanskii is known to parasitize six species of Sorex in Eurasia (Binkienė et al. 2011). The tapeworm fauna of the smallest and scarcest Sorex species, the least shrew S. minutissimus, is unknown in Finland.
The tapeworm fauna of Sorex shrews in Finland is very similar to that found elsewhere in Europe and western Eurasia. In Europe, there are only two species that have not been found from Finland, that is, Skrjabinacanthus jacutensis Spasskii &Morozov, 1959 andSoricinia soricis (Baer, 1928). Skrjabinacanthus jacutensis is a rare parasite of Sorex shrews with an extensive but very patchy distribution in Eurasia (Binkienė et al. 2011). It is possible that it occurs in Finland, but has not been found yet because of its rarity. The apparent absence of S. soricis in Finland may be due to the fact that it has been confused with Soricinia infirma (Żarnowski, 1955) (see Karpenko 1999).
Among the tapeworms of Sorex shrews, only Spasskylepis ovaluteri Schaldybin, 1964 can be regarded as a northern species; according to Binkienė et al. (2011) it has not been reported further south than Belarus in Europe, and it seems to have a northern distribution also elsewhere in Eurasia.
The molecular systematic analysis of Haukisalmi et al. (2010b) indicated that there is a Ditestolepis species in the taiga shrew Sorex isodon in Finland that is distinct from the type species Ditestolepis diaphana (Cholodkovsky, 1906) and related species representing other genera. Because there should not be other Ditestolepis species in Europe or western Eurasia (Binkienė et al. 2011), the cestode from S. isodon may be a previously unknown species. Alternatively, it may one of the poorly known Ditestolepis species described from Japan (see the Global Cestode Database; Caira et al. 2012).
The water shrews of the genus Neomys have an almost entirely separate tapeworm fauna when compared with the genus Sorex, although there is a number of scattered records of Sorex tapeworms parasitizing Neomys shrews (Binkienė et al. 2011). The tapeworm fauna of Neomys fodiens and N. anomalus in Europe comprise 15 species, all of them hymenolepidids (Binkienė et al. 2011(Binkienė et al. , 2015, whereas only two tapeworm species are known from N. fodiens in Finland. One of these is typically a parasite of Sorex shrews [Vigisolepis spinulosa (Cholodkovsky, 1906)], and the other (Polycercus sp.) is a parasite of birds that accidentally infects shrews and other mammals (reported also from the raccoon dog Nyctereutes procyonoides in the present checklist). The specific identity of V. spinulosa from the water shrew has been confirmed by DNA sequences (Haukisalmi et al. 2010b).
The apparent absence of host-specific tapeworms of Neomys in Finland could be due to biased sampling of water shrews and restricted distribution of freshwater amphipod crustaceans (Segerstråle 1954), the intermediate hosts of tapeworms of water shrews (Georgiev et al. 2006). The absence of host-specific tapeworms in Neomys in Finland seems to follow the general pattern for other parts of the northern Europe (Binkienė et al. 2011). Binkienė et al. (2011) suggested that the reason for the absence or extreme rarity of host-specific tapeworms in Neomys in the north is the low abundance of the definitive hosts. However, the restricted/patchy distribution of the amphipod intermediate hosts and their low numbers in the diet of water shrews seems to be an equally plausible explanation.

Rodents (voles and lemmings)
Finland has a relatively diverse fauna of arvicoline rodents (Cricetidae), consisting of nine species of voles, including the introduced muskrat Ondatra zibethicus, and two species of lemmings.
In Finland, voles and lemmings have ten species of tapeworms parasitic in the adult stage, eight of them anoplocephalids, one catenotaeniid and one hymenolepidid cestode. The Finnish/northern European tapeworm fauna of arvicoline rodents can be classified into three main types: "endemics" of northenmost Europe (two species), species with a Holarctic distribution (one species) and species with extensive European/ western Eurasian distribution (seven species).
The restricted distribution of P. kalelai seems curious, because its primary definitive host (M. rufocanus) has a continent-wide distribution in northern Eurasia. It is possible that P. kalelai has been misidentifed in earlier studies. For example, the extensive faunistical study of mammalian helminths in the north-west of the Ural mountains (Yushkov 1995) lists Aprostatandrya macrocephala (Douthitt, 1915), A. caucasica (Kirshenblat, 1938) and Paranoplocephala omphalodes (Hermann, 1783) as parasites of the grey-sided vole [the valid name of A. macrocephala is Paranoplocephala macrocephala (Douthitt, 1915) and A. caucasica is considered a junior synonym of P. omphalodes; see Haukisalmi et al. 2014]. Of these species, P. macrocephala is morphologically rather similar to P. kalelai (see Tenora et al. 1985a, Haukisalmi et al. 2007) and may have been confused with the latter. It is now known that P. macrocephala has a strictly North American distribution, parasitizing voles of the genus Microtus and geomyid rodents there Henttonen 2003, Haukisalmi et al. 2004), although this name still appears as a parasite of arvicoline rodents in Eurasia. Thus, the true distribution of P. kalelai remains to be verified, but, based on the collections of the Beringian Coevolution Project (Hoberg et al. 2003, Cook et al. 2005, it does not occur in M. rufocanus in easternmost Siberia (Chukotka Peninsula and adjacent regions).
If the restricted northern distribution of P. kalelai is found to be real, this would support the idea that P. kalelai has diverged as a result of a host shift from a northern European Microtus lineage (most likely M. oeconomus) to the Fennoscandian subclade of M. rufocanus after its divergence from the Siberian M. rufocanus populations (Cook et al. 2004, Haukisalmi et al. 2007). This scenario is supported by two phylogenetic/ phylogeographic analyses on tapeworms of the genus Paranoplocephala (see Haukisalmi et al. 2004Haukisalmi et al. , 2007. Lemminia fellmani is known only from the Norwegian lemming L. lemmus (a Fennoscandian endemic) from the mountains of southern Norway (Finse, type locality) and from northern Finland (Lapland) (Haukisalmi and Henttonen 2001). However, a morphologically and genetically related, congeneric cestode occurs in Lemmus trimucronatus is Alaska (Haukisalmi et al. 2010b), but it is uncertain if it is conspecific with L. fellmani. No tapeworms have been found from the wood lemming Myopus schisti-color in Finland, although Lemminia gubanovi (Gulyaev & Krivopalov, 2003) occurs in this host in eastern Siberia (Gulyaev and Krivopalov 2003).
Paranoplocephala jarrelli Haukisalmi, Henttonen & Hardman, 2006 is known to parasitize the tundra/root vole Microtus oeconomus (and accidentally other Microtus species) from northern Finland to Alaska (Haukisalmi et al. 2004), therefore being the only tapeworm of Finnish rodents to have a Holarctic distribution, with the possible exception of L. fellmani (above). The conspecificity of P. jarrelli populations in northern Finland, Hungary, the Russian Far East (Magadan) and Alaska has been verified by molecular methods (Haukisalmi et al. 2004).
Present data for the geographical distribution of tapeworms of the field vole Microtus agrestis in Fennoscandia (Fig. 2) show that the range of A. cf. dentata, M. cf. variabilis, M. blanchardi and E. gracilis extends to the northenmost Fennoscandia, whereas P. omphalodes and H. asymmetrica are absent from the truly northern regions. Of the latter two species, P. omphalodes has a more northerly distribution than H. asymmetrica. The absence of these species from northernmost Finland is primarily based on nearly 40 years' monitoring of arvicoline rodents and their helminths in western Finnish Lapland by H. Henttonen and coworkers, although extensive helminth datasets have been gathered also from other northern localities in Finland. The absence of these two species from the north seems peculiar, because their main definitive host (M. agrestis) occurs in the whole of the Fennoscandia, and is often the numerically dominant rodent species in open habitats throughout its range (Myllymäki et al. 1977).
It is noteworthy that no tapeworms of the genus Arostrilepis Mas-Coma & Tenora, 1997 (Hymenolepididae) have been reported from Finland or elsewhere from Fennoscandia, except for the finding of A. horrida (von Linstow, 1901) from the bank vole M. glareolus from southern Norway (Baruš et al. 1977) and Russian Karelia (Mozgovoj et al. 1966). Arostrilepis species are ubiquitous parasites of arvicolines (and sporadically other rodents) in the Holarctic region, their range encompassing the central and southern Europe. Of the 12 valid species of Arostrilepis, at least eight occur in Eurasia (see the Global Cestode Database; Caira et al. 2012).
Another Holarctic tapeworm species evidently missing from Fennoscandia is Anoplocephaloides lemmi (Rausch, 1952), a parasite of lemmings of the genus Lemmus in northern Siberia and North America. The absence of this species seems real, because hundreds of Norwegian lemmings have been examined for helminths in Finnish Lapland and southern Norway by H. Henttonen and coworkers. It is hard to propose any general explanation for the absence of Arostrilepis species in most of Fennoscandia, but the absence of A. lemmi and another host-specific, Holarctic tapeworm species of Lem-mus spp. [Arostrilepis beringiensis (Kontrimavichus & Smirnova, 1991)] may be the result of the severe population bottle-neck experienced by L. lemmus in Fennoscandia during the the last glacial maximum Stenseth 2001, Haukisalmi andHenttonen 2001, Haukisalmi et al. in press).
Hymenolepis diminuta (Rudolphi, 1819) (a parasite of Rattus spp.) and H. hibernia Montgomery, Montgomery & Dunn, 1987 (a parasite of Apodemus spp.) may also be listed as "missing" species, although there do not exist extensive helminthological studies for rats in Finland. The unverified record of H. "diminuta" from Apodemus flavicollis (Raitis 1968; no voucher specimen exists), may, however, represent the latter tapeworm species.

Carnivores
There are 14 species of terrestrial carnivores in Finland. The present study lists 17 tapeworm species parasitizing carnivores in the adult stage, Taeniidae (nine species) being the dominant element of the fauna. However, the taeniid fauna of Finnish carnivores should also include two additional species, Taenia martis and Versteria mustelae (parasites of mustelids), which have been found so far only as metacestodes from rodents. The metacestode of the latter species has also been found unexpectedly from the otter Lutra lutra. There are no published studies on tapeworms of mustelids in Finland.
Echinoccus multilocularis is one of the tapeworm species that is mysteriously absent from Finland, although it has a Holarctic distribution and the definitive hosts (red fox Vulpes vulpes and other canids, including the raccoon dog) and intermediate hosts (rodents) are present in Finland. In addition, Taenia crassiceps (Zeder, 1800), a parasite of foxes that occurs basically throughout the Holarctic region, has not been found in Finland despite very extensive long-term studies on helminths of rodents (intermediate hosts of T. crassiceps) in Finland (H. Henttonen et al., unpublished). The absence of E. multilocularis and T. crassiceps may due to the fact that the density of the red fox, their primary definitive host, is below an (unknown) critical density for successful transmission of the parasite, and/or due to the pronounced density fluctuations of arvicoline rodents in Finland (Henttonen and Haukisalmi 2000). However, E. multilocularis has recently appeared in Denmark and Sweden (Kapell and Saeed 2000, Osterman Lind et al. 2011, Wahlström et al. 2012, and is predicted to spread to Finland as well. Taenia pisiformis, with canids (including dog) as definitive hosts and hares as intermediate hosts, has evidently disappeared from Finland. In the 1940-50s, T. pisiformis was still a very common parasite in the country, known as the "bladder worm disease" of hares (Lampio 1946(Lampio , 1950. However, no metacestodes of T. pisiformis were found from hares in early 1980s (Soveri and Valtonen 1983), and a recent survey of Taenia tapeworms in wolves from Finland and Sweden based on molecular identification (Lavikainen et al. 2011) also failed to find it. It is clear that the hunters' awareness of the transmission of the parasite (hare offal should not be fed to dogs) and anthelmintic teatment of hunting dogs have played a major role in the disappearence of this parasite, but do not completely explain it, because suitable wild hosts are still numerous in Finland.
Recently, molecular methods have had a revolutionary impact on taeniid systematics. For example, the application of DNA based methods has enabled distinction of more or less cryptic, new species of Taenia, including T. arctos, a parasite of bears (definitive host) and cervids (intermediate hosts) in Finland, Alaska and Canada (Haukisalmi et al. 2011, Catalano et al. 2014. Taenia arctos had previously been confused with other Taenia species, mainly with Taenia krabbei Moniez, 1879, but it was found to be a genetically and biologically distinct entity (Lavikainen et al. 2010). Recently, another new species of Taenia, with the lynx (Lynx lynx) as a definitive host and cervids as intermediate hosts, has been found in Finland based on the molecular identification of adults and metacestodes (V. Haukisalmi, A. Lavikainen et al., unpubl.).

Tapeworm diversity in different parts of Europe
One of the main patterns emerging from the present checklist and associated comparisons is that the tapeworm fauna of vertebrates in Finland is significantly less speciose than the corresponding fauna in other parts of Europe. The difference is mainly due to the low number of bird tapeworms in Finland.
Such a pronounced difference may be a real one or due to a number of confounding factors, including differences in latitude, available habitats (freshwater, marine, montane etc.), the number of host species present and the proportion of host species examined (adequately) for tapeworms. It is not possible to determine how these factors (interactively) determine the variation in tapeworm diversity in Europe, but the last factor probably explains most of the variation.
First, most of the tapeworms of vertebrates considered here have a wide European or western Eurasian (or more extensive) distribution, and are expected to occur in Fennoscandia, provided that their definitive and intermediate hosts are present. Therefore, latitude alone should not explain the differences in tapeworm diversity among regions. The availability of habitats is not a sufficient explanation either, because Finland is a long country stretching from the Baltic Sea (Gulf of Finland) to near the Arctic Ocean, and freshwater habitats (including thousands of lakes) are ubiquitous. Semi-montane landscape prevails in northern Finland (Lapland). The number of vertebrate host species certainly affects tapeworm diversity, and the high overall tapeworm diversity in the Iberian Peninsula is probably partly explained by this factor. However, there are no marked differences in vertebrate diversity between Slovakia, Poland and Finland, except that there are slightly fewer species of fishes and water birds in Slovakia because of the absence of marine habitats.
These patterns favour the idea that low tapeworm diversity in Finland is mainly due to insufficient sampling of vertebrates, particularly anseriform, podicipediform, charadriiform and passeriform birds. The tapeworm fauna of Poland, which is among the best known in Europe (Pojmańska et al. 2007), forms the most suitable model when predicting the true number of tapeworm species in Finland. The diversity of vertebrates is roughly equal in Poland and Finland, and there are no major faunistical differences either. In addition, Poland and Finland are both situated on the Baltic sea.
The tapeworms of fishes and mammals in Finland are relatively well known and the number of tapeworm species in these hosts is taken as such. In Poland, there are 172 species of tapeworms in birds, which is taken as the predicted number for the Finnish fauna. Based on this method, there should be ca. 270 species of tapeworms in Finland, instead of the 170 species listed in the present study.

Acknowledgements
I acknowledge the following persons for providing tapeworms, intestines or intact hosts from Finland: Heikki Henttonen, Antti Lavikainen, Antti Oksanen, Marja Isomursu, Jukka Niemimaa, Juha Laakkonen, Janne Sundell, Paavo Hellstedt, Eva Kallio, Ilpo K. Hanski, Ari Puolakoski and Netta Lempiäinen. Besides collecting a very large number of specimens, H. Henttonen has played a crucial role in research concerning the fauna and ecology of helminths of small mammals in Finland (and elsewhere). Rolf A. Ims and Nigel Yoccoz provided field voles from northen Norway, and Maarit Jaarola kindly allowed me to use her extensive collections of field voles from Sweden. Lotta M. Hardman, Michael Hardman and Jarkko Hantula performed many of the existing molecular phylogenetic analyses on tapeworms of Finnish rodents; Lotta is thanked also for guiding me patiently into the mysterious world of DNA and phylogenetics. I have enjoyed collaboration with A. Lavikainen, who has made pioneering research on the fauna and molecular systematics of tapeworms of Finnish carnivores and humans. Hans Silfverberg, E. Tellervo Valtonen, Seppo Saari and A. Lavikainen are acknowledged for help with the literature pertaining to the Finnish cestode fauna. Varpu Vahtera gave invaluable help with the tapeworm collection of the Zoological Museum of the University of Turku. I am also indebted to the late František Tenora, who was first to study the helminths of rodents in Finland (with H. Henttonen and the present author) and who introduced us to the fascinating world of tapeworm systematics. Ian Beveridge, Heikki Henttonen, Roman Kuchta, Arseny Makarikov and Gergana Vasileva provided helpful comments on the manuscript.