Research Article |
Corresponding author: Voitto Haukisalmi ( voitto.haukisalmi@helsinki.fi ) Academic editor: Boyko Georgiev
© 2016 Voitto Haukisalmi, Sergey Konyaev, Antti Lavikainen, Marja Isomursu, Minoru Nakao.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Haukisalmi V, Konyaev S, Lavikainen A, Isomursu M, Nakao M (2016) Description and life-cycle of Taenia lynciscapreoli sp. n. (Cestoda, Cyclophyllidea). ZooKeys 584: 1-23. https://doi.org/10.3897/zookeys.584.8171
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A new species of tapeworm, Taenia lynciscapreoli sp. n. (Cestoda, Cyclophyllidea), is described from the Eurasian lynx (Lynx lynx), the main definitive host, and the roe deer (Capreolus capreolus and C. pygargus), the main intermediate hosts, from Finland and Russia (Siberia and the Russian Far East). The new species was found once also in the wolf (Canis lupus) and the Eurasian elk/moose (Alces alces), representing accidental definitive and intermediate hosts, respectively. The conspecificity of adult specimens and metacestodes of T. lynciscapreoli sp. n. in various host species and regions, and their distinction from related species of Taenia, was confirmed by partial nucleotide sequences of the mitochondrial cytochrome c oxidase subunit 1 gene. Morphologically, T. lynciscapreoli sp. n. can be separated unambiguously from all other species of Taenia by the shape of its large rostellar hooks, particularly the characteristically short, wide and strongly curved blade. If the large rostellar hooks are missing, T. lynciscapreoli may be separated from related species by a combination of morphological features of mature proglottids. It is suggested that T. lynciscapreoli has been present in published materials concerning the tapeworms of L. lynx and L. pardinus in Europe, but has been misidentified as Taenia pisiformis (Bloch, 1780). Taenia lynciscapreoli sp. n. has not been found in lynx outside the range of roe deer, suggesting a transmission pathway based on a specific predator–prey relationship. The present study applies a novel, simple approach to compare qualitative interspecific differences in the shape of rostellar hooks.
Tapeworms, Lynx , Capreolus , Alces , wolf, Finland, Russia, Siberia
Morphological differences between independent species of the genus Taenia Linnaeus, 1758 and related genera are often limited, and it can be expected that extensive surveys based on molecular methods will reveal unknown, more or less cryptic species. In favour of this idea, at least two probable new species were recently identified in molecular phylogenetic analyses by
A recent molecular phylogenetic study on Taenia spp. in the Eurasian lynx (Lynx lynx) from Finland revealed a genetic lineage, which could not be associated with any known species based on sequence data (
Since the report by
The material used in the description of the new species consisted of 14 adult specimens: seven from L. lynx from Finland (four host individuals), five from the same host species from the Russian Federation (four host individuals), and two from the wolf (Canis lupus) from Russia (one host individual).
In addition, 11 metacestodes (cysticerci) were examined to characterize the rostellar hooks of the new species: two specimens from the European roe deer Capreolus capreolus and five specimens from the Eurasian elk/moose Alces alces (one host individual each) from Finland, and four specimens from the Siberian roe deer Capreolus pygargus (one host individual) from Russia.
Conspecificity of adults and metacestodes in various host species was confirmed using a partial nucleotide sequence (396 bp) of the mitochondrial cytochrome
Adult cestodes were relaxed in water and fixed flat (without pressure) and preserved in 70–75% ethanol. Fragments of each specimen, representing various developmental stages, were stained with alum carmine, cleared in eugenol and mounted in Canada balsam. Hand–cut transverse sections of mature proglottids were prepared to determine the number of dorso–ventral testicular layers and the dorso–ventral position of terminal genital ducts with respect to the longitudinal ventral osmoregulatory canals and the nerve cord.
Cysticerci were fixed and preserved in 70–75% ethanol. The hook crowns extracted from cysticerci were mounted in Berlese’s medium for study. Only hooks aligned well in the horizontal plane were used for the morphometric analysis.
Five linear measurements, as defined by
Variation in measurements (µm) of large rostellar hooks in Taenia lynciscapreoli sp. n. Figures show the range with the mean in parentheses. TL, total length; TW, total width; PL, posterior length; AL, anterior length; GL, guard length (see Fig.
Hosts, region | TL | TW | PL | AL | GL |
---|---|---|---|---|---|
Lynx, Finland (n=11) | 168–228 (195.9) | 78–94 (84.5) | 114–162 (133.8) | 76–97 (86.3) | 42–54 (47.7) |
Lynx, Russia (n=16) | 214–231 (223.4) | 79–96 (89.4) | 138–162 (152.1) | 87–101 (94.9) | 40–59 (50.8) |
Lynx, combined (n=27) | 168–231 (212.2) | 78–96 (87.4) | 114–162 (144.7) | 76–101 (91.4) | 42–59 (49.5) |
Capreolus, Finland (n=3) | 213–222 (216.5) | 85–92 (87.5) | 136–153 (144.2) | 95–98 (96.9) | 48–56 (49.9) |
Capreolus, Russia (n=15) | 215–238 (230.7) | 94–109 (103.4) | 148–171 (162.7) | 92–111 (104.3) | 54–88 (65.6) |
Alces, Finland (n=7) | 213–230 (222.3) | 82–97 (90.9) | 145–162 (154.8) | 86–100 (94.0) | 46–60 (52.3) |
Cervids, combined (n=25) | 213–238 (225.9) | 82–109 (97.2) | 136–171 (157.2) | 86–111 (100.3) | 46–88 (59.2) |
Lynx + cervids, combined (n=52) | 168–238 (219.1) | 78–109 (92.3) | 114–171 (150.9) | 76–111 (95.8) | 40–88 (54.4) |
The shape of the large rostellar hooks was compared by scaling a representative hook of each species to the same total length, and then aligning a pair of hooks using the outline of the junction between the blade and the guard as an anchor region. The form of the anchor region was almost invariable among the species considered here.
Type and voucher specimens have been deposited in the
DNA sequences showed unambiguously that the specimens from various host species and regions represent the same species. Four cox1 haplotypes were identified, the most common of which was identical with the cox1 haplotype observed by
A phylogenetic tree of selected species of Taenia inferred from a 396 bp fragment of mitochondrial cox1 gene by the maximum likelihood method. Bootstrap values >50% are shown. The scale bar represents the estimated number of substitutions per site. Accession numbers or references of the previously published sequences are in parentheses. The haplotypes of T. lynciscapreoli sp. n. are designated with numbers 1–4, and their geographical origins and hosts are indicated with abbreviations: Fin, Finland; Rus, Russia; L, lynx; W, wolf; R, European or Siberian roe deer; M, moose.
Adult. Type–material: Holotype
Voucher material from L. lynx:
Voucher material from Canis lupus (wolf): SVK-2265 and SVK-2581, Mikhailovskiy raion, Altai Rai, Russia.
Other museum specimens from L. lynx from Finland (in ethanol):
Other records from L. lynx: Kolosovsky and Bolsheukovsky raions, Omskaya oblast’, Western Siberia, Russia (morphological identification), coll. Bykova, 2006 [identified as Taenia pisiformis (Bloch, 1780)].
Lynx lynx Linnaeus, 1758, the Eurasian lynx. Other hosts: Canis lupus Linnaeus, 1758, the wolf.
Salo, Perniön Ylikulma (WGS 84: 60°16.948'N; 23°13.288'E), southern Finland.
Site. Small intestine.
Host: European roe deer Capreolus capreolus (Finland), Siberian roe deer Capreolus pygargus (Russia) and Eurasian elk/moose Alces alces (Finland).
N16553, Museum of All–Russian K. I. Skryabin Scientific Research Institute of Helminthology (Moscow), C. pygargus, Tuva Republic, Southern Siberia, Russia (identified as T. hydatigena).
Site. Liver and lungs.
Adults and metacestodes of T. lynciscapreoli sp. n. can be separated unambiguously from all other species of Taenia by the shape of their large rostellar hooks, particularly the characteristically short, wide and strongly curved blade. If the large rostellar hooks are missing in adults, T. lynciscapreoli may be separated from related species by a combination of morphological features of mature proglottids (see Discussion).
Measurements are in micrometres if not otherwise stated.
Adult (Figs
Terminal genital ducts of Taenia lynciscapreoli sp. n. (holotype) in whole mount (A) and in hand–cut transverse section (B). VC, ventral longitudinal osmoregulatory canal; DC, dorsal longitudinal osmoregulatory canal; NC, nerve cord; VA, vagina; CV, copulatory part of vagina; CS, cirrus sac; VD, vas deferens; TE, testes. Scale-bars: 100 μm.
Medium–sized species of Taenia; length of fully gravid specimens 55–90 cm (n=4). Maximum width of strobila 5–7 mm (n=4). Scolex 1.1 mm (n=2) wide in specimens mounted in Berlese’s medium (BM), 0.85 mm (n=1) wide in specimens mounted in Canada balsam (CB). Maximum diameter of suckers 269–289 in BM (n=7), 213–255 in CB (n=4). Diameter of rostellum 375–425 in BM (n=2), 300–365 in CB (n=2); rostellum larger than suckers. Neck approximately as wide as scolex, of variable length.
Rostellum bearing two rows of hooks; rostellar armature usually incomplete in adult specimens. In combined material, length of large hooks 168–231 (mean=212.2, n=27) and length of small hooks 106–137 (mean=126.2, n=25). Total length and other dimensions of large hooks consistently smaller in specimens from Finland than in those from Siberia and Russian Far East. Large hooks characterized by long, thick and straight handle sometimes provided with apical bulge, relatively short, wide and strongly curved blade and prominent, usually slightly pointed guard. Border between hidden and exposed parts of large hooks marked with distinct oblique ridge. Margin of ridge provided with pits of various sizes at middle of handle; similar but less distinct pits sometimes present at guard portion of ridge.
Proglottids craspedote, but velum poorly developed. Mature proglottids 2.8–5.3 mm (mean=4.3 mm, n=15) wide and 2.0–3.4 mm (mean=2.6 mm, n=15) long, with length/width ratio of 1:1.2–2.6 (mean=1:1.7, n=15) in well–relaxed specimens. Proglottids becoming more elongate posteriorly; fully–gravid proglottids up to 14 mm long, with length/width ratio of 1:4.7.
Genital pores irregularly alternating, positioned in middle of lateral margin of proglottids. Genital atrium weak, usually not protruding, 238–425 (mean=302, n=12) wide at base and 144–264 (mean=186, n=12) deep. Ventral longitudinal osmoregulatory canals 34–110 (mean=75, n=13) wide in mature proglottids, up to 200 in postmature/pregravid proglottids; connected by narrower transverse canals. Dorsal osmoregulatory canals narrow (seen only in transverse sections), running medially to ventral longitudinal canals. Terminal genital ducts positioned between dorsal and ventral longitudinal osmoregulatory canal and dorsal to nerve–cord.
Testes 591–725 (mean=653, n=5) in number, 80–130 in largest diameter, positioned primarily in one dorso–ventral layer. Testicular field widely confluent anteriorly and occupying all parts of median field lacking female organs, except small well–defined region anterior to ovary. Continuous posterior testicular field absent, but sometimes individuals testes positioned posterior to or overlapping vitellarium. Antero–poral testicular field longitudinally as long as postero–poral field (as separated by vas deferens). Testicular field separated from ventral osmoregulatory canals by distinct free space laterally, anteriorly and posteriorly. Cirrus–sac elongate, 340–425 (mean=382, n=11) long and 153–179 (mean=166, n=11) wide in mature proglottids, usually not extending to longitudinal ventral canal; muscle layers of cirrus–sac well–developed. Distal part of ductus cirri armed with delicate hair–like structures. Vas deferens forming few irregular loops inside cirrus–sac, prominently convoluted outside cirrus–sac.
Ovary bilobed, 98–172 (mean=150, n=15) wide and 57–103 (mean=84, n=15) long; lobes of roughly equal size, but antiporal lobe extending slightly more anteriad than poral lobe; ovary does not reach midline of proglottid longitudinally. Vitellarium distinctly elongated transversely, 80–145 (mean=126, n=15) wide and 19–41 (mean=31, n=12) long, slightly narrower than ovary; lateral extremities usually pointed. Vagina opens posterior to male pore, provided by distinct sphincter ca. 5 from distal end of vagina; sphincter ca. 3 long and 6 wide; sphincter sometimes absent or incomplete (present on one side of vagina only). Copulatory part of vagina shorter than cirrus sac, thick–walled, distinctly widened, curved posteriorly; maximum width of copulatory part 94–111 (mean=106, n=10). Proximal vagina narrow, of uniform width, runs posterior to vas deferens, usually slightly undulating, rarely looped. Lumen of vagina lined with delicate hair–like structures almost throughout its length; hairs particularly long in widened copulatory part. Prior to joining seminal receptacle, vagina forms differentiated region, 10–12 long, with tapered lumen lacking hairs. Sperm–filled seminal receptacle elongate, 9–17 (mean=12.4, n=15) long. Mehlis’ gland spherical, 18–22 (mean=19.6, n=11) in diameter. Uterus in pre–gravid and early gravid proglottids with 8–11 primary branches on each side, often with secondary and tertiary bifurcations; lateral branches not reaching ventral osmoregulatory canal; terminal branches usually with multiple anterior or posterior sacculations. Eggs spherical or subspherical, with maximum diameter of 34–39 (mean=36.8, n=26) in whole–mounts. Outer egg shell thick (4.0–4.5), distinctly two–layered.
Metacestode (Fig.
Metacestode is cysticercus. Ethanol–fixed cysticerci with fully–developed rostellar hooks 3–14 mm long and 2–5 mm wide; larger cysticerci with elongate or sac–like posterior bladder and, in one case, with short (8 mm) strobila between bladder and scolex region. Rostellum armed with 30–34 (mean=32.0, n=7) hooks forming two rows. Large hooks 213–238 (mean=225.9, n=27) and small hooks 123–145 (mean=136.7, n=23) long. Average hook dimensions are consistently smaller in specimens from Finland than in specimens from Siberia and Russian Far East. Rostellar hooks of metacestodes are similar in shape to those of adult cestodes.
Eurasia, from Finland to Russian Far East.
The specific epithet refers to the main definitive and intermediate hosts of the new species.
Taenia lynciscapreoli sp. n. is compared with all congeneric species parasitizing felids (definitive hosts) or cervids (intermediate hosts) in the Holarctic region (12 species), and also with the phylogenetically closely related T. regis (see
Host species and characteristics of rostellar hooks of Taenia spp. compared with T. lynciscapreoli sp. n., based on
Taenia spp. | Definitive hosts | Intermediate hosts | Geographic distribution | Number of hooks | Large hooks, length | Small hooks, length |
---|---|---|---|---|---|---|
T. lynciscapreoli sp. n. | felids (Lynx) | cervids (Capreolus) | Eurasia | 30–34 | 168–238 | 106–145 |
T. arctos Haukisalmi, Lavikainen, Laaksonen & Meri, 2011 | bears (Ursus) | cervids (Alces) | 22–36 | 153–180 | 96–130 | |
T. hydatigena Pallas, 1766 | canids | cervids and other ruminants | worldwide | 28–44 | 169–235 | 110–168 |
T. ingwei Ortlepp, 1938 | felids (Panthera) | unknown | Africa | 32–34 | 197–202 | 148–151 |
T. kotlani Murai, Gubanyi & Sugar, 1993 | unknown, probably felids (Panthera) | bovids (Capra) | Central Asia | 30–36 | 187–218 | 118–143 |
T. cf. kotlani of |
Panthera | unknown, probably cervids | Central Asia | 30–35 | 190–209 | 127–144 |
T. krabbei Moniez, 1879 | canids | cervids and other ruminants | Holarctic region | 22–36 | 137–195 | 84–141 |
T. laticollis Rudolphi, 1819 | felids (Lynx) | lagomorphs | Eurasia | 58–66 | 370–420 | 150–247 |
T. macrocystis (Diesing, 1850) | felids (Lynx, Leopardus, Puma) | lagomorphs | America, Asia | 54–74 | 297–430 | 180–247 |
T. omissa Lühe, 1910 | felids (Puma, Leopardus) | cervids (Odocoileus) | America | 38–44 | 223–297 | 165–223 |
T. parenchymatosa Pushmenkov, 1945 | canids | cervids | Russia | 30–34 | 210–240 | 124–160 |
T. parenchymatosa of |
felids (Lynx) | cervids (Capreolus) | Siberia | 27–34 | 195–234 | 118–149 |
T. pisiformis (Bloch, 1780) | canids, occasionally felids including Lynx | lagomorphs | worldwide | 34–46 | 220–300 | 114–177 |
T. pseudolaticollis Verster, 1969 | felids (Lynx, Leopardus) | unknown (probably lagomorphs) | America | 38–42 | 352–415 | 214–240 |
T. regis Baer, 1923 | felids (Panthera) | bovids (antelopes), suids (Phacocoerus) | Africa | 32–49 | 223–273 | 142–199 |
T. rileyi Loewen, 1929 | felids (Lynx, Puma) | rodents | America | 36–46 | 238–258 | 145–198 |
When aligned using the outline of the junction between the blade and the guard, the large rostellar hooks of T. lynciscapreoli have a shorter blade and longer handle, and a wider and more strongly curved blade than those of the other species, with the partial exception of T. pisiformis (Fig.
Pairwise comparisons of the shape of the large rostellar hooks in Taenia lynciscapreoli sp. n. and related species, using the junction between the blade and the guard as an anchor region for alignment. The hook of T. lynciscapreoli sp. n. is indicated by a black outline. A legend for measurements taken from the large hooks of the new species (Table
Interspecific differences in the morphology of mature proglottids between T. lynciscapreoli and the species showing the highest overlap in hook characteristics are listed in Table
Comparison of morphological features of mature proglottids in T. lynciscapreoli sp. n. and species showing highest overlap in the number and length of rostellar hooks. There is no adequate description for the morphology of the adult of T. kotlani. Based on
Taenia spp. | Vaginal sphincter | Longitudinal extent of ovary | Antiporal lobe of ovary distinctly larger than poral lobe | Free space around testes | Length of poral testicular fields | Width of anterior testicular field | Number of testicular layers |
---|---|---|---|---|---|---|---|
T. lynciscapreoli sp. n. | + | < midline | – | + | A = P† | wide | 1 |
T. arctos | + | > midline | + | – | A = P | wide | 2–3 |
T. hydatigena | – | < midline | + | – | A > P | wide | 1 |
T. ingwei | + | ≤ midline | – | ? | A = P | wide | 1 |
T. krabbei | + | < midline | + | + | A > P | wide | 1–2 |
T. parenchymatosa | + | = midline | – | + | A < P | narrow | ? |
T. pisiformis | – | < midline | + | – | A > P | wide | 2–4 |
In practice, the identification of T. lynciscapreoli based on rostellar hooks is straightforward; the new species has shorter hooks than other congeneric species parasitizing felids in the Holarctic region, with the possible exception of T. kotlani, the definitive host of which is unknown. The identification of metacestodes parasitizing cervids is slightly more challenging, but the present comparison shows that the unique shape of the large hooks of T. lynciscapreoli, particularly the short, wide and strongly curved blade, separates it from other species with rostellar hooks of similar length. If properly compared, the characteristic shape of the large hooks of T. lynciscapreoli also serves to separate it from all other species of Taenia, including those not compared here with the new species (see
Total length has often been the only feature used to characterize the rostellar hooks of Taenia spp., although it may be assumed that the shape of the hooks is a taxonomically more informative feature. Interspecific differences in the shape of rostellar hooks have been analysed using multivariate morphometrics (
The large hooks of the cestode from Capreolus pygargus from Siberia, identified by
Besides T. lynciscapreoli, there are published DNA sequence data for five species of Taenia s.s. parasitizing felids, i.e. T. cf. kotlani (
Taenia lynciscapreoli was not compared here morphologically with Taenia spp. parasitizing felids in Africa and Asia, because, according to present knowledge, their fauna is separate from the corresponding fauna in the Holarctic region. However, T. regis, a parasite of the lion in Africa, is included in the present comparison, because it is phylogenetically related to T. lynciscapreoli. It is possible that there are more extensive phylogenetic connections between Taenia spp. of Holarctic and southern felids, but there are no published DNA sequence data for species of Taenia other than T. regis parasitizing felids in Africa or Asia. However, our unpublished data suggest that T. gonyamai Ortlepp, 1938 and T. selousi Mettrick, 1963, parasites of felids in Africa, are phylogenetically distinct entities and therefore not conspecific with T. lynciscapreoli.
A group of taeniid cestodes, including two species parasitizing felids [Hydatigera taeniaeformis (Batsch, 1786) and H. krepkogorski Schulz & Landa, 1934], was recently shown to form a distinct clade by molecular phylogenetic methods, and therefore proposed to represent the resurrected genus Hydatigera Lamarck, 1816 (see
The existing data on T. lynciscapreoli strongly suggests that it uses specifically the lynx and the roe deer as definitive and intermediate hosts, respectively. Being small cervids, roe deer are optimal and, where available, preferred prey items for the lynx (
The lynx and the roe deer have almost continent–wide, overlapping distributions in Eurasia, although the latter host is represented by two allopatric species (C. capreolus and C. pygargus). However, the distribution of the Eurasian lynx extends further north than the distribution of the roe deer, and, if the occurrence of the parasite is dependent on the presence of both primary hosts, we would expect to find the parasite in the lynx only in regions inhabited by the roe deer. This seems to be case in Finland, as
However, despite the basically strict host–specificity, accidental infections of other definitive host species are likely to occur, especially with unrelated predators utilizing same intermediate host species. The present finding of T. lynciscapreoli in the wolf, confirmed by molecular methods, shows that such spill–over does happen. In this case the obvious explanation is that wolves prey on roe deer, the primary intermediate host of T. lynciscapreoli.
The finding of T. lynciscapreoli in the Eurasian moose calf, confirmed by molecular methods, shows that the new species is able to infect also cervids other than the roe deer. Although the lynx may succeed in killing a moose calf (
It may be that infections of larger cervids (Alces, Cervus) by the metacestodes of T. lynciscapreoli occur only in regions where there exists a transmission cycle between the lynx and the roe deer.
Because T. lynciscapreoli is evidently a predictable, wide–spread component in the tapeworm fauna of the lynx and the roe deer, it is probably represented in some previous studies, but has been misidentified or remained unidentified.
A survey of helminths of the lynx in Estonia (
The identification of Taenia spp. by
It is obvious that some of the existing reports of Taenia metacestodes in roe deer, particularly in regions where it co–occurs with lynx, may also be T. lynciscapreoli. Three other valid species of Taenia using cervids as intermediate hosts in Eurasia, i.e. T. krabbei (including the probable junior synonym T. cervi Christiansen, 1931), T. hydatigena and T. parenchymatosa, may all be confused with T. lynciscapreoli because of overlapping hook number and dimensions (as shown above, T. parenchymatosa of
Antti Oksanen (Finnish Food Safety Authority Evira) is acknowledged for support and shared enthusiastic attitude towards parasites of all kinds. We thank Minna Nylund (Evira) for collecting and preserving tapeworms from lynx. Pekka Spets, Esko Huuhtanen, Mikko Suomela and Valtteri Söderman kindly submitted the Finnish animal samples from which the parasites were found. Dr Seryodkin provided specimens of Taenia lynciscapreoli from Russian Far East and Dr Bondarev helped in the collection samples from Altai Krai. Ian Beveridge, Rodney A. Bray and Eric P. Hoberg kindly checked the language and provided helpful comments on other aspects of the manuscript. This study was supported in part by a Grant-in-Aid for Scientific Research (no. 26460503) from Japan Society for the Promotion of Science (JSPS KAKENHI) to MN.