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26Russian Journal of Nematology, 2022, 30 (1), 69 - 78
Molecular and morphological characterisation of Syphacia stroma (Linstow, 1884) (Nematoda, Oxyurida) from the Lipetsk region, Russia
Daria I. Gorelysheva1 and Ivan M. Ermakov2
JA.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninskii Prospect 33, 119071, Moscow, Russia 2Faculty of Biology, Moscow State University, Leninskie Gory 1-12, 119991, Moscow, Russia
e-mail: [email protected]
Accepted for publication 21 March 2022
Summary. Morphological data and nucleotide sequences are provided for specimens of the pinworm, Syphacia stroma, collected from two specimens of yellow-necked mouse, Apodemus flavicollis, in the Lipetsk region, Russian Federation. Unlike other pinworms, S. stroma inhabits the small intestine of the host. The obtained nucleotide data are the first sequence data for S. stroma from Russia. The phylogeny of the genus Syphacia is discussed.
Key words: coevolution, host specificity, pinworm, rodents, Syphaciini, yellow-necked mouse.
The nematodes of the genus Syphacia parasitise rodents, mainly Muridae. Unlike the majority of congeners common in the caecum, Syphacia stroma inhabit the small intestine. The species was described from wood mice, Apodemus sylvaticus, by Linstow (Linstow, 1884) as Oxyuris stroma. Then Seurat (1915) synonymised Oxyuris stroma with Syphacia obvelata Rudolphi, 1802. Later Morgan concluded that S. stroma is a separate species from S. obvelata (Morgan, 1932).
After comprehensive revision, the genus Syphacia Seurat, 1916 was divided into ten groups according to morphological features (Quentin, 1971). Syphacia stroma was included into the 'group IX' together with sister species Syphacia emileromani Chabaud, Rausch & Desset, 1963. Smaller size of egg-shells was proposed as a distinguishing feature of S. emileromani. Hugot (1988) suggested splitting the genus Syphacia into three subgenera, and S. stroma was included into the type subgenus Syphacia (Syphacia sensu stricto).
An application of molecular methods to pinworm phylogeny elucidated the relationships between Syphacia species. Phylogenetic analysis of the genus is based on two loci of nuclear ribosomal repeats: partial 28S rDNA and complete ITS1-5.8S-ITS2 and a portion of mitochondrial cytochrome c oxidase gene subunit 1 (Stewart et al., 2018; Behnke et al., 2022). Topology of the trees inferred from these sequences was mainly concordant with the phylogenetic
hypothesis based on morphology: S. stroma is a sister species to S. emileromani and together with S. agraria these belong to the separate clade in the subgenus Syphacia (Gorelysheva et al., 2021).
Syphacia stroma is considered to be a specific parasite of Apodemus mice: A. sylvaticus and A. flavicollis (Quentin, 1971; Tenora & Meszaros, 1975; Genov, 1984; Stewart et al., 2018; Behnke et al. , 2022). In some cases, S. stroma was reported as a parasite of other rodent hosts, e.g., Mesocricetus auratus (Hasegawa et al., 2008), but such identifications were not supported by molecular data. Remarkably, the co-invasion of the same host with S. stroma and S. frederici was reported in the UK (Stewart et al., 2018). Identification of Syphacia under light microscope is complicated due to the scarcity of males and similarity of female morphology throughout the genus; S. stroma and S. frederici are quite similar in appearance. Stewart et al. (2018) suggested to discriminate these species under low magnification microscopy by the shape of the tails. The tail of S. frederici was thinner and usually bent, but in some cases, it was straight. While the tail was straighter, the point of flexion is still clearly visible. This feature should be carefully studied for accurate identification.
In Russia, S. stroma was reported in Voronezh reserve in Voronezh region parasitising A. flavicollis, A. uralensis and Mus musculus (Romashova & Romashov, 2019), and in
© Russian Society of Nematologists, 2022; doi: 10.24412/0869-6918-2022-1-69-78 Published online 27 June, 2022
'Belogorye' reserve in Belgorod region parasitising A. flavicollis (Kononova & Prisniy, 2020). Referring to the book of Ryzhikov et al. (1979), S. stroma is a parasite of mice: M. musculus, A. flavicollis, A. uralensis, Micromys minutus in Europe and Apodemus speciosus in Asia. Also, it was reported for a wide range of hosts, but these findings seem to be accidental (Ryzhikov et al., 1979).
All the identifications of S. stroma in Russia were based only on morphology. The significance of morphological features for the identification of species of Syphacia is quite obscure and the composition of local populations is not clear. Thus, the aim of this research is to provide new morphological data for S. stroma and to base further identification of the genus Syphacia on nucleotide analysis.
MATERIAL AND METHODS
Trapping mammals. The fieldwork was carried out in August 2019 in Podgornoe, Lipetsk region (52°32' N, 39°30' E). Mammals were collected using Shchipanov's traps (Shchipanov, 1987). Two specimens of A. flavicollis were examined.
Nematode sampling. In the laboratory, rodents were euthanised by cervical dislocation and then dissected. Their intestinal tracts were placed in saline and examined in separate Petri dishes. Worms recovered from the intestinal tract of each animal
were then divided into two groups: some nematodes were transferred to 1.5 ml glass tubes containing 96% ethanol, while the remaining specimens were fixed in similar tubes using 4% formalin in saline heated to 60-80°C until further processing for DNA extraction and microscopy, respectively.
Morphological observation. Nematodes from the samples were transferred to a glycerin solution, and after evaporation of the water, were mounted in glycerin drops embedded into paraffin rings. Eleven females and seven males were studied under light microscopy and measured using a Leica DFC 425 C (Leica Microsystems, Germany) microscope.
For scanning electron microscopy (SEM) analysis, five female and three male nematodes of Syphacia were selected. The nematodes were dehydrated in ethanol series and acetone, underwent critical point drying, mounted onto aluminium stubs with double-face tape, and studied using a CamScan MV 2300 (TESCAN, Czech Republic).
Molecular profiles. Two loci of the Syphacia genome were selected for the study: the partial sequence of cytochrome c oxidase 1 (CO1 mtDNA) gene of the mitochondrial genome, the partial sequence of the large subunit (LSU). For DNA isolation, we used QIAmp DNA Mini Kit® (Qiagen, Germany). For DNA amplification, the Encyclo Plus PCR kit® (Evrogen, Russia) was used in accordance with the manufacturer's protocol. After screening CO1 mtDNA primers, we found the most
Table 1. Accession numbers and additional information for CO1 mtDNA sequences of Syphacia species from NCBI
GenBank.
Syphacia species Accession number Host Locality Reference
Syphacia agraria AB282589 Apodemus speciosus Japan: Hokkaido, Hidaka Okamoto et al., 2007
Syphacia agraria MN641848 Microtus arvalis Russia Gorelysheva et al., 2021
Syphacia agraria MN641850 Apodemus agrarius Russia Gorelysheva et al., 2021
Syphacia agraria MN641844 Apodemus agrarius Russia Gorelysheva et al., 2021
Syphacia emileromani AB282590 Apodemus argenteus Japan: Ehime, Saijyo Okamoto et al., 2007
Syphacia frederici AB282586 Apodemus speciosus Japan: Okayama, Hiruzen Okamoto et al., 2007
Syphacia frederici AB282587 Apodemus speciosus Japan: Iwate, Morioka Okamoto et al., 2007
Syphacia frederici AB282588 Apodemus speciosus Japan: Hokkaido, Hidaka Okamoto et al., 2007
Syphacia frederici AB282593 Apodemus speciosus Japan: Oita, Oita Okamoto et al., 2007
Syphacia frederici MN641868 Apodemus uralensis Russia Gorelysheva et al., 2021
Table 1 (continued). Accession numbers and additional information for CO1 mtDNA sequences of Syphacia species
from NCBI GenBank.
Syphacia frederici MF142425 Apodemus sylvaticus United Kingdom Stewart et al., 2018
Syphacia frederici MF142426 Apodemus sylvaticus Portugal Stewart et al., 2018
Syphacia frederici MF142429 Apodemus sylvaticus United Kingdom Stewart et al., 2018
Syphacia nigeriana AB282581 Eothenomus smihii Japan: Ehime, Saijyo Okamoto et al., 2007
Syphacia nigeriana MN641860 Microtus obscurus Russia Gorelysheva et al., 2021
Syphacia nigeriana MN641851 Microtus arvalis Russia Gorelysheva et al., 2021
Syphacia nigeriana MN641856 Microtus arvalis Russia Gorelysheva et al., 2021
Syphacia nigeriana MN641853 Microtus arvalis Russia Gorelysheva et al., 2021
Syphacia nigeriana MN641866 Microtus arvalis/ obscurus hybrid Russia Gorelysheva et al., 2021
Syphacia nigeriana MN641859 Microtus arvalis/ obscurus hybrid Russia Gorelysheva et al., 2021
Syphacia nigeriana MN641865 Microtus obscurus Russia Gorelysheva et al., 2021
Syphacia nigeriana AB282583 Clethrionomys rufocanus Japan: Hokkaido, Niseko Okamoto et al., 2007
Syphacia nigeriana AB282584 Clethrionomys rufocanus Japan: Hokkaido, Tobetsu Okamoto et al., 2007
Syphacia nigeriana AB282585 Clethrionomys rufocanus Japan: Hokkaido, Rishiri Is. Okamoto et al., 2007
Syphacia obvelata MF142430 Mus domesticus United Kingdom Stewart et al., 2018
Syphacia obvelata MF142432 Mus musculus Poland Stewart et al., 2018
Syphacia obvelata MH427273 Mus musculus Czech Republic Gouy de Bellocq et al., 2018
Syphacia obvelata MF142433 Mus musculus United Kingdom Stewart et al., 2018
Syphacia obvelata NC029239 - China Wang et al., 2016
Syphacia ohtaorum AB282592 Mus caroli Japan: Okinawa Okamoto et al., 2007
Syphacia stroma MF142427 Apodemus sylvaticus United Kingdom Stewart et al., 2018
Syphacia stroma MF142422 Apodemus sylvaticus United Kingdom Stewart et al., 2018
Syphacia stroma MF142419 Apodemus sylvaticus Ireland Stewart et al., 2018
Syphacia stroma MF142428 Apodemus sylvaticus United Kingdom Stewart et al., 2018
Enterobius vermicularis -outgroup NC011300 - Republic of Korea Kang et al., 2009
effective primer mix to be ScyphCO1F (5'-TGG TCT GGT TTT GTT GGT AGT T-3') and ScyphCO1R (5'-AAC CAC CCA ACG TAA ACA TAA A-3'), as proposed by Okamoto et al. (2007). The thermal cycling protocol used for these primers was 94°C for 5 min and then 35 cycles of 94°C for 30 s, 48°C for 1 min, and 72°C for 1.5 min,
followed by a final extension at 72°C for 5 min. To amplify LSU rDNA, the primers C1 (5'-ACC CGC TGA ATT TAA GCA T-3') and D2 (5'-TCC GTG TTT CAA GAC GG-3') proposed by Okamoto et al. (2009) were used. PCR cycling parameters for the amplification of LSU rDNA included primary denaturation at 94°C for 1 min, followed by 35
cycles of 94°C for 30 s, 55°C for 30 s, and 72°C for 30 s, followed by post-amplification extension at 72°C for 7 min. DNA sequencing was performed at the Genome Centre for Collective Use 'Genotech'. Sequences were obtained for several specimens from two different hosts, but all of them were identical, so we deposited only one sequence for each locus. Accession number of the obtained S. stroma LSU rDNA (28S rDNA) sequence is ON510071. Accession number of the obtained S. stroma CO1 mtDNA sequence is ON479655.
RESULTS Syphacia stroma (Linstow, 1884)
All the measurements are given in pm in the form of mean ± standard deviation with size range in brackets, for example: 3275 ± 65 (3200-3350).
Sequences retrieved from NCBI GenBank (http://www.ncbi.nlm.nih.gov) for 28S rDNA (LSU) are given in Table 1; for CO1 mtDNA they are given in Table 2. Sequences were aligned with MUSCLE method (Edgar, 2004). Models of molecular evolution were defined with jModeltest (Posada, 2008). Phylogenetic analyses were performed using two ML method. ML tree was reconstructed in IQtree program in webserver http://iqtree.cibiv.univie.ac.at/ with 100,000 iterations.
Morphology. Cephalic vesicle present. The cuticle is transversely striated. Cervical alae are absent.
Male (n = 7). Body 1649 ± 76 (1552-1737) long; 98 ± 4 (94-103) wide. Pharynx 262 ± 18 (237-281) long with 197 ± 11 (184-210) long procorpus and 60 ± 10 (56-63) diameter bulb. Nerve ring at the level
Table 2. Accession numbers and additional information for 28S rDNA (LSU) sequences of Syphacia and Syphabulea
species from NCBI GenBank.
Syphacia species Accession number Host Locality Reference
Syphabulea tjanschani MH443065 Sciurotamias davidianus China: Zhangjiakou, Hebei Province Li et al., 2019
Syphacia agraria AB500167 Apodemus speciosus Japan: Hokkaido, Hidaka Okamoto et al., 2009
Syphacia agraria MT929757 Apodemus agrarius Russia Gorelysheva et al., 2021
Syphacia emileromani AB500169 Apodemus argenteus Japan: Hokkaido, Apoi Okamoto et al., 2009
Syphacia frederici MT929764 Apodemus uralensis Russia Gorelysheva et al., 2021
Syphacia frederici AB500173 Apodemus speciosus Japan: Hokkaido, Hidaka Okamoto et al., 2009
Syphacia montana AB500165 Clethrionomys rex Japan: Hokkaido, Rishiri Is. Okamoto et al., 2009
Syphacia montana MT929762 Microtus arvalis Russia Gorelysheva et al., 2021
Syphacia muris EF464553 - USA Feldman et al., 2007
Syphacia obvelata AB500176 Mus musculus Japan: Honshu, Osaka, Suita Okamoto et al., 2009
Syphacia ohtaorum AB500177 Mus caroli Japan: Okinawa, Okinawa Is. Okamoto et al., 2009
Syphacia petrusewiczi AB500166 Clethrionomys rutilus Japan: Hokkaido, Notsuke Okamoto et al., 2009
Syphacia rifaii LC038095 Bunomys penitus Indonesia: Southeast Sulawesi, Mekongga Dewi, 2015
Syphacia stroma LC038098 Mesocricetus auratus Czech Republic Dewi, 2015
Syphacia vandenbrueli AB500178 Micromys minutus Japan: Honshu, Hiroshima, Hiroshima Okamoto et al., 2009
Syphatineria sp. LC038099 Lariscus hosei Indonesia: Kalimantan Dewi, 2015
111 ± 5 (106-118) from apex. Excretory pore at the level 418 ± 25 (383-442). Three cuticular 59 ± 11 (49-73), 67 ± 17 (55-91), 81 ± 15 (53-84) long mamelons present on the ventral side of the body at 663 ± 16 (646-685) from apex. Second mamelon at 475 ± 25 (449-506), third 229 ± 24 (200-259) from anus. The tail is truncated ventrally, ends with a conical process with sharp tip. Process length 166 ± 12 (159-184). Spicule length 74 ± 3 (71-78), gubernaculum spindle-shaped length 43 ± 5 (36-49).
Female (n = 11). Body 3816 ± 327 (3395-4305) long; 272 ± 21 (237-300) wide. The pharynx 361 ± 23 (337-394) long with 261 ± 17 (234-284) long procorpus and 84 ± 6 (74-90) diameter bulb. Nerve ring at the level 134 ± 4 (131-142). Excretory pore and vulva at 580 ± 55 (519-662) and 780 ± 109 (614-942) from the anterior end, respectively. Eggs 131 ± 4 (125-137) long and 43 ± 1 (42-44) wide. Conical tail elongated and narrow 509 ± 34 (451539) long.
Fig. 1. Morphological features of the studied Syphacia stroma, SEM: A - female apical view, B - male apical view, C - fourth-stage larvae (L4) apical view, D - female cuticular teeth, E - male cuticular teeth, F - female tail, G - female anterior end of the body, H - male anterior end of the body, I - female cuticle.
Locality. Podgornoe, Lipetsk region (52°32' N, 39°30' E).
Localisation. Small intestine.
SEM. The facial mask is slightly laterally elongated, with two hemispherical submedian papillae and one amphid on each side, cephalic plate is rounded (Fig. 1A-C). Three cuticular teeth are present (Fig. 1D & E). The longitudinal media thickening of each tooth is not developed. A transverse round thickening is present at the edge of each tooth. Transverse ridges of denticles near the anterior margin are absent. Cuticular collar is not well developed and present on females only. An annulated cuticle without longitudinal ridges on each cuticular ring (Fig. 1I). Lateral alae are thin (Fig. 1I); cervical alae are absent (Fig. 1G & H). Lateral alae are at 30 ^m from the apex (Fig. 1G & H). Tail is conical (Fig. 1F).
Phylogenetic relationships. Phylogenetic relationships of the studied Syphacia inferred from analysis of partial LSU rDNA (28S rDNA) are shown in Figure 2. The obtained sequence and the most similar sequences found on the NCBI GenBank enabled us to construct the 685 bp long alignment. The S. stroma sequences obtained in this study and sequences retrieved from the NCBI GenBank form a clade with 99% support. Monophyly of Syphacia including S. petrusewiczi (subgenus Seuratoxyuris) is strongly supported (100%). Syphacia stroma was in one clade with sister species S. emileromani from Japan and with S. agraria from Europe. The clade that included Syphacia parasitising rats, S. muris, S. rifaii and S. ohtaorum, was not supported.
A phylogenetic tree inferred from analysis of the partial mitochodrial CO1 mtDNA is shown in Figure 3. Its topology and composition are similar to that inferred from LSU rDNA data. The total length of the analysed matrix for CO1 mtDNA region was 660 bp.
In this cladogram, there was 100% posterior probability support of monophyly S. stroma populations. The isolate from Russia is identical to the isolates from the UK. Syphacia stroma is a sister species to S. emileromani from Japan; these two species form a clade with 87% support.
The genus Syphacia splits into two branches. The first one consists of S. stroma, S. emileromani, S. agraria and S. ohtaorum (100% support). The second one includes S. nigeriana, S. frederici and S. obvelata.
DISCUSSION
All the studied Syphacia specimens recovered from the small intestine of A. flavicollis showed uniform morphology that corresponds to the descriptions of S. stroma (Morgan, 1932; Ryzhikov et al., 1979). Morphological identification was supported by sequences of the nuclear 28S rDNA (Fig. 2) and CO1 mtDNA (Fig. 3). The co-invasion of this host with both S. stroma and S. frederici was previously reported in the UK (Stewart et al., 2018), but uniform morphology of the specimens from this Russian population indicates the presence of a single Syphacia species. Also, the localisation of the discovered nematodes in the small intestine supports their identification as S. stroma, as S. frederici was mainly discovered in the caecum of A. flavicollis.
100
87
53
100
85r S. stroma Russia
100
LC038098 S. stroma Indonesia - AB5001S9 S emileromani Japan 99 r AB500167 S. agraria Japan MT929757 S. agraria Russia AB500177 S. ohtaorum Japan
100 I-LC038095 S. rifaii Indonesia
I-EF464553 S. muris USA
96
97
-AB500178 S. vandenbrueiiJapan MT929764 S. frederici Russia — AE500173 S. frederici Japan
i— AB500176 S. obvelata Japan i AB5D0165 S. montana Japan 1 OCr MT929762 S. montana Russia -- AB500166 S. petrusewiczi Japan
LC038099 Syphatineria sp. -MH443065 Syphabuiea tjanschani
0.20
Fig. 2. ML tree of Syphacia species inferred from the analysis of the LSU (28S rDNA) data with bootstrap values near the nodes. The scale bar represents the number of nucleotide substitutions per site. Nucleotide substitution model - TN93.
100
97
- АВ2825Э2 S. ohtaorum Japan -AB282589 S. agraria Japan
SO г_rU
79I Ml
62
87
100
97
60
96
79
82I
60
MN641848 S. agraria Russia MN641850 S. agraria Russia MN641B44 S. agraria Russia
-AB282590 S. emileromani Japan
MF142427 S. stroma UK 100 MF142422 S. stroma UK
S. stroma Russia -
MF142419 S. stroma UK MF142428 S. stroma UK AB282581 5. nigeriana Japan MN641860 S. nigeriana Russia MN641851 S. nigeriana Russia MN641856 S. nigeriana Russia MN641853 S. nigeriana Russia MN641866 S.nigeriana Russia
99
99
Гм
98] AI
98lAB
93
93
MN641859 S. nigeriana Russia MN641865 S nigeriana Russia 98| AB282583 S. nigeriana Japan AB282584 5. nigeriana Japan AB282585 S. nigeriana Japan
r AB282586 S. frederici Japan gg, AB282587 S. frederici Japan _TT—AB2825B8 S. frederici Japan 95T— AB282593 S. frederici Japan
— MN641868 S. frederici Russia
- MF142425 S. frederici UK MF142426 S. frederici UK
100
100
LT'
¡3L IUI
99
93 96 84'
93L MF142429 S. frederici UK MF142430 S. obvelata UK MF142432 S. obvelata UK MH427273 S. obvelata Czech MF142433 S. obvelata UK АБ282591 S. obvelata Japan
-NC029239 S. obvelata USA
--NC011300 E. vermiculares
0.050
Fig. 3. ML tree of Syphacia species inferred from the analysis of the CO1 mtDNA data with bootstrap values near the nodes. The scale bar represents the number of nucleotide substitutions per site. Nucleotide substitution model -TIM3 + F + G4.
The body sizes of the studied male and female specimens correspond to those described for S. stroma in the literature (Morgan, 1932; Ryzhikov et al., 1979), with only the range for some features differing, e.g., the minimal length values of the pharynx for both sexes were smaller than previously described. The same goes for the minimal value of pharyngeal bulb size of females, egg-shell length, and distance from anterior end to vulval opening. The size of the male spicules is the same as in original and other descriptions, but the gubernaculum (36-49) is larger than described by Morgan (30). At the same time, the minimal value for gubernaculum length is smaller than reported by Ryzhikov (40-50).
The cuticular surface morphology of Syphacia studied under SEM proved to be a rich source of diagnostic features for this genus (Wiger et al., 1978;
Barns et al., 1979). The surface structures of S. stroma were considered by Wiger et al. (1978) as the most primitive between congeners. The surface structures of the Russian specimens (Fig. 1) were similar to those reported by Wiger et al. (1978), but there were still some differences. In Russian specimens we showed that the collar is weakly developed and can be found only in females (Fig. 1G). The collar of S. stroma is an invagination of a thinner cuticle, and it differs from that of S. frederici. Moreover, the annulated cuticle of our specimens lacks longitudinal depressions on each cuticular ring (Fig. 1I), which were reported previously (Wiger et al., 1978: P. 27, Fig. 4). However, such differences might be an artefact of the dehydration/drying of nematodes for SEM study.
We analysed the structure of the anterior end, cuticular teeth and surface of the body cuticle for
females, males and fourth-stage larvae (L4). No difference between them was observed except the size and slight variation in the shape of the facial mask and cephalic plate (Fig. 1A-C). Cephalic plate (area around lips) and facial mask (term proposed by Wiger et al. (1978) for an area around a plate -usually ornamented with tiled pattern, surrounding cephalic papillae and amphids) are slightly elongated in females of the Russian population along the transverse axis (Fig. 1A) but more round in males (Fig. 1B). In our opinion the round shape of plate and facial mask are basal features for the genus Syphacia as in males and larvae it is always round (Fig. 1C).
As mentioned above, morphological identification of S. stroma was confirmed by nucleotide sequences of the nuclear 28S rDNA (Fig. 2) and CO1 mtDNA (Fig. 3). In both phylogenetic trees (Figs 2 & 3) S. stroma forms a clade with its sister species S. emileromani from Japan and S. agraria from Europe. Common features can be found in S. stroma and S. agraria morphology (Gorelysheva et al., 2021): the absence of prominent longitudinal ornamentation of cuticuar rings and the lack of cervical alae (Fig. 1G-I). Representatives of another clade of Syphacia, which includes S. nigeriana, S. frederici and S. obvelata, had an annulated cuticle with longitudinal ornamentation on each cuticular ring (Dick & Wright, 1974; Wiger et al., 1978; Barus et al., 1979; Gorelysheva et al., 2021). Thus, at least some features of the cuticular surface correspond to the Syphacia clades inferred from analysis of nucleotide sequences.
In conclusion, our study provides the first report of S. stroma in Russia supported by molecular data. We confirmed that S. stroma haplotype from the European part of Russia is identical to S. stroma from the UK and obtained new morphological data, extending the information of body size variability, and providing SEM images. Further studies on additional samples collected from various hosts and localities would be required to obtain the full picture of morphological and genetic variability.
ACKNOWLEDGMENTS
We thankfully acknowledge the practical and logistic help of our colleagues, namely: Mr B.D. Efeykin, Drs E.S. Ivanova and S.E. Spiridonov from the Centre of Parasitology of Severtsov's Institute of Ecology and Evolution of the Russian Academy of Sciences. All the SEM studies were carried out at the Joint Usage Centre 'Instrumental Methods in Ecology' at the Severtsov's Institute of Ecology and Evolution of the Russian Academy of Sciences, and
we would like to thank Dr A.N. Neretina from this Centre. The study was supported by RSF (grant no. 19-74-20147).
All procedures in the present study were approved by the Animal Care and Use Committee of the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences and complied with the Federal Law of the Russian Federation no. 498-FZ from 19 December 2018 (on responsible treatment of animals). The collection of rodent material was possible through the general permit issued by the government for the scientific institutions of the Russian Academy of Sciences (including A.N. Severtsov Institute of Ecology and Evolution) to study non-endangered species of animals throughout the territory of the Russian Federation.
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URL: http://www.ncbi.nlm.nih.gov (accessed: March 25, URL: http://iqtree.cibiv.univie.ac.at/ (accessed: April 5, 2022). 2022).
Д.И. Горелышева и И.М. Ермаков. Молекулярная и морфологическая характеристика Syphacia stroma (Linstow, 1884) (Nematoda, Oxyurida) из России, Липецкая область.
Резюме. Предоставлены новые молекулярные и морфологические данные об острицах Syphacia stroma из Российской Федерации, собранных от двух особей желтогорлой мыши Apodemus flavicollis в Липецкой области. В отличие от других остриц S. stroma обитает в тонком кишечнике грызунов. Полученные нуклеотидные данные по S. stroma из России публикуются впервые. Также обсуждается филогения рода Syphacia на основе молекулярных данных и сканирующей электронной микроскопии.
