Kontrimavichusia hobergi, Makarikov & Stakheev, 2024

Makarikov, Arseny A. & Stakheev, Valeriy V., 2024, New species of Kontrimavichusia Makarikov & Binkienė, 2022 (Eucestoda: Hymenolepididae) from arvicoline rodents (Rodentia: Cricetidae) from the North Caucasus, European Journal of Taxonomy 947, pp. 268-288 : 275-282

Kontrimavichusia hobergi sp. nov.

urn:lsid:zoobank.org:act:8EBE9219-C6BA-4B85-8740-3A3E05F51581

Figs 3–6 , Tables 1–2

Diagnosis

Kontrimavichusia hobergi sp. nov. has morphological characters typical of the genus Kontrimavichusia , namely rhynchus armed with cricetoid-like hooks, apex of rostellum invaginable and blades of retracted hooks directed anteriorly, suckers armed with minute spines, ventral canals connected by irregularly spaced transverse anastomoses, copulatory part of vagina surrounded by circular musculature and covered externally by dense layer of intensely-stained cells, labyrinthine uterus extending beyond osmoregulatory canals into both lateral fields, situated dorsally to osmoregulatory canals and genital ducts and embryophore without polar filaments ( Makarikov & Binkienė 2022).

Etymology

This species has been named in honour of the outstanding parasitologist Dr Eric P. Hoberg in recognition of his seminal and critical studies of parasites of vertebrates, helminth systematics, biogeography, ecology, phylogeny and evolution. It is also recognition of his significant contribution to the advancement of parasitology and the preservation of important archival materials on helminths during his tenure as chief curator of the U.S. National Parasite Collection from 1990 to 2014.

Type material

Holotype

RUSSIA • Republic of North Ossetia-Alania, Alagirsky District, suburbs of Verkhniy Tsey ; 42º48′02″ N, 43º56′03″ E; 27 Jul. 2017; A.A. Makarikov leg.; ISEA AM17-236#3 (ex 379).

Paratypes

RUSSIA • 1 spec; same data as for holotype; ISEA AM17-236#1 • 1 spec; same data as for holotype; ISEA AM17-236#2 (ex 378) • 1 spec; same data as for holotype; ISEA AM17-240#2 • 1 spec; same data as for holotype; ISEA AM17-242 (ex 382) • 1 spec; same data as for holotype; ISEA AM17-243#1 (ex 377) • 1 spec; same data as for holotype; ISEA AM17-243#2 • 1 spec; same data as for holotype; SEA AM17-243#3 (ex 376) • 1 spec.; same data as for preceding; 25 Jul. 2017; ISEA AM17-206 (ex 477) • 1 spec.; same data as for preceding; ISEA AM17-211 (ex 474) • 1 spec.; same data as for preceding; ISEA AM17-213 • 1 spec.; same data as for preceding; 26 Jul. 2017; ISEA AM17-222#1 (ex 368) • 1 spec.; same data as for preceding; ISEA AM17-222#2 (ex 369) • 1 spec.; same data as for preceding; ISEA AM17-226#1 (ex 482) .

Other material examined

RUSSIA • 1 spec.; same data as for holotype; 26 Jul. 2017; ISEA AM17-221#3 (ex455) • 1 spec.; same data as for preceding; ISEA AM17-221#4 (ex456) .

Type host

Microtus daghestanicus (Shidlovsky, 1919) ( Rodentia : Cricetidae : Arvicoline).

Description ( Figs 3–4 )

[Based on 11 stained and mounted specimens and 7 scoleces mounted in Berlese’s medium.] Fully developed strobila 65–78 (74; n = 7) mm long, with maximum width 1.7–2.1 (1.8; n = 5) mm at level gravid proglottides. Strobila flat, consisting of 400–480 craspedote proglottides. Scolex slightly compressed dorso-ventrally, 245–360 wide (301; n = 3), not clearly distinct from neck. Suckers small, thick-walled, rounded or oval, cup-shaped, 120–155 × 100–120 (138 × 109; n = 12), usually reaching lateral margins of scolex, armed with minute (less than 1 long) spines; spines covering entire sucker surface ( Fig. 3A–B ). Rostellar pouch 130–164 × 95–125 (148 × 112; n = 3), with muscular walls, its bottom not reaching level of posterior margin of suckers. Rostellum 105–161 × 50–70 (130 × 61; n = 3), sac-like, muscular, apex invaginable; when rostellar apparatus retracted, rostellar hooks with blades directed anteriorly ( Fig. 3B ). Rhynchus 60–73 long and 50–75 wide, with well-developed circular musculature, armed with single crown of 18–22 (n = 7) rostellar hooks of cricetoid-like type ( Fig. 3C ). Rostellar hooks with relatively short handle and straight blade; axis of blade situated to axis of guard at acute angle; guard narrow in anterior surface; handle and blade slightly shorter or equal in length with guard. Hook measurements: total length 20–24 (21.8; n = 39), handle 8–9.5 (8.7; n = 39), blade 7.8–9.4 (8.6; n = 39) and guard 8–10.6 (9; n = 39). Neck 200–240 wide (n = 3), approximately equal in width with scolex ( Fig. 3A–B ).

Ventral osmoregulatory canals 40–110 (79; n = 36) wide, connected by irregularly spaced transverse anastomoses (present in up to 23% proglottides) ( Fig. 3D ). Dorsal osmoregulatory canals very thin, 3–8 (5; n = 36) wide at level of hermaphroditic proglottides, usually situated directly dorsal (not shifted left or right) to ventral canals. Genital pores unilateral, dextral ( Fig. 3D–E ). Genital ducts pass dorsally to both ventral and dorsal longitudinal osmoregulatory canals. Development of proglottides gradual, protandrous.

Mature proglottides 180–240 × 970–1140 (210 × 1085; n = 29), transversely elongate, trapezoid ( Fig. 3D–E ). Testes 3, relatively large, almost equal in size, 135–210 × 95–150 (169 × 119; n = 36), round or oval, most often situated in triangle with flat angle (anterior antiporal testis shifted to lateral side of proglottis in relation to posterior antiporal testis) or, rarely, in triangle with right angle or in one row, poral testis separated from two antiporal testes by female gonads. Number and distribuition of testes constant, no variation in testes number observed, proglottis with three antiporal testes or two poral testes appear infrequent. Cirrus-sac relatively short, with thick muscular walls, club-shaped, 270–320 × 56–75 (296 × 66; n = 28). Antiporal part of cirrus-sac substantially crossing poral ventral longitudinal canal ( Fig. 3E–F ). Genital atrium simple, cup-shaped, opens laterally, approximately in middle of lateral proglottis margin. Cirrus large, 100–128 × 24–39 (112 × 31; n = 25), cylindrical, armed with very small (up to 1.0–1.5 long), needle-shaped spines ( Fig. 4A ). Internal seminal vesicle with circular musculature, ovoid, 130–180 × 52–70 (155 × 58; n = 28), occupying half of cirrus-sac length ( Fig. 3E–F ). External seminal vesicle, 105–190 × 82–120 (127 × 93; n = 28), round or oval, clearly distinguishable from vas deferens, normally smaller than seminal receptacle.

Ovary 280–396 (330; n = 25) wide, median, transversely elongate, fan-shaped, irregularly lobed, ventral to male genital organs, occupying less than half of median field, overlapping testes ( Fig. 3E ). Vitellarium 70–116 × 120–185 (85 × 145; n = 25), postovarian, slightly shifted to lateral side of proglottis, slightly lobed. Vagina tubular, clearly distinct from seminal receptacle; ventral to cirrus-sac. Copulatory part of vagina 94–120 × 8–32 (105 × 16; n = 25), shorter than cirrus-sac, thick-walled, surrounded by circular musculature and covered externally by dense layer of intensely stained cells; proximal part of vagina infundibular ( Figs 3F , 4A ). Conductive part of vagina indistinct. Seminal receptacle relatively large, transversely elongate, 315–470 × 55–100 (387 × 75; n = 25).

Uterus appears as perforated, transversely-elongate band, situated dorsally to testes, genital ducts and osmoregulatory canals and extending laterally beyond longitudinal osmoregulatory canals. With proglottis development, uterus forms numerous diverticula on ventral side and becomes labyrinthine in terminal postmature proglottides. Testes persist in postmature proglottides; cirrus-sac and vagina persist in gravid proglottides ( Fig. 4B ). Gravid proglottides transversely elongate, 260–390 × 1690–2040 (325 × 1856; n = 20). Fully developed uterus labyrinthine, occupying entire median field, extending bilaterally, dorsally, beyond longitudinal osmoregulatory canals ( Fig. 4C ). Uterus contains numerous (up to 1500–1600) small eggs. Eggs 52–57 × 60–66, subspherical, with very thin outer coat (up to 0.7–1 thick); oncospheres 19–23 × 26–31 ( Fig 4D ). Embryophores very thin, 23–28 × 33–38, without polar filaments. Embryonic hooks small, antero-lateral hooks (9.8–10.7), much more robust than slender postero-lateral (9.8–10.5) and median (10.3–11) hooks ( Fig. 4E ).

Distribution

Russia (Republic of North Ossetia – Alania).

Remarks

Kontrimavichusia hobergi sp. nov. is readily distinguishable from K. asymmetrica by the triangular arrangement of the testes; those in the type species most often are situated in one row. The number of testes distinguishes the new species from K. testiculata sp. nov.: the former has three 3 per proglottis, the latter has 4–6 per proglottis. The cirrus-sac in K. hobergi substantially crosses the poral osmoregulatory canals; in contrast, the cirrus-sac of K. asymmetrica overlaps or rarely crosses the ventral longitudinal canal. The distal end of the rostellar pouch does not attain the level of the posterior margins of the suckers in K. hobergi , directly contrasting with the condition in K. asymmetrica . In addition, specimens of K. hobergi differ from K. asymmetrica and K. testiculata by distinctly smaller dimensions of the fully developed strobila. Further, the cirrus-sac is larger than in K. asymmetrica but smaller than in K. testiculata ; the cirrus of the new species is smaller than in K. testiculata . The ovary of K. hobergi is narrower than in both congeners ( Table 1 ).

Molecular phylogenetic analysis

Phylogeny was based on the nuclear ribosomal 28S rRNA gene. The length of the alignment after trimming was 1042 nucleotides. Consistent with a previous study, the monophyly of each of the two clades corresponding to Kontrimavichusia and Hymenolepis is well supported (0.97 and 1.0 posterior probability, respectively) ( Makarikov & Binkienė 2022). Further, we demonstrated at least four independent phylogenetic lineages within the Kontrimavichusia clade including the two species from the North Caucasus described herein, with differences between all available sequences up to 1–11 bp ( Fig. 5 ). Current analyses strongly support the generic allocation of those species to the genus. One of those lineages is represented by specimens of K. asymmetrica (sensu stricto) from Europe from Microtus agrestis (Linnaeus, 1761) (GenBank: GU166232, HM138528, ON562540 and ON562542–ON562544) and M. arvalis (Pallas, 1778) (GenBank: ON562541). The second lineage consists of species from the North Caucasus, namely K. testiculata sp. nov. and K. hobergi sp. nov. including the sequence from M. majori from Turkey (GU166234) attributed to K. asymmetrica (sensu lato) by Haukisalmi et al. (2010). It distinctly differs from the K. asymmetrica lineage by 8–9 bp. However, interspecific differences based on 28S gene in the Caucasian cluster are not pronounced. The two remaining lineages represented by specimens from Chionomys nivalis (Martins, 1842) from France (GU166231) and Dinaromys bogdanovi (Martino, 1922) from Bosnia (GU166233). Those differ from Caucasian linage by up to 11 bp and 7 bp respectively.

Phylogeny was based on the mitochondrial nad1 gen. The length of the alignment after trimming was 731 nucleotides. Until present, sequences of nad1 gen of K. asymmetrica were missing in GenBank. We used for analysis the sequences of K. asymmetrica (sensu stricto) from Eastern Europe ( Lithuania and the Republic of Bashkortostan, Russia) and two new species from the North Caucasus K. testiculata sp. nov. and K. hobergi sp. nov. that we obtained. Three well-supported lineages within Kontrimavichusia corresponded to morphologically recognized species ( Fig. 6 ). Unlike the 28S rRNA gene sequences, mitochondrial gene nad1 provided strong evidence for the description of K. testiculata and K. hobergi . The interspecific pairwise distances between lineages of K. testiculata and K. hobergi vary within 4.76– 5.81% (33–40 bp). Also, both species distinctly differ from K. asymmetrica (sensu stricto) by 13.36– 14.35% (84–92 bp) and 14.51–15.32% (91–98 bp) respectively ( Table 2 ).

Among these, the level of intraspecific differences of the lineages based on nad1 gen has the following values: in the lineage of K. asymmetrica (sensu stricto) the two specimens from the same locality (Republic of Bashkortostan, Russsia) have no intraspecific variability, while the sequence originated from the relatively remote population (more than 2000 km) in Lithuania differs from these by 0.69% (5 bp) ( Table 2 ); in K. testiculata sp. nov. from the Republic of Adygeya the intraspecific differences reached up to 0.97% (7 bp), while the sequences from Karachay-Cherkess Republic showed slightly higher values of intraspecific variability 1.11%–1.81% (8–13 bp); all sequences of K. hobergi sp. nov. originating from the same locality showed up to 0.14%–0.41% (1–3 bp) intraspecific variability.

Figures

Fig. 3. Kontrimavichusia hobergi sp. nov. A. Paratype (ISEA AM17-242), scolex, dorso-ventral view. B. Paratype (ISEA AM1 17-243#3), scolex, sub-lateral view. C. Holotype (ISEA AM17-236#3) (left) and paratype (ISEA AM 17-236#2) (centre, right), rostellar hooks in profile and frontal view (note narrow hook guard). D. Holotype, male mature proglottides, dorsal view. E. Holotype, hermaphroditic mature proglottis, dorsal view. F. Holotype, genital ducts, dorsal view. Scale bars: A–B, F = 100 µm; C = 10 µm; D–E = 300 µm.

Fig. 4. Kontrimavichusia hobergi sp. nov. A. Paratype (ISEA AM17-236#1), cirrus and vagina, ventral view. B. Holotype (ISEAAM17-236#3), pregravid proglottis, showing appearance of uterine diverticula, dorsal view. C. Holotype, gravid proglottis, showing labyrinthine uterus, dorsal view. D. Holotype, egg. E. Holotype, embryonic hooks. Abbreviations: al = anterolateral; m = median; pl = postero-lateral. Scale bars: A = 50 µm; B–C = 300 µm; D = 20 µm; E = 10 µm.

Fig. 5. Maximum likelihood phylogenetic tree of Kontrimavichusia Makarikov & Binkienė, 2022 and Hymenolepis Weinland, 1858 based on analysis of partial sequences of the 28S rRNA gene. Bootstrap support given for maximum likelihood analysis based on 1000 replicates. Bootstrap support values lower than 70% are not shown.

Fig. 6. Maximum likelihood phylogenetic tree of species of Kontrimavichusia Makarikov & Binkienė, 2022 based on analysis of partial sequences of the nad1 gen. Bootstrap support given for maximum likelihood analysis based on 1000 replicates. Bootstrap support values lower than 70% are not shown.