Oswaldocruzia lisnykiensis, Svitin, Roman, 2017

Svitin, Roman, 2017, Two new species of Oswaldocruzia (Nematoda, Molineidae) parasitising lizards in Ukraine, Zootaxa 4263 (2), pp. 358-368 : 359-363

Oswaldocruzia lisnykiensis sp. n.

Type-material: holotype male (collection no. NH6), allotype female (NA6); 4 male and 3 female paratypes (NP6.1). Type - specimens are stored in the collection of the Department of Parasitology of the Institute of Zoology, NAS of Ukraine .

Type-host. Anquis fragilis (Reptilia, Squamata , Anquidae).

Type-locality. Lisnyki village (Kyivska oblast, Ukraine); [50°17'18.3"N 30°33'58.6"E].

Other localities. Volynska oblast (3), Sumska oblast (2), Chernivets'ka oblast (2), Lvivska oblast (1), Khmelnytska oblast (1) ( Fig. 1 ).

Site of infection. Small intestine.

Etymology. The species is named after the type - locality.

Remarks. The new species is assigned to the genus Oswaldocruzia based on the presence of a well-developed cephalic vesicle, longitudinal cuticular ridges, the arrangement of caudal bursal rays and parasitism in squamate reptiles ( Durette-Desset, 1985; Anderson, 2000). The new species belongs to the Palaearctic group of Oswaldocruzia species characterised by “idiomorphic” spicules consisting of three main branches (blade, fork and shoe), with the spicular fork divided above the level of its distal third ( Ben Slimane et al., 1996). Within this group, two species, namely O. filiformis O. guyetanti and O. duboisi , are similar to O. lisnykiensis in synlophe structure. Oswaldocruzia filiformis have narrow cervical alae with slightly increased dorsal and ventral crests of each ala and O. guyetanti have wide cervical alae supported with one crest in contrast of what we observed in O. lisnykiensis having wide cervical alae consisting of three crests. Oswaldocruzia duboisi have cervical alae consisting of three crests on transverse section: a large triangular ventral crest is followed by two smaller crests on the dorsal side (a larger dorsal and a smaller, often indistinct, central one) (Ben Slimane et al., 1993; Svitin and Kuzmin, 2012). In O. lisnykiensis the ventral crest is less prominently increased than that in O. duboisi . Males in O. filiformis , O. guyetanti and O. duboisi possess a caudal bursa of type II, whereas O. lisnykiensis has a type III bursa. All three species are parasitic in amphibians.

A caudal bursa of type III was described for two other European species: O. skrjabini and O. problematica Ivanitsky, 1940 ( Travassos, 1937, Ivanitsky, 1940). However, Svitin (2015) assigned the bursa of O. skrjabini to type II, since rays 6 and 8 are joined at mid-length in this species. Cervical alae are much wider in O. skrjabini than in O. lisnykiensis , and the spicular fork and shoe in O. skrjabini have an extra branch each ( Svitin, 2015), in contrast to those in O. lisnykiensis .

Oswaldocruzia lisnykiensis can be easily distinguished from O. problematica by the shape of spicular shoe and synlophe structure: there are a distally folded shoe and wide cervical alae in O. problematica , whilst in O. lisnykiensis the shoe is distally expanded and cervical alae are narrow. Oswaldocruzia problematica is parasitic in an anuran amphibian Rana temporaria L. ( Anura , Ranidae ), whereas O. lisnykiensis is described from a reptilian host.

Description. General. In both sexes body thin, elongated with maximum width near mid-length. Cephalic vesicle smooth, undivided or consisting of two parts: wider anterior and narrow posterior. Body cuticle thin, without conspicuous transverse striations and with longitudinal ridges irregularly interrupted along body. Ridges appearing at level of anterior third of oesophagus and disappearing near caudal bursa in males and at level of phasmids in females. Apical structures ( Fig. 2 B; Fig. 3 C): 4 cephalic papillae, 6 externo-labial papillae, 2 amphids; oral opening triangular; dorsal oesophageal tooth present.

Oesophagus thin, club-shaped, cylindrical in anterior half, with constriction at level of nerve-ring, then widening posteriorly, posterior end rounded forming oesophageal bulb. Two excretory glands dissimilar in size, both somewhat longer than oesophagus. Position of excretory pore varying within posterior quarter of oesophagus. Nerve-ring encircling oesophagus near its mid-length ( Fig. 2 A). Small deirids situated at level of oesophagealintestinal junction in mature specimens; in juvenile specimens deirids observed at level of oesophagus mid-length.

Synlophe ( Fig. 2 C–E; Fig. 3 D,E) symmetrical; narrow cervical alae present at level of posterior 2/3 of oesophagus. On transverse sections at mid-oesophagus level each ala consisting of enlarged rounded triangular ventral crest and small crest on its dorsal side. Maximum width of cervical alae at level of posterior third of oesophagus. At this level, dorsal crest prominent, additional small central crest present, sometimes indistinct, and ventral one large, triangular, with rounded top. Struts and chitinoid reinforcements present. Cervical alae transforming into simple crests slightly posterior to level of oesophageal-intestinal junction. Number of crests at oesophagus level varying from 33 to 36, including cervical alae. About 44 simple irregularly interrupting crests at mid-body level ( Fig. 3 B).

Males. Measurements in text given for holotype followed by mean values, ranges of 29 specimens and standard deviation. Body 6.97 (7.0, 2.9–9.3; 1.1) mm long, 111 (138, 60–210; 28.4) wide ( Fig. 3 A). Cervical alae (measured in 4 specimens) 301 (308, 288–330) long, appearing at 153 (127, 83–171) from anterior end of body. Cephalic vesicle 79 (78, 55–108; 11.0) long, 44 (36, 30–44; 3.4) wide. Oesophagus 374 (400, 317–471; 32.9) long; 5.4% (5.9%, 4.8%–11.0%; 1.1) of body length. Oesophagus 24 (25, 20–30; 2.8), 27 (27, 22–57; 8.5) and 57 (55, 35–68; 8.2) wide at level of anterior end, mid-length and posterior dilation, respectively. Nerve ring at 203 (200, 152–245; 25.5) from anterior end of oesophagus; 54.3% (50.1%, 38.9%–61.6%; 5.5) of oesophagus length. Excretory pore at 378 (342, 208–446; 51.5) from anterior end of oesophagus; 5.4% (5.0%, 3.3%–8.0%; 0.9) of body length. Deirids at 398 (386, 320–488; 32.9) from anterior end of body; 5.7% (5.5%, 4.5%–6.3%; 0.6) of body length.

Caudal bursa symmetrical, tri–lobed, arrangement of rays corresponding to type III (classification of Durette- Desset, 1985) ( Fig. 2 G; Fig. 3 F). Rays 2 and 3 parallel, slightly separated from each other at tips, reaching edge of bursal membrane; ray 4 separated from rays 5 and 6, not reaching bursal margin; rays 5 and 6 parallel, slightly separated at tips, reaching bursal margin; ray 8 of independent origin, joined with ray 6 for 2/3 of its length, not reaching bursal margin. Dorsal ray of bursa bifurcated into two rays 10 posterior to base of rays 9. Each ray 10 with small extra branch. Genital cone (measured in 3 specimens) small, 20 (22, 18–29) long, 22 (23, 19–29) wide, bearing two papillae 0. Gubernaculum absent.

Spicules equal, 187 (192, 151–215; 17.2) long, surrounded by thin membrane, consisting of three main branches: blade, fork and shoe. Blade posteriorly divided in 4 tips; fork bifurcated in its distal half; shoe distally expanded with elongated knob-like process. All branches of same length and without extra branches ( Fig. 2 F).

Females. Measurements in text given for allotype followed by mean values, ranges of 29 specimens and standard deviation. Body 10.6 (10.7, 5.0–13.1; 1.9) mm long, 138 (171, 73–220; 34.8) wide. Cervical alae (measured in 4 specimens) 242 (295, 218–347) long, appearing at 158 (163, 70–167) from anterior end of body. Cephalic vesicle 73 (80, 43–100; 12.8) long, 33 (38, 26–45; 4.1) wide. Oesophagus 397 (434, 249–485) long; 3.4% (4.1%, 3.4%–7.6%; 0.8) of body length. Oesophagus width 17 (26, 16–35; 5.2), 18 (25, 13–35; 4.7) and 39 (57, 34– 78; 13.6) at level of anterior end, mid-length and posterior dilatation, respectively. Nerve-ring at 193 (204, 115– 225; 21.7) from anterior end of oesophagus; 47.9% (47.1%, 41.6%–50.0%; 2.2) of oesophagus length. Excretory pore at 331 (346, 220–450; 55.5) from anterior end of oesophagus; 2.8% (3.2%, 2.3%–4.9%; 0.5) of body length. Deirids 374 (436, 225–550, 81.2) from anterior end of body; 4.6% (4.1%, 3.1%–5.3%; 0.5) of body length. Tail tapering, 207 (231, 96–283; 34.6) long with or without thin cuticular needle on its end ( Fig. 2 I).

Vulva transverse slit, at 6.7 (6.9, 2.9–8.7; 1.3) mm from anterior end of body, postequatorial in position (at 64% (64.4%, 58.0%–72.7%; 2.7) of body length) ( Fig. 2 H).

Details of female genital system shape and measurements are given for allotype and 3 paratypes. Anterior uterus containing 11 (28, 41–48) eggs, posterior uterus containing 9 (16, 20–28) eggs; size of eggs at late morula stage 48–53 × 75–88 (N=20). All eggs observed in uteri at morula stage, eggs in ovejector and vagina containing larvae. Vagina vera 23 (22, 18–25) long, 60 (55, 50–60) in diameter. Anterior ovary beginning posterior to longer excretory gland, forming 1 (4, 1–22) bend. Posterior one beginning slightly anterior to vulva, forming 0 (4, 0–7) bends. Distance from anterior end of body to anterior ovary and from end of tail to posterior one 690 (683, 610– 750) and 370 (490, 450–650), respectively. Length of anterior infundibulum 50 (70, 48–113), width 35 (45, 45–55). Length of posterior infundibulum 58 (69, 63–85), width 45 (45, 35–50). Anterior sphincter 30 (34, 30–38) long, 35 (35) wide; posterior one 38 (37, 30–43) long and 30 (35) wide. Length of anterior part of ovejector 168 (169, 168– 170), maximum width 70 (60, 35–75), minimum width 48 (44, 30–53). Length of posterior part of ovejector 153 (141, 118–153), maximum width 68 (69, 70–83), minimum width 65 (66, 50–68).

Figures

FIGURE 1. Type localities and distribution of O. lisnykiensis sp. n. and O. lacertica sp. n. in Ukraine.

FIGURE 2. Oswaldocruzia lisnykiensis. A—anterior part of body, male, lateral view; B— (scale bar— 50 µm) anterior end, female, apical view; C – E—transverse sections: C—female, mid-oesophagus level, D—male, oesophageal-intestinal junction level, E—male, mid-body level; F—left spicule, lateral view; G—caudal bursa, ventral view; H—part of female genital system near vulva, lateral view; I—posterior part of body, female, lateral view.

FIGURE 3. Oswaldocruzia lisnykiensis. A—holotype, male, general view; B—fragment of synlophe at mid-body level, female, lateral view (arrows point to irregularly interrupted ridges); C—anterior end, female, optical section at oesophageal tooth level; D—male, transverse section at anterior third of oesophagus level; E—male, transverse section at mid-oesophagus level; F—caudal bursa, ventral view.