Research Article |
Corresponding author: Naoya Sata ( sata@zoo.zool.kyoto-u.ac.jp ) Academic editor: Andreas Schmidt-Rhaesa
© 2018 Naoya Sata.
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Citation:
Sata N (2018) Two new skink-endoparasitic species of Meteterakis (Nematoda, Heterakidae, Meteterakinae) from East Asian islands. Zoosystematics and Evolution 94(2): 339-348. https://doi.org/10.3897/zse.94.27091
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Here, two new nematodes of Meteterakis Karve, 1930 from Taiwan and the western Japanese Archipelago that are endoparasitic to scincid lizards are described. The Taiwanese Meteterakis formosensis sp. n. and the Japanese Meteterakis occidentalis sp. n. can be distinguished from other congeners by the following characteristics: spicules 437–537 μm in length in M. formosensis sp. n. and 359–538 μm in M. occidentalis sp. n.; spicules with narrow alae, funnel-shaped, proximal ends ventrally bent; prevulval flap well-developed; gubernaculum mass absent; preclocal sucker with diameter of 35–47 μm in M. formosensis sp. n. and of 32–36 μm in M. occidentalis sp. n.; 9–15 caudal papillae on both lateral sides in M. formosensis sp. n. and 10–14 in M. occidentalis sp. n.; and relatively narrow lateral alae, ending at region near proximal end of spicule in male or at region anterior to anus in female. Meteterakis formosensis sp. n. is distinguished from M. occidentalis sp. n. by possessing spicules with hyaline pointed distal ends and well-developed cuticular backing structures. The present study suggests that lateral alae can be used as diagnostic character among the Meteterakis species, and it revealed that meteterakine nematodes mature in the host’s small intestine and then migrate to the rectum to oviposit.
Ascaridida , Meteterakis , new species, Plestiodon chinensis , Plestiodon japonicus , Japan, Taiwan
Meteterakis Karve, 1930 is a parasitic nematode genus, which is specific to amphibians (frogs and caecilians) and reptiles (lizards and land turtles) (
A molecular phylogenetic study revealed that the East-Asian insular Meteterakis nematodes are divided into two major clades (
Clarifying the systematic accounts of the aforementioned unidentified species will lead to a better understanding of the species diversity and evolutionary history of Meteterakis parasites inhabiting the East Asian islands. In the present study, therefore, the taxonomic states of the unidentified Taiwanese species and the M. amamiensis populations in the western Japanese Archipelago are investigated, and each is described as a new species.
The Meteterakis specimens examined in this study were obtained from the scincid lizard hosts, Plestiodon chinensis (Gray, 1838) and Plestiodon japonicus (Peters, 1864), which were collected from Taiwan and the western Japanese Archipelago (Fig.
Map showing the known populations of Meteterakis Karve, 1930 inhabiting the Japanese Archipelago, the Ryukyu Archipelago and Taiwan: Meteterakis occidentalis sp. n. (sites 1–4), M. amamiensis Hasegawa, 1990 (sites 5–9;
For comparison, the following Meteterakis specimens deposited in the KUZ collection were examined: M. amamiensis (sensu
Meteterakis
sp. 3;
Holotype: KUZ Z1779, whole specimen, adult male, obtained from the rectum of a Plestiodon chinensis specimen (KUZ R69425), collected from Mt. Guanyinshan, Bali District, New Taipei City, Taiwan (25°08'53.1"N, 121°25'47.3"E; elevation 199 m) (site 10 in Fig.
The following scincid lizard specimens, which were collected from Taiwan, were also dissected to reveal the geographic range of the new Taiwanese taxon: P. chinensis from Taipei City (KUZ R51443, R51444 and R51449–R51453), from New Taipei City (KUZ R46132, R46134 and R46136–R46139), and from Miaoli County (KUZ R70946, R70948–R70951, R70953 and R70963); Plestiodon leucostictus (Hikida, 1988) from Hualien City, Hualien County (KUZ R69421 and R69424); Plestiodon elegans (Thompson, 1912) from Taipei City (KUZ R66354), from the Xindian District, New Taipei City (KUZ R30191, R36205), from Miaoli County (KUZ R50394, R70957 and R70964), from Yilan County, (KUZ R36552), and from Tainan City (KUZ R70090 and R70091); and Eutropis longicaudata (Hallowell, 1857) from Tainan City, (KUZ R70089). One Meteterakis-like specimen (KUZ Z2021) was obtained from a P. chinensis specimen (KUZ R70948).
Taiwan, New Taipei City: Bali District, Mt. Guanyinshan.
Plestiodon chinensis (Gray, 1838) (Reptilia, Scincidae); site of infection: rectum and small intestine.
Relatively stout body, with narrow lateral and caudal alae; lateral alae commencing from region anterior to nerve ring or front end of nerve ring in both sexes and ending at region near proximal end of spicule in male (never reaching region of preclocal sucker) or at region anterior to anus in female. Prevulval flap present and well developed in female. Gubernacular mass absent. Spicules with thin alae, funnel-shaped proximal ends, hyaline tips, and both proximal and distal ends bent ventrally. Right spicule, 437–510 long; left spicule 457–537 long. Each spicule with thick and long cuticular backing structures, not covered by cuticular pouch. Caudal papillae present in male, 8–13 (N=4) pairs with additional papillae: 12–15 (N=4) on right side; 9–15 (N=5) on left side.
The specific name is an adjective, derived from the old name for Taiwan, which is the type locality of the new species.
General. Body short and relatively stout with tapered extremities. Cephalic end with 3 lips, each lip with 2 minute apical papillae. Dorsal lip with a pair of cephalic papillae (each papilla with 2 minute papillae); each subventral lip with single papilla (each papilla with 2 minute papillae), 1 amphid and 1 smaller papillae. Flanges in inner edge of each lip unobservable. Esophagus comprise of pharynx, cylindrical portion and bulb. Bulb bearing three valves. lateral alae commencing from region anterior to nerve ring or front end of nerve ring in both sexes and ending at region near proximal end of spicule in male (never reaching region of preclocal sucker) or at region anterior to anus in female.
Male (N=6; KUZ Z1777–Z1779, Z1783, Z1992 and Z1993). Body length 5.03 mm (4.84–5.67 mm), maximum width 206 (151–228). Body length/body width = 24.4 (24.8–36.3). Diameter of head 46 (38–50). Total length of esophagus 724 (681–774) long with width of 36 (31–44) at cylindrical portion. Body length/esophagus length = 7.0 (7.0–7.8). Pharynx 47 (34–45) long, bulb 85 (79–95) long by 110 (91–114) wide. Grooves between lips shallow and 8.2 (7.5–9.3) long. Nerve ring and excretory pore 221 (207–243) and 396 (337–400), respectively, from cephalic end. Spicules equal or slightly different, with narrow alae, strongly chitinized, tessellated from 153 (120–141) from proximal end to distal end in right spicule (i.e. corresponding to 68.1% [68.3%–75.7%] of total length), and from 66 (95–159) to distal end in left spicule (i.e. corresponding to 86.8% [65.2%–81.9%] of total length); both proximal and distal ends bent ventrally, with wide funnel-shaped proximal ends, and pointed hyaline distal ends. Right spicule 480 (437–510) long (i.e. corresponding to 9.5% [8.0%–9.8%] of body length), left spicule 500 (457–537) (i.e. corresponding to 9.9% [8.3%–10.5%] of body length). Each spicule with thick and long cuticular backing structure, not covered by cuticular pouch. Gubernacular mass absent. Narrow caudal alae present, supported by three pairs of large papillae. Caudal papillae present, 13 (8–13) (N=4) pairs with additional papillae: 13 (12–15) (N=4) on right side; 15 (9–15) (N=5) on left side. Occasionally, single median papilla present. Among 13 (8–13) pairs: 1–4 pairs anterior to preclocal sucker; 2 large pairs supporting caudal alae around sucher; 1–3 small pairs around sucker; 0–2 pairs between sucker and cloaca; 1 large pair supporting caudal alae at lateral to posterior cloacal lip; 0–1 pair immediately posterior to posterior cloacal lip; and 0–2 pairs in caudal region. Precloacal sucker 47 (35–47) in diameter, 54 (26–50) from cloaca. Posterior cloacal lip developed. Tail bent ventrally, conical with pointed tip, and 304 (238–315) long. Body length/tail length = 16.6 (15.4–23.0).
Female (N=3; KUZ Z1780–Z1782). Body length 6.05 mm (5.56–6.30 mm), and maximum width 224 (200–244). Body length/body width = 27.0 (25.8–27.8). Diameter of head 51 (49–52). Total length of esophagus 783 (753–806) long with width of 45 (39–50) at cylindrical portion. Body length/esophagus length = 7.7 (7.0–8.4). Pharynx 51 (38–61) long; bulb 95 (91–99) long by 108 (104–114) wide. Grooves between lips shallow and 8.5 (7.2–9.4) long. Nerve ring and excretory pore 230 (228–232) and 367 (359–372), respectively, from cephalic end. Vulva 2.71 mm (2.44–2.87 mm) from cephalic end, and located at anterior to middle of body (44.8% [43.9%–45.6%] of body length). Prevulval flap well developed. Vagina muscular running posteriorly. Tail long conical, slightly bent ventrally, and 560 (518–583) long. Body length/tail length = 10.8 (10.7–10.9). Eggs elliptical, 60 (49–68) by 41 (34–51) (N=29), thick shelled, containing morula stage embryos.
This new species was located on Mt. Guanyinshan, Bali District, New Taipei City, Taiwan (type locality) (site 10 in Fig.
This new species can be discriminated from almost half of the other Meteterakis species by the lengths of the spicules. Because M. formosensis sp. n. has spicules that are 437–537 μm in length, it can be distinguished from the following eight congeners, which are diagnosed by their spicules longer than 600 μm: M. aurangabadensis Deshmukh & Choudhari, 1980 (620–720 μm), M. karvei Naidu & Thakare, 1981 (660–840 μm), M. longispiculata (Baylis, 1929) (630–680 μm), M. louisi Inglis, 1958 (970–1100 μm), M. singaporensis (Sandosham, 1953) (740–960 μm), M. striaturus Oshmarin & Demshin, 1972 (680 μm), M. vaucheri Adamson, 1986 (1057–1242 μm) and M. wangi Zhang & Zhang, 2011 (740–930 μm). This new species is also distinguishable from M. bufonis (Biswas & Chakravarty, 1963) (left, 270 μm; right, 310 μm), M. gambhiri
In addition to the spicule length, the new species is distinguishable from the eight congeners by the following characteristics of spicules: proximal end wide, funnel-shaped and ventrally bent vs. proximal end slightly widened in M. ishikawanae (
Meteterakis formosensis sp. n. is distinguished from M. lombokensis Purwaningshi et al., 2016 by the presence of a well-developed prevulval flap in the female. Additionally, this species possesses a 35–47 μm (diameter) preclocal sucker and elliptically-shaped eggs. These characteristics can be used to discriminate this new species from M. andamanensis Soota & Chaturvedi, 1972, which has a 55–66 μm (diameter) preclocal sucker and spherical-shaped eggs. The number of caudal papillae (9–15) on both lateral sides of the new species can distinguish it from M. paucipapillosa Wang, 1980 because the latter possesses only 6 caudal papillae on both lateral sides. The new taxon is clearly distinguishable form M. japonica and M. hurawensis
Morphologically, M. formosensis sp. n. most resembles M. occidentalis sp. n., which is described below, but it differs from the latter species by the female having a relatively stout body (body length/body wide: 25.8–27.8 in M. formosensis sp. n. vs. 31.8–41.2 in M. occidentalis sp. n.), relatively longer tail length in the female (body length/tail length: 10.7–10.9 in M. formosensis sp. n. vs. 13.6–17.8 in M. occidentalis sp. n.), spicules with hyaline tips (lacking in M. occidentalis sp. n.) and well-developed backing structures for spicules (undeveloped in M. occidentalis sp. n.).
Meteterakis formosensis sp. n., holotype (KUZ Z1779: A, B, F, G), paratypes (KUZ Z1781: D, J; KUZ Z1782: E; KUZ Z1994: H, I; KUZ Z1995: C). A anterior region, lateral view; B pharynx, lateral view; C anterior end, apical view; D vulvar area of female, lateral view; E caudal region of female, lateral view; F caudal region of male, lateral view; G caudal papillae arrangement of male, lateral view; H spicule; I accessory of spicule; J egg.
Meteterakis
amamiensis
;
Holotype: KUZ Z2000, whole specimen, adult male, obtained from the small intestine of a P. japonicus specimen (KUZ R69034), collected from Mt. Yoshida, Kyoto City, Kyoto Prefecture, Japan (35°01'43.7"N, 135°47'09.4"E; elevation 70 m) (site 1 in Fig.
To reveal the geographic range of M. occidentalis sp. n., the following specimens deposited in the KUZ collection were examined: M. amamiensis (sensu
Japan, Kyoto: Kyoto, Mt. Yoshida.
Plestiodon japonicus (Peters, 1864) (Reptilia, Scincidae); site of infection: rectum and small intestine.
Short and slender body, with narrow lateral and caudal alae; lateral alae commencing from region anterior to nerve ring in both sexes and ending at region near proximal end of spicule (never reaching region of preclocal sucker) in male or at region anterior to anus in female. Prevulval flap well developed in female. Male with well-developed posterior cloacal lip. Gubernacular mass absent. Spicules with narrow alae, funnel-shaped proximal end, and both proximal and distal ends bent ventrally. Right spicule 359–517 long, left spicule 368–538 long. Dorsal surfaces of each spicule covered by thin cuticular pouch. Caudal papillae present in male, 7–11 (N=6) pairs with additional papillae: 10–14 (N=6) on right side; 10–14 (N=6) on left side.
The specific name is a Latin adjective in the nominative singular, occidentalis (western), referring to its distribution in the western Japanese Archipelago.
Description.General. Body short and slender with tapered extremities. Cephalic end with 3 lips, each lip with 2 minute apical papillae. Dorsal lip with a pair of cephalic papillae (each papilla with 2 minute papillae); each subventral lip with single papilla (each papilla with 2 minute papillae), 1 amphid and 1 papilla. Inner edge of each lips with flange. Esophagus comprise of pharynx, cylindrical portion and bulb. Bulb has three valves. Narrow lateral alae present in both sexes, commencing from region anterior to nerve ring in both sexes and ending at region near proximal end of spicule (never reaching region of preclocal sucker) in male or at region anterior to anus in female.
Male (N=6; KUZ Z1996–Z2001). Body length 4.68 mm (4.19 mm –5.75 mm), maximum width 132 (120–163). Body length/body width = 35.5 (29.2–39.7). Diameter of head 42 (42–47). Total length of esophagus 621 (621–732) long with width of 39 (32–44) wide at cylindrical portion. Body length/esophagus length = 7.5 (6.7–7.9). Pharynx 36 (35–47) long, bulb 83 (65–97) long by 83 (84–100) wide. Grooves between lips shallow and 7.3 (7.0–13.5) long. Nerve ring and excretory pore 217 (203–241) and 328 (307–350), respectively, from cephalic end. Spicules with narrow alae, equal or slightly different, strongly chitinized, tessellated from 95 (78–104) from proximal end to distal end in right spicule (i.e. corresponding to 76.7% [76%–84%] of total length), and from 101 (43–118) to distal end in left spicule (i.e. corresponding to 76% [74.7%–91.4%] of total length), both proximal and distal ends bent ventrally, wide funnel-shaped proximal end and distal end pointed. Right spicule 408 (359–517) long (i.e. corresponding to 8.7% [8.6%–10.3%] of body length), left spicule 421 (368–538) (i.e. corresponding to 9.0% [8.3%–10.5%] of body length). Dorsal surface of each spicules covered by thin cuticular pouch. Gubernacular mass absent. Narrow caudal alae present, supported by three pairs of large papillae. Caudal papillae present, 11 (7–11) (N=6) pairs with additional papillae: 14 (10–12) (N=6) on right side; 14 (10–14) (N=6) on left side. Occasionally, single median papilla present. Among 11 (7–11) pairs: 1–2 pairs anterior to preclocal sucker; 2 large pairs supporting caudal alae and 0–1 small pair lateral to preclocal sucker; 0–2 pairs between posterior region of sucker and cloaca; 1 large pair supporting caudal alae at lateral to posterior cloacal lip; 0–2 pair immediately posterior to posterior cloacal lip; 1–3 pairs posterior region of tail; 0–1 pair lateral to cloaca. Precloacal sucker 36 (32–36) in diameter and 33 (23–38) from cloaca. Posterior cloacal lip developed. Tail bent ventrally, conical, with pointed tip, 258 (234–282) long. Body length/tail length = 18.1 (17.9–20.4).
Female (N=7; KUZ Z2002–Z2008). Body length 5.49 mm (4.85 mm –5.98 mm), maximum width 158 (145–182). Body length/body width = 34.8 (31.8–41.2). Diameter of head 48 (41–56). Total length of esophagus 731 (648–798) long with width of 37 (31–42) at cylindrical portion. Body length/esophagus length = 7.5 (6.7–8.0). Pharynx 43 (38–52) long; bulb 94 (87–106) long by 90 (79–101) wide. Grooves between lips shallow and 10.5 (7.3–13) long. Nerve ring and excretory pore 230 (162–275) and 355 (311–388), respectively, from cephalic end. Vulva 2.36 mm (2.09–2.54 mm) from cephalic end. Vulva located at anterior to middle of body (43.0% [39.9%–47.4%] of body length). Prevulval flap well developed. Vagina muscular running posteriorly. Tail long conical, slightly bent ventrally, 353 (329–415) long, with a few specimens possessing a few small papillae. Body length/tail length = 15.6 (13.6–17.8). Eggs elliptical, 62 (52–72) by 40 (32–47) (N=70), thick shelled, containing morula stage embryo.
Meteterakis occidentalis sp. n. occurs in the following locations in Japan: Kyoto City, Kyoto Prefecture, Honshu (site 1 in Fig.
Most Meteterakis nematodes collected from recta were adult individuals. Several larval nematodes were collected from the small intestines of the host individuals, which were inhabited by M. occidentalis sp. n., and a small number of ensheathed Meteterakis were also found from there. The rate of females having eggs in hosts’ small intestines and recta were 36.2% (21/58) and 72.5% (50/69), respectively.
M. occidentalis sp. n. differs from M. formosensis sp. n. as discussed above. Because most of the morphological characteristics of M. occidentalis sp. n. are concordant with those of M. formosensis sp. n., this new species can be distinguished from the other congeners by the features mentioned in comparisons with M. formosensis sp. n. and the other Meteterakis species. Therefor, M. occidentalis sp. n. can receive the taxonomic status of a distinct species within the genus.
Distributions of Meteterakis formosensis sp. n., Meteterakis occidentalis sp. n., and M. amamiensis Hasegawa, 1990.
Species | Site # | Locality | Geographic coordinates | References |
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M. occidentalis sp. n. | 1 | Mt. Yoshida, Kyoto City, Kyoto Pref., JP (Honshu) | 35°01'43.7"N, 135°47'09.4"E |
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M. occidentalis sp. n. | 2 | Uwajima City, Ehime Pref., JP (Shikoku) | 33°13'56.8"N, 132°33'13.7"E |
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M. occidentalis sp. n. | 3 | Kumamoto City, Kumamoto Pref., JP (Kyushu) | 32°47'N, 130°41'E |
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M. occidentalis sp. n. | 4 | Kagoshima City, Kagoshima Pref., JP (Kyushu) | 31°35'39.76"N, 130°27'31.55"E |
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M. amamiensis | 5 | Yakushima Town, Kagoshima Pref., JP (Yakushima Island) | 30°27'N, 130°29'E |
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M. amamiensis | 6 | Kodakarajima, Toshima Village, Kagoshima Pref., JP (Kodakarajima Is.) | 29°13'22.6"N, 129°19'39.2"N |
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M. amamiensis | 7 | Amami City, Kagoshima Pref., JP (Amamioshima Is.) | 28°24'01.3"N, 129°28'33.6"E |
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M. amamiensis | 8 | Yamato Village, Kagoshima Pref., JP (Amamioshima Is.) | 28°21'30.8"N, 129°20'11.7"E |
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M. amamiensis | 9 | Mt. Yuwan, Uken Village, Kagoshima Pref., JP (Amamioshima Is.) | N/A |
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M. formosensis sp. n. | 10 | Mt. Guanyinshan, Bali District, New Taipei City, TW | 25°08'53.1"N; 121°25'47.3"E |
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Meteterakis occidentalis sp. n., holotype (KUZ Z2000: A, B, F, G), paratypes (KUZ Z2005: D, E, I; KUZ Z2010: H; KUZ Z2013: C). A anterior region, lateral view; B pharynx, lateral view; C anterior end, apical view; D vulvar area of female, lateral view; E caudal region of female, lateral view; F caudal region of male, lateral view; G caudal papillae arrangement of male, lateral view; H spicule; I egg.
Heterakidae has been classified into three subfamilies, Heterakinae, Spinicaudinae, and Meteterakinae (
Most of the M. occidentalis sp. n. specimens of both sexes collected from the recta were at the adult stage. Moreover, mature female of M. occidentalis sp. n. bearing eggs occurred less frequently in the hosts’ small intestines than in the recta, suggesting that the larvae of this species may mature in the small intestine and then migrate to the rectum to oviposit. A similar life cycle has been recorded for two spinicaudine species that are parasites in the rectum of Malagasy chameleons (
The spicule length, which has been regarded as a useful taxonomic character of the genus Meteterakis (e.g.
Because a previous phylogenetic study (
This discordant pattern between the endoparasites and their host species was indicated by the two unidentified Meteterakis species on Ishigakijima and Iriomotejima Islands (
The author is grateful to K. Kurita (Kyoto University) for providing host specimens; T. Hikida (Kyoto University) for useful comments on this study and for allowing me to dissect the lizard specimens of the KUZ collection; and T. Nakano and T. Okamoto (Kyoto University) for useful comments on this study. I thank L. Benyon from Edanz Group (www.edanzediting.com/ac) for editing a draft of this manuscript, and CR. Bursey for reviewing of the early version of this manuscript. The open access publication of this manuscript was supported by the Museum für Naturkunde.