Meteterakis formosensis

Sata, Naoya, 2018, Two new skink-endoparasitic species of Meteterakis (Nematoda, Heterakidae, Meteterakinae) from East Asian islands, Zoosystematics and Evolution 2, pp. 339-348: 339-341

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scientific name

Meteterakis formosensis

sp. n.

Meteterakis formosensis  sp. n. Fig. 2

Meteterakis  sp. 3; Sata 2018: figs 2, 3 (in part), table 1 (in part).

Type materials.

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. 1) on 20 March 2013. Paratypes: KUZ Z1777, Z1778, Z1783, Z1992 and Z1993, whole specimens, five adult males; KUZ Z1780-Z1782, three adult females, obtained from the same host specimen of the holotype; KUZ Z1994, one prepared slide of male spicules; and KUZ Z1995, a section of the anterior end and a remaining body (KUZ Z1994 is also derived from this individual), obtained from the same host specimen of the holotype.

Additional material.

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).

Type locality.

Taiwan, New Taipei City: Bali District, Mt. Guanyinshan.

Type host.

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. 1). Although a Meteterakis  -like specimen (KUZ Z2021) with undeveloped spicules was obtained from the rectum of a P. chinensis  specimen (KUZ R70948) from Miaoli County, Taiwan, its taxonomic account is unclear. P. chinensis  is the only known host of this species.


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  Gambhir et al., 2006 (220-270 μm), M. govindi  (180-270 μm; Karve 1930, Inglis 1958) and M. mabuyi  (Chakravarty, 1944) (300 μm), because its spicules are longer than 400 μm. Moreover, the new species differs from M. lyriocephali  (Crusz & Ching, 1975) because the spicules are similar in length on the left (457-537 μm) and right (437-510 μm) sides (in M. lyriocephali  : left, 595-754 μm; right, 340-561 μm).

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  ( Hasegawa 1987) and M. wonosoboensis  Purwaningshi, 2015 or vs. proximal end straight in M. guptai  Gupta & Naiyer, 1993 and M. triaculeata  (Kreis, 1933) ( Inglis 1958); surface smooth, vs. rough surface in M. saotomensis  Junker et al., 2015; and spicule alae narrow vs. wider in M. baylisi  Inglis, 1958, M. crombiei  Bursey et al., 2005 and M. sinharajensis  Crusz & Ching, 1975.

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  Bursey et al., 2017 by the absence of a gubernacular mass ( Wilkie 1930, Inglis 1958, Bursey et al. 2017). M. formosensis  sp. n. bears narrow lateral alae ending at the region near the proximal end of the spicule in the male or at the region anterior to the anus in the female. Thus, this new species differs from M. amamiensis  , which is diagnosed by possession of the wider lateral alae ending at the preclocal region in the male, and at the region near the posterior end in the female ( Hasegawa 1990).

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

Sata, Naoya 2018



Karve 1930