Meteterakis occidentalis, Sata, Naoya, 2018

Sata, Naoya, 2018, Two new skink-endoparasitic species of Meteterakis (Nematoda, Heterakidae, Meteterakinae) from East Asian islands, Zoosystematics and Evolution 94 (2), pp. 339-348 : 341-343

Meteterakis occidentalis sp. n. Fig. 3

Meteterakis amamiensis ; Sata 2015: 17 (in part); Sata 2018: figs 2, 3 (in part), table 1 (in part).

Type materials.

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. 1) on 16 May 2012. Paratypes: KUZ Z1996-Z1999 and Z2002-Z2008, whole specimens, four adult males and seven adult females, obtained from the rectum and small intestine of the same specimen of holotype’s host and another P. japonicus specimen (KUZ R69036), data same as those from the holotype’s host-specimen; KUZ Z2001, whole specimen, adult male, obtained from the small intestine of a P. japonicus specimen (KUZ R69575), collected from Ohura, Uwajima City, Ehime Prefecture, Japan (33°13'56.8"N, 132°33'13.7"E; elevation 4 m) (site 2 in Fig. 1) on 8 April 2013; KUZ Z2009, prepared slides of male spicules with the spicule pouch; Z2010, prepared slides of male spicules; KUZ Z2011 and Z2012, remaining body specimens of KUZ Z2009 and Z2010, respectively; KUZ Z2013, a section of the anterior end and a remaining body. KUZ Z2009, Z2010 and Z2013 were obtained from the rectum of a P. japonicus specimen (KUZ R69030), collected from same locality as the holotype’s host-specimen on 9 May 2012.

Additional material.

To reveal the geographic range of M. occidentalis sp. n., the following specimens deposited in the KUZ collection were examined: M. amamiensis (sensu Sata 2015): KUZ Z2014 from Kumamoto City, Kumamoto Prefecture, Japan (site 3 in Fig. 1), and KUZ Z658 and Z2022 from Kagoshima City, Kagoshima Prefecture, Japan (site 4 in Fig. 1).

Type locality.

Japan, Kyoto: Kyoto, Mt. Yoshida.

Type host.

Plestiodon japonicus (Peters, 1864) ( Reptilia, Scincidae ); site of infection: rectum and small intestine.

Diagnosis.

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.

Etymology.

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.

Occurrence.

Meteterakis occidentalis sp. n. occurs in the following locations in Japan: Kyoto City, Kyoto Prefecture, Honshu (site 1 in Fig. 1); Uwajima City, Ehime Prefecture, Shikoku (site 2 in Fig. 1); Kumamoto City, Kumamoto Prefecture, Kyushu (site 3 in Fig. 1); and Kagoshima City, Kagoshima Prefecture, Kyushu (site 4 in Fig. 1). P. japonicus is the only known host of this species ( Sata 2015, 2018).

Notes on the life cycle.

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.

Comparisons.

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.