Paracanthonchus kamui Kito, 1981

Lee, Hyo Jin, Jung, Jongwoo & Rho, Hyun Soo, 2016, Two unrecorded marine nematode species of Paracanthonchus (Nematoda: Cyatholaimidae) from the East Sea of Korea, Journal of Species Research 5 (3), pp. 503-513 : 511-512

2. Paracanthonchus kamui Kito, 1981

ṳợậṻṄṵệ (ṳAE)

Paracanthonchus kamui Kito, 1981, p. 273 , fig. 12.

Material examined. 5♂♂ and 3$$, Bugu­ri , Uljingun, Gyeongsangbuk­do, Korea (37°06′21.39″N,

129°22′37.42″E), collected on 9 July 2014; Jangsa­dong, Sokcho­si, Gangwon­do, Korea (38°13′37.77″N, 128°35′16.92″E); Janghohang­gil, Geundeok­myeon, Samcheok­si, Gangwon­do, Korea (37°17′21.24″N, 129°19′8.34″E); Ayajin­gil, Toseong­myeon, Goseong­gun, Gangwon­do, Korea (38°16′11.53″N, 128°33′27.23″ E), collected on 2 Oct. 2014. The specimens are kept in the collection of the author. All are mounted in anhydrous glycerin between two coverslips on H­S slides, sealed with nail polish .

Measurements. See Table 2 for detailed measurements and morphometric ratios.

Description. Males: Body length 1,774 ­1,991 μm long, comparatively stout and cylindrical, slightly tapers to anterior region ( Figs. 4A , 6A ). Maximum body diameter 62­82 μm. Cuticle marked with transverse rows of fairly distinct dots starting at level of cephalic setae, but slightly lager and irregular in tail region. In pharyngeal region, distance of rows about 1.7 μm, slightly wide. Cuticle pore about 2 μm wide, distributed throughout body. About six to seven rows arranged in 10 μm at posterior part of body region, and about eight to ten rows situated at middle of body region within same distance ( Figs. 4C , 6D ). Head with inner circle of six labial papillae about 3.5 μm long and outer circle of 10 (6 + 4) cephalic setae, four shorter cephalic setae 7.8­9.8 μm and six longer setae 12.1­13.7 μm, about 41-46% of head diameter. Buccal cavity with prominent large dorsal tooth and two small subventral teeth ( Figs. 4C , 6B ). Amphideal fovea with 4.25 turns in ventral direction, about 39­41% of head diameter ( Figs. 4C , 6C ). Ocelli 4.8­7.0 μm long, situated at lower side of amphideal fovea. Esophagus cylindrical, 343­358 μm long, no distinct cardia. Nerve ring encircling pharynx, situated at 42­46% of pharynx length from anterior end. Excretory pore opening located at 73.5­84.8 μm from anterior end ( Fig. 4B ). Tail fairly stout, conical, 136­165 μm long, about 2.4-2.8 times of anal body diameter. Cell bodies of three caudal glands situated in proximal third, 4­5 μm setae distributed throughout tail region ( Fig. 4D ). Spicules slender, arcuate and tapering distally; proximal end with swellon appearance and rapidly narrowing from middle part to distal end. Gubernaculum paired, slightly bent; proximal end with hook­shaped appearance, distally from one­third widening with shape of ribs, distal end expanded, with small and numerous cusps ( Figs. 4F , 6F ). Six precloacal supplements present; curved tubular shape; posteriormost supplement rather delicate. Distance between adjacent two supplements, relatively constant, but posterior two supplement very close together ( Figs. 4E , 6E ). A series of short setae distributed on both lateral side of subventral region.

Females: General morphology similar to that of males in structure of cuticle and anterior body end ( Fig. 5B, 5D ). Body length 1,851 ­2,044 μm long; maximum body diameter 72­85 μm ( Fig. 5A ). Reproductive system didelphic, ovaries paired opposed, reflexed. Vulva 907­ 974 μm from anterior end, situated at 48-49% of total body length ( Fig. 5E ). Tail short and conoid, 148­158 μm long, about 2.8-3.0 times of anal body diameter ( Fig. 5C ).

Remark. Paracanthonchus kamui Kito, 1981 was firstly described from Japan Sea coast in Hokkaido. Paracanthonchus kamui is distinguished from other species of the genus by having the 4.25 turns amphideal fovea, six tubular supplement, rib­shaped gubernaculums with proximally hook­shaped and distally broaden. The present species is most like P. austrospectabilis Wieser, 1954 and P. sonadiae Timm, 1961 by possessing gubernaculum with slightly dilated distal end, six precloacal supplements, buccal cavity with large dorsal tooth and two small subventral teeth. However, the present Korean species is significantly differs from P. austrospectabilis by the distance of among six precloacal supplements and the presence of tiny denticles of the distal plates of gubernaculums. The present species clearly distinguished from P. sonadiae by shorter tail length (2.7­3.0 abd vs. 3.1­4.0 abd) and turns of the amphideal fovea (4.25 turns vs. 5.5 turns). The present Korean specimens agree well with Kito’s (1981) original description, in general features, especially in the detailed structure of the gubernaculum, in the number and shape of the precloacal supplement, and in the features of the buccal armatures and the amphideal fovea. However, the Korean specimens of P. kamui are not accord with the original description by having a longer overall body length (1774­1991 μm in male, 1851­2044 μm in female vs. 1658-1728 μm, 1761- 1816 μm) and ocelli situated at 24-28 μm from anterior end.

Figures

Fig. 4. Paracanthonchus kamui, male, lateral view.A, total body; B, anterior body region; C, head region; D, tail region; E, precloacal sup­ plements; F, spicules with gubernaculum. Scale bars: A=100μm, B, E=50μm, C, D, F=20μm.

Fig. 6. Paracanthonchus kamui, DIC photomicrographs, male, lateral view. A, habitus; B, head region; C, amphideal fovea; D, cuticle on the anterior region; E, precloacal supplement; F, spicules with gubernaculums. Scale bars:A=100 μm, B-F=10μm.

Fig. 5. Paracanthonchus kamui, female, lateral view. A, total body; B, head region; C, tail region; D, anterior body region; E, reproductive system. Scale bars:A=100 μm, B, C=20μm, D, E=50μm.