Parasphaerolaimus pilosus, Zograf, Julia K., Pavlyuk, Olga N., Trebukhova, Yulia A. & Tu, Nguyen Dinh, 2017

Zograf, Julia K., Pavlyuk, Olga N., Trebukhova, Yulia A. & Tu, Nguyen Dinh, 2017, Revision of the genus Parasphaerolaimus (Nematoda: Sphaerolaimidae) with description of new species, Zootaxa 4232 (1) : -

Parasphaerolaimus pilosus sp. n.

( Figs 2–6 ; Table 1 )

Diagnosis. Parasphaerolaimus pilosus sp. n. is characterized by moderately plump body, presence of lateral alae, long cervical setae, small amphids in males, and relatively short spicules.

Etymology. The species name is derived from the Latin “ pilosus ”, meaning “hairy”.

Holotype. VIETNAM: ♂, formalin-fixed, mounted on slide ( MIMB 3 3138), in glycerin; deposited in the Zoological Museum IMB NSCMB FEB RAS; collected in Tien Yen Estuary, northern Vietnam, 21°18,997’ N, 107°36,075’ E; fine silty sands, water depth 0.5‒0.8 m.

Paratypes. VIETNAM: 1 ♂, 2 ♀♀, formalin-fixed, mounted on slides ( MIMB 3 3139 – 33141); deposited in the Zoological Museum IMB NSCMB FEB RAS; collected in Tien Yen Estuary, northern Vietnam, 21°18,997’ N, 107°36,075’ E; fine silty sand, water depth 0.5‒0.8 m.

Type locality. Northern Vietnam, Tien Yen Estuary , 21°18,997’ N, 107°36,075’ E ( Fig. 1 ); fine silty sand, water depth 0.5‒0.8 m.

Description. Male. Body stout, moderately long (1380‒1545 µm); tail conical. Cuticle finely striated with 20 µm wide lateral alae, which begin in the cervical region and extend to the base of tail ( Fig. 6 ). Anterior end blunt. Inner labial setae short, six in number; outer labial setae short (3 µm), six; and cephalic setae longer (4.5‒5.5 µm), four. A circle of 12 subcephalic setae (4 µm in length) located right behind cephalic setae. Below, the circle of eight bunches of setae are situated, 2‒3 setae in each bunch. Subcephalic setae of next circle arranged more irregularly in groups of 1‒3. Cervical setae (26‒27.5 µm) numerous. Somatic setae (27‒30 µm) scattered along the body. Cheilostom with longitudinal ribs. Anterior part of gymnostom with 6 regular sclerotized plates. Posterior part with 3 dentate plates. Stegostom funnel-shaped with longitudinal ribs. Amphids circular, 11.5–12 µm in diameter or 30‒32% of corresponding body diameter. Distance from the anterior end to amphid 19.5–24 µm. Distance from the anterior end to nerve ring 40‒44% of pharynx length. Secretory-excretory pore located behind nerve ring. Pharynx muscular, cylindrical; cardia small. Anterior testis single, outstretched. Spicules short (ca 1 cloacal body diameter), slightly curved. Gubernaculum with small apophyses. Tail conical, 12–13% of total body length or 3.3 cloacal body diameters, with three caudal glands. Somatic setae irregularly distributed along the tail. Terminal setae (23– 25 µm in length), three in number.

Females. Similar to males but slightly bigger (1630–1800 µm). Amphids 6.5–7 µm in diameter or 10‒12% of corresponding body diameter. Distance from the anterior end to amphid 28 µm. Distance from the anterior end to nerve ring 149–173 µm. Single anterior outstretched ovary, 730 µm long. Vulva post equatorial, V = 55.5–67.1%. Tail conical, 11.5–12% of total body length or 2.6–3.8 anal body diameters.

Relationships. The described species is closely related to Parasphaerolaimus paradoxus and P. crassus . The new species is distinguished from P. paradoxus by a smaller body size (1380–1800 µm vs 2300–2400 µm), smaller a index (11–20 vs 37–49), and longer spicules (54–56 µm vs 47.5 µm). Parasphaerolaimus pilosus sp. n. is distinguished from P. crassus by shorter cervical setae (26–28 µm vs 30–40 µm), relatively larger amphids in male (30–32% vs 25% of the corresponding body diameter), more curved and bigger spicules (54–56 µm vs 51 µm), and smaller gubernacula (18–20 µm vs 29 µm).

Figures

FIGURE 1. Map of sampling localities.

FIGURE 2. Parasphaerolaimus pilosus sp. n., male. A. General view; B. Head end; C. Tail end. Scale bars: A— 200 µm, B— 20 µm, C— 50 µm.

FIGURE 3. Parasphaerolaimus pilosus sp. n., A. Female, General view; B. Female, head end; C. Spicules and gubernaculums; D. Female reproductive system. Scale bars: A— 200 µm, B— 25 µm, C— 20 µm, D— 100 µm.

FIGURE 4. Parasphaerolaimus pilosus sp. n., male (DIC). A. General view; B. Cuticle surface with alae; C. Head end with amphid; D. Head end, buccal cavity structure; E. Tail end; F. Spicules and gubernaculum. Scale bars: A— 200 µm, B, C, D, F— 20 µm, E— 50 µm.

FIGURE 5. Parasphaerolaimus pilosus sp. n., female (DIC). A. General view; B. Head end with amphid; C. Head end with buccal cavity; D. Female eating a nematode; E. Tail end. Scale bars: A— 200 µm, B, C— 20 µm, D, E— 50 µm.

FIGURE 6. Parasphaerolaimus pilosus sp. n., SEM. A. Anterior end of male, lateral view; B. Head of male, lateral view; C. Head of male, frontal view; D. Head of female; E. Lateral alae; F. Tail of male. Scale bars: A, B, C, D, F – 10 µm, E – 20 µm.

Tables

TABLE 1. Morphometrics of Parasphaerolaimus pilosus sp. n. (µm).

	Holotype male	Paratype male	Allotype female	Paratype female
L a b	1545 19.7 5.1	1380 16.2 4.6	1630 11.4 4.6	1800 15.5 4.7
c c’ Tail length	8.4 3.3 184	7.9 3.3 174	8.7 2.6 186	8.3 3.8 216
Max. body diameter Head diameter Anal/cloacal diameter	78.5 45 54	85.5 37.5 52	142 52 73	116 52.5 57
Cephalic setae Cervical setae Amphid diameter	5.5 26 11.5	4.5 27.5 12	6.5 28 6.5	6.0 28 7
Anterior end to amphid distance Anterior end to secretory-excretory pore distance Anterior end to nerve ring distance	24 248 137	19.5 236 128	28 264 149	28 288 173
Pharynx length Spicules (along arch/along chord) Spicule length along arch/cloacal diameter ratio	303 54.5/50.5 1	298 56.5/52 1.1	350	377
Gubernaculum Anterior end to vulva distance V (%)	18	20	1092 67.1	999 55.5