Paramonohystera eurycephalus, Huang & Wu, 2011

Huang, Y. & Wu, X. Q., 2011, Two new free-living marine nematode species of Xyalidae (Monhysterida) from the Yellow Sea, China, Journal of Natural History 45 (9 - 10), pp. 567-577 : 568-576

Paramonohystera eurycephalus sp. nov.

( Figures 1 , 2 )

Type material

Four males and two females were measured and studied.

Holotype. ♂ 1 on slide 3300-303 (Station 3300-3).

Paratypes. ♀ 1 on slide 3400-301 (Station 3400-3); three males and one female on slides 3300-404 (Station 3300-4) and 3400-301 (Station 3400-3), respectively.

Type locality and habitat

Subtidal muddy sediment at Station 3300–3 (33 ◦ N, 122 ◦ 30 ′ E, water depth 22 m), 3300–4 (33 ◦ N, 123 ◦ E, water depth 30 m) and 3400–3 (34 ◦ N, 121 ◦ 30 ′ E, water depth 17 m) in the Yellow Sea.

Etymology

This species is named for its broad head.

Measurements

Measurements are listed in Table 1; all measurements are given in µm. For holotype: total body length 1710 µm; De man ratios a, 23.8; b, 4.5; c, 6.5; and Spic., 168. For paratype ♀ 1: total body length 1760 µm; a, 27; b, 4.7; c, 7.2; and V%, 54%.

Description

Males. Body cylindrical and gradually tapering towards tail end, 1695–1780 µm long and 60–70 µm wide at maximum body diameter. Head 33 µm wide. Cuticle with fine annulations. Numerous somatic setae scattered all over body, dense and longer (up to 28 µm) at cervical region.

Buccal cavity large with hemispherical cheilostome and conical pharyngostome, 18 µm wide. Anterior sensilla arranged in two circles: an anterior one with six inner labial papillae and an outer one with 10 sensilla, i.e. six longer (13 µm) outer labial setae and four shorter (11 µm) cephalic setae.

Amphidial fovea round, 18–20 µm in diameter or 50% of c.b.d., anterior border of fovea almost at base of buccal cavity. Pharynx cylindrical, about 384 µm long (22% of total body length). Pharyngo-intestinal junction with small cardia. Nerve ring at about 130 µm from anterior end (at 34% of pharyngeal length).

Excretory pore and ventral gland not seen.

Tail conico-cylindrical, 260–263 µm (about 5.4 a.b.d.) long, with distal third cylindrical. Three terminal setae 30–36 µm long. Three caudal glands obviously restricted to tail.

Reproductive system diorchic, testes opposite and outstretched. Spicules slender and arcuate, 157–168 µm or 3.1–3.2 a.b.d., slightly cephalate proximally and taper distally. Gubernaculum tubular with a distal hook. Five to six minute precloacal supplements.

Females. Similar to males, but amphidial fovea smaller, 13 µm in diameter or 34% of c.b.d. A single anterior outstretched ovary with reflexed tip, situated to the left of the intestine. Some eggs and spermatozoa present in uterus ( Figure 1B ). Vulva at about 53% of the body length from the anterior end.

Differential diagnosis

Paramonohystera eurycephalus sp. nov. is characterized by relatively wide head diameter (33 µm in width), large cup-shaped buccal cavity; presence of numerous long cervical setae; sexual dimorphism in the size of the amphideal fovea: 50% of c.b.d. in males and 34% of c.b.d. in females; spicules slender, 3.1–3.2 a.b.d. long; gubernaculum tubular with a distal hook; and tail with three long terminal setae (up to 36 µm).

Paramonohystera eurycephalus sp. nov. is close to Paramonohystera megacephala Steiner, 1916 in general morphology; however, P. megacephala has much longer spicules (260–303 µm vs 157–168 µm or 5.1 vs 3.2 a.b.d.), the distal part of the gubernaculum expanded and with a tooth-like protrusion, whereas the gubernaculum is without tooth-like protrusion, but with a distal hook in P. eurycephalus sp. nov.. Furthermore, the head diameter of P. megacephala is narrow (15 µm vs 33 µm), and the cervical setae are few and short. In head diameter, P. eurycephalus sp. nov. is similar to P. wieseri Ott, 1977 but the latter has much longer cephalic setae (40–58 µm vs 11– 15 µm or 1.4 vs 0.5 head diameters) and shorter spicules (40–46 µm vs 157–168 µm or 1.1–1.3 vs 3.1–3.2 a.b.d.).

Order MONHYSTERIDA Filipjev, 1929 Family XYALIDAE Chitwood, 1951 Genus Steineria Micoletzky, 1921 Steineria sinica sp.nov.

( Figures 3 , 4 )

Type material

Four males and two females were measured and studied.

Holotype. ♂ 1 on slide 3825305 (Station 3825-3).

Paratype. ♀ 1 on slide 3825302 (Station 3825-3); paratypes: three males and two females on slides 3825403 (Station 3825-4) and 3825302, respectively.

Type locality and habitat

Subtidal muddy sediment at Station 3825-3 (38 ◦ 25 ′ N, 122 ◦ 30 ′ E, water depth 50 m) and Station 3825-4 (38 ◦ 25 ′ N, 123 ◦ E, water depth 58 m) in the Yellow Sea.

Etymology

This species is named for the country of the type locality, China. Notes: Hol., holotype; Av., average; a, body length / max. body diameter; a.b.d., anal body diameter; b, body length / pharynx length; c, body length / tail length; c ′, tail length / a.b.d.; c.b.d., corresponding body diameter; V %, position of vulva from anterior end expressed as a percentage of total body length .

Measurements

Measurements are listed in Table 2; all measurements are given in µm. For holotype: total body length 1175 µm; a, 30.9; b, 5.2; c, 7.0; and Spic., 39. For paratype ♀ 1: total body length 1265 µm; a, 30.1; b, 5.2; c, 6.8; and V%, 61%.

Description

Males. Body cylindrical and gradually tapering towards anterior and posterior ends, 1174–1225 µm long and 38–46 µm wide at maximum body diameter. Head 18 µm in width. Cuticle with fine annulations. Numerous somatic setae scattered all over body, dense at tail region.

Buccal cavity conical. Anterior sensilla arranged in two circles: an anterior one with six inner labial papillae and an outer one with 10 sensilla, i.e. six longer (8 µm) outer labial setae and four shorter (6 µm) cephalic setae. Eight groups of three long subcephalic setae at almost same level as cephalic setae, 48–55 µm long. Eight groups of two long cervical setae (up to 46 µm) situated between subcephalic setae and amphidial fovea.

Amphidial fovea round, 9 µm in diameter or 35% of c.b.d., about one head diameter from anterior end. Pharynx cylindrical, about 228 µm long (19% of total body length). Pharyngo-intestinal junction with small cardia. Nerve ring at about 95 µm from anterior end (at 39% of pharyngeal length).

Excretory pore behind nerve ring or at middle of pharynx.

Tail conico-cylindrical, 169–178 µm (about 5.3 a.b.d.) long, conical for half of its length, then cylindrical with slightly swollen tip. Three terminal setae very long, up to 62 µm. Three caudal glands obviously restricted to tail.

Reproductive system diorchic, testes opposite and outstretched. Spicules slender, 39–43 µm or 1.2 a.b.d., cephalate proximally and taper distally. Gubernaculum pipeshaped with about 16 µm dorsocaudal apophysis.

Females. Similar to males in general morphology. A single anterior outstretched ovary, situated to the left of the intestine. Vulva at about 61% of the body length from the anterior end.

Differential diagnosis

Steineria sinica sp. nov. is characterized by eight groups of three subcephalic setae at almost same level as cephalic setae, some subcephalic setae three head diameters long; eight groups of two long cervical setae situated between subcephalic setae and amphidial fovea; amphidial fovea round, 35% of c.b.d., about one head diameter from anterior end; spicules slender; gubernaculum pipe-shaped with dorsocaudal apophysis; and tail conico-cylindrical with three long terminal setae.

Steineria sinica sp. nov. is similar to Steineria pilosa (Cobb, 1914) in general morphology. However, the gubernaculum of S. pilosa is sigmoid not pipe-shaped; and the amphidial fovea is 1.5 head diameters from anterior end. The new species is easily identified as Steineria by eight groups of three long subcephalic setae and eight groups of two long cervical setae between the subcephalic setae and amphidial fovea.

Figures

Figure 1. Paramonohystera eurycephalus sp. nov. (A) Lateral view of male anterior end; (B) lateral view of male tail end; (C) lateral view of female body, showing ovary, eggs and vulva.

Figure 2. Paramonohystera eurycephalus sp. nov. (A) Lateral view of male anterior end (holotype: male 1); (B) lateral view of female anterior end, showing buccal cavity and cervical setae (female 1); (C) lateral view of male cloacal region, showing spicules and caudal glands (male 1); (D) lateral view of male cloacal region, showing spicules and gubernaculum (male 2).

Figure 3. Steineria sinica sp. nov. (A) Lateral view of male anterior end; (B) lateral view of female body; (C) lateral view of male tail end.

Figure 4. Steineria sinica sp. nov. (A) Lateral view of male anterior end, showing cephalic setae and subcephalic setae (holotype: male 1); (B) lateral view of male anterior end, showing subcephalic setae, cervical setae and amphidial fovea (male 1); (C) lateral view of male cloacal region, showing spicules, gubernaculum and caudal glands (male 2); (D) lateral view of male tail end, showing spicules and terminal setae (male 1).