Conilia sinensis, Chen, Yu Zhen & Guo, Yu Qing, 2015

Chen, Yu Zhen & Guo, Yu Qing, 2015, Three new and two known free-living marine nematode species of the family Ironidae from the East China Sea, Zootaxa 4018 (2), pp. 151-175 : 152-156

Conilia sinensis sp. nov.

( Figure 1 , Figure 2 , Table 1 )

Type material. Six males and two females were collected from Station ZZDS L1, L2 and L 3 in July 2012. Holotype: ♂1 on slide number ZZDS 20120707 L1U123. Paratypes: ♂2 and ♀2 on slide number ZZDS 20120707 L2U003, and ♂3 on slide number ZZDS 20120707 L2U004, ♂4 on slide number ZZDS 20120707 L3U001, ♂5 and ♀1 on slide number ZZDS 20120707 L2U002, ♂6 on slide number ZZDS 20120707 L4D001.

Type locality and habitat. Intertidal sandy sediment at Dongshan Island, Zhangzhou City, East China Sea. Station ZZDS: 117.4836°E, 23.7081°N. Silt+clay: 3.27%.

Etymology. The name of the species makes reference to the country of origin, China.

Measurements ( Table 1 )

Description. Male. Body slender and cylindrical, maximum body diameter 33–36 µm. Head end blunt, lip region well developed and swelling, with several wrinkles on the outside wall of lips ( Figure 1 F. G). Six inner labial sensilla papilliform, six outer labial setae and four cephalic setae stout and blunt, arranged in a ring. Head diameter 25–26 µm. Head region set off from remaining body part by a strip, width about 4 µm. Buccal cavity consists of a cup-shaped anterior section length 5–12 µm, and a strong cuticularized posterior tube length 29–31 µm. Three solid curved claw-like teeth of almost equal size lie on the border of cup-shaped anterior section of buccal cavity, one of the teeth seems to be slightly double-tipped in two observed specimens. The anterior edges of cup-shaped section of buccal cavity bear a row of small cuticular denticles. Amphid not observed. Pharynx 0.18– 0.21 times of body length, with distinct anterior peribuccal swelling, posteriorly without obvious bulb. Nerve ring located at 37%–40% of pharynx length. Tail conico-cylindrical, 4.5–5.7 abd long, obviously ventrally bent, one small ventro-median swelling occurred in the middle of tail. Three elongated caudal glands are precloacal. Terminal spinneret small. Cuticle smooth, almost all specimens are more or less adhered by rod-shaped bacteria, somatic setae cannot be accurately observed in most of specimens. While in one specimen, which is little adhered by bacteria can be observed several scattered ventro-sublateral somatic setae arranged in one row in each side, two are located near the cloaca.

Reproductive system diorchic with two testes arranged in tandem, situated to right of intestine. Spicule single and elongate, transversely or slightly obliquely striated, length 87–100 µm as arc, 3.5–4.2 abd. Telamons paired, length 25–28 µm, with thickened anterio-ventral and posterio-dorsal ribs which is bent distally with two strong hook-like structures, as well as rounded changeable proximal projection ( Figure 1 C. D. E; Figure 2 G. H. I. J). Gubernaculum is a slightly curved thin strip, length 18–22 µm. One precloacal supplement present as simple ventral swelling.

Female. Similar to male in general characteristics, but body plumper and slightly swollen at midbody, maximum body diameter 41–48 µm. Head diameter 29–33 µm; Head region continuous with body contour. The cuticularized posterior tube of buccal cavity longer, length 35–36 µm. Tail straight, without setae or swelling.

Reproductive system with two reflexed equally developed ovaries. Vulva at 53.9–56.7% of body length.

Diagnosis and discussion. The genus Conilia was established by Gerlach in 1956 with the type species Conilia divina Gerlach (Gerlach 1954) . It belongs to Ironidae with a cuticularized elongate-tubular buccal cavity and three claw-like teeth at anterior end of buccal cavity. It is a rare genus, with only two species described to date, and some diagnostic characters are still questionable ( Gerlach & Riemann 1974, Aryuthaka 1989, Platonova & Mokievsky 1994, Electronic database: http://nemys.ugent.be; http://www.marinespecies.org/index.php). In general, it can be distinguished from other genera of Ironidae by male copulatory apparatus. According to the original descriptions of this genus and the type species C. divina , the male copulatory apparatus consists of three parts: the first part is short and paired, its proximal end expands to a funnel shape and distal end bends as two stout hooks; the second part is a narrow strip, longer than the first part; the third part is a very long obliquely striate sclerotized tube, which adjoins the first part and the second part ( Gerlach 1954). A structure similar to the third part was first found in Mesacanthion diplechma ( Southern, 1914) Filipjev, 1927 , which was described as a spicule ( Southern 1914); Schuurmans Stekhoven (1935) suspected that it might act as the ejaculatory duct. Gerlach (1954) regarded these three parts as spicules, gubernaculum and spicular accessory, respectively. Aryuthaka (1989) considered the third part to be a tubiform spicule and the first part to be the gubernaculum. Keppner & Tarjan (1989) regarded the first part and second part as asymmetrical spicules of different length (see also Platonova & Mokievsky 1994). In C. divina , the third part of the copulatory apparatus may protrude up to two-thirds of its length from the cloaca ( Gerlach 1954). In Conilia sinensis sp. nov., the third part of the copulatory apparatus may also protrude from the cloaca ( Figure 1 D; Figure 2 G), while the second part was never observed to protrude in all of our specimens. The former is more likely to act as the ejaculatory duct, so we describe the single striate sclerotized tube as a spicule and the short and paired structures as telamons in this paper. A pictorial key including C. divina , C. monospiculata Aryuthaka, 1989 and the newly described species is given in Figure 3 .

The new species is identified by its relatively large body size, well developed lips, single, striated and shorter spicule, fewer supplements, etc. It differs from C. divina in the following characters: body (1883–2399 µm vs. 1535–1630 µm) and buccal cavity (37–45 µm vs. 36 µm) longer; length of cephalic setae smaller (17–22 µm vs. 25 µm); spicule (87–100 µm vs. 112 µm) shorter; telamons (25–28 µm vs. 12 µm) and buccal cavity (37–45 µm vs. 36 µm) longer; supplements fewer (1 vs. 4); male tail ventrally bent (straight in C. divina ), relatively longer (4.5–5.7 abd vs. 4 abd) and with a small ventro-median swelling (absent in C. divina ); female tail shorter (5.3–5.7 abd vs. 6 abd); lip well developed (lip region not particularly strengthened in C. divina ). ( Gerlach 1954). It can be easily distinguished from C. monospiculata by the absence of amphid (amphid present in C. monospiculata ) and the presence of supplement (supplement absent in C. monospiculata ); the striated and longer spicule (87–100 µ m vs. 60–64 µm); the longer male body length (1956–2399 µm vs. 1529–1990 µm) and telamon (25–28 µm vs. 15–20 µm); the posterior location of vulva (V 53.9%–56.7% vs. 48%); the bigger head diameter (♂: 25–26 µm vs. 17–22 µm; ♀: 29–33 µm vs. 21–22 µm) and male maximum body diameter (33–36 µm vs. 23–33 µm) ( Aryuthaka 1989).

Figures

FIGURE 1. Conilia sinensis sp. nov. A: lateral view of female anterior part; B: lateral view of female posterior part; C – D: lateral view of different male tail region; E: lateral view of male body part, showing copulatory apparatus; F: lateral view of male head end; G: lateral view of female head end; H: lateral view of male anterior part. Scale bar: 20 Μm.

FIGURE 2. Conilia sinensis sp. nov. A: lateral view of male head end, showing buccal cavity and solid teeth; B: lateral view of female head end, showing buccal cavity and bacteria adhered; C: lateral view of male head end, showing wrinkles of lips, cephalic setae and strip; D: lateral view of juvenile head end, showing replacement teeth; E: lateral view of male head end, showing small cuticular denticles; F – G: lateral view of different male body part, showing spicule; G – J: lateral view of male body part, showing telamon; K: lateral view of male body part, showing gubernaculum; L: lateral view of female body part, showing vulva; M: lateral view of male tail region; N: lateral view of female tail region. Scale bar: A ~ L = 10 Μm; M – N = 25 Μm.

FIGURE 3. Pictorial key for genus Conilia. (A) a: female head; b: male copulatory apparatus; c: small denticles of buccal cavity; d: male posterior part. (B) a: male head end; b: male posterior part; c: male copulatory apparatus; (C) a: male copulatory apparatus; b: male posterior part; c: male head end; d: female head end.

Tables

TABLE 1. Individual measurements of Conilia sinensis sp. nov. (in µm).

	Holotype			Paratypes
Characters	♂1	♂2	♂3	♂4 ♂5 ♂6 ♀1	♀2
Body length	2122	2399	2101	2141 2141 1956 2080	1883
Head diameter	26	26	25	25 26 25 29	33
Length of outer labial cephalic setae	17	20	20	20 18 17 20	22
Length of cephalic setae	8	8	9	10 9 8 9	8
Total length of buccal cavity	42	37	37	43 37 38 45	40
Nerve ring from the anterior end	152	155	150	164 156 147 167	160
Nerve ring cbd	29	28	29	28 28 28 32	32
Pharynx length	390	423	390	420 393 380 444	397
Pharynx cbd	29	30	32	30 30 29 37	35
Maximum body diameter	34	34	35	36 34 33 48	41
abd	24	24	25	22 22 25 24	24
Tail length	134	121	123	125 120 112 126	136
c’	5.6	5.0	4.9	5.7 5.5 4.5 5.3	5.7
Spicule length as chord	87	76	79	83 76 80 -	-
Spicule length as arc	99	100	100	90 90 87 -	-
Supplement	1	1	1	1 1 1 -	-
Length of telamon	28	25	25	25 28 27 -	-
Length of gubernaculum	18	20	-	19 20 22 -	-
V’	-	-	-	- - - 1179	1015
vbd	-	-	-	- - - 44	40
V (%)	-	-	-	- - - 56.7	53.9
a	62.4	70.6	60.0	59.5 63.0 59.3 43.3	45.9
b	5.4	5.7	5.4	5.1 5.4 5.1 4.7	4.7
c	15.8	19.8	17.1	17.1 17.8 17.5 16.5	13.8