Paragnomoxyala breviseta, Jiang, Weijun & Huang, Yong, 2015

Jiang, Weijun & Huang, Yong, 2015, Paragnomoxyala gen. nov. (Xyalidae, Monhysterida, Nematoda) from the East China Sea, Zootaxa 4039 (3), pp. 467-474 : 470-473

Paragnomoxyala breviseta sp. nov.

( Fig. 2–3 )

Type material. Holotype: ♂1 on slide DH12-812-1; paratypes: ♂2, ♂3, ♂4, ♂5, ♂6, ♀1, ♀2, ♀3, ♀4 and ♀5 on slides DH12-812-1, DH12-812-2, DH12-815-4, DH12-817-2, DH12-817-5 and DH12-817-6 respectively.

Type locality and habitat. Sublittoral in the East China Sea. Station DH8–1: 26º 46´N, 120º 50΄ E, water depth 51 m, muddy with a little sand sediment fraction.

Etymology. The species name refers to the short cephalic setae.

Measurements Table 1 .

Characters Holotype Paratypes Description. Male. Body slender, gradually tapering towards terminal ends. Cuticle finely striated, arising at base of buccal cavity and ending at tail tip. Lips very high. Internal labial sensilla not visible, outer labial setae absent. Only four short cephalic setae, 3–4 µm long. Sub-cephalic setae absent. Buccal cavity large, funnel-shaped with cuticularized walls and extended anteriorly, lacking teeth, not surrounded by pharyngeal tissue, 11–26 µm deep (1.6–1.8 hd long), 5–11 µm wide (63–79% of cbd) in its middle; without teeth. Amphidial fovea circular, 4–9 µm µm in diameter (50% of cbd), situated at level of base of buccal cavity. Secretory-excretory system not visible. Pharynx cylindrical, slightly expanded towards the base, not formed into bulb. Cardia well developed, conical, 5– 12 µm long. Nerve ring at 45–46% of pharyngeal length. Tail tapering with distal third cylindrical, 5–6.3 abd long, with a short spinneret and three terminal setae. Some caudal setae scattered at suberventral sides of tail. Three caudal glands in a string.

male cloacal region, showing spicule and caudal glands. Scales: A, B, C, D=20 µm.

Testis not visible. Spicules almost straight with slightly curved proximal and distal ends, 15–30 µm long. Gubernaculum and precloacal supplements absent.

Females. Similar to males in most respects. Reproductive system monodelphic with an anterior outstretched ovary located left of the intestine and extending to pharynx base. Vulva with slightly raised lips, located at post-mid body length (66–69% of body length from the anterior end). Post-vulval uterine sac oval in shape, 40 µm long, packed with rounded sperms.

Diagnosis and discussion. Paragnomoxyala breviseta sp. nov. is characterized by having high lips; a large funnel-shaped buccal cavity with cuticularized walls and extended anteriorly; four cephalic setae 3–4 µm long; circular amphids 6–9 µm in diameter; spicules straight but slightly bent at both ends; absence of gubernaculum and procloacal supplements. Paragnomoxyala breviseta sp. nov. is the only one species found in the genus so far. The size of individuals is variable. Body length varies from 720 µm to 1100 µm, and the maximum body diameter varies from 21 µm to 55 µm. Discovery of Paragnomoxyala gen. nov. further proves that Xyalidae is a diverse and widespread family. Establishment of the new genus is significant for study of the feeding habits of each genus of Xyalidae and their system evolution. Paragnomoxyala gen. nov. is the genus with the largest buccal cavity in family Xyalidae found at present. It is potentially able to ingest foods of a wider size range including diatoms and small nematodes.

Figures

FIGURE 2. Paragnomoxyala breviseta sp. nov. (A) lateral view of male pharyngeal region, showing buccal cavity, cephalic setae and amphidial fovea; (B) lateral view of female anterior end; (C) entire view of female body, showing ovary, eggs and vulva; (D) lateral view of male posterior end, showing spicule and tail; (E) lateral view of male cloacal region, showing spicule; (F) dorsal view of male anterior end, showing buccal cavity, cephalic setae and amphidial fovea.

FIGURE 3. Paragnomoxyala breviseta sp. nov. (A) lateral view of female anterior end, showing buccal cavity and cephalic setae; (B) dorsal view of male anterior end, showing amphidial fovea; (C) lateral view of male posterior end; (D) lateral view of

Tables

TABLE 1. Individual measurements of Paragnomoxyala breviseta sp. nov. (in µm).

♂1	♂2	♂3	♂4	♂5	♂6	♀1	♀2	♀3	♀4	♀5
Total body length 1059	968	1100	1054	902	720	1037	1140	1043	760	767
Maximum 46 body diameter	42	53	52	38	21	55	52	42	30	27
Head diameter 13	11	14	13	11	7	14	15	15	7	8
Length of buccal cavity 23	20	22	24	18	11	24	26	20	12	12
Length of cephalic setae 4	3	4	4	2	3	3	3	2	3	2
Amphid diameter 9	8	8	9	7	4	6	9		4	-
Nerve ring from 106 anterior	112	116	112	107	72	103		119	76	-
Nerve ring cbd 38	34	38	40	31	19	36		35	22	-
Pharynx length 242	220	258	250	215	162	250	275	243	175	180
cbd at base of pharynx 46	40	46	48	36	20	50	47	40	27	26
Spicule length 30	25	25	29	27	15	-	-	-	-	-
abd 26	22	24	23	22	15	29	32	27	20	19
Tail length 142	128	152	142	130	89	152	160	154	110	107
c ′ 5.5	5.8	6.3	6.2	5.9	5.9	5.2	5.0	5.7	5.5	5.6
Vulva from anterior end -	-	-	-	-	-	710	790	708	505	510
Vulva c.d. -	-	-	-	-	-	55	52	42	30	27
V% -	-	-	-	-	-	68	69	68	66	66
a 23.0	23.0	20.8	20.3	23.7	34.3	18.9	21.9	24.8	25.3	28.4
b 4.4	4.4	4.3	4.2	4.2	4.4	4.1	4.1	4.3	4.3	4.3
c 7.5	7.6	7.2	7.4	6.9	8.1	6.8	7.1	6.8	6.9	7.2