Parodontophora microseta, Li, Yongxiang & Guo, Yuqing, 2016

Li, Yongxiang & Guo, Yuqing, 2016, Free living marine nematodes of the genus Parodontophora (Axonolaimidae) from the East China Sea, with descriptions of five new species and a pictorial key, Zootaxa 4109 (4), pp. 401-427 : 414-419

Parodontophora microseta sp. nov.

( Figure 8 , Figure 9 , Table 7 , Table 8 )

Type material. ♂1 and ♀2 were collected respectively from Station ZZJL in October 2013 and January 2013, ♂2 was collected from Station XMFL in July 2013, and ♂3, ♂4, ♂5, ♀1 were collected from Station QZLY in October 2012.

Holotype: ♂1 on slide number ZZJL 201310 L1105. Paratypes: ♂2 on slide number XMFL 201307 H4114, ♂3 on slide number QZLY 201210 M3102, ♂4 on slide number QZLY 201210 M4109, ♂5 on slide number QZLY 201210 L4106, ♀1 on slide number QZLY 201210 L3106, ♀2 on slide number ZZJL 201301 L1102. The holotype and paratypes are deposited in the Third Institute of Oceanography, State Oceanic Administration, Xiamen.

Type locality and habitat. All specimens were collected from mangrove forests in Luoyang River estuary in Quanzhou City, East China Sea, Fenglin mangrove forest in Xiamen City, East China Sea, and Jiulong River estuary in Zhangzhou City, East China Sea. Station ZZJL: 117.82°E, 24.45°N. Station XMFL: 118.10°E, 24.58°N. Station QZLY: 118.67°E, 24.94°N.

Etymology. This species is named microseta (latin: micro, micro; latin: seta, seta) for its micro opisthocephalic setae, only 1 µm long.

Measurements. Table 7 .

Description. Body narrows gradually in the anterior region. Cuticle with distinct outer striation discernible in the lateral field. Lip region more or less rounded, with six outer labial papillae. Four cephalic setae 3–4 µm, 19–29% of head diameter, 3–4 µm from the anterior end. The head behind the cephalic setae has a distinct constriction. Opisthocephalic setae 1 µm, arranged as two single subdorsal setae and two single subventral setae, i.e. (1D- 1V)2. Somatic setae length 2–3 µm, arranged as two groups of two longitudinally arranged setae respectively located on both sides of the amphid, extended from the posterior part of buccal cavity to the conical portion of the tail. Buccal cavity 33–35 µm long and 6–7 µm wide, cylindrical with conspicuous sclerotized parallel walls and conoid posterior parts. Six bifurcate teeth at the tip of the buccal cavity with the anterior tip narrower than the posterior one. Armilliths absent. Amphid 3–4 µm from the anterior end, crook-shaped with the shorter dorsal branch and parallel much longer ventral branch extending past the base of buccal cavity. Length of the dorsal branch equals 0.13–0.16 of ventral branch length and the amphid length is 1.71–2.1 times the buccal cavity length. Pharynx starts at the base of buccal cavity, muscular, and gradually broadens to the base. Cardia small, roundedconoid, surrounded with intestinal tissue. Renette cell slightly behind the base of pharynx, elongated oval or rectangular, 63–84 µm, 34–41% of the pharynx length. Nerve ring at 58–63% of pharynx length. Excretory pore located at 1 µm from the anterior end of body. Tail length 168–218 µm, conical anteriorly and cylindrical posteriorly, pointed terminal end without terminal setae. Three caudal glands open to the tail terminal.

Male: Five pairs of subventral setae and several irregular setae on the conical portion of the tail, length 4–5 µm. Reproductive system diorchic. Testes paired, opposed and outstretched. Anterior testis to the right and posterior testis to the left of the intestine. Vas deferens well developed. Spicules length 44–46 µm, paired, equal and arcuate, several slight thickened septa respectively closes to dorsal sides and ventral sides, circle aperture next to posterior-ventral rib in distal end and enlarged thickened proximal end with a front, ventral and dorsal constriction. Gubernaculum with dorsal-caudally directed apophysis 14–16 µm long, thickened rib-like edge extended into two distinct points. A precloacal seta present, length 3–4 µm, about 13–15 fibriform precloacal supplements present in front of it, they extend 346–482 µm from cloaca to the anterior end, 27–30% of body length.

Female: Morphologically similar to the male. Unpaired setae on tail. Reproductive system ampdidelphic, ovaries outstretched. Anterior gonad to the right and posterior gonad to the left of the intestine. Vulva is at the midbody. Short vagina with thick walls is perpendicular to the longitudinal body axis. Vulval glands are present anterior and posterior to the vagina. No spermathecae and spermatozoa are found in uteris.

Diagnosis and relationships. Parodontophora microseta sp. nov. is characterized by relatively short cephalic setae (0.19–0.29 h. d.); the positon of the posterior end of the amphid extending past the base of the buccal cavity (1.71–2.1 times the length of the buccal cavity); opisthocephalic setae arranged as (1D- 1V)2; regular arranged somatic setae respectively located on both sides of the amphid from the posterior part of buccal cavity to the conical portion of the tail; excretory pore almost at the anterior end of body; armilliths absent; renette cell occupying 34–41% of the pharynx length; a precloacal seta present; 13–15 fibriform precloacal supplements present and extend 346–482 µm anteriad; anterior gonad to the right and posterior gonad to the left of the intestine. P. microseta sp. nov. comes close to P. obesa Gagarin & Thanh, 2008 and P. leptosoma Gagarin & Thanh, 2008 in relatively short cephalic setae, the ratio of dorsal branch length of the amphid to the ventral branch length, the ratio of amphid ventral branch length to buccal cavity length and the size of renette cell. Whereas it can be separated from P. obesa and P. leptosome by opisthocephalic and somatic setae present, a more anterior position of the excretory pore (almost at the anterior end of body), longer spicule as arc and males have supplements ( Table 8 ).

Notes: 1, excretory pore about at the level of cephalic setae; 2, excretory pore almost at the anterior end of body; *, the data were calculated from original data or published pictures; Y, present; N, absent.

Figures

FIGURE 8. Parodontophora microseta sp. nov. A: lateral view of male anterior part; B: lateral view of female head; C: lateral view of copulatory apparatus; D: lateral view of male tail and spicule; E: lateral view of female tail; F: lateral view of female reproductive system. Scale bar: A, B, C, D, E = 20 Μm; F = 50 Μm.

FIGURE 9. Light micrographs of Parodontophora microseta sp. nov. A: anterior body end of female, showing amphid; B: anterior body end of male, showing buccal cavity; C: lateral view of male body part, showing copulatory apparatus and supplements; D: vulva region; E: longitudinally arranged somatic setae on the ventral side of the amphid; F: posterior body end of female; G: ovary region; H: full view of male body. Scale bars: A, B, C = 10 Μm; D, E = 25 Μm; F, G = 50 Μm; H = 200 Μm.

Tables

TABLE 7. Individual measurement of Parodontophora microseta sp. nov. (in µm).

Characteristics	Holotype	Paratypes
	♂1	♂2 ♂3	♂4	♂5	♀1	♀2
Total body length	1521	1625 1385	1266	1451	1430	1717
Head diameter	15	13 14	15	17	14	16
Cephalic setae	3	3 4	3	4	4	3
Opisthocephalic setae	1	1 1	1	1	1	1
Buccal cavity length	35	34 33	33	33	33	33
Buccal cavity diameter	7	6 7	6	7	6	7
Amphid from anterior end	4	3 3	3	4	4	3
Amphid c. b. d.	30	30 27	29	30	27	37
Amphid dorsal branch length	9	10 10	9	9	9	9
Amphid ventral branch length	60	68 64	69	55	57	61
Excretory pore from anterior end	1	1 1	1	1	1	1
Excretory pore c. b. d.	10	10 9	11	14	10	13
Nerve ring from anterior end	113	117 118	115	114	112	126
Nerve ring c. b. d.	43	47 36	39	53	41	55
Pharynx length	194	200 189	183	188	183	205
Pharynx c. b. d.	49	62 42	40	55	47	68
Renette gland length	68	69 73	68	74	63	84
Maximum body diameter	50	80 43	41	59	49	84
a. b. d.	37	42 34	30	39	31	46
Tail length	201	174 168	180	181	180	218
c'	5.4	4.1 4.9	6.0	4.6	5.8	4.7
Spicule length as chord	39	40 39	38	40	-	-
Spicule length as arc	44	46 44	45	46	-	-
Gubernaculum length	11	10 10	11	11	-	-
Apophysis length	16	14 15	14	16	-	-
Vulva c. b. d.	-	- -	-	-	48	75
Vulva, %	-	- -	-	-	49.7	50.3
a	30.4	20.3 32.2	30.9	24.6	29.2	20.4
b	7.8	8.1 7.3	6.9	7.7	7.8	8.4
c	7.6	9.3 8.2	7.0	8.0	7.9	7.9

TABLE 8. Comparison of Parodontophora microseta sp. nov. and P. paramicroseta sp. nov. with allied species.

Species	P. leptosoma	P. microseta	P. obesa	P. paramicroseta
Buccal cavity length (Μm)	15–17	33–35	20–25	32–34
Cephalic setae length/head diameter	0.27–0.3	0.19–0.29	0.13–0.15	0.2–0.29
Amphidael dorsal branch length/amphidael ventral branch (%)	23*	13–16	20*	19–21
Amphidael dorsal branch length/buccal cavity length	2–2.2*	1.71–2.1	2–2.18*	1.35–1.5
Opisthocephalic setae arrangement	absent	(1D-1V)2	absent	(1D-1V)2
Renette gland length/pharynx length (%)	40–45	34–41	33–41	33–37
Position of excretory pore	Anterior1	Anterior2	Anterior1	Anterior2
Spicule length as arc (Μm)	21–22	44–46	28–31	44–48
Supplements	N	Y	N	Y
Armilliths	N	N	N	N
Reference	Gagarin & Thanh 2008	Present sp. nov.	Gagarin & Thanh 2008	Present sp. nov.