Chinese Journal of Oceanology and Limnology   2016, Vol. 34 issue(2): 295-300     PDF       
http://dx.doi.org/10.1007/s00343-015-4395-0
Institute of Oceanology, Chinese Academy of Sciences
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Article Information

WANG Chunming(王春明), HUANG Yong(黄勇)
Pseudolella major sp. nov.(Axonolaimidae, Nematoda) from the intertidal zone of the East China Sea
Chinese Journal of Oceanology and Limnology, 34(2): 295-300
http://dx.doi.org/10.1007/s00343-015-4395-0

Article History

Received Dec. 26, 2014
accepted in principle Jul. 16, 2016
Pseudolella major sp. nov.(Axonolaimidae, Nematoda) from the intertidal zone of the East China Sea
WANG Chunming(王春明)1,2, HUANG Yong(黄勇)1        
1 College of Life Sciences, Liaocheng University, Liaocheng 252059, China;
2 College of Life Sciences, Shandong Normal University, Jinan 250014, China
ABSTRACT: A new species of free-living nematode, Pseudolella major sp. nov. is described from the intertidal mudflats of Ximen Island in the East China Sea. Pseudolella major sp. nov. is characterized as follows:body length~1300μm; short cephalic setae, 2-3μm long; amphidial fovea loop-shaped with elongated ventral branch; ventral branch 50-60μm long and extending past the base of buccal cavity; buccal cavity cylindrical with arching or spherical base; three heavy outwardly-curving odontia with blunt tips located at anterior of buccal cavity; pharynx short with posterior bulb; ventral gland cell elongate oval-shaped, located posterior to pharyngo-intestinal junction; excretory pore situated at the level of the middle of buccal cavity; tail conical to cylindrical; spicules arched, with double-cephalate proximal end; gubernaculum with a strong dorsal caudal apophysis.
Key words: free-living marine nematode     Pseudolella major sp. nov.     taxonomy    
1 INTRODUCTION

During an investigation of the biodiversity of freeliving nematodes in the East China Sea in 2013, a species of genus Pseudolella Cobb, 1920 from the intertidal mudflats of Ximen Island, Wenzhou City (121°20'E, 28°6'N.) was identified as a new species. Genus Pseudolella was established by Cobb in 1920 with the type species P . granulifera . The genus Pseudolella is characterized as: buccal cavity large, cylindrical with sclerotized parallel walls, arching inward sharply at base; three heavy outwardlycurving odontia located at anterior of buccal cavity; amphidial fovea loop-shaped with elongated ventral branch. To date, a total of 14 species are known worldwide (Gerlach and Riemann, 1973; Gagarin and Thanh, 2008). The list of 14 recorded species of Pseudolella is as follows:

P . bengalensis (Timm, 1957) Gerlach, 1962, St. Martin's Island

P. brevamphida Timm, 1952=Parodontophora brevamphida (Timm, 1952)

P . capera Tchesunov, 1978

P . cephalata Cobb, 1920, Pacific coast of Costa Rica

P . cobbi Timm, 1952 = Parodontophora cobbi (Timm, 1952)

P . ferox Smoljanko and Belogurov, 1993, Vietnam

P . granulifera Cobb, 1920, New Caledonia

P . intermedia Gerlach, 1957, Cananéia

P . irritans Smoljanko and Belogurov, 1993, Vietnam

P . minor Gagarin and Thanh, 2008, Vietnam

P . norvegica Allgén, 1947, Norway

P . paragranulifera Timm, 1952= Parodontophora paragranulifera (Timm, 1952)

P . polita Gerlach, 1955= Parodontophora polita (Gerlach, 1955)

P . parva Gagarin and Thanh, 2006, Vietnam

2 MATERIAL AND METHOD

In February 2013, sediment samples were collected at the intertidal mudflats of Ximen Island in the East China Sea. Sampling was carried out using a syringe of2.6 cm internal diameter pushed into the sediment to a depth of 8 cm. The samples were divided into 0–2 and 2–8 cm segments and fixed with an equivalent volume of 10% formalin in seawater for long-term preservation. In the laboratory, samples were stained with 0.1% rose bengal for 24 h (Higgins and Thiel, 1988). The stained samples were washed with tap water to remove residual formalin and then sieved through two mesh sizes to separate macrofauna (500 μm mesh) from meiofauna (42 μm mesh). Heavier sediment particles were removed by centrifugation in Ludox- TM (a 50% suspension of colloidal silica in water; Sigma-Aldrich Co., USA) with specific gravity adjusted to 1.15 g/mL (de Jonge and Bouwman, 1977). Each sample was washed into a grid-lined Petri dish with distilled water and the meiofauna was sorted under a stereoscopic microscope into the higher taxonomic levels. Nematodes were transferred into 10 mL of a 9׃1 (v/v) mixture of 50% ethanol in fresh water and pure glycerin, in a cavity block. The ethanol and water were then slowly evaporated and the specimens were mounted in glycerin on permanent slides (McIntyre and Warwic, 1984). The descriptions were made from glycerin mounts using a differential interference contrast microscope (Eclipse 80i, Nikon Corp., Chiyoda, Tokyo, Japan). Line drawings were made with the aid of a camera lucida. Type specimens were deposited in the Institute of Oceanology, Chinese Academy of Sciences, Qingdao.

All measurements were made in μm, and all curved structures were measured along the arc. Abbreviations are as follows: a: body length / max. body diameter; a.b.d.: anal body diameter; b: body length / pharynx length; c: body length / tail length; c.b.d.: corresponding body diameter; c': tail length / a.b.d; h.d.: head diameter; M.: maximum body diameter; Spic: spicule length along the arc; V: corresponding body diameter of vulva; V%: position of vulva from anterior end expressed as a percentage of total body length.

3 SPECIES DESCRIPTION

Order MONHYSTERIDA

Family AXONOLAIMIDAE De Coninck and Stekhoven, 1933

Genus Pseudolella Cobb, 1920

Pseudolella major sp. nov. (Figs.1, 2)

Figure 1 Pseudolella major sp. nov.
Figure 2 Pseudolella major sp. nov.
3.1 Type material

Four males and two females collected from Ximen Island, Wenzhou.

Holotype ♂1 and Paratype ♀1 both on the slide wzxmd20132-6; Paratypes ♂2—♂5 and ♀2 on the slides wzxmd20132-10 and wzxmd20132-14, respectively.

3.2 Type locality and habitat

Intertidal mudflats of Ximen Island, Wenzhou in the East China Sea, 121°20'E, 28°6'N.

3.3 Etymology

This species is named for its character of a comparatively large body within the genus.

3.4 Measurements (Table 1)

Holotype ♂1 313 μm; a=32, b=8.9, c=9.1, Spic=35

Paratype ♀1 1 383 μm; a=33, b=8.3, c=8.1, V%=51%

Note: Filipjev formula:pl: pharynx length; ble: total body length excluding tail length; p.cbd: cbd at pharynx base .

Table 1 Individual measurements of Pseudolella major sp. nov. (in μm except for ratios)
3.5 Description based on holotype

Holotype male. Cuticle finely striated. Head tapering, rounded. Four cephalic setae 2 μm long. Four longitudinal rows of 2 or 3 cervical setae, about 2 μm long, arranged as two subdorsal groups and two subventral groups. Amphidial fovea loop-shaped, lying at the very anterior, with the short branch reaching just to the level of the odontia and the long branch extending 50 μm posteriorly and slightly beyond the base of buccal cavity. Buccal cavity cylindrical, sclerotized, 40 μm long, with parallel walls and then arching inward sharply at base. Three heavy outwardly-curving odontia with blunt tips located at anterior of buccal cavity. Pharynx starting at stoma base, short with posterior bulb. Cardia small, conical to rounded. Ventral gland cell large, elongate oval-shaped, cell body 58 μm long, located posterior to pharyngo-intestinal junction (250 μm from anterior end of body). Excretory pore situated at the level of the middle of buccal cavity. Tail conical-cylindrical with one third cylindrical part, length 4.6 times a.b.d. Three caudal glands open through spinneret.

Testes extended, opposed. Anterior testis to the right and posterior testis to the left of the intestine. Spicules arched, with double-cephalate proximal end and tapered distal end, 35 μm long. Gubernaculum with a dorsal apophysis, 15 μm long with a projection at the middle of its ventral side. Precloacal supplements absent.

Female. Reproductive system amphidelphic, ovaries extended. Anterior ovary situated to left side of intestine, posterior ovary situated to right side of intestine. Vulva located at about the mid-body.

3.6 Diagnosis and discussion

Pseudolella major sp. nov. is characterized as follows: ~1 300 μm body length; very finely striated cuticle; short cephalic setae, 2 μm long (20% h.d.); amphidial fovea loop-shaped with elongated ventral branch (50–60 μm long or 1.2 times stoma length) and slightly beyond the base of the buccal cavity; buccal cavity cylindrical with arching or expanded base; three heavy outwardly-curving odontia with blunt tips located at anterior of buccal cavity; pharynx short with posterior bulb; ventral gland cell elongate oval-shaped, located posterior to pharyngo-intestinal junction; excretory pore situated at the level of middle of buccal cavity; tail conical to cylindrical, spicules arched, with double-cephalate proximal end and tapered distal end; gubernaculum with a dorsal apophysis. Pseudolella major sp. nov. is closely related to P . bengalensis (Timm, 1957) Gerlach, 1962 in having three odontia, but it differs from P . bengalensis in having a comparatively longer body (1 228–1 383 μm vs 1 100 μm), shorter cephalic setae (2 μm, 20% h. d. vs 5 μm, 40% h. d.), shorter ventral branch of amphidial fovea (50–60 μm, 1.2 times stoma length vs 65–74 μm, more than 1.7 times stoma length), comparatively shorter tail (4.2–5.2 a.b.d., 2/3 conical and 1/3 cylindrical vs 5.5–6 a.b.d., 1/2 conical and 1/2 cylindrical) and, in P . bengalensis, spicules of male with a double internal division, female's ovaries reflexed. The new species is similar to P . minor Gagarin & Thanh, 2008, P. ferox Smoljanko & Belogurov, 1993 and P . granulifera Cobb, 1920. But it differs from P . minor in the longer body length (1 228–1 383 μm vs 535–721 μm), comparatively long ventral branch of amphidial fovea (50–60 μm without transverse striation vs 42–45 μm long with transverse striation), longer spicules (35– 49 μm vs 21–22 μm). It differs from P . ferox in the longer pharynx (b=7.6–8.9 vs b=13–19), comparatively shorter ventral branch of amphidial fovea (50–60 μm vs 77 μm) and comparatively shorter and thicker tail (c' 4.7–5.2 vs c' 6.0). It differs from P . granulifera Cobb, 1920 in the longer body (1 228–1 383 μm vs 690–810 μm), longer buccal cavity length (40–50 μm vs 32–35 μm), longer ventral branch of amphidial fovea (50–60 μm vs. 41 μm), longer spicules (35–49 μm vs 28 μm long.), longer dorsal-caudal apophysis of gubernaculum (15–23 μm vs 9 μm long) and shorter tail (4.6 a.b.d.vs 5.9 a.b.d.).

Key to 11 valid species of Pseudolella Cobb, 1920 based on Smoljanko & Belogurov, 1993

1 Body very large, longer than 3 000 μm …………………………………………P . norvegica

Body length shorter than 2 000 μm……………2

2 Buccal cavity with three odontia ……………3

Buccal cavity with two odontia ………………4

3 Ventral branch of amphid longer than 1.7 times stoma length …………………… P . bengalensis

Ventral branch of amphid shorter than 1.2 times stoma length ………………… P . major sp. nov.

4 Ventral branch of amphid very long, reaching mid-body…………………………… P . cephalate

Ventral branch of amphid twice of stoma length… ……………………………………… P . ferox

Ventral branch of amphid shorter than twice stoma length …………………………………5

5 Ventral branch of amphid not extending beyond stoma base ……………………………………6

Ventral branch of amphid extending beyond stoma base …………………………………………7

6 Amphids short, ventral branch half of stoma length ..…………………………………… P . parva

Ventral branch of amphid equal to stoma length ……………………………………… …… P . capera

7 Cuticle smooth ………………… P . intermedia

Cuticle ringed ………………………………8

8 Presence of tubular precloacal supplement …………………………………………… P . irritans

Absence of tubular precloacal supplement ……… ………………………………9

9 Ventral branch of amphid with transverse striation ………………………………………… P . minor

Ventral branch of amphid smooth without transverse striation ……………P . granulifera

4 ACKNOWLEDGEMENT

We are sincerely grateful to Prof. Vladimir G. Gagalin for providing related references.

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