ZHAI Hongxiu , WANG Chunming , , HUANG Yong , ,

1 College of Life Sciences, Liaocheng University, Liaocheng 252059, China

2 Key Laboratory of Ecology and Biodiversity of Shandong Colleges and University, Liaocheng 252059, China

Abstract A new free-living marine nematode species of the genus Sabatieria was documented from the sediment of the Jiaozhou Bay, Qingdao, China, and it has been named Sabatieria sinica sp. nov. It is characterized by homogeneous cuticle without lateral diff erentiation, relatively short cephalic setae, spiral amphideal fovea with 2-2.25 turns; thick spicules with a mid constriction or joint, gubernaculum with a long straight dorso-caudal apophyses, and 6-7 prominent papillar precloacal supplements. This new species could be distinguished from other congener species by the combination of its characteristics: body size,length of cephalic setae, number of amphid turns, structures of spicules and gubernaculum, and type and number of precloacal supplements. An update dichotomous key is provided for nine species of pulchra group of Sabatieria including the new species.

Keyword: new species; free-living marine nematode; taxonomy; Jiaozhou Bay

1 INTRODUCTION

The genusSabatieriawas established by Rouville based on the type speciesSabatieriacettensisin 1903.It is a dominating and large genus in a variety of habitats. To date, 99 valid species have been recorded around the world (Leduc, 2017; Guo et al., 2018;Bezerra et al., 2019). Platt (1985) reviewed the genus and divided 36 valid species into f ive groups(praedatrixgroup,armatagroup,pulchragroup,celticagroup, andornatagroup) according to the main characteristics including the length of cephalic setae, the number of turns of amphideal fovea, the type and distribution of precloacal supplements,features of gubernaculum and apophyses and character of cuticle punctation. Subsequently, Botelho et al. (2014) reviewed the genus in 2014, conf irmed 66 valid species, and concurrently described two new species from Brazil:SabatierialabiumandSabatieria verteris. In the same year, Rosli et al. (2014) also revised the genus, and gave the modif ied list including 68 valid species that were divided into f ive groups.Meanwhile, they described a new speciesSabatieria dispunctatafrom New Zealand. The newly recorded species in this genus wereSabatieriamegadenaLeduc (2017) also from New Zealand andSabatieria conicosetaGuo, Chang & Yang, 2018 from China.

Sediment samples were collected in many sites from intertidal to sublittoral regions in 2015 and 2016 with the aim to study the biodiversity of free-living marine nematodes in the Jiaozhou Bay of Qingdao,China. The average abundance of the nematodes was 2 538±676 inds./10 cm2. Up to now, 198 nematode species were identif ied from these habitats (Gao,2017; Huang et al., 2018, 2019).Sabatieriais the common and abundant genus in the Jiaozhou Bay.Four species ofSabatieriawere discovered, and among them, an unrecorded species was identif ied and is described here asSabatieriasinicasp. nov.

2 MATERIAL AND METHOD

Undisturbed samples of seaf loor sediment were taken using a 0.1-m2improved Gray-O’Hara boxcorer at a grid of sixteen sampling stations(36°7′10″N-36°35′6″N; 120°14′12″E-120°30′58″E,water depth 3.8-18 m) in July 2016 in the Jiaozhou Bay, Qingdao. The nematodes were collected, sorted,and slide mounted as already indicated in our previous papers (Gao and Huang, 2017; Huang et al., 2018).The descriptions were made from glycerin mounts using a diff erential interference contrast microscope(Leica DM-2500). Line drawings were made with the aid of a camera lucida. All measurements were obtained using Leica LAS X version 3.3.3, and all curved structures were measured along the arc or median line. Type specimens were deposited in the Key Laboratory of Biodiversity, Liaocheng University, Shandong, China.

Table 1 Individual measurements of Sabatieria sinica sp. nov. (in μm except a, b, c, c′, and V%)

3 SPECIES DESCRIPTION

Order Araeolaimida de Coninck and Schuurmans Stekhoven, 1933

Family Comesomatidae Filipjev, 1918

GenusSabatieriaDe Rouville, 1903

Sabatieriasinicasp. nov. (Figs.1, 2)

3.1 Type material

Two males and three females were collected from the Jiaozhou Bay. Holotype, ♂1 on slide number JZW11-4. Paratypes: ♂2, ♀1, ♀2, and ♀3 on the slide number JZW11-2, JZW11-4, and JZW11-3, respectively.

3.2 Type locality and habitat

Specimens were collected from the surface 0-2 cm sublittoral silt sediment at station JZW-11 in the Jiaozhou Bay (JZW-11: 36°10′16″N; 120°16′51″E),water depth of 5.5 m.

3.3 Etymology

The new species is named after the national name of type locality belonging to, China.

3.4 Measurement

All measurement data are given in Table 1.

3.5 Description

Fig.1 Sabatieria sinica sp. nov.

Males: body cylindrical, attenuated at both ends.Cuticle homogeneous with transverse rows of punctuations from the anterior border of the amphideal fovea to the cylindrical part of tail, and without lateral diff erentiation of coarse dots. Cervical setae twinning,short, 2.5-3 μm long, three to four pairs. Somatic setae short and sparse. Head slightly set off by constriction posterior to cephalic setae. Inner labial sensilla invisible. Outer labial sensilla papilliform.Four cephalic setae, 3-4.5 μm long. Multi-spiral amphideal fovea with 2.25 turns, 8-9 μm in diameter or 47% of corresponding body diameter. Anterior border of amphideal fovea at the level of cephalic setae. Buccal cavity small, cup-shaped with slightly sclerotized walls. Pharynx cylindrical, with an ovalshaped posterior bulb. Cardia conical. Nerve ring near middle of pharyngeal length, 119-122 μm from the anterior end, 56%-57% of the pharyngeal length.Secretory-excretory system distincte, excretory pore slightly posterior to nerve ring, 141 μm from the anterior end; ampulla large; renette cell large and conspicuous, located posterior to pharyngealintestinal junction.

Fig.2 Sabatieria sinica sp. nov.

Reproductive system diorchic, testes opposite and outstretched. Spicules thick with median hollow region, proximal half oval and straight, distal half tapered and curved, with a distinctive constriction or joint between the two halves, 54-69 μm (1.3-1.7 times as long as body diameter at the level with cloaca) long along arcuate. Gubernaculum with a long straight dorso-caudal apophysis, 28-30 μm long.6-7 papillar precloacal supplements, more or less evenly spaced. Tail 3.2-3.8 body diameter at anus,conico-cylindrical with rounded swollen tip bearing three terminal setae, 6-7 μm long. Cylindrical part about third of total length. A row of ventral caudal setae located at conical portion of tail. Three caudal glands obvious.

Females: similar to males in most morphologicaly aspects excepting tail without ventral caudal setae,amphideal fovea with 2 turns. Reproductive system didelphic with two opposite and outstretched ovaries.Vagina trumpet-shaped, 0.3 times vulval body diameters long. A large sack-like spermatheca situated at each side anterior and posterior to vulva and f illed with oval sperms. Vaginal glands present. Vulva with slightly raised lips and situated at about mid-body.

3.6 Diff erential diagnosis and discussion

Sabatieriasinicasp. nov. is characterized by homogeneous cuticle without lateral diff erentiation;cephalic setae 3-5 μm; spiral amphideal fovea with 2-2.25 turns; thick and arcuate spicules with median hollow region and a mid-constriction or joint;gubernaculum with relatively long dorso-caudal apophyses; 6-7 prominent papillar precloacal supplements.Sabatieriasinicasp. nov. belongs topulchragroup mainly because of the low number of supplements (5-9), the gubernaculum with median pieces, relatively short cephalic setae and short paired cervical setae. Most species in the pulchra group have the amphids with 3-4 turns, but some species such asS.propisinnaandS.brevisetahave the amphids with only 2.5 and 2.25 turns, respectively. The described species is most close to thepulchragroup to comprehensively consider its main characteristics and does not f it under the other groups. Thepulchragroup currently includes eight species:S.brevisetaStekhoven, 1935;S.maboyaeGourbault & Vincx,1990;S.mortenseni(Ditlevsen, 1921) Leduc &Wharton, 2008;S.pisinnaVitiello, 1970;S.propisinnaVitiello, 1976;S.pulchra(Schneider, 1906)Tchesunov, 1978;S.pumilaLeduc, 2013;S.punctata(Kreis, 1924) Timm, 1952 (Botelho et al., 2014; Rosli et al., 2014).

This new species is most similar toSabatieria pulchra(Schneider, 1906) Tchesunov, 1978 in morphological features, but diff ers from the latter species in having thick and jointed spicules (vs slender spicules only enlarged proximal end not constricted at mid inS.pulchra), longer gubernacular apophyses (28-30 μm vs 19-22 μm), slightly shorter cephalic setae (3-5 μm vs 6-7 μm long), and the disposition of precloacal supplements (6-7 papillar precloacal supplements, more or less evenly spaced vs 7-9 tubular precloacal supplements, anterior ones more closely spaced). The diff erence ofSabatieria sinicasp. nov. with other congeners can be referred to the key below.

Update key to known species of pulchra group

1 Cephalic setae longer than 0.5 head diameter.........2 Cephalic setae shorter than 0.5 head diameter...........3

2 Spicule 2.1 abd, 4-5 precloacal supplements..........................S.maboyaeGourbault & Vincx, 1990 Spicule 1 abd, 6 precloacal supplements........................S.mortenseniLeduc & Wharton, 2008

3 Spicule with distal hook and short distal lamella.................................................S.pumilaLeduc, 2013 Spicule without distal hook........................................4

4 Body length shorter than 800 μm............................5 Body length longer than 1 000 μm............................6

5 Cephalic setae 0.22 head diameter, lateral diff erentiation absent..............S.pissinaVitiello, 1970 Cephalic setae 0.43-0.44 head diameter, lateral diff erentiation present.......S.propissinaVitiello, 1976

6 Lateral diff erentiation present, amphideal fovea 3 turns.......................................S.punctataTimm, 1952 Lateral diff erentiation absent.....................................7

7 Spicule thick with mid constriction, cephalic setae 3-5 μm..............................................S.sinicasp. nov.Spicule slender without mid constriction...................8

8 Body 1.9-2.3 mm, amphids 2.5 turns, cephalic setae 6-7 μm.............................S.pulchraTchesunov, 1978 Body 1.1-1.3 mm, amphids 3.5 turns, cephalic setae 3-4 μm...........................S.brevisetaStekhoven, 1935

4 DATA AVAILABILITY STATEMENT

The authors declare that the data supporting the f indings of this study are available within the article.The data will be available on request from the corresponding author.

5 ACKNOWLEDGMENT

The authors are greatly thankful to Dr. HUANG Mian and Mrs. GAO Qun for their kind help in specimen sorting and slide mounting. We are sincerely grateful to two anonymous referees for reviewing and improving the manuscript.