INTRODUCTION
In the past few years, in order to study the biodiversity of free-living marine nematodes in the Yellow Sea, China, sediment samples were collected in many sites from the intertidal to the sublittoral region of the Yellow Sea. A total of 223 species of nematodes, of which three new genera and 21 new species have been described were determined from these habitats (Huang & Zhang, Reference Huang and Zhang2004, Reference Huang and Zhang2005, Reference Huang and Zhang2006a, Reference Huang and Zhangb, Reference Huang and Zhang2007; Zhang & Zhang, Reference Zhang and Zhang2006). The present paper describes two new species which belong to the genera Daptonema Cobb, Reference Cobb1920 and Cobbia De Man, Reference De Man1907 (Xyalidae).
MATERIALS AND METHODS
Meiofauna samples were collected in intertidal sediments at the Huangdao coast of Qingdao (120°10′E 35°59′N.) and Rizhao coast of Shandong province (119°34′E 35°26′N.) along the littoral of the Yellow Sea using a sawn-off syringe with a 2.9 cm inner diameter. The syringes were pushed into the sediment down to 8 cm. Samples were fixed with 5% formalin in filtered seawater. In the laboratory, samples were stained with 0.1% rose Bengal for more than 24 hours (Higgins & Thiel, Reference Higgins and Thiel1988). All samples were washed to remove the formalin and sieved over two mesh sizes (500 µm and 42 µm) in order to separate the macrofauna (500 µm) from the meiofauna (42 µm). Heavier sediment particles were removed using centrifugation in Ludox™ with a specific gravity adjusted to 1.15 (Jonge & Bouwman, Reference Jonge and Bouwman1977). Each sample was washed into a lined Petri dish and the meiofauna was sorted under a stereoscopic microscope up to higher taxonomic levels. Nematodes were transferred into a 9 : 1 (V : V) solution of 50% alcohol : glycerol in block cavity to slowly evaporate alcohol and then mounted in glycerol on permanent slides (McIntyre & Warwick, Reference McIntyre, Warwick, Holme and McIntyre1984). The descriptions were made from glycerin mounts using interference contrast microscopy. Drawings were made with a camera lucida. Type specimens have been deposited in the Institute of Oceanology, Chinese Academy of Sciences.
Measurements are in µm. Abbreviations are as follows: de Man a, body length/maximum body diameter; a.b.d., anal body diameter; de Man b, body length/oesophagus length; de Man c, body length/tail length; c. d., corresponding body diameter; Sc, spicule length along the chord; V, distance of vulva from the anterior end of body; V%, V/body length%.
Fig. 1. Daptonema longiapophysis sp. nov. (A) lateral view of male head end, showing buccal cavity, cephalic setae and excretory pore; (B) lateral view of female head end; (C) lateral view of male tail end, showing spicules, gubernaculum and somatic setae; (D) lateral view of female body, showing ovary, eggs, sperm packet and vulva; (E) lateral view of female tail end, showing vulva, anus and caudal glands.
Fig. 2. Daptonema longiapophysis sp. nov. (A) lateral view of male head end, showing buccal cavity and cephalic setae; (B) lateral view of female anterior end, showing cephalic setae and cuticle striated; (C) lateral view of male tail end, showing spicules and gubernaculum; (D) lateral view of male tail end, showing spicules, gubernaculum, pre-cloacal seta and post cloacal seta.
TYPE MATERIAL
Six males and three females were measured and studied. Holotype, ♂1, specimen number: LUH018 (slide number: LUJ080301); paratypes: ♂2, ♂3, ♂4, ♂5, ♂6, ♀1, ♀2, ♀3, specimen numbers LUH019–026 (slide numbers: LUJ080302–09).
TYPE LOCALITY AND HABITAT
Intertidal sandy sediment at Rizhao coast (119°34′E 35°26′N.) and the Huangdao coast (120°10′E 35°59′N.)
ETYMOLOGY
This species is named after its unusually long apophysis of the gubernaculum.
MEASUREMENTS (TABLE 1)
Table 1. Individual measurements (and average) of Daptonema longiapophysis sp. nov. (absolute numbers in µm).
DESCRIPTION
Males: body slender, with conico-cylindrical tail. Cuticle with coarse annulations. Annules separated by refractive lines, beginning at base of buccal cavity and ending at tail tip. Six large and raised lips, each of them strengthened by arcuate, curved, slender, cuticularized ribs (Figure 1A, B). Six labial sensilla setiform, 3.5 µm long; 12 cephalic setae, six longer ones (17 µm) and six shorter ones (13 µm). Somatic setae scattered over body and dense posterior to cloaca. Buccal cavity spacious and conical (Figure 2A, B), about 20 µm long and 15 µm wide. Amphids inconspicuous. Excretory pore present, situated about 2 head diameters from the anterior (Figure 1A). Pharynx cylindrical. Nerve ring at about 125 µm from anterior end, i.e. at 34% of pharyngeal length. Tail 183 µm long (6 a.b.d.), tapering with distal third cylindrical and two terminal setae (Figure 1C). Three caudal glands with common opening.
Spicules curved, about 24 µm long (measured along chord), tapered distally, with a projection on ventral and dorsal side respectively at about middle part. Gubernaculum parallel to distal part of spicules, with long (25 µm) dorso-caudally directed apophysis (Figures 1A & 2C, D). One pre-cloacal and one post-cloacal seta.
Females: similar to male in most respects. A single anterior outstretched ovary dorsally of left side of intestine, about 570 µm long. One or two sperm packets in uterus (Figure 1D). Vulva at 77% of body length (Figure 1E).
DIFFERENTIAL DIAGNOSIS
Daptonema longiapophysis sp. nov. are characterized by setiform labial sensilla, spicules with a projection on the ventral and dorsal side respectively. The length of the apophysis of the gubernaculum is longer than the length of the spicules. This new species is close to D. deconincki Sharma, 1985 in the size and structure of the body. Nevertheless, the spicules of the latter species have bifid tips, are 49 µm long, the gubernaculum surrounds the distal half of the spicules. The length of the apophysis of the gubernaculum is shorter than the spicules in that species. This new species also resembles D. setosum (Bütschli, 1874) Filipjev, 1930, which also has a very big and broad gubernaculum and a spicule with one or two small spines. However, its spicules are L-shaped, distally bifurcate and the length of the apophysis of the gubernaculum is also shorter than the spicules in this species (18–22 µm versus 62–64 µm).
DISCUSSION
The genus Daptonema was established by Cobb in 1920 with the type species D. fissidens Cobb, Reference Cobb1920. This genus includes many species and presents particular difficulty for identification. Wieser (Reference Wieser1956) considered Daptonema as one of five subgenera of Theristus. This subdivision was refuted again by Lorenzen (Reference Lorenzen1977) in a review of the Xyalidae. Daptonema species are separated from those of Theristus only by the shape of the tail: conico-cylindrical with terminal setae in the former, conical without terminal setae in the latter. Within Daptonema, species are distinguished by rather few characters: mainly the relative length of the setation, size and position of the amphids, size and structure of the copulatory apparatus and the shape and length of the tail (Warwick et al., Reference Warwick, Platt and Somerfield1998).
So far, 120 species of Daptonema have been described (Tchesunov & Miljutin, Reference Tchesunov and Miljutin2006; Electronic databases http://nemys.ugent.be and http://www.marinespecies.org). The new species D. longiapophysis sp. nov. differs from the other species in this genus by labial setae, annules separated by refractive lines, an inconspicuous amphid, projected spicules and the apophysis of the gubernaculum longer than the spicules.
Fig. 3. Cobbia sinica sp. nov. (A) lateral view of female body, showing oesophagus and vulva; (B) lateral view of male head end, showing cephalic setae, buccal cavity, dorsal teeth and amphid; (C) lateral view of female head end, showing cephalic setae, buccal cavity, dorsal teeth and amphid (D) lateral view of male tail, showing spicules, gubernaculum and caudal glands.
Fig. 4. Cobbia sinica sp. nov. (A) lateral view of male head end, showing buccal cavity and; (B) lateral view of female head end, showing two sections of buccal cavity; (C) lateral view of male head end, showing subspiral amphid; (D) lateral view of male head end, showing buccal cavity and a distinct dorsal teeth.
TYPE MATERIAL
Five males and three females were measured and studied. Holotype: ♂1, specimen number: LUH027 (slide number: LUR080401); paratypes: ♂2, ♂3, ♂4, ♂5, ♀1, ♀2, ♀3, specimen numbers LUH028–034 (slide numbers LUR080402–08).
TYPE LOCALITY AND HABITAT
Intertidal muddy sediment at Rizhao coast of Shandong province: 119°34′E 35°26′N.
ETYMOLOGY
This species is named after the country where the type locality is situated: China.
MEASUREMENTS (TABLE 2)
Table 2. Individual measurements (and average) of Cobbia sinica sp. nov. (absolute numbers in µm).
DESCRIPTION
Males: body slender, with conico-cylindrical tail (Figure 3A). Body length 1109 µm; maximal diameter 22 µm. Cuticle striated. Labial setae 4 µm in length. Six longer cephalic setae (19 µm) and four shorter (14 µm) cephalic setae. Somatic setae scattered along the body. Buccal cavity conical, with three slightly cuticularized teeth. Dorsal tooth extending further anteriorly, big and distinct (Figures 3B, C & 4A, B); two subventral teeth very small and indistinct. Amphid circular, 6 µm wide (0.35 c.d.), situated 20 µm from anterior. Pharynx cylindrical. Nerve ring not obvious. Tail conico-cylindrical, 141 µm long (7 a.b.d.), with distal half cylindrical, with two terminal setae (Figure 3D).
Spicules equal in size, L-shaped, 22 µm long as chord (26 µm long measured along arc), cephalate proximally. Gubernaculum parallel to distal portion of spicules and with small dorsal apophysis (Figure 4C, D).
Females: similar to male. Only one prodelphic, outstretched ovary. Vulva at 70% of body length.
DIFFERENTIAL DIAGNOSIS
Cobbia sinica sp. nov. are characterized by one big dorsal tooth, a small amphid, a long conico-cylindrical tail and a gubernaculum with a small dorsal apophysis. This new species is close to Cobbia caledonia Warwick & Platt, 1973 in the size of the teeth in the buccal cavity, but different in size and position of the amphids and the structure of the gubernaculum. In the latter species, amphids are bigger (11 µm wide versus 6 µm wide) and positioned farther from the anterior end (more than three head diameters versus less than two head diameters). Gubernaculum without apophysis. The new species is also similar to Cobbia dentata Gerlach, 1953. However, the tail of the latter species is conical, not conico-cylindrical, its cephalic setae are longer (two head diameters versus one head diameter) and their De Man ratios are different too. The new species differs from another similar species, Cobbia trefusiaeformis De Man, Reference De Man1907, by: (1) the tail length of the latter species being 12–17 a.b.d. versus 7 a.b.d. of the former; (2) tail with a conical first quarter, then long filiform, without terminal seta; and (3) spicules with a lateral spine at the distal end.
DISCUSSION
The genus Cobbia was erected by De Man in Reference De Man1907 with the type species Cobbia trefusiaeformis De Man, Reference De Man1907. It differs from the other genera in the family Xyalidae by a buccal cavity with three teeth and setiform labial sensilla. Up to now, nine species in this genus have been described (Wieser, Reference Wieser1959; Gerlach & Riemann, Reference Gerlach and Riemann1973; Warwick et al., Reference Warwick, Platt and Somerfield1998). They are distinguished from each other by the combination of the size of the dorsal tooth, the diameter and distance from the anterior end of the amphid, the shape of spicules and gubernaculum and the length of the labial setae and cephalic setae.
ACKNOWLEDGEMENTS
This work was supported by National Science Foundation of China (No: 30770250). The authors are very thankful to both anonymous reviewers for their valuable revision and remarks. We are very grateful to MSc. Xiuqin Wu for her kind help in sample collection and slide making.
