Bathylaimus denticulatus, Chen & Guo, 2014

Chen, Yuzhen & Guo, Yuqing, 2014, Three new species of free-living marine nematodes from East China Sea, Zootaxa 3841 (1), pp. 117-126 : 118-120

Bathylaimus denticulatus sp. n.

( Figure 1 , Table 2 )

Type material. Five males and two females were collected from Station XMHC L1 and XMHC L 2 in October 2011 .

Holotype, ♂ 1 on slide number XMHC 20111015 L211 . Paratypes: ♂ 2 and ♂ 3 on slide number XMHC 20111015 L207, ♂ 4, ♂ 5 and ♀ 2 on slide number XMHC 20111015 L204, ♀ 1 on slide number XMHC 20111015 L101.

Type locality and habitat. Intertidal sandy sediments at Huangcuo coast, Xiamen. Characteristics of surface sediments: see Table 1 .

Etymology. This species is named for the presence of two small teeth in the second section of the buccal cavity.

Description. Body more or less cylindrical, cuticle smooth, length 971–1318 µm, maximum diameter average 33 µm (25–36 µm). Mouth surrounded by three rounded, incised lips. Labial setae 2 µm long, conical. Of the ten cephalic setae, six are three-jointed and 12–16 µm long (0.60–0.75 hd), and four are unjointed and 4 µm long. Buccal cavity, relatively smaller than in other species, divided into two separate sections: the anterior broad, rectangular, heavily cuticularized with an obvious dorsal tooth; the posterior small, weakly cuticularized, with two obvious subdorsal teeth. Amphids 6–7 µm in diameter, about 0.27–0.31 times corresponding body diameter, almost one-looped spiral (0.8–0.9 turns), situated behind the buccal cavity, 29–33 µm from the anterior end. Pharynx cylindrical, 0.17–0.20 times body length. Nerve ring located about mid-way along pharynx from anterior end. Tail in male is thumb-like in shape, 3.2–4.4 abd long, with several scattered short setae and three caudal glands.

Males: Spicules slender, slightly curved, 20–24 µm long as arc. Gubernaculum 17–22 µm long, kidney-like, with thickened anterio-ventral rib, narrow ala and rounded lateral projection with ventro-laterally directed tooth structure distally.

Females: Body slightly smaller than male (female 971–1091 µm vs. male 1106–1318 µm). Ovaries paired, opposed, reflexed. Vulva at 54.3%–57.3% of total body length.

Diagnosis and discussion. The genus Bathylaimus was established by Cobb in 1894 with the type species B. australis Cobb, 1894 . So far, 37 species are known in this genus ( Huang & Zhang 2009). Bathylaimus denticulatus sp. n. is similar to B. huanghaiensis Huang & Zhang, 2009 as well as B. stenolaimus Schuurmans Stekhoven & De Coninck, 1933 , which have a buccal cavity relatively smaller than that in other species. B. denticulatus sp. n. differs from B. huanghaiensis in the following characters: The second part of buccal cavity has two small distinct teeth (teeth lacking in B. huanghaiensis ); amphids approaching one-looped spiral (0.8–0.9 turns vs. 1.2 turns in B. huanghaiensis ); shorter body (971–1318 µm vs. 2177–2435 µm).

B. stenolaimus was first described by Schuurmans Stekhoven and De Coninck in 1933 based on only one female from Oostende, Belgium. Gerlach (1953) redescribed the species based on one male and one female from the Mediterranean and showed the cephalic setae unjointed ( Gerlach 1953). Hopper (1962) made a detailed redescription using two male and three female specimens from Rhode Island, USA. According to Hopper’s description, B. denticulatus sp. n. is close to B. stenolaimus in having smooth cuticle, similar body length (971–1318 µm vs. 1118–1435 µm), and very similar vulva position (54–57% vs. 54–55%) ( Hopper 1962). However, B. denticulatus sp. n. can be distinguished from B. stenolaimus by shorter labial and cephalic setae (2–3 µm and 12–16 µm vs. 5 µm and 18–22 µm), amphids further from anterior end (31–33 µm in male, 29–30 µm in female vs. 23–24 µm in male, 26–28 µm in female); amphids never a complete ring in all observed specimens (0.8–0.9 turns vs. 1 complete turn). Compared with Platt and Warwick’s descriptions, B. denticulatus sp. n. can be distinguished by its smooth cuticle, smaller body length (971–1318 µm vs. 2010–2330 µm), fewer amphid turns (0.8–0.9 vs. 1.5), unjointed labial setae and short cephalic setae ( Platt & Warwick 1983).

Figures

FIGURE 1. Bathylaimus denticulatus sp. n. A: lateral view of male head end; B: lateral view of female anterior part; C: lateral view of male tail, showing spicules and gumbernaculum; D: lateral view of female tail. Scale bar: A, B, C, D = 20µm.