Laimella tongyeongensis, Barnes & Kim & Lee, 2012

Barnes, Natalie, Kim, Hyeong Geun & Lee, Wonchoel, 2012, New species of free-living marine Sabatieriinae (Nematoda: Monhysterida: Comesomatidae) from around South Korea *, Zootaxa 3368 (1), pp. 263-290 : 273-275

Laimella tongyeongensis sp. nov.

( Figs. 3 & 4 )

Type material. Three males, one female and three juveniles. Holotype male NIBRIV0000245028 and paratype males NIBRIV0000245030 and NIBRIV0000245032. Paratype female NIBRIV0000245031 and paratype juveniles NIBRIV0000245029, NIBRIV0000245033 and NIBRIV0000245034.

Type locality. All specimens were collected sub-tidally, near the islands of the southern extent of the Tongyeong sea, South Korea (34.5789º N 128.4169º E), at a depth of 49 m, in muddy sediment. Specimens were collected by Kwang-Soo Kim, Dong-Ju Lee, and Kichoon Kim in February, May and December 2010, respectively, from Research Vessel Tam-Gu 7 .

Measurements. See Tables 3 and 4 for detailed measurements and calculations.

4 205 - 977 1494 934 1897

male 1

17 42 43 36

4 172 219 629 205 1124 1505

female 1

11 33 35 27

Description. Male holotype ( Fig. 3 ). Habitus tubular, tapering to elongate tail posteriorly, blunt anteriorly. Cuticle with faint punctation in lateral field of cervical region, otherwise weakly striate, most visible as subcuticular character. Narrow region just behind cephalic setae, body diameter increasing to at most 2hd from anterior, then approximately stable to cloaca. Tail conico-cylindrical.

Labia as 6 small lips, labial papillae minute. Six anterior cephalic setae (0.3 hd long) located about 0.3 hd from anterior extremity, 4 posterior cephalic setae (0.8 hd long) immediate behind. Amphid multi-spiralled with 3.25 turns (diameter 0.6 cbd), close behind cephalic setae (0.4 hd from anterior). Cervical setae about 7 µm long, in 4 uneven longitudinal rows starting as a pair directly behind amphid, possibly some breakage. Somatic setae rare. Around the cloaca, setae as sub-dorsal and dorso-sublateral rows. Last observed setae at base of conical section of tail.

Buccal cavity with minute anterior section (4 µm deep) and posterior portion as weakly sclerotized collapsed tube, base not differentiated, with three teeth at anterior margin, 6 µm long. Slightly swollen oesophageal musculature surrounds buccal cavity, anteriorly faintly sclerotized, then cylindrical to elongate oesophageal bulb (22 % of oesophagus length) with thickened lining of lumen. Cardia short (12 µm long). Nerve-ring at 51 % of oesophageal length from anterior, ventral pore posterior to nerve ring (55 % of oesophagus length). Ventral gland small, rounded, distance from pore to base of gland 108 µm (53 % of oesophageal length).

Diorchic, outstretched testes, anterior testis 977 µm long, posterior testis 934 µm long. Spicules arcuate (length 1.7 abd, as curve), gubernaculum with posteriorly directed paired apophyses (0.6 abd long). Ejaculatory glands not observed. Cloaca as lateral slit. One short mid-ventral papilla (2 µm long) located 0.3 abd anterior to cloaca. Precloacal supplements not observed in holotype, 5 supplements noted in only one paratype male (male2); posterior supplement 0.5 abd from cloaca and anteriormost supplement 2.8 abd from cloacal. Three small caudal glands positioned posterior to gubernacular apophyses in conical region of tail. Tail 10.7 abd long, with elongate cylindrical portion 83 % of total tail length, terminal setae absent.

Female paratype ( Fig. 4 ). Cephalic setae foreshortened in figure. Similar to male, except body shorter and de Man's a smaller, tail longer (14 abd, 77 % cylindrical). Vulva at 42 % of body length, as simple lateral slit without epiptygmata. Vagina short and straight, sclerotization appearing in lateral view as 2 closely spaced rods parallel to vaginal lumen. Didelphic, outstretched ovaries, anterior 218 µm, posterior 202 µm long. Supplements absent.

Etymology. The species name refers to the sampling location, specifically the Tongyeong Sea

Affinities. Laimella tongyeongensis sp. nov. is one of the longest Laimella species so far described. It differs from the previously described species of the genus with regards to combinations of features, rather than one specific difference. It is most similar to L. annae and L. vera: It is similar to L. annae with regards to de Man's ratios b, c and c', but differs from it in terms of de Man's a (being much fatter), and the longer relative length of the R3 sensilla (R2/R3 = 0.3 vs 0.6). In addition, L. annae was described without teeth, whilst these were clearly visible in L. tongyeongensis . In contrast it is similar to L. vera , with regards de Man's ratios a and c', but differs with regards to the ratio between the anterior and posterior cephalic setae (1:3 vs 1:2), the tail length (c': 12.7 vs 9.1) and the spicule length (s’: 1.6 vs 2.0). In the male specimens studied here, the precloacal supplements were extremely difficult to observe, being visible only in those specimens with an ideal rotation. They should therefore not be used to differentiate the species.

Concluding remarks on Laimella . A search of the ecological literature finds the genus frequently recorded, though rarely in high numbers, in mainly muddy or fine sand sediments from the intertidal and estuarine habitats to the deep sea ( Alongi, 1987; Dando et al., 1991; Moreno et al 2008; Miljutina et al 2010). However, it is unlikely that Laimella species are widely distributed. Eskin & Palmer (1985) found that in a turbulent creek, the two species of Laimella observed were never found in the water column (from a total of 71 species, these were two of only eight species that were never recorded in the water column); and indeed, long tails tend to be found in animals anchored to the substrate for long periods ( Riemann 1974).

It is likely that the diversity of this genus is highly underestimated, partly owing to a paucity of specimens usually found, which does not aid formal description. Also, illustrated records of many species, including species of Laimella , indicate that the accepted within-species range of morphological characters has resulting in the probable 'clumping' of species. The specimens recorded as Laimella vera by Gourbault (1980), for example, probably represents a 'new' species owing to the shape of the oesophageal bulb (approximately 50 % of oesophageal length, in comparison to the original description of 21 %); the caudal setation pattern; the length of the spicule (1.7 vs 1.4 abd); and the relative length of the oesophagus (a:14–15 vs 10). Whilst the latter two differences appear small, they are consistent across specimens within the genera and should be considered as speciesinformative characters, particularly in such a relatively character poor genus.

Figures

FIGURE 3. Laimella tongyeongensis sp. nov., olotype male: A, oesophagus; B, head; C, tail; D, gonads; E, habitus. Scale bars: 10 µm (A–C), 20 µm (D), and 100 µm (E).

FIGURE 4. Laimella tongyeongensis sp. nov., aratype female: A, oesophagus; B, head; C, anus; D, tail tip; E, vulva; F, tail; G, gonads; H, habitus. Scale bars: 10 µm (A–E), 40 µm (G), and 50 µm (H).