Lauratonema dongshanense, Chen & Guo, 2015

Chen, Y. Z. & Guo, Y. Q., 2015, Two new species of Lauratonema (Nematoda: Lauratonematidae) from the intertidal zone of the East China Sea, Journal of Natural History 49 (29), pp. 1777-1788 : 1782-1787

Lauratonema dongshanense sp. nov.

( Figures 3 , 4 , Table 2)

Type material

Three males and two females were collected from mid tide level of Station ZZDS in July 2012. Holotype: one male (♂ 1 on slide number ZZDS20120707 M1U117). Paratypes: two males and two females (♂ 2 on slide number ZZDS20120707 M1U110, ♂ 3 on slide number ZZDS20120707 M1U126, ♀ 1 on slide number ZZDS20120707 M1U105, ♀ 2 on slide number ZZDS20120707 M1U128). Types are deposited in the Institute of Oceanology, Chinese Academy of Sciences .

Type locality and habitat

Intertidal sandy sediment on the coast of Dongshan Island, Zhangzhou City. Silt+clay: 3.27%. Station ZZDS: 23.7081°N, 117.4836°E .

Etymology

This species is named for the type locality, intertidal sediment on Dongshan Island .

Measurements ( Table 2)

– 310 W 1421

Holotype ♂ 1: 1547 µm; a = 61.2, b = 5.0, c = 12.3, Sc = 14 µm 14242524

– 323 V 1358

Paratype ♀ 1: 1495 µm; a = 44.7, b = 4.6, c = 10.9

14313330

Description

Body elongated and attenuating towards the ends. Cuticle marked with fine and prominent transverse striations from posterior border of amphids to tip of tail and with rod-shaped bacteria more or less adhered. Inner labial sensilla not seen. Six outer labial setae and four cephalic setae in single crown, length 8 – 10 µm and 5 – 7 µm respectively, situated 8 – 10 µm posterior to anterior end. Funnel-shaped buccal cavity with strong cuticularized transverse strip structure, depth almost equal to width. Amphids cup-shaped, situated just posterior to the lateral outer labial setae, with diameter 0.32 – 0.44 times of corresponding body diameter. Pharynx cylindrical and musсular, with corresponding body diameter 23 – 31 µm at posterior extremity. Сardia large, nearly heart-shaped, surrounded by intestinal tissue. Nerve ring surrounding pharynx situated at 47 – 51% of its length. Excretory duct very short, excretory pore situated 54 – 73 µm anterior to nerve ring, ventral gland located at 40 – 50 µm anterior to end of pharynx. Caudal glands well developed. Terminal seta absent.

Male. Tail elongate conoid, length 123 – 126 µm, 5.3 – 5.6 a.b.d. long. Two rows of setae just located at ventrosublateral of tail. Reproductive system diorchic with two testes arranged in tandem; anterior testis situated to right, posterior testis to left of intestine. Spicules blade-like, short and straight, 0.58 – 0.67 times a.b.d. long. In three measured specimens, one with spicules with proximal end unclosed ( Figure 3F ), others with slightly cephalated proximal end ( Figure 3E ). No gubernaculum observed. A small papilla situated at about 15 µm anterior to cloaca.

Female. Similar to male in general characteristics, but tail a little longer, length 137 – 141 µm, without ventrosublateral seta. Reproductive system monodelphic, single ovary reflexed, situatеd entirely to right of intestine. Gеnital zonе of oogonia arrangеd in onе or two rows; growth zonе with a singlе row of gradually enlarging ooсytеs. Female genital duct united with rectum forming a cloaca.

Diagnosis and discussion

Lauratonema dongshanense sp. nov. is morphologically close to L. pugiunculus Wieser, 1959 , L. reductum Gerlach, 1953 and L. hospitum Gerlach, 1954 in several characteristics, such as their small buccal cavities, which are as short as or shorter than wide; outer labial setae and cephalic setae of unequal length; gubernaculum absent. However, the new species can be easily distinguished by the shape of buccal cavity (funnel-shaped with strong cuticularized transverse strip structure, depth almost equal to width versus small and conical) and spicules (blade-like, short and straight versus slender, more or less straight but with an S-like bend), the number and arrangement of male caudal papillae (one small precloacal ventral papilla versus three to four postcloacal ventral papillae), the tail length (c 10.7 – 12.5 versus 18; c ′ 4.6 – 6.0 versus 6.8), etc. It differs from L. reductum in the length of the body (1372 – 1547 μm versus 1601 – 1977 μm), pharynx (b 4.4 – 5.0 versus 5.3 – 7.6), spicules (14 – 15 μm versus 21 – 24 μm) and adult tail (c 10.7 – 12.5 versus 8.8 – 10.4), the presence of precloacal papilla, etc. ( Gerlach 1953). From L. hospitum the new species differs by having small precloacal papilla, shorter spicules (14 – 15 μm and 0.58 – 0.67 a.b.d. versus 21 μm and about one a.b.d.) and tail (c ′ 4.6 – 6.0 versus 6.5 – 7.5), and plumper body form (a 44.7 – 61.3 versus 68 – 118) ( Gerlach 1954).

General discussion and key to Lauratonema

So far, a total of eight valid species in genus Lauratonema Gerlach, 1953 are known ( Gerlach and Riemann 1974; http://nemys.ugent.be; http://www.marinespecies.org/ index.php; http://entomology.tamu.edu/; http://pipedev.tamu.edu/Biocat/Search/ SearchTaxa.aspx). A dichotomous key including eight species in this genus was provided by Hopper (1961), and three new species were described later: L. obtusicaudatum Murphy and Jensen, 1961 , L. minutum Platonova, 1971 and L. juncta Fadeeva, 1989 . However, L. originale was moved to Lauratonemoides by De Coninck (1965). Tchesunov (1984) gave a dichotomous key to the family Lauratonematidae , transferred Lauratonema minutum , the gonad of which is very similar to L. originalis , to Lauratonemoides , and established the genus Lauratonemella solely for L. spiculifer Gerlach, 1959 ( De Coninck 1965; Tchesunov 1984; Gourbault and Vincx 1986; Fadeeva 1989). Therefore, this genus contains eight valid species. We revise the key base on Hopper (1961) and Tchesunov (1984) including all known eight valid species in this genus as well as the two newly described species, according to the size of buccal cavity, the shape and situation of the amphids, the length of the cephalic setae, the length and shape of spicules, the existence of ventral papillae, etc., as follows ( Gerlach 1953, 1954; Wieser 1959; Hopper 1961; Murphy and Jensen 1961; Tchesunov 1984; Fadeeva 1989).

Key to species of the genus Lauratonema

1. Stoma spacious, length more than width ............................................................. 2

– Stoma small, length equal to, or less than, width ................................................ 4

2. Amphids anterior to lateral outer labial setae, at the level of buccal cavity .......... .................................................................................... L. mentulatum Wieser, 1959

– Amphids posterior to lateral outer labial setae, below buccal cavity .................. 3

3. Stoma length 1.5 times width. Amphids reniform ............................................ ........................................................................ L. reniamphidum Hopper, 1961

– Stoma length 2.1 – 2.3 times width. Amphids cup-shaped (if visible) ...................... ........................................................................................... L. macrostoma sp. nov.

4. Outer labial setae and cephalic setae of equal length ....................................... ............................................................................. L. adriaticum Gerlach, 1953

– Outer labial setae and cephalic setae of unequal length ...................................... 5

5. Male caudal region with ventral papilla .............................................................. 6

– Male caudal region without ventral papilla ......................................................... 9

6. Stoma with dentate cuticularized ...................................... L. juncta Fadeeva, 1989

– Stoma without dentate cuticularized ................................................................... 7

7. Cephalic region set off by a slight constriction. Male with one precloacal and two postcloacal ventral papillae ............. L. obtusicaudatum Murphy and Jensen, 1961

– Cephalic region not set off. Male with either precloacal or postcloacal ventral papillae ................................................................................................................ 8

8. Spicule slender, with a slight S-like bend. Gubernaculum small, thin. Male with three to four postcloacal ventral papillae .................. L. pugiunculus Wieser, 1959

– Spicules blade-like, short and straight. Gubernaculum absent. Male with one small precloacal ventral papilla ................................................. L. dongshanense sp. nov.

9. Body form slender, a more than 65; outer labial setae 8.5 μm ............................... ...................................................................................... L. hospitum Gerlach, 1954

– Body form plumper, a less than 50; outer labial setae 11 to 15 μm ....................... ...................................................................................... L. reductum Gerlach, 1953

Figures

Figure 3. Lauratonema dongshanense sp. nov. (A) lateral view of male head end, showing amphid and cephalic setae; (B) lateral view of female head end, showing buccal cavity; (C) lateral view of female head end, showing amphid and bacteria; (D) lateral view of female body part, showing eggs; (E, F) lateral view of male body part, showing spicules; (G) lateral view of male tail. Scale bar: A–F = 10 µm; G = 25 µm.

Figure 4. Lauratonema dongshanense sp. nov. (A) lateral view of female anterior part; (B) lateral view of female tail; (C) lateral view of spicule; (D) lateral view of male tail and spicule; (E) full view of female, showing reproductive system; (F) lateral view of male anterior part. Scale bar: 25 µm.