Lauratonema macrostoma, 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, pp. 1-12 : 2-6

Lauratonema macrostoma sp. nov.

( Figures 1 , 2 , Table 1)

Type material

Five males and three females were collected from mid tide level of Station ZZDS in July 2012. Holotype: one male (♂ 1 on slide number ZZDS20120707 M1U124). Paratypes: four males and three females (♂ 2 on slide number ZZDS20120707 M1U104, ♂ 3 on slide number ZZDS20120707 M1U110, ♂ 4 on slide number ZZDS20120707 M1U118, ♂ 5 on slide number ZZDS20120707 M1U122, ♀ 1 on slide number ZZDS20120707 M1U106, ♀ 2 on slide number ZZDS20120707 M1U101, ♀ 3 on slide number ZZDS20120707 M1U104). 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 its large buccal cavity.

Measurements ( Table 1)

– 297 W 1476

Holotype ♂ 1: 1615 µm; a = 53.0, b = 5.4, c = 11.6, Sc = 16 µm 13283029

– 305 V 1454

Paratype ♀ 1: 1592 µm; a = 51.6, b = 5.2, c = 11.5

13273128

Description

Body cylindrical, slightly tapering towards both extremities. Cuticle marked with fine and conspicuous striations, which reach base of cephalic setae, and with rod-shaped bacteria more or less adhered. Inner labial sensilla not visible. Six outer labial setae and four cephalic setae in one ring, length 13 – 17 µm and 9 – 12 µm respectively, situated at the level of about two-thirds of the buccal cavity depth. Spacious barrelshaped buccal cavity with strong cuticularized wall, depth 2.1 – 2.3 times width, slightly constricted at half its depth. Amphids unclear in some specimens, while obviously cup-shaped in others, located immediately posteriorly of the lateral outer labial setae, diameter about one-third of corresponding body diameter. Corresponding body diameter at posterior extremity of pharynx is 26 – 30 µm. Сardia large, nearly heart-shaped, surrounded by intestinal tissue. Nerve ring encircled pharynx at about 42 – 47% of its length. Excretory pore opening ventrally 77 – 91 µm from anterior end, 49 – 65 µm in front of nerve ring. Ventral gland small, situated about 40 µm anterior to end of pharynx. Tail elongate conoid, 4.6 – 5.7 a.b.d. long. Caudal glands well developed. Terminal seta absent. Spinneret small, terminal.

Male. Reproductive system diorchic with two testes arranged in tandem; anterior testis situated to right, posterior testis to left of the intestine. Spicules symmetrical and

straight, blade-like with distal proximal end closed, 0.55 – 0.65 a.b.d. long. No gubernaculum observed. Tail armed with two rows of ventrosublateral setae.

Female. Similar to male in general characteristics, but tail without ventrosublateral seta. Reproductive system monodelphic, reflexed, singlе ovary situatеd еntirеly to right of intestine. Gеnital zonе of oogonia arrangеd in onе or two rows; growth zonе with a singlе row of gradually enlarging ooсytе. Female genital duct united with rectum forming a cloaca.

Diagnosis and discussion

Lauratonema macrostoma sp. nov. is characterized by the size of the buccal cavity and spicules, the shape of the amphids and the length of the cephalic setae. It is close to L. mentulatum Wieser, 1959 and L. reniamphidum Hopper, 1961 , which also have buccal cavity longer than wide. However, several differences can be seen. The new species differs from L. mentulatum Wieser, 1959 by its shorter body (1.54 – 1.76 mm versus 2.44 mm), the deeper buccal cavity (2.1 – 2.3 versus 1.6 times as long as width), the shorter outer labial setae (13 – 17 µm versus 19 µm) and cephalic setae (9 – 12 µm versus 14 µm) and spicules (14 – 16 µm versus 26 µm), as well as the longer pharynx (b 5.1 – 6.0 versus 7.6) and tail (c 11.1 – 12.8 versus 15.2) ( Wieser 1959). It can be distinguished from L. reniamphidum Hopper, 1961 by the size of body (length 1.54 – 1.76 mm versus 1.97 – 2.10 mm; a 47.9 – 60.9 versus 65.7 – 70.0), buccal cavity (6 – 7 µm wide and 13 – 16 µm long versus 5 µm wide and 7 µm long) and spicules (14 – 16 µm versus 20 µm), and the shape and size of the amphids (cup-shaped and about one-third of c.b.d. versus reniform and about a quarter of c.b.d.) ( Hopper 1961).

Figures

Figure 1. Lauratonema macrostoma sp. nov. (A) lateral view of male anterior part; (B) lateral view of female tail; (C) lateral view of male tail; (D) lateral view of female posterior part, showing reproductive system; (E) lateral view of female anterior part. Scale bar: A, B, C, E = 20 µm; D = 50 µm.

Figure 2. Lauratonema macrostoma sp. nov. (A) lateral view of male head end, showing amphids and bacteria; (B) lateral view of male body part, showing spicule; (C) lateral view of female body part, showing eggs; (D) lateral view of female head end, showing buccal cavity; (E) lateral view of female tail. Scale bar: A–D = 10 µm; E = 25 µm.