Dichromadora major, Huang & Zhang, 2010

Huang, Y. & Zhang, Z. N., 2010, Three new species of Dichromadora (Nematoda: Chromadorida: Chromadoridae) from the Yellow Sea, China, Journal of Natural History 44 (9 - 10), pp. 545-558 : 546-550

Superfamily CHROMADOROIDEA Filipjev, 1917 Family CHROMADORIDAE Filipjev, 1917

Subfamily HIPODONTOLAIMINAE De Coninck, 1965 Genus Dichromadora Kreis, 1929 Dichromadora major sp. nov.

( Figures 1 , 2 )

Type material

Five males and two females were observed. Holotype: one male, Specimen number of new species: LU54 (slide number: LUH084091 ) ; paratypes: 14 males, six females: LU55–61 ( LUH084091-2 , LUH083306 , LUH083308 ) .

Type locality and habitat

Intertidal sandy sediment at Huangdao coast of the Yellow Sea: 35°59′ N, 120°10′ E.

Etymology

This species is named after the character of its relatively large body size.

Measurements

The measurements are given in Table 1. For the male holotype: 210 M 1170 1335 µm; a = 35.1, b = 6.4, c = 8.1, spic = 44, 26, 36, 38, 34. For a male paratype: 202 V 1134 1276 µm; a = 33.6, b = 6.3, c = 9.0, V% = 51%, 28, 37, 38, 29.

Description

Males. Body is cylindrical, blunt at the anterior end and attenuating at the tail end ( Figure 1B ); 1247–1341 µm in length and 34–38 µm maximem diameter. Cuticle is homogeneous with transverse rows of punctations. There are two longitudinal rows of thick round dots as lateral differentiation that extend from the anterior end to the tail leaving small (3–4 µm) non-punctated end part. The dots are connected by transverse bars along the lateral differentiation. The somatic setae are sparse, 8–13 µm long and in four longitudinal rows.

The head is flattened and has four cephalic setae, about 14 µm long. Amphids are crescents, about 11 µm wide, located at the centre below the bases of the cephalic setae. In the buccal cavity a prominent hollow dorsal tooth and two smaller ventral teeth are present ( Figure 1A ). Pharynx is 206 µm in length, cylindrical, with a anterior bulb and a pyriform posterior bulb that is 27 µm in diameter at the widest part. Nerve ring surrounds the pharynx at 57% of its length from the anterior. The ventral gland is small, located at posterior of the pharyngo-intestinal junction. The gland opening was not seen.

The reproductive system is monarchic, with outstretched testis, located to the right of the intestine. The spicules are slender and simple, arcuate with rounded proximally and tapered distally, 46 µm (1.4 a.b.d.) long. The gubernaculum is 31 µm long with a lateral swelling in about the middle part ( Figure 1C ). There are nine small cup-shaped precloacal supplements located from about 30 µm to 190 µm from the cloaca.

Tail is conical with a pointed tip, 5 a.b.d. Three caudal glands are located close to the anterior end of tail.

Females. Similar to males. The reproductive system is amphidelphic with reflexed ovaries, anterior branch located to the right of the intestine and posterior branch is to the left of it. The vulva is simple, at about 51% of body length from the anterior end.

Differential diagnosis

Dichromadora major sp. nov. is characterized by the combination of the presence of a clearly anterior pharyngeal bulb, crescent-shaped amphides, nine precloacal supplements, slender, arcuate spicules and gubernaculum with a lateral swelling in about the middle. It is similar to D. hyalocheile De Coninck and Stekhoven, 1933 in the size of the body and the number of precloacal supplements, but it is identified by the structure of cuticle punctations and the shape of the spicules and gubernaculum. The spicules of the latter is S-shaped with prominent hooks distally and gubernaculum with a distal pair of lateral projections that are terminally hooked. The size of two longitudinal rows of lateral punctation is not even along the length of the body. Dichromadora polaris Vermeeren et al, 2004 is the other species with nine precloacal supplements in this genus, but the body length of this species is shorter (667–930 µm versus 1247–1341 µm) and swollen anterior bulb is absent.

Figures

Figure 1. Dichromadora major sp. nov. (A) lateral view of female anterior end, showing cephalic setae, dorsal tooth, amphids, anterior bulb and posterior bulb, lateral punctuation; (B) lateral view of male body; (C) lateral view of male tail end, showing spicule, gubernaculum and precloacal supplements; (D) lateral view of female tail, showing caudal glands.

Figure 2. Dichromadora major sp. nov. (A) lateral view of male anterior end, showing cephalic setae and posterior bulb; (B) lateral view of female anterior end, showing dorsal tooth; (C) lateral view of male tail end, showing spicule and gubernaculum; (D) lateral view of male tail end, showing nine precloacal supplements.