Elzalia heterospiculata, Jia & Huang, 2019

Jia, Susu & Huang, Yong, 2019, Elzalia heterospiculata sp. nov. (Nematoda: Monhysterida: Xyalidae) from the South China Sea, Zootaxa 4603 (3), pp. 568-574 : 570-573

Elzalia heterospiculata sp. nov.

( Figs 2–3 )

Type material. Four males, three females and one juvenile were collected from Stations NH2017-8. Holotype: male 1 on slide NH8-191-1, paratypes: male 2, male 3, male 4, female 1, female 2 and female 3 on slides NH 8-16-1, NH 8-20-1, NH8-191-1 and NH 8-83-1, respectively.

Type locality and habitat. Seafloor clay sediment at Station NH2017-8: 114º 45′29″ E, 19º 51′43″ N, water depth 795 m.

Etymology. The species name refers to its unequal length of paired spicules.

Measurements. Table 1.

Description. Males. Body slender with tapering anterior and posterior ends, greatest body diameter at the middle of body. Cuticle with very fine striations. Somatic setae short and irregularly arranged. Inner labial sensilla not visible. Six outer labial setae and four cephalic setae arranged in one circle. Outer labial setae longer than cephalic setae. Amphideal fovea circular, 7–8 μm wide, close to the top of the head, its front edge situated at level of cephalic setae. Buccal cavity cylindrical, cuticularized, 15–17 µm deep and 7.6–8.6 µm wide. Pharynx cylindrical, slightly swollen at base, not forming posterior terminal bulb. Cardia conical, projecting into intestine. Nerve ring situated just anterior to middle of pharynx. Secretory-excretory system not observed. Tail conico-cylindrical with a slightly enlarged tip. Two rows of longitudinal subventral setae located along conical portion of tail, each seta 5–7 μm long. Three contiguous caudal glands with common opening. Three terminal setae about 12 µm long.

Testis indistinct. Spicules paired, elongated, slender and unequal in length, tapered distally and not thickened proximally. Left spicule 211–248 µm, i.e. 6–7.5 cloacal body diameters long; right spicule 115–125 µm, i.e. 3.3–3.8 cloacal body diameters long. Gubernaculum rather complex and can be divided into four sections ( Fig. 2F ). The ventral main section (VMS) with three distal projections, wrapping around the distal end of spicules; the sheath (S) extending along the spicules (up to 30 µm long); leaf-like projections (P) with three distinct triangular endpoints; apophyses (A) dorsally straight and clavate, 12–14 μm long. Five small precloacal papilliform supplements.

Females. Similar to males in most morphological characteristics except slightly larger body size, slightly shorter outer labial and cephalic setae, more posterior position of amphideal fovea and lacking of somatic setae. Reproductive system monodelphic with a single anterior outstretched ovary, located to left of intestine, 140 µm long. Uterus a wide tube. Vagina straight, 0.4 times vulval body diameters long. Vaginal glands present. Vulva situated at about mid-body. In one specimens, a large sack-like spermathecae present and filled with granular sperms.

Juvenile. Similar to females on the morphological characteristics except the body slightly slenderer (a=31) and the tail terminal setae longer (17.4µm long).

Differential diagnosis and discussion. Elzalia heterospiculata sp. nov. is characterized by elongated spicules unequal in length, left spicule (211–248 µm) longer than right spicule (115–125 µm), ratio of body length to longer spicule length 4.7–6.2; complex gubernaculum consisting of four sections, apophyses clavate, 12–14 µm long; the position of amphideal fovea near the top of the head.

Elzalia heterospiculata sp. nov. is the only known species of the genus with unequal spicules and is easily distinguished from the congeneric species by this unique feature. The present species is very close to E. federici Castillo-Fernandez & Lambshead 1990 and E. floresi Gerlach 1957 in general morphological characteristics, especially in length of spicules and ratio of body length to spicule length. Nevertheless, the present new species differs from E. federici in having unequal spicules and its left spicule remarkably longer than right one, gubernaculum containing four sections, five small papilliform precloacal supplements, amphideal fovea located near the top of the head. In comparison, E. federici has small body, 860–1071 µm long, equally long spicules, gubernaculum only containing three sections, without leaf-like projection, and amphideal fovea situated posterior to cephalic setae. The present new species differs from E. floresi in having unequal spicules, greater value “a” (27–32 vs 17) and ventral main section of gubernaculum with three distal projections (vs only one ventral projection, without lateral and dorsal projections in E. floresi ). Moreover, the present new species is similar to E. gerlachi Zhang and Zhang 2006 in the structure of the gubernaculum. However, the latter species has spicules of equal size, relatively larger body (1460–1780 µm), and greater ratio of body length to spicule length (10.3–11.4 vs 4.7–6.2). Further differences of Elzalia heterospiculata sp. nov. from the other congeners are specified in the key below.

Figures

FIGURE 2. Elzalia heterospiculata sp. nov. (A) anterior end of male, showing buccal cavity, cephalic seta, amphideal fovea; (B) anterior end of female; (C) entire view of female, showing vulva, ovary and eggs; (D) pharyngeal region of male; (E) posterior end of male, showing spicules, gubernaculum, and precloacal supplements; (F) gubernaculum and distal end of spicule; (G) female vulval region, showing vagina, spermathecae and vaginal glands.

FIGURE 3. Elzalia heterospiculata sp. nov. (A) anterior end of male, showing buccal cavity; (B) anterior end of male, showing amphideal fovea and cephalic setae; (C) posterior end of male, showing right spicule (short) and gubernaculum; (D) posterior end of male, showing left spicule (long). Scale bars: 20 µm.