Halichoanolaimus anisospermus, Leduc, Daniel & Zhao, Zeng Qi, 2016

Leduc, Daniel & Zhao, Zeng Qi, 2016, Molecular characterisation of five nematode species (Chromadorida, Selachinematidae) from shelf and upper slope sediments off New Zealand, with description of three new species, Zootaxa 4132 (1), pp. 59-76 : 66-70

Halichoanolaimus anisospermus n. sp.

( Figures 3 & 4 , Table 2 )

Diagnosis. Halichoanolaimus anisospermus n. sp. is characterised by having an amphideal fovea with six (males) or five turns (female) and ~0.9 cbd from anterior end, anterior portion of buccal cavity with cuticularised rhabdions terminating in three sets of seven pairs of teeth (denticles), with central pair of each set positioned above the other six, pore of secretory-excretory system situated slightly posterior to nerve ring, dimorphism in size of sperm cells between anterior and posterior testes, spicules 1.6–1.9 cloacal body diameters long, with gland protruding from proximal extremity, gubernaculum consisting of two detached lateral pieces (crurae) tapering distally, three small precloacal supplements present, consisting of slightly thickened and raised cuticle, and conicocylindrical tail with conical portion 32–38% of total tail length.

Etymology. The species name is derived from the Greek terms anisos (= unequal) and sperma (= seed), and refers to the dimorphism in the size of the sperm cells between the anterior and posterior testes.

Material examined. Holotype male ( NIWA 99779), collected 8 May 2015 ( NIWA cruise TAN 1506, station 14), upper continental slope off Hauraki coast, New Zealand (175.3163º E, 35.5402º S); water depth: 432 m. One paratype male and one paratype female ( NIWA 99780, NNCNZ 3201), same data as holotype.

Description. Male Body cylindrical. Cuticle with transverse rows of punctations; lateral differentiation consisting of larger, more widely-spaced punctations. Somatic setae short, 1–2 µm long, sparse, irregularly arranged along body. Head rounded, with slight constriction immediately posterior to cephalic setae. Lip region not conspicuously differentiated. Six inner labial papillae; six short outer labial papillae, 2 µm long, at same level as four cephalic sensilla of similar length. Amphideal fovea multispiral with 6.0 turns, situated ~0.9 cbd from anterior end. Buccal cavity large, 21–28 µm deep, divided into anterior (cheilostom) and posterior portions (pharyngostom). Anterior portion of buccal cavity cup-shaped, with cuticularised rhabdions terminating in three sets of seven pairs of teeth (denticles), with central pair of each set positioned above the other six; posterior portion of buccal cavity narrower, cylindrical, surrounded by three Y-shaped pairs of cuticularised rhabdions. Pharynx cylindrical, muscular, without anterior or posterior bulb. Nerve ring at 40% of pharynx length from anterior. Secretory-excretory system present, renette cell small, 19 × 12 mm, situated at anterior extremity of intestine; ampulla small, pore situated slightly posterior to nerve ring.

Reproductive system diorchic with short outstretched testes. Anterior testis to the right or left of intestine, posterior testis on opposite side. Sperm cells globular, conspicuously larger in anterior testis (6–7× 8 mm) than in posterior testis (3–4 × 5–6 mm). Spicules paired, curved, tapering distally, 1.6–1.9 cloacal body diameters long, with gland protruding from proximal extremity; gubernaculum consisting of two detached lateral pieces (crurae) tapering distally, median portion of gubernaculum (corpus and cuneus) apparently absent. Three precloacal supplements present, consisting of slightly thickened and raised cuticle ( Fig. 3 C). Tail conicocylindrical, conical portion 32–38% of total tail length; a few short and sparse somatic setae present. Caudal glands not observed, spinneret present.

*tail length was measured from, and anal body diameter at, the posterior-most extremity of the intestine.

Species Halichoanolaimus anisospermus n. sp. Bendiella longicauda n. sp.

Male Female Male Holotype Paratype Paratype

Female Similar to males but amphideal fovea slightly smaller with 5.0 turns. Reproductive system didelphicamphidelphic, with reflexed ovaries. Anterior ovary to the left of intestine and posterior ovary to the right of intestine. Vulva situated at mid-body. Mature eggs 22–26 × 26–27 mm. Proximal portion of vagina surrounded by constrictor muscle, vaginal glands not observed. Intestine blind, anus not observed.

Differential diagnosis. Halichoanolaimus anisospermus n. sp. differs from most other species of the genus by the unusual shape of the precloacal supplements, which are usually papilliform or setiform, but which consist of areas of slightly thickened and raised cuticle in this species. H. anisospermus n. sp. is most similar to H. macrophallus Gourbault & Vincx, 1985 in the number of amphid turns, tail shape, and spicule shape, but differs from the latter by the markedly shorter spicules (45 vs 115 mm) and gubernaculum (13–14 vs 45 mm), and the number (3 vs 4) and shape of precloacal supplements. H. anisospermus n. sp. is also similar to H. brandtae Zograf et al., 2015 but can be distinguished from the latter by the different spicule size and shape (45 µm long with gland protruding from proximal extremity vs 81–94 µm long and without gland), number (3 vs 5) and shape of precloacal supplements, and absence of lateral rows of cuticular pores (present in H. brandtae ).

Figures

FIGURE 3. Halichoanolaimus anisospermus n. sp. A: Male anterior body region; B: male head; C: cloacal region; D: male posterior body region. Arrows show the location of the precloacal supplements. Scale bar: A & D = 40 mm, B & C = 25 mm.

FIGURE 4. Halichoanolaimus anisospermus n. sp. A: Female anterior body region; B: female posterior body region; C: entire male; D: entire female. Scale bar: A = 40 mm, B = 30 mm, C = 110 mm, D = 135 mm.

Tables

TABLE 2. Morphometrics (mm) of Halichoanolaimus anisospermus n. sp. and Bendiella longicauda n. sp. (a, body length / maximum body diameter; b, body length / pharynx length; c, body length / tail length; c', tail length / anal or cloacal body diameter; cbd, corresponding body diameter; L, total body length; n, number of specimens; V, vulva distance from anterior end of body; % V, V / total body length)

n -	1	1	-
L 1251	718	1187	2762
a 3 4	2 2	3 2	3 8
b 5	6	5	6
c 8	6	7*	5
c' 5.3	5.4	5.9*	13.3
Body diam. at cephalic setae 19	16	21	40
Body diam. at amphid 27	22	31	57
Body diameter at nerve ring 34	29	33	73
Body diam. at base of pharynx 37	30	36	73
Length of cephalic setae 2	2	3	6
Amphid height 13	13	13	18
Amphid width 13	13	13	17
Amphid width/cbd (%) 48	59	42	30
Amphid from anterior end 23	10	24	20
Nerve ring from anterior end 98	67	108	172
Pharynx length 230	120	222	432
Max. body diam. 37	32	37	73
Number of precloacal supplements 3	-	-	-
Spicule length 45	45	-	98
Gubernaculum length 13	14	-	32
Cloacal/Anal body diam. 28	24	27*	46
Tail length 148	129	159*	611
Length of tail conical portion 47	49	45	50
V -	-	6 0 6	-
%V -	-	51	-
Vulval body diam. -	-	36	-