Zalonema vicentei, Larrazábal-Filho, Alexandre L., Silva, Maria Cristina Da & Esteves, André M., 2015

Larrazábal-Filho, Alexandre L., Silva, Maria Cristina Da & Esteves, André M., 2015, Four new species of free-living marine nematodes of the family Desmodoridae (Nematoda: Desmodorida) and a redescription of Desmodora nini (Inglis, 1963) from the continental shelf off northeastern Brazil, Zootaxa 4021 (1), pp. 63-92 : 66-70

Zalonema vicentei sp. n.

(measurements in Table 2 ; Figs 2 , 3 and 4)

Type material: Holotype Male, adult MNRJ 342 (03°00’00”S, 038°45’00”W) collected in June 2009, from the Potiguar Basin, between 45 and 100 m deep. Sediment: fine to coarse bioclastic sand.

Paratype female: Adult, MNRJ 343 (03°00’00”S, 038°45’00”W) collected in June 2009 from the Potiguar Basin, between 45 and 100 m deep. Sediment: fine to coarse bioclastic sand.

Other paratypes: 9 females (158–162 LMZOO-UFPE), 9 males (153–157 LMZOO-UFPE), 1 juvenile in second stage of development (J2) (163 LMZOO-UFPE), collected on same date as holotype.

Etymology. The species name is a tribute to Vicente Chiaverini, the first author’s grandfather.

Description. Holotype male ( Figs 2 , 4). Body long and cylindrical, yellowish brown, with stout cephalic capsule and conical tail. Cuticle annulated except on cephalic capsule and final portion of tail. Short somatic setae arranged in six longitudinal rows; two dorsal, two lateral and two ventral. Head rounded, triangular, with long cephalic capsule. Fovea amphidialis spiral (3.5 turns). Buccal cavity relatively long, with two small teeth (one dorsal and one ventral), six lips with 12 folds. Anterior sensilla arrangement: six inner labial sensilla, six outer setae, four cephalic setae positioned above the fovea amphidialis, and base of cephalic capsule with ring of four short subcephalic setae. Pharynx with rounded endbulb with cuticularized lumen divided into four distinct regions. Nerve ring surrounds pharynx, position variable, present in mid pharynx-length or region closest to head. Ventral gland and secretory-excretory pore not observed. Cardia inserted in intestine. Reproductive system with extended testes. Spicules strongly sclerotized, with rounded capitulum and broad velum. Gubernaculum simple, lacking apophysis. Lateral alae present on each side of body in posterior region (Fig. 4E), along one-fifth of total body length. Ventral ala measuring 304 µm. Three caudal glands. Tail conical with elongated non-annulated tail end, and spinneret.

Female ( Figs 2 , 3 ) Similar to male; but lacking ventral ala and lateral alae (sexual dimorphism). Female with three plasmatic interruptions in pharynx (four in male). Reproductive system with paired opposite and reflexed ovaries. Vulva as transverse slit. Vagina vera short, vagina uterina with sphincter muscle. Two eggs found: one in posterior oviduct and another in anterior uterus ( Fig. 3 D). Two parallel glands observed. Tail slightly larger than in male.

Juveniles. Similar to adults except for size and absence of lateral alae and ventral ala. Only one juvenile in stage 2 (Fig. 4) was found.

Diagnosis and relationships. Zalonema vicentei sp. n. is characterized by having a multispiral fovea amphidialis (3.5 turns), and relatively long buccal cavity, with small dorsal tooth and small ventral tooth. Pharynx with rounded endbulb and four plasmatic interruptions. Lateral alae present on each side of body, and ventral ala.

Zalonema vicentei sp. n. has some features in common with several species of the genus, e.g. Zalonema myrianae Verschelde & Vincx, 1996 (ventral ala), Zalonema propinqua ( Allgén 1951) (two teeth: one dorsal and one ventral; 4 cephalic and 4 subcephalic setae); Zalonema megalosoma ( Steiner 1918) (sexual dimorphism associated with fovea amphidialis) and Zalonema ditlevseni ( Micoletzky 1922) (presence of lateral alae and cuticularized lumen). However, this new species has unique characteristics: lateral alae combined with a ventral ala (not seen in any other species of Zalonema ) and the cephalic arrangement: four cephalic setae above the fovea amphidialis and 4 subcephalic setae on the posterior portion of the fovea amphidialis. This differs from other known species, which have more than 4 subcephalic setae ( Z. ditlevseni ; Z. malvidenses = 8 subcephalic setae and Z. myrianae = 6 subcephalic setae). In relation to sexual dimorphism, Z. vicentei sp. n. has the fovea amphidialis with more turns in the male than in the female. In contrast, in Z. megalosoma , sexual dimorphism appears in the proportion of the fovea amphidialis in relation to corresponding body diameter (% amph), being larger in male than female. Z. vicentei sp. n. has strongly sclerotized spicules and a rounded capitulum, but the spicules differ in length from those of Z. myrianae (spic = 38-43 µm; Z. vicentei spic = 73.5 µm); and the species also differs in having a velum.

Figures

FIGURE 2. Zalonema vicentei sp. n.: Holotype MNRJ 342 cephalic region of male A: dorsal tooth and B: fovea amphidialis. C: overview. D: right lateral ala. E: posterior region and copulatory apparatus. Paratype female MNRJ 343 F: overview. G: vulva opening. H: fovea amphidialis. I: tail region.

FIGURE 3. Zalonema vicentei sp. n. Paratype female MNRJ 343 - A: overview. B: anterior region. C: head region. D: ovary and vulva opening. E: tail region.

Tables

TABLE 2. Measurements (µm) of Zalonema vicentei sp. n. in the Potiguar Basin, Brazil. n = number of specimens; * = not applied; n. o. = not observed. Abbreviations as in Table 1.

	Male Holotype n = 1	Male Paratypes n = 9	Female Female Paratype Paratypes n = 1 n = 9	Juvenile Paratype n = 1
L ph nr	1663 193.5 118.5	(1065–2175) (135–223.5) (90–132)	1890 (1245–2130) 201 (132–210) 132.5 (91–135)	1170 138 72
mbd abd t	52.5 51 73.5	(44–79.5) (34.5–63) (57–102)	66 (57–85) 36 (28–55) 127 (111–147)	42.5 32 118.5
tf hd cap.ceph	18 22.5 22.5	(12–30) (22.5–33) (15–28.5)	26.5 (23–29) 30 (21–52) 25 (16–39)	57 24 13
at spic gub	3 73.5 31.5	3 (37.5–79.5) (15–33)	3 3 * * * *	3 * *
Alae Velum T	304 43 948	(227.5–442) (30–66) (745–1356)	* * * * * *	* * *
ext. lab. cs subc s.	6.5 6 3.5	(3–4) (4–7) (3–7)	7 (3–4) 6 (4–6) 3.5 (5–6)	5 5.5 n.o.
annul % bulb % amph	2.5 67 35	(3–4) (69–80) (30–57)	3 (3–4) 80 (75–82) 60 (29–42)	3 78 45
ov v v (%)	* * *	* * *	654.5 (567–902) 990 (570–1095) 52 (37–60)	* * *
a b c	31.5 8.5 22.5	(21.5–36) (7–10) (15–21)	29 (21–28) 9.5 (9.5–11.5) 15 (10–16)	27.5 8.5 10
c'	1.5	(1.5–3)	3.5 (2.5–4)	4