Metachromadora (Metachromadoroides) zaixsi Pastor & Ward, 2004, sp. n.
Creators: name: Pastor, Catalina T.
name: Ward, De
Publisher: name: Zenodo
Year: 2004
Subjects: Biodiversity
Taxonomy
Animalia
Nematoda
Adenophorea
Desmodorida
Desmodoridae
Metachromadora
Metachromadora zaixsi

description: Metachromadora (Metachromadoroides) zaixsi sp. n.   
(Figure 3 A–I; Plate 2 A–K; Table 4; Table 5)  
 Systematic position: Desmodoridae Filipjev, 1922; Spirniinae Gerlach & Murphy, 1965 (according to Lorenzen, 1981)   
 Type material: Eight males, eight females, and four juveniles on slide numbers: HOLOTYPE, MACN N1 34720; ALLOTYPE, MACN N° 34726; PARATYPES, MACN N° 34722–34727; 35810–35816. Col.: Lic. H. Zaixso.   
 PLATE 2: M. (M.) zaixsi sp. n. A. Head anterior end of male, latero­dorsal view; B. Head anterior end female; C. Buccal cavity of male, dorsal tooth; D. Head anterior end male, lateral view; E. Vulva opening, female; F. Buccal cavity of female; G. Entire allotype female; H. Copulatory apparatus, distal end; I. Copulatory apparatus, proximal end; J. Entire holotype male; K. Lateral alae posterior to oesophagus in male.   
 Type locality San José Gulf and San Matías Gulf, Chubut province, Argentina.   
 Stations: Holotype: S106: 1M; Allotype: S49: 1F; Paratypes: S18: 1juv.; S49: 1M, 1F; S50: 2M, 1F, 1Juv; S90: 2M, 1F; S105:1M, 1F; S106: 1M, 3F, 2Juv.   
 Habitat: M. (M.) zaixsi sp. n. has been found in very fine sand (median particle size 59.8–81.3 µm), 53.5–120.1m depth, from San José Gulf and south coast of San Matías Gulf (Fig. 1).   
 Etymology: Dedicated to H. E. Zaixso, San José Project Director and samples collector.   
 Measurements: see Table 4.   
 Description. Males. Cylindrical body gradually tapering to anterior extremity, with smooth head capsule and with conical tail. Body with thick annulated cuticle. Lateral alae present, extending from the posterior end of the pharynx to the anal region. Body annuli interdigitate at level of the lateral alae.   
There are alternating long 8 (7–8 µm) and short 4 (3–4 µm) somatic setae in eight longitudinal rows beginning at the pharyngeal region.  
Head capsule with offset labial region. Six inner and six outer labial setae located at the labial region 1.0 (0.5–1.0) µm long. Four cephalic setae on head capsule 4 (3–4) µm long, present in all the specimens. Amphids 19 (14–20) µm, 76 (57.1–80.0) % bda in diameter and loop­shaped with one and a quarter closed turns. Amphids situated on labial region to the end of head capsule and surrounded by punctuations.  
Stoma armed with strong dorsal tooth and several ventral­subventral teeth, and surrounded posteriorly by anterior end of muscular pharynx. Muscular pharynx cylindrical 190 (160–220) µm long, posteriorly enlarged with a long tripartite terminal bulb with cuticular valves. Cardia is conspicuous.  
Male reproductive system monorchic with one anterior testis in left position to the Intestine. Spicules arched 50 (40–52) µm 1.1 (0.7–1.1) abd in chord length from tip to tip, with the proximal end cephalated. Gubernaculum well developed formed by one piece 36 µm long (0.8 abd). There are 7–10 pairs of 4 (3–4) µm long pre­cloacal setae in sub­ventral position. No pre­cloacal supplements present. Tail 120 (115–130) µm long, 2.5 (1.7– 2.8) abd, with a non striated end zone 24 (20–23) µm long.  
 Females: Females are similar to males in general body shape, anterior sensilla, amphids, somatic setae and cuticle. Reproductive system didelphic, amphidelphic with reflexed ovaries, anterior ovary branch on right and posterior ovary branch on left of intestine. No brood protection has been observed. Tail 140 (95–140) µm, 2 (2.5–2.7) abd.   
 Differential diagnosis:   
 M. (M.) zaixsi sp. n. is characterized by the absence of pre­cloacal supplements and the presence of four cephalic setae. This new species resembles M. (M.) vulgaris Timm 1961 in body length, a and b values but it can be distinguished from it by the length of the amphid in relation to the head capsule length (50% in M.(M.) vulgaris) and the length of the spicules (72 µm).
description: Published as part of Pastor, Catalina T. & Ward, De, 2004, New species of Hopperia (Nematoda, Comesomatidae) and Metachromadora (Nematoda, Desmodoridae) from Patagonia, Chubut, Argentina, pp. 1-15 in Zootaxa 542 on pages 9-13, DOI: 10.5281/zenodo.157676