Axonchium amplicolle Cobb, 1920

Naz, Tabbasam & Ahmad, Wasim, 2012, Description of two new and five known species of the genus Axonchium Cobb, 1920 (Nematoda: Dorylamida) from India with diagnostic compendia and keys to species of the genera Axonchium and Syncheilaxonchium Coomans & Nair, 1975, Zootaxa 3264, pp. 1-37 : 4-9

Axonchium amplicolle Cobb, 1920

( Figs. 1 , 2 )

Dorylaimus (Axonchium) amplicollis ( Cobb, 1920) Micoletzky, 1922 Discolaimium pakistanicum Timm & Bhuiyan, 1963 A. amphidium Thorne, 1964

A. mauritiense Williams, 1958

Measurements. Table 1.

Description. Female: Cuticle 3–4 µm thick at mid body and 8–9 µm on tail. Lateral chords without distinct glandular bodies, about one-seventh to one-fifth of body width at mid body.

Lip region offset, about one-fifth of body width at neck base; lips separate. Amphids cup-shaped, their aperture about 0.7–1.0 times the lip region width. Odontostyle about one lip region width long. Odontophore 1.2–1.5 times the odontostyle length. Anterior part of pharynx muscular, abutting the posterior expanded part; the latter occupying about 62–73% of total neck length. Cardia cylindroid, about one-fourth to one-third of the corresponding body width long.

Anterior genital branch represented by a small sac, about 0.4–0.8 times the corresponding body width long. Posterior branch well developed; ovary reflexed, not reaching the oviduct-uterus junction, measuring 73–200 µm; oviduct measuring 60–90 µm, consisting of a long slender part with prismatic cells and a slightly wider pars dilatata with wide lumen. Sphincter present at oviduct-uterus junction. Uterus bipartite, measuring 75–130 µm, differentiated into an expanded distal part with wide lumen and a tubular, narrower proximal part with narrow lumen. Vagina slightly bent posteriad, extending inwards about half of corresponding body width; pars distalis vaginae well developed, nearly as long as pars proximalis; pars refringens vaginae absent. Prerectum 3.0–8.5 times anal body width long. Rectum about as long as anal body width. Tail short, rounded to convex conoid, about 0.6–0.9 times anal body width long. Caudal pores two on each side.

Male: Not found. (Sperms not present in the female gonads)

Habitat and locality. From soil around the roots of teak tree ( Tectona grandis ) from reserve forest area near Electricity Department complex, Shillong, Meghalaya.GPS coordinate 25.56892/91.88313; latitude 25o34'N, longitude 91o53'E

Remarks. Cobb (1920) proposed the genus Axonchium with A. amplicolle , collected from Brazil, as its type species. Thorne (1939) redescribed this species based on the study of type material. Jairajpuri (1964) reported it from India and in 1965, synonymized Discolaimium pakistanicum Timm & Bhuiyan, 1963 with this species. Nair (1973) provided a detailed description of A. amplicolle and synonymised A. mauritiense Williams, 1958 and A. amphidium Thorne, 1964 with this species. Dhanachand and Jairajpuri (1981) for the first time reported a single male of this species. Heyns and Furstenberg (1993) reported another solitary male from Nosi-Komba Island in the western Indian Ocean. Ahmad and Naz (2010a, 2010b) reported this species from Japan and Singapore respectively. The present population of A. amplicolle from India conforms well to the earlier descriptions except for the absence of males. Sperms were not recorded in the genital tract of any of the females studied. It may be noted that the males are very rare in this species ( Dhanachand & Jairajpuri, 1981; Heyns & Furstenburg, 1993). The present population from Shillong, India differs from all other described populations of A. amplicolle (except the Singapore population of Ahmad & Naz (2010b) in having a shorter and more robust body. Further, it differs from the population of U.P., India ( Jairajpuri, 1964) and Mauritius (Williams, 1958) in having a shorter odontostyle and shorter expanded part of pharynx. It also differs from the Puerto Rico ( Thorne, 1964) population in tail shape (round tail vs. convex-conoid), and from the Singapore population ( Ahmad & Naz (2010b) in having a longer anterior uterine sac. A. amplicolle seems to be a widely distributed species in India and South East Asia and is characterized by having 1.20–1.98 mm long body; offset lip region; 7–12 µm long odontostyle; vulva at 49–57% from anterior end; anterior uterine branch measuring 8–40 µm and tail rounded to convex-conoid, 0.6–0.9 times anal body width long.

A. bulbosum Williams, 1958 and A. nitidum Jairajpuri, 1964 closely resemble A. amplicolle in having a short anterior uterine sac. A. amplicolle , however, is distinguished from the former in the shape and direction of the vagina (vagina bent posteriad with concave walls vs straight vagina with spheroid walls) and from the latter in its tail shape (rounded to convex-conoid vs cylindroid).

Figures

FIGURE 1. Axonchium amplicolle Cobb, 1920. A: Entire female. B: Anterior region. C: Anterior end showing amphid. D – E: Junction between two parts of pharynx. F – G: Pharyngo-intestinal junction. H: Female genital system. I – J: Vulval region showing anterior uterine sac. K – L: Female posterior end.

FIGURE 2. Axonchium amplicolle Cobb, 1920. A: Anterior region. B: Anterior end showing amphid. C: Junction between two parts of pharynx. D: Pharyngo-instestinal junction. E – G: Vulval region. H – I. Female posterior end. (Scale bars: A, B = 10 µm; C – I = 20 µm).