STILBONEMATINAE CHITWOOD, 1936

Armenteros, Maickel, Ruiz-Abierno, Alexei & Decraemer, Wilfrida, 2014, Taxonomy of Stilbonematinae (Nematoda: Desmodoridae): description of two new and three known species and phylogenetic relationships within the family, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 171 (1), pp. 1-21 : 4-6

SUBFAMILY STILBONEMATINAE CHITWOOD, 1936 EUBOSTRICHUS HOPPERI ( HOPPER & CEFALU, 1973) MUTHUMBI, VERSCHELDE & VINCX, 1995

Measurements: Table 1; Figures 1 , 2 .

Material examined: Two ♂, five ♀, four juveniles (J). Description: Body habitus slender. Cuticle finely striated (annuli ∼0.2 μm width), often covered by a coat of mucus; dense groups of crescent-shaped bacteria grown in a ‘rope-like’ pattern; in most of the specimens the pattern was disrupted or bacteria were detached during processing. Head shape rounded, no head capsule, striation surrounding the amphidial fovea. Six inner and outer labial sensilla both papilliform (<1 μm long). Four cephalic sensilla setiform (4–8 μm long) at anterior border of amphidial fovea and very close to the outer labial c′, tail length relative to the anal body diameter; c.b.d., corresponding body diameter; N, number of specimens; V %, distance (relative to body length) of vulva to anterior apex .

All measurements are in μm.

sensilla. Four subcephalic setae (5–10 μm long) at level of the fovea: two subdorsal and two subventral. Four additional subcephalic setae (5–10 μm long) laterally at the posterior border of the fovea. Other two pairs of setae (5–10 μm) (two subdorsal and two subventral) not always present. Eight longitudinal rows of somatic setae associated with epidermal glands running along body length; the first circles longer (5–10 μm), two to three subventral pairs of enlarged setae at the level of posterior pharynx; on the rest of the body, somatic setae considerably shorter or replaced by porids. Amphidial fovea spiral, difficult to observe in most of the specimens because of film on the cuticle, diameter approximately 0.5 corresponding body diameter (c.b.d.), located lateral in the head. Pharynx muscular without anterior widening, terminal bulb almost round, cardia small, rounded. Tail conical-tapered, tip rounded and possessing two separate outlets of caudal glands; four subventral pairs of enlarged setae in male; two to three caudal pairs in females and juveniles.

Male monorchic, anterior testis to the left of the intestine. Spicules paired and curved, capitulum present; gubernaculum a narrow rod with distal end curved hook-like, no supplements.

Female didelphic, ovaries antidromously reflexed, both genital branches to the left of intestine.

Remarks: The specimens of Eubostrichus collected mostly agree with the original description of E. hopperi in Hopper & Cefalu (1973) based on the most important diagnostic features: body size, relative tail length, and cephalic setae pattern. The closest congeneric species is Eubostrichus parasitiferus but it differs by being larger (♂: 2800–2920 μm, ♀: 2800 μm) than the specimens of E. hopperi described by Hopper & Cefalu (1973) (♂: 2140–2180 μm, ♀: 2640–2680 μm). The specimens measured by us have a broader body size range (♂: 1905–2256 μm, ♀: 1475–2745 μm) but includes the size range of the type population of E. hopperi . For our specimens, the ratio of the tail length to anal diameter (c′) (♂: 3.3, ♀: 4.1–4.7) was also closer to E. hopperi (♂: 3.4–3.9, ♀: 4.5–4.9 in type population) than to E. parasitiferus described by Chitwood (1936) (♂: 2.5–2.6; ♀: 3.5). Hopper & Cefalu (1973) stated the existence of 16 subcephalic setae in a pattern of 8 + 8 for E. hopperi but this is not in agreement with our observations of a more complicated pattern of subcephalic setae (i.e. 4 + 4 + 4). Unfortunately, we could not check the type material of E. hopperi to resolve this apparent mismatch.

The number of enlarged subventral setae (i.e. porids sensu Hopper & Cefalu, 1973) is not always easy to determine and appears to be variable as we recorded some females and juveniles with fewer pairs of setae.

The disposition of cephalic sensilla of E. hopperi is quite similar to Robbea porosum ; the main difference is that first two circles of subcephalic setae in the former are longer compared to the remarkably short setae in R. porosum . Two juvenile specimens of Eubostrichus had bacteria attached in a ‘fuzzy’ pattern, i.e. attached to a single point on the cuticle. Therefore, we suspect they belong to Eubostrichus dianeae but we could not recover any adult of this putatively sympatric species. The cuticle often has a coating that is mucous in nature and therefore is probably secreted by the epidermal glands to keep the bacteria adhered.

Eubostrichus hopperi has a few pairs of subventral setae enlarged at the level of pharynx that differ from the features given in Table 1 by Tchesunov (2013) (i.e. no male anterior structures). Two to three pairs of these enlarged setae were depicted by Hopper & Cefalu (1973) and we noted a similar number of these structures.

Figures

Figure 1. Eubostrichus hopperi. A, habitus, specimen 1♂; B, anterior region, specimen 2♂; C, tail, specimen 1♂; D, tail, specimen 3♀.

Figure 2. Eubostrichus hopperi. A, anterior region (lateral view), specimen 1♂; B, head (lateral−frontal oblique dorsoventral view), specimen 2♀; C, habitus (partim), specimen 3♂; D, mid-body with crescent-shaped bacteria, specimen 4 (indeterminate sex); E, tail (lateral view), specimen 1♂; F, tail, specimen 2♀.