Robbea, POROSUM

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 : 12-13

ROBBEA POROSUM ( HOPPER & CEFALU, 1973) TCHESUNOV, 2013

Measurements: Table 1; Figures 7 , 8 .

Material examined: Five ♂, one ♀, two J.

Description: Body habitus filiform. Cuticle finely striated (annuli ∼0.3 μm width), covered by coccoid bacteria and mucus (also adhered to the setae). Head capsule weak marked by thickening of the cuticle, revealing in SEM photographs a pattern-like fingerprint anteriorly and fine transverse striations posteriorly, surrounding the amphidial fovea; six lips partially fused, each provided with an inner labial papilla, and surrounded by a differentiated collar; six outer labial papillae (∼1 μm long) at border of labial region. Four cephalic sensilla setiform (11–14 μm long) at level of outer labial sensilla. Four shorter subcephalic setae at anterior level of amphidial fovea (7–8 μm long): two subdorsal and two subventral. Additional four subcephalic setae (5–8 μm long) flanking posteriorly the fovea. Eight longitudinal rows of short setae connected to epidermal glands (1–2 μm long) running along the body length. Amphidial fovea spiral, lateral, and far anteriorly on the head, diameter approximately 0.5 c.b.d. Pharynx divided into three portions, an anterior muscular corpus with sclerotized lumen, a narrow isthmus, and a posterior bulb with glandular aspect and lumen nonsclerotized; cardia rounded and inconspicuous. Tail conical, striations extending subterminally, tail tip rounded. Males with spicules paired, blade ventrally curved and marked capitulum; gubernaculum with relatively large dorsally orientated caudal apophysis; neither precloacal nor postcloacal supplements.

Female didelphic, ovaries antidromously reflexed, vulva at mid-body position, no other features could be ascertained because of the strong coiling of the single female examined.

Remarks: Robbea porosum has recently been transferred from the genus Catanema to Robbea based on its large, spirally coiled amphidial fovea in lateral position ( Tchesunov, 2013). The fingerprint pattern in the head capsule appears to be a diagnostic feature in this species as it has not been recorded for the other five known species of the genus. The arrangement of the bacterial coat could not be ascertained because in most of the specimens the bacteria were detached from the host upon processing. Several specimens of R. porosum had the intestine full of bacteria, support- ing the hypothesis that the latter serve as a food source for the nematode.

Figures

Figure 7. Robbea porosum. Specimen 1♂. A, habitus, B, neck region, C, testis and epidermal glands connected to somatic setae, D, tail region.

Figure 8. Robbea porosum. A, anterior region (lateral view), specimen 1♂; B, head (lateral-frontal view), specimen 1♂; C, head (frontal view), specimen 2 (indeterminate sex); D, mid-body, specimen 3 (indeterminate sex); E, symbiotic bacteria, specimen 1♂; F, tail region, specimen 1♂.