Stilbonema, BREVICOLLE COBB, 1920

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 : 13-14

STILBONEMA BREVICOLLE COBB, 1920

Measurements: Table 1; Figures 9 , 10 .

Material examined: One ♂, two ♀, two J.

Description: Body habitus slender. Cuticle coarsely striated (annuli 1.4–2.0 μm width). A coat of rodshaped bacteria covering the cuticle; the axis of bacteria cells perpendicular to the cuticle. Head profile anteriorly flattered (but may look globular in some specimens), head capsule well developed, surface with slight depressions. Inner labial sensilla papilliform, outer labial sensilla setiform (∼6 μm long).

14 M. ARMENTEROS ET AL .

Four cephalic sensilla setiform (10–15 μm long), two circles of eight subcephalic setae (10–12 μm long), first one anteriorly on the head, second one close to the border of the cephalic capsule; one or two pairs of additional subcephalic setae can occur between both circles. Somatic setae short (5–6 μm long) probably arranged in eight longitudinal rows but few are visible because of the bacterial coat or broken off; somatic setae connected to epidermal glands but not always clear. Amphidial fovea pore-like with corpus gelatum protruding, located subterminally on the head. Pharynx muscular, corpus largely cylindrical but slightly wider near head region, posteriorly widened to a small pyriform bulb; cardia triangular/ elongated and conspicuous. Tail conical, tip smooth and spinneret present.

Male monorchic, anterior testis to the left of intestine; spicules curved and paired. Six to eight conspicuous cup-like precloacal supplements present at level of pharynx.

Female didelphic, vulva not conspicuous, ovaries antidromously reflexed, both genital branches to the left of intestine.

Remarks: There are four species of Stilbonema formally described: Stilbonema annulatum Gerlach, 1963 ; S. brevicolle Cobb, 1920 ; Stilbonema majum ( Cobb, 1920) , and Stilbonema smurovi Tchesunov, 2013 . The descriptions of the first three species are rather poor in morphological details and with only a single male specimen per species. The name S. majum appeared in Urbancik et al. (1996a) but without comments on the transfer of Laxonema majum Cobb, 1920 , to Stilbonema majum . Tchesunov (2013) formally transferred L. majum to the genus Stilbonema but without explanation. We agree with this classification because L. majum in Cobb (1920) resembles some features characteristic of the genus Stilbonema such as cephalic capsule clearly set-off and coarse annulation. Additionally, specimens identified as S. majum in Urbancik et al. (1996a) were 8.5 mm in average length, which agrees roughly with the single specimen described as L. majum by Cobb (10 mm). Our specimens fit well with the original description by Cobb (1920) based on specimens from the Caribbean Basin (Kingston Harbor, Jamaica). The male specimen of S. annulatum described by Gerlach (1963) is larger than our male specimen (5977 vs. 1870 μm) and was collected far away (i.e. Indian Ocean).

Figures

Figure 9. Stilbonema brevicolle. A, habitus, specimen 1 juvenile; B, anterior region, specimen 1 juvenile; C, anterior region, specimen 2♀; D, pharyngeal bulb and epidermal glands, specimen 2♀; E, tail region, specimen 2♀.

Figure 10. Stilbonema brevicolle. A, habitus, specimen 1 (indeterminate sex); B, anterior region, specimen 1; C, head (lateral view), specimen 2♂; D, anterior region with ventral supplements (pharynx level), specimen 2♂; E, mid-body with rod-shaped bacteria, specimen 1; F, tail region with rod-shaped bacteria, specimen 1.