Syringolaimus annae, Coelho Lima, Lins, Da Silva & Esteves, 2009

Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, Zootaxa 4306 (4), pp. 478-500 : 483-489

Syringolaimus annae Lima, Lins, Da Silva & Esteves, 2009

( Figures 2–3 )

Labels. Male: DIVA 1, M 48/1, st 346/2, Muc 3; female: DIVA 1, M 48/1, st 346/1, Muc 3.

Material and conditions. One male, one female and two juveniles. All specimens are slightly compressed and have broken tail tips; the slightly shortened tails reduce tail lengths and body lengths, and raise body indices to a certain extent.

Description. Body nearly cylindrical, but tapered to the anterior end. Male: L=1553 µ m, a=31.1, b=6.19, c=6.47, c'=5.71; body diameter at the level of: labial region 15 µ m, nerve ring 33 µ m, cardia 53 µ m, midbody 50 µ m, cloaca 39 µ m. Female: L=1236 µ m, a=35.7, b=5.57, c=8.83, c'=5.83, V=58.7%; body diameter at the level of: labial region 13 µ m, nerve ring 26 µ m, cardia 28 µ m, midbody 35 µ m, anus 24 µ m.

Cuticle smooth along the entire body. Metanemes not visible. Head apex truncate. Anterior sensilla (besides amphids) not seen. Amphid as a rather broad transverse slit, amphidial fovea shallow and hardly discernible. In male, width of the amphidial aperture 6 µ m or 33% of the corresponding body diameter, distance from the head apex to the aperture 12 µ m. The same measurements in female are 4 µ m, 22%, 13 µ m, respectively. No somatic sensilla visible along the body. Three double teeth of the anterior stoma everted. Each tooth consists of two slightly unequal claws. Teeth length is 5 µ m in male and 3 µ m in female. Pharyngostom long, cylindroid, its length is 72 µ m in male and 32 µ m in female. In juveniles, replacing teeth are present just below the functioning teeth. Replacing teeth are distinctly double, consisting of two separate claws. Pharyngostom surrounded by narrow cuff with nonevident muscular striation. Pharynx nearly cylindrical up to terminal swelling, with transverse muscular striation and thick internal cuticular lining. There is a rounded terminal swelling with stronger muscular striation at posterior pharynx. Internal lining of the swelling not modified. In male, terminal bulb is 47 µ m long and 44 µ m wide; the same in female—31 µ m and 26 µ m, respectively. Cardia muscular, small, 12 µ m long, its posterior half surrounded by intestinal tissue. Ventral gland not found. In male, a poorly discernible structure resembling ventral pore situated at half distance between pharyngostom base and nerve ring. Tail consists of two distinct portions, anterior conical and posterior slim cylindrical parts; tail tip broken. No evident caudal glands. Since tail tip is broken in both specimens, spinneret can not be described.

Females didelphic, amphidelphic; ovaries antidromously reflexed. Anterior ovary ventral and slightly to the right of the intestine, posterior ovary ventral to the intestine.

Males monorchic, anterior testis outstretched and situated ventral to the intestine. Spicules half drawn out from the cloacal opening, short, arcuate, broad and weakly cuticularized, 49 µ m long. Gubernaculum as a pair of weakly cuticularized bars perpendicular to the body axis, with curved distal ends, 15 µ m long. There is a midventral precloacal supplementary papillum just anterior to the cloacal opening; there is also one more or less prominent anterior midventral elevation devoid of an internal canal, likely a cuticular fold. A pair of conical lateroventral papillae at the end of conical portion of the tail.

Diagnosis. Body length 1236–1553 µm, a=31–36. Tubular pharyngostom 32–72 µm long. Terminal pharyngeal bulb 31–47 µm long and 17–34 µm wide. Spicules 49 µm, weakly cuticularized. Precloacal supplementary papillum present. Tail cylindro-conical, with posterior cylindrical portion comprising 72–85% of entire tail; no terminal tube or spinneret.

TABLE]. Morphometry of Syringolaimus species, males (valiđ species in bolđ, values rounđeđ).

Species Characters Source

Bođy a b c c' Distal Buccal Amphiđ wiđth as Distance from Length of Length of length, µ m slenđer tail cavity % of heađ apex to terminal spicules part as % of length, µ m corresponđing amphiđ, µ m pharyngeal along arc, entire tail bođy điameter bulb, µ m µ m length

morphometric value calculateđ from đrawings of publisheđ species đescriptions.

sex not specifieđ in the source citeđ.

Species Characters Source

Bođy a b c c' Distal slenđer Buccal Amphiđ wiđth as Distance Length of

length, µ m tail part as % cavity % of from heađ terminal of entire tail length, corresponđing apex to pharyngeal length µ m bođy điameter amphiđ, µ m bulb, µ m morp hometric value calculateđ from đrawings of publisheđ species đescriptions.

sex not specifieđ in the source citeđ.

Discussion. This species fits well with the description of S. annae except for index a in males (31 vs. 41–73, likely because of compression of the body) and greater length of spicules (49 µ m vs. 17–34 µ m, spicules can be inaccurately measured because of their weakness and indistinctness), indices c and c' in females (c 8.8 vs. 4.8–7.4, c' 5.8 vs. 7.3–10.8, because of broken tail tip). Length of the buccal cavity differs notably in male and femalehowever, these values vary considerably in type specimens as well (28–55 µ m in males and 27–57 µ m in females, Lima et al., 2009). According to the original diagnosis of Lima et al. (2009), a spinneret is absent in this species (tail tips of our specimens are broken). Postcloacal lateroventral papillae are not indicated in the original diagnosis ( Lima et al., 2009), probably because these small structures are poorly visible and hence could be overlooked.

Figures

FIGURE 2. Syringolaimus annae. A: male, entire body; B: female, entire body; C: male, anterior end; D: female, anterior end. Scale bars: A – B = 200 µ m; C – D = 20 µ m.

FIGURE 3. Syringolaimus annae. A: male, anterior body; B: female, anterior body; C: male, tail; D: female, tail; E: male, pericloacal region. Scale bars: A – E = 50 µ m.