Paracomesoma sigmoidalis, Riera, Rodrigo, Núñez, Jorge & Brito, María Del Carmen, 2006

Riera, Rodrigo, Núñez, Jorge & Brito, María Del Carmen, 2006, Two new species of Comesomatidae Filipjev, 1922 (Nematoda: Chromadorida) from sandy bottoms of Tenerife, Canary Islands, Zootaxa 1126, pp. 53-61 : 55-57

Paracomesoma sigmoidalis sp. nov.

( Figures 1 , 2 , Table 1 )

Type locality. Los Abrigos beach (Tenerife, Canary Islands).

Type material. Holotype, adult male 2.6 mm long, mounted on a slide (coordinates 28º08´34´´N / 16º26´21´´W; 3 m depth) [TFMCBMNA/00010]. Collected by R. Riera, May 2000. Allotype, adult female, 2.2 mm long, mounted on a slide (coordinates 28º02´59´´N / 16º42´55´´W; 3 m depth) [DBAULL NE/TC7S11].

Paratypes. Adult male, 2.6 mm long, mounted on a slide (coordinates 28º08´34´´N / 16º26´21´´W; 3 m depth) [DBAULL NE/TA11S11]. Collected by R. Riera, March 2000. Adult male, 2.3 mm long, mounted on a slide (coordinates 28º08´34´´N / 16º26´21´´W; 3 m depth) [DBAULL NE/TAS12]. Additional specimens (two males and four females) in R. Riera collection.

Meristic data. Abrigos subtidal: May, 2 males (Holotype and m4), March, 1 male (m2), December, 1 male (m3) and 3 females (f3, f4 and f5); Cristianos subtidal: November, 1 female (Allotype), April, 1 female (f2).

Etymology. The specific name refers to the S­shaped spicules of this species.

Description.

Male: Body slender, attenuating towards both ends. Head slightly round and not set off. Cuticle smooth, without marked punctations nor lateral differentiation. Amphids are 50% of the corresponding body diameter in width, multispiral of 3.5 turns, located at 5 m from the anterior end. Buccal cavity conical and small, with three small teeth, difficult to discern. Inner labial setae inconspicuous. 6 outer labial setae 0.3 cephalic diameters long and 4 cephalic setae 1.6 cephalic diameters long, situated at the median part of the head. Subcephalic setae 14 m long, located at 28 m from the anterior end. Pharynx slender and cylindrical. Ventral gland and nerve ring not seen.

The reproductive system is diorchic, with two opposed testes, difficult to discern. Spicules 3.6–5.2 anal diameters long, slender, S­shaped, without marked capitulum. Gubernaculum 0.8–0.9 anal diameters long, slender, proximally compressed. An elliptical plaque present at the distal end of the gubernaculum. 35 precloacal supplements, each penetrated by a duct; posteriormost precloacal supplement situated at 45 m from the cloaca. Tail 2.4–4.4 anal diameters long, cylindrical and filiform in most of its length, with a swollen posterior tip. 2 subterminal setae 15 m long, located at 5 “m from the posterior tip. Spinneret well developed.

Female: They are similar to males. Total body length slightly shorter than in males (1.7–2.3 mm). Tail longer than in males (5–6 anal diameters).

The reproductive system is didelphic, with two outstretched ovaries, almost inconspicuous. Vulva located in the posterior half of the body, at the level of 53.9–55.2% of the total body length.

Discussion. Paracomesoma sigmoidalis new species is closely related to P. inaequale Jensen & Gerlach, 1977 , in general body shape, but the latter species differs in having a longer tail, 6.3–7.5 anal diameters in males and 8–9 anal diameters in females, and the number of precloacal supplements (25–32 in P. inaquale and 35 in P. sigmoidalis ). P. sipho (Gerlach, 1956) and P. hexasetosum (Chitwood, 1937) resemble P. sigmoidalis new species although they differ, like not as P. inaequale , in the presence of a larger tail and the number of precloacal supplements (30 in P. sipho and 40 or more in P. hexasetosum ). Moreover, P. sipho has more developed amphids (80% cbd) and P. sigmoidalis new species can be distinguished from the latter two species by having subcephalic setae more anteriorly located.

Holotype m 2 m 3 m 4 Allotype f2 f3 f4 f5

m1 f1

Maximum body diameter 70 50 46 65 37.3 40 39.3 39.3 39.5 Ecology. This species was recorded in Los Abrigos subtidal from medium sands (280 µm, median particle size). The organic matter content was 0.78% and 5.47% carbonates. In Los Cristianos it was collected from fine sands (150–160 µm, median particle size). The organic matter content ranged from 0.006% to 0.53% and 19.32–22.56% carbonates.

Figures

FIGURE 1. Paracomesoma sigmoidalis sp. nov. Holotype. A. Anterior end. B. Posterior end. Scale = 22 m.

FIGURE 2. Paracomesoma sigmoidalis sp. nov. Holotype. A. Spicule. B. Distal end of the spicule, gubernaculum and precloacal supplements. Scale A = 75 m, B = 50 m.

Tables

TABLE 1. Measurements of Paracomesoma sigmoidalis sp. nov. in µm.

Total body length	2600	2657.1 2342.9 2485.7 1757.1	2000 2185.7 2314.3 1998. 7
a	37.1	53.1 50.9 38.2 47.1	50 55.6 58.9 50.6
b c	7.7 7.9	10.8 10.8 8.7 8.9 14.3 15 10.4 9.8	7.4 11.8 10.1 10.9 6.7 10.6 11.8 9.8
Cephalic diameter	22.1	21.4 22.6 21.7 11.4	12.5 14.3 14.3 12.9
Inner labial setae Outer labial setae	­ 7.1	­ ­ ­ ­ 6.9 8.1 7.5 7.1	­ ­ ­ ­ 10 8.6 8.6 9.2
Cephalic setae	34	39.3 35.7 30 25.7	31.4 31.4 34.6 28.9
Subcephalic setae Buccal cavity diameter	14.3 8.6	13 14.3 11.4 10 10.7 14.3 8.6 7.1	11.4 11 13 10 7.1 5.7 5.7 7.2
Amphid diameter	8.6	14.3 12.9 12.9 7.1	10.0 8.6 11.4 7.1
Amphid height Amphid from anterior	11.4 8.6	21.4 14.3 12.9 7.1 10 5.7 5.7 5.7	11.4 10 12.9 7.1 5.7 8.6 5.7 6.3
Pharynx length	335.7	246.4 217.9 285.7 196.4	271.4 185.7 228.6 183.9
Pharynx cbd	60.7	46.4 32.1 53.6 35.7	38.4 35.7 35.7 39.1