Desmoscolex (Desmoscolex) valkyria, García-Cobo & González-Casarrubios & Sánchez, 2025

García-Cobo, Marta, González-Casarrubios, Alberto & Sánchez, Nuria, 2025, Description of two new species of Desmoscolex Claparède, 1863 (Nematoda: Desmoscolecidae) from the Cassidaigne Canyon, Mediterranean Sea, European Journal of Taxonomy 1004, pp. 211-236 : 227-229

Desmoscolex (Desmoscolex) valkyria sp. nov.

urn:lsid:zoobank.org:act:69FE1E2F-4C1B-47F0-9988-3AD8CACA371A

Figs 5–6 , Tables 1 , 4–5

Diagnosis

The main diagnostic characteristics of Desmoscolex (Desmoscolex) valkyria sp. nov. include: (1) high number of main rings (22–24); (2) rounded cephalic region with prominent vesicular amphid; (3) thick cephalic setae; (4) reddish pigment globules along the interior of body; (5) penultimate main ring with both pairs of subdorsal and subventral setae; (6) wide, short and conical end ring with very long spinneret.

Etymology

The specific name ‘ valkyria ’ as noun in apposition refers to the female figures in Norse mythology who guide the souls of the dead to the Valhalla Hall of the god Odin and who star in the second opera of ‘The Ring of the Nibelung’.

Material examined

Holotype MEDITERRANEAN SEA • ♂, adult (mounted in glycerine); Cassidaigne Canyon , Station U13 ; 43º0′47.050″ N, 5º45′32.220″ E; depth 952 m; 27 Apr. 2022; CREOCEAN enterprise leg.; ZMB 12962 ; ZMB.

Paratypes

MEDITERRANEAN SEA • 1 ♂, adult (mounted in glycerine); Cassidaigne Canyon , Station U08 ; 42°57′25.770″ N, 5°14′2.430″ E; depth 1530 m; 12 Jan. 2022; CREOCEAN enterprise leg.; ZMB 12963 ; ZMB • 1 ♂, adult (mounted in glycerine); Cassidaigne Canyon , Station U09 ; 42°51′32.040″ N, 5°14′34.620″ E; depth 1968 m; 13 Jan. 2022; CREOCEAN enterprise leg.; ZMB 12964 ; ZMB .

Description

See Table 4 for a summary of the most relevant measurements of the type material.

Body short (278–385µm), ventrally coiled in holotype, M1, and paratype, M2, but straight in paratype, M3. Body becomes tapered at level of cephalic region and at level of tail. Body wider at middle region. Body with 22–24 main rings.

Nine pairs of subdorsal somatic setae and nine subventral somatic setae. Male holotype (23 main rings) with subdorsal setae on the 1 st, 3 rd, 5 th, 8 th, 11 th, 14 th, 18 th and 22 nd –23 rd rings. On the other hand, subventral ones appear on the 2 nd, 4 th, 7 th, 10 th, 13 th, 16 th, 19 th and 21 st –22 nd main rings. Arrangement of setae exhibits variability between specimens, starting from 11 th main ring for the subdorsal setae and from 13 th main ring for subventral setae ( Table 4 ). Penultimate ring always with both dorsal and ventral pairs of setae ( Fig. 5A ).

Cephalic region globular, slightly wider than long. Cephalic region cuticle completely covered with concretion material. Vesicular amphid extending to first main ring. Labial sensilla not identified. Thick cephalic setae, shorter than cephalic region width, located laterally ( Figs 5C , 6B, 6C ). Small mouth opening, leading to short (hardly extending over 2 rings), nearly cylindrical pharynx without posterior pharyngeal bulb ( Figs 5B , 6A ).

Pigment spot located between 3 th and 5 th rings. Reddish pigment globules appear along internal structures, from end of pharynx until middle region of body ( Figs 5B , 6A ), apparently associated with intestine.

Males monorchic with single testis outstretched and extending anteriorly up to level of 12 th main ring. Spicule almost straight and cephalated ( Figs 5B , 6A ). Gubernaculum parallel to spicule. Cloacal tube broad, opening outside always on antepenultimate main ring, occurring on 21 st main ring in holotype and paratype M3, and on 22 nd ring in paratype M2. No females found.

Tail with two main rings. Last ring wide, short and conical with long and thin spinneret (12–13 µm) ( Figs 5A , 6A, 6D ).

Differential diagnosis

Among the 12 described species of D. ( Desmoscolex ) that have more than 18 rings, 10 of them have more than 27 main rings. The most important features of Desmoscolex (D.) valkyria sp. nov. that characterize the species include: number of main rings (22–24), two pairs of somatic setae from the penultimate ring and elongated spinneret ( Table 5 ). Female specimens of D. (D.) aquaedulcis Stammer, 1935 have 22 rings, but differ in the number of subdorsal somatic setae: two pairs in D. (D.) aquaedulcis and nine pairs in D. (D.) valkyria . Females of D. (D.) aquaedulcis also have a long end-ring with a short and pointy spinneret, unlike the short and conical tail of D. (D.) valkyria with a long spinneret. Males of D. (D.) californicus Timm, 1970 have between 22 and 23 main rings, a vesicular amphid, a short and conical end-ring and red pigment globules. Nevertheless, D. (D.) californicus lacks two pairs of setae on the penultimate ring, and a long spinneret but has a triangular cephalic region instead of the globular cephalic region of D. (D.) valkyria .

Figures

Fig. 5. Line art illustrations of Desmoscolex (Desmoscolex) valkyria sp. nov, ♂, adult. A–B. Holotype (ZMB 12962; ZMB). C. Paratype (ZMB 12963; ZMB). A. Habitus in lateral view. B. Habitus in optical section. C. Cephalic region region in ventral view. Scale bars = 20 µm.

Fig. 6. Desmoscolex (Desmoscolex) valkyria sp. nov. A–B. Holotype, ♂ (ZMB 12961; ZMB). C–D. Paratype, ♂ (ZMB 12964; ZMB). A. Overview in lateral position. B. Detail of the cephalic region in lateral view. C. Detail of the cephalic region in ventral view. D. Detail of the tail in lateral position. Scale bars: A = 20 µm; B–D = 10 µm.