Dorymenia Heath, 1911

Salvini-Plawen, Luitfried von, 2008, Contributions to West European Cavibelonia (Mollusca, Solenogastres) with two new species, Zoosystema 30 (4), pp. 873-897 : 887-888

Genus Dorymenia Heath, 1911

TYPE SPECIES. — Dorymenia acuta Heath, 1911 by original designation ( ICZN 1981).

DIAGNOSIS. — Acicular hollow spicules in two or more intercrossing layers, with epidermis papillae; mouth opening within common atrio-buccal cavity. Secondary genital opening single. With copulatory stylets and dorso-terminal sense organ; no respiratory organs.

Dorymenia sarsii ( Koren & Danielssen, 1877) ( Figs 13-15 )

Solenopus sarsii Koren & Danielssen, 1877: 128 .

Simrothiella sarsi auct.

Dorymenia sarsi auct.

Dorymenia tortilis Scheltema & Schander, 2000: 126 (cf. Handl & Salvini-Plawen 2002)

DIAGNOSIS. — Up to 53 mm long, slender, with dorsoposterior finger-like projection. Mantle with epidermis papillae, tangential hollow spicules (needles) interspersed with delicate, slender, solid, radial, paddle-like sclerites. Opening of mantle cavity anterio-laterally with numerous distally hooked abdominal spicules. One pedal fold, not extending into mantle cavity. Radula with 14 teeth per transverse row, symmetrically arranged, tooth length increasing towards lateral; with unpaired ventral radula sack surrounded by strong musculature. Radula sheath proximally bifid. Longitudinal musculature with paired ventral reinforcement, in part distinctly separated as paired musculus longitudinalis ventralis. Midgut caecum unpaired, extending far anterior. Heart as a dorsally open

2 The name Proneomeniidae is traditionally attributed to Simroth (1893), but according to Dr P. Bouchet (pers. comm.) the name Proneomenidae introduced by Mitchell (1892: 58) is available and is to be considered as the valid name for this family. The present author, however, is of the opinion that Mitchell used the name Proneomenidae instead of the missing genus name as a plural noun rather than as a family name (cf. Salvini-Plawen [2004]; ICZN [1999: Art. 11.7.1.2]).

invagination of pericardium. Prior becoming fused, each spawning duct with a prominent ventral enlargement (ampulla, lobe); unpaired opening of fused duct with a sphincter. Paired ventro-anterior pouch of mantle cavity encircling copulatory stylets. One pair (rarely two or three pairs) of copulatory stylets, distally three- or four-edged.

DISTRIBUTION. — Scandinavian to Lusitanic waters, 164- 681 m.

MATERIAL EXAMINED. — France. Cap Breton 88, DE 05, 43°57.42’N, 02°05.16’W, 164 m, 5.VII.1988, Sorbe & Gofas, 2 specimens and a fragment, size 27 mm × max. 1.3 mm, and 23 mm × max. 1 mm. After removing sclerites, the body ends of the longer specimen were histologically investigated by serial cross sections of 10 µm ; these series (and the midbody in alcohol) are deposited as voucher material in MNCN (no. 15.02/0016).

Material examined for comparison: D. sarsii , holotype ( SMNH 4737), paratype ( SMNH 4738).

DISCUSSION

The present specimens, with their characteristic dorso-posterior extension of the body ( Fig. 13 ), are organizationally identical with Dorymenia sarsii ; all important specific characters (see diagnosis; Odhner 1921; Scheltema & Schander 2000, including D. tortilis ; Handl & Salvini-Plawen 2002) are

present in the specimen examined; this is mature (egg diam. 100 µm), the pericardioducts show small pouches (vesiculae seminales) surrounded by the common muscular layer ( Fig. 15 ), the spawning ducts have ventral ampullae close to their fusion and there is one pair of copulatory stylets. Neither Odhner (1921) nor Handl & Salvini-Plawen (2002), however,mention the existence of two pairs of bolster vesicles within the radula support (big “chondroid

cells”; Fig. 14 ; region not retained in the type material). In the sectioned specimen at hand, each pair is differentiated at the end of two lateral radula support or bolster muscles; in addition, the ventral sack retractors are attached to four vesicles.

The body dimensions of 70 × 3 mm given by Koren & Danielssen (1877) are most probably erroneous (cf. Scheltema & Schander 2000: 126): the records of three fragments in the Arctic Ocean at 71°25’N, 15°41’E in 1134 m depth ( Odhner 1921) neither geographically nor bathymetrically fit into the known range and are thus doubtful (Salvini-Plawen 1997). As already underlined (Salvini-Plawen 1997; Handl & Salvini-Plawen 2002), the geographical range of D. sarsii (including D. tortilis ) thus includes the Scandinavian waters from the Trondheimŋord to the Skagerrak on the one hand, and the Gorringe Bank (off Cap São Vicente, Portugal) on the other. The geographical gap in the records is now bridged by the present findings in the southeastern Bay of Biscay at 164 m.

Figures

FIG. 13.— Dorymenia sarsii (Koren & Danielssen,1877),specimen of 27 mm length (posterior end with “bill” below).

FIG. 14. — Dorymenia sarsii (Koren & Danielssen, 1877), cross section through region of radula bolster. Abbreviations: cu, mantle cuticle; gl, ventral foregut glandular organ; mg, midgut; mu, bolster musculature; nsv, ventral nerve cord; ph, terminal portion of pharynx opening; ras, radula sheath; sra, subradular sack; tv, bolster vesicles. Scale bar: 100 μm.

FIG. 15. — Dorymenia sarsii (Koren & Danielssen,1877), cross section through anterior pericardioduct.Abbreviations:cu, mantle cuticle; pd, pericardioduct;sd, spawning duct; vs, small pouches of vesicula seminalis. Scale bar: 50 μm.