Phascolion (Lesenka) salgadoi, Gómez-Vásquez, 2024

Gómez-Vásquez, Julio D., 2024, New records and five new species of sipunculans (Sipuncula) from the central and northwestern Mexican Pacific, European Journal of Taxonomy 925, pp. 179-219 : 194-196

Phascolion (Lesenka) salgadoi sp. nov.

urn:lsid:zoobank.org:act:3DEAE010-73D3-4FFC-B41C-B81BD6722667

Fig. 7

Etymology

Named after the researcher José Salgado-Barragán, a crustacean specialist from the Universidad Nacional Autónoma de México (UNAM) and a good friend who provided the specimens of this species. The epithet is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Material examined

Holotype

MEXICO • Sonora, Guaymas Bay ; 24 Oct. 1991; depth 45 m; inside empty shells of Polystira sp. ; EMU-13448 .

Paratypes

MEXICO • 7 specs; same collection data as for holotype; UMAR-SIPU 131 • 6 specs; same collection data as for holotype; EMU-13449 • 7 specs; same collection data as for holotype; EMU-13450 .

Other material

MEXICO • 4 specs; same collection data as for holotype; UMAR-SIPU 132 .

Description (EMU-13448)

Body coiled to the left; trunk 25 mm in length ( Fig. 7A ). Light brown skin, translucent at mid trunk. Ventral region of trunk with numerous simple, round and flat papillae, mid trunk with scattered circular papillae with hardened U-shaped border with a tooth ( Fig. 7D ), denser and smaller on caudal region and on each side of ventral papillae. Introvert partially protruded; 12 short, thin digitiform peripheral tentacles encircling mouth. Scattered claw-shaped, dark hooks ( Fig. 7F ) of type I ( Cutler 1994), 37 µm long, occupying 10% of distal length of introvert. Anus on proximal portion of introvert, near edge of trunk; posterior introvert with bladder-shaped holdfast papillae ( Fig. 7E ), extending slightly to trunk.

Longitudinal musculature continuous; retractor muscle in a single column, attached to body wall at 90% of posterior trunk length. Esophagus attached to retractor muscle. A single nephridium of approximately 15% of trunk length attached in all its length to body wall; nephridiopore opens posterior to anus. Spindle muscle attached anterior to anus and attached to intestine in caudal region of trunk; intestine without coils, with same torsion as body ( Fig. 7B ).

Variation

Some of the hardened holdfast papillae have a U-shaped border. The density of papillae is variable among the specimens.

Habitat

Subtidal (45 m); inhabiting shells of the gastropod Polystira sp. ( Fig. 7C ).

Distribution

Gulf of California: only known from Guaymas Bay, Sonora.

Remarks

The specimens can easily be placed in the subgenus Phascolion (Lesenka) by the presence of a single retractor muscle and by having less than 20 tentacles. Phascolion (L.) salgadoi sp. nov. is similar to two subspecies: P. (L.) valdiviae valdiviae Fischer, 1916 (from the Indian Ocean) and P. (L.) valdiviae sumatrense Fischer, 1916 (from Sumatra). The two subspecies and the specimens examined here have U-shaped holdfast papillae, in addition to having a single retractor muscle; however, the specimens from the Mexican Pacific are geographically separated from previous subspecies. Also, they have several morphological differences from both subspecies.

Phascolion (Lesenka) salgadoi sp. nov. differs from Fischer’s subspecies because they have dark hooks, while P. (L.) valdiviae valdiviae has pale hooks and P. (L.) valdiviae sumatrense lacks hooks. Phascolion (L.) salgadoi does not show intestinal coils, the intestine instead following the torsion of the body, while the Indian subspecies has 20–22 coils. Regarding habitat, Ph. (L.) salgadoi was found at a depth of approximately 45 m, living in an empty shell of the gastropod Polystira sp. , while the subspecies P. (L.) valdiviae valdiviae was obtained at a depth of 158 m, living in shells of the scaphopod Dentalium sp. , which does not have whorls. The description of P. (L.) valdiviae sumatrense did not mention anything about its habitat, except that the species was found at a bathyal depth (750 m) ( Fischer 1916).

Comparing Phascolion (Lesenka) salgadoi sp. nov. with other species of the subgenus, the following differences are noted: P. (L.) collare Selenka & de Man, 1883 has conical papillae and small type III hooks ( Cutler 1994); P. (L.) cryptum Hendrix, 1975 has four main tentacles followed by accessory tentacles and it has no hooks; and P. (L.) hupferi Fischer, 1894 has the anus at half of the introvert length and, like P. (L.) rectum Ikeda, 1904, has neither hooks nor holdfast papillae ( Cutler 1994). On the other hand, P. (L.) salgadoi possesses flat oval papillae with a hardened U-shaped border, bladder-shaped holdfast papillae, type I hooks, short digitiform tentacles and the anus is situated at the base of the introvert.

Figures

Fig. 7. Phascolion (Lesenka) salgadoi sp. nov. (EMU-13448). A. Trunk overview, introvert contracted. B. Internal anatomy. C. Shell containing Ph. (L.) salgadoi. D. Hardened U-shaped holdfast papilla. E. Bladder shaped holdfast papillae. F. Type I hook. Abbreviations: see Material and methods. Scale bars: A = 3 mm; B = 2 mm; C = 2 cm; D = 0.5 mm; E = 1 mm; F = 15 µm.