Apionsoma (Edmondsius) hendrickxi, 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 : 201-203

Apionsoma (Edmondsius) hendrickxi sp. nov.

urn:lsid:zoobank.org:act:4E699E8D-05D4-4A09-A29E-70D79B1562AC

Figs 10–11

Etymology

This species is named after the researcher Michel Hendrickx, a carcinologist from the Universidad Nacional Autónoma de México (UNAM), in recognition of his contribution to our knowledge of Mexican marine biodiversity. He also provided the specimens examined here. The epithet is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Material examined

Holotype

MEXICO • Gulf of California ; 28°20ʹ57ʺ N, 112°37ʹ16ʺ W; 11 Apr. 2011; depth 310 m; core; TALUD XIV cruise, stn 16, on board R/V El Puma; EMU-13437 .

Paratype

MEXICO • same collection data as for holotype; UMAR-SIPU 150 .

Description (EMU-13437)

Trunk 14 mm in length; slender body, six times as long as wide: body wall rough, brownish, with some dark patches ( Fig. 10A ); scattered mammillate papillae on entire body. Introvert twice as long as trunk, partially protruded; with 10 small digitiform tentacles in an arc surrounding nuchal organ. Hooks 45 µm long, with four basal spinelets ( Fig. 10B ), arranged in 15 complete rings.

Longitudinal musculature divided into highly anastomosing bands, with a soft appearance; 16 bands at level of ventral retractor muscles. Four retractor muscles, both pairs equally displaced from ventral nerve cord; dorsal pair originating at and attached to body wall anterior to ventral pair. Esophagus attached to right ventral retractor muscle; contractile vessel thick, without bulbs or villi. A pair of bilobed nephridia, with rough surface, 4 mm long; posterior lobe four times as long as anterior lobe; nephridiopores posterior to anus. Spindle muscle attached anterior to anus; free intestine ( Fig. 11A ).

Habitat

Bathyal (310 m); in muddy sand.

Distribution

Only known from stn 16 of the TALUD XIV cruise, near Cabo San Miguel, Baja California.

Remarks

The specimens belong to the monospecific subgenus Apionsoma (Edmondsius) by having the longitudinal muscles separated into bands. Apionsoma (E.) hendrickxi sp. nov. differs from A. (E.) pectinatum ( Keferstein, 1867) by having four basal spinelets on the hooks ( Fig. 10B ), while A. (E.) pectinatum has seven to nine spinelets ( Fig. 12C ); furthermore, A. (E.) pectinatum has much more conspicuous longitudinal muscle bands than those of A. (E.) hendrickxi ( Fig. 11A ). Another difference is in the origin of the retractor muscles: in A. (E.) pectinatum all four retractor muscles originate at the same level, whereas in A. (E.) hendrickxi the dorsal muscle pair originates anterior to the ventral one. Finally, A. (E.) pectinatum is found from the intertidal to the subtidal zone (depth 5 m) associated with rocks and coral, while Apionsoma (E.) hendrickxi sp. nov. was found in the bathyal zone (depth 310 m) on muddy sand bottoms. With the description of A. (E.) hendrickxi sp. nov., the subgenus is no longer monospecific.

Figures

Fig. 10. Apionsoma (Edmondsius) hendrickxi sp. nov. (EMU-13437). A. Lateral overview, introvert contracted. B–C. Hook. Scale bars: A = 5 mm; B = 20 µm.

Fig. 11. Apionsoma (Edmondsius) hendrickxi sp. nov. (EMU-13437). A. Internal anatomy; asterisk indicates ripped part of rectum. B. Illustration of internal anatomy. Abbreviations: see Material and methods. Scale bar = 5 mm.

Fig. 12. Phascosolomatids. A, C. Apionsoma (Edmondsius) pectinatum (Keferstein, 1867 (ECOSUR- S0281). A. Lateral overview, introvert partially contracted.C. Hook.B, D. Phascolosoma (P.) puntarenae Grube & Öersted in Grube, 1858 (UMAR-SIPU 138). B. Lateral overview, introvert contracted. D. Hook. Scale bars: A–B = 5 mm; C = 20 µm; D = 40 µm.