Themiste (Themiste) cf. blanda

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 : 196-197

Themiste (Themiste) cf. blanda (Selenka & Man in Selenka et al., 1883)

Fig. 6F

Type locality of nominal species

Enoshima, Japan ( Selenka et al. 1883: 85–86, pl. 1 fig. 9, pl. 11 figs 159–162).

Material examined

MEXICO • 1 spec.; Jalisco, Barra de Navidad, Corrales Beach ; 19°11ʹ14.08ʺ N, 104°41ʹ42.84ʺ W; 3 Dec. 2004; depth 4 m; PSS et al. leg.; under rocks; ECOSUR-S0256 .

Description ( ECOSUR-S 0256)

Trunk 8 mm in length; smooth, whitish brown body wall. Introvert with distal tentacular crown surrounding mouth; tentacular crown divided into four stems, each divided symmetrically into two branches; each branch with 10 terminal tentacles and 8 tentacles on inner face of each stem and branches. Introvert with anterior purple collar.

Longitudinal musculature continuous; two retractor muscles attached to body wall at 60% of trunk length; contractile vessel with 20 tubules. Two nephridia, 40% of trunk length; nephridiopores open before anus; spindle muscle anterior to anus, does not attach to intestine at posterior part of trunk.

Habitat

Shallow subtidal (4 m); under rocks.

Distribution

Central Mexican Pacific: Corrales Beach, Jalisco.

Remarks

The nominal species, Themiste (Themiste) blanda ( Selenka & de Man, 1883) , was described from Enoshima, Japan ( Selenka et al. 1883). Morphologically, the only difference between the description of the nominal species compared to the specimen from Jalisco is that the Japanese species was described as having five or six stems on its tentacular crown, while the Jalisco specimen only showed four stems. This difference may be due to the size of the specimen examined; it might not have completely developed all its stems. However, if this feature is actually indicative of a new species, more specimens are needed to properly study and describe it. It should be noted that studies conducted on the reproduction of other species of the genus ( Williams 1972; Rice 1976; Adrianov et al. 2009; Adrianov & Maiorova 2010) show that species of Themiste have larval development type 3, with larvae living 2–14 days in the water column. This period is not long enough to explain how the species could be transported from the Temperate Western Pacific to the Tropical Eastern Pacific. Thus, the presence of T. (T.) blanda in the Mexican Pacific is questionable, at least as long as no more specimens of this taxon are found.

Figures

Fig. 6. Golfingids. A. Golfingia (Golfingia) cf. muricaudata (EMU-13446). B–E. Nephasoma (Nephasoma) wodjanizkii wodjanizkii (Murina, 1973) (UMAR-SIPU 133). B. Lateral overview. C. Lateral view of posterior introvert. D. Internal anatomy. E. Close-up of retractor muscle origins from body wall. F. Themiste (Themiste) cf. blanda (ECOSUR-S0256). G. T. (T.) hennahi Gray, 1828 (ECOSUR-S0255). H. T. (T.) pyroides Chamberlin, 1920 (UMAR-SIPU 130). Abbreviations: see Material and methods. Scale bars: A = 2 cm; B, H = 2 mm; C, E = 1 mm; D, F = 4 mm; G = 3 mm.