Aspidosiphon (Aspidosiphon) elegans ( Chamisso & Eysenhardt, 1821 )

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 : 185-188

Aspidosiphon (Aspidosiphon) elegans ( Chamisso & Eysenhardt, 1821)

Fig. 3A–C

Sternaspis elegans Chamisso & Eysenhardt, 1821: 351–352 , pl. 14 fig. 5a–e (type locality: Radack, Marshall Islands, in dead coral).

Aspidosiphon exilis Sluiter, 1886: 497 , pl. 3 figs 11–12 (type locality: Tausend Island, Java).

Aspidosiphon ravus Sluiter, 1886: 495–496 , pl. 3 figs 9–10 (type locality: Bay of Bantam, Malaya).

Aspidosiphon spinosus Sluiter, 1902: 28 , pl. 2 figs 17–19 (type locality: Damar Island, Indonesia).

Aspidosiphon brocki Augener, 1903: 34–36 , figs 9–13 (type locality: Polo Ednam, Amboina, Malaya).

Aspidosiphon spinalis Ikeda, 1904: 47–49 , fig. 12 (type locality: Koniya, Amami-Osima, Japan).

Aspidosiphon coralinus Sato, 1935: 318–319 , pl. 4 fig. 19 (type locality: Arukoron Island, West Caroline Islands).

Aspidosiphon homomyarium Johnson, 1964: 332–334 , pl. 8 (type locality: Okha, India).

Aspidosiphon brocki – Rice 1970: 44, fig. 8 (Florida, northern Caribbean Sea).

Aspidosiphon (Aspidosiphon) elegans – Fonseca & Cortés 1988: 172–173 (Pacific coast of Costa Rica). — Cutler & Cutler 1989: 842–844 (subgenus assignment). — Dean 2001: 89 (Golfo Dulce, Costa Rica). — Silva-Morales & Gómez-Vásquez 2021: 97–99 , fig. 11 (Southern Mexican Pacific).

Material examined

MEXICO – Baja California Sur • 5 specs; La Paz, Calerita Beach; 1 Mar. 2006; DHP et al. leg.; intertidal; UMAR-SIPU 151 . – Nayarit • 1 spec.; Punta Mita; 15 Jul. 1990; depth 4 m; JPU leg.; inhabiting Porites sp. ; UMAR-SIPU 152 .

Description ( UMAR-SIPU 151)

Trunk 12 mm in length; whitish, slightly translucent body wall ( Fig. 3A ); scattered flat oval papillae. Introvert slightly longer than half of trunk length. Twelve small digitiform tentacles, encircling nuchal organ. Anterior hooks 40 µm long, laterally compressed and bidentate ( Fig. 3B ), arranged in 14 complete rings; posterior scattered, dark unidentate hooks 50 µm long ( Fig. 3C ), anterior hooks pyramid-shaped, mid and posterior ones conical. Anal shield yellowish, formed by small, packed granules with well-defined margin. Without caudal shield; specimen UMAR-SIPU 151 in asexual reproduction phase, seen by presence of a bud occupying 1/10 of trunk length.

Longitudinal musculature in a continuous layer, in bands under anal shield. A pair of retractor muscles, attached to body wall at posterior end of trunk. Two nephridia of 40% of trunk length; nephridiopores open posterior anus. Spindle muscle attaches to intestine anteriorly and trunk posteriorly.

Habitat

Intertidal to subtidal (4 m); in dead coral.

Distribution

Pantropical, widespread and common in the Indian and western Pacific Oceans, from south-central Japan to northern Australia, the Red Sea and Israel; in the Caribbean from northern Brazil to the Florida Keys and Bermuda ( Cutler 1994). In the eastern Pacific from southern Gulf of California to Costa Rica ( Fonseca & Cortés 1988).

Remarks

The presence of A. (A.) elegans in the eastern Pacific was not discovered (sensu Cutler 1994) until Fonseca & Cortés (1988) recorded it from Costa Rica, and Silva-Morales & Gómez-Vásquez (2021) from the southern Mexican Pacific.

Silva-Morales & Gómez-Vásquez (2021) compared specimens identified as Aspidosiphon (A.) elegans from the southern Mexican Pacific with those present in the Mexican Caribbean, and no differences in body features were found; however, some differences in the bidentate hooks, regarding both teeth and internal anatomy, were noted. Also, consulting the descriptions and illustrations of species synonymized with A. (A.) elegans (i.e., A. brocki , A. coralinus and A. exilis ; Stephen & Edmonds 1972), I found that the configuration of the bidentate hooks is also different from the one seen in specimens from the Mexican Pacific. This may suggest that A. (A.) elegans is a species complex, and more detailed examination is required to determine the validity of worldwide records and whether the species is truly pantropical or the synonymized species can be considered as valid, and therefore be reinstated. Between the material of the southern Mexican Pacific and the specimens reviewed here, there are no morphological differences, indicating that there is only one morphospecies in the entire Mexican Pacific.

With the present records, the distribution of A. (A.) elegans is extended to the northern Gulf of California. It has been observed that the species has asexual reproduction by transverse fission in the posterior region of the trunk (Rice 1970; Acik 2008), as was also observed in the specimens examined here ( Fig. 3A ).

Figures

Fig. 3. Aspidosiphonids. A–C. Aspidosiphon (Aspidosiphon) elegans (Chamisso & Eysenhardt, 1821 (UMAR-SIPU 151). A. Lateral overview of specimen with budding. B. Anterior bidentate hook. C. Posterior conical hook. D–F. Aspidosiphon (Paraspidosiphon) pastori Silva-Morales & Gómez- Vásquez, 2021 (UMAR-SIPU 154).D. Lateral overview, introvert partially everted.E. Anterior bidentate hook. F. Posterior pyramidal hook. Bd = bud. Scale bars: A, D = 3 mm; B–C = 20 µm; E–F = 10 µm.