Sipunculus (Sipunculus) bastidai, 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 : 210-213

Sipunculus (Sipunculus) bastidai sp. nov.

urn:lsid:zoobank.org:act:1723EDBB-D6C3-4079-9215-75CD2237F0A8

Fig. 15 , Table 2

Etymology

This species is named after the researcher J. Rolando Bastida-Zavala, who has been my mentor and friend, as a token of appreciation for his kindness and teaching about different taxonomic groups, and for his remarkable work on polychaetes. He also collected the specimens examined here. The epithet is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Material examined

Holotype

MEXICO • W coast of Baja California Sur; 26°17ʹ25ʺ N, 112°56ʹ39ʺ W; Feb. 1989; depth 54 m; RBZ leg.; Van Veen grab; subtidal muddy/sand bottom; EP-8902 cruise, stn E21, on board R/V El Puma; UMAR-SIPU 129 .

Paratypes

MEXICO • 70 specs; same collection data as for holotype; UMAR-SIPU 001 • 5 specs; same collection data as for holotype; ECOSUR-313 • 5 specs; same collection data as for holotype; EMU-13451 • 5 specs; same collection data as for holotype; EMU-13452 .

Other material

MEXICO • 64 specs; W coast of Baja California Sur; 26°17ʹ25ʺ N, 112°56ʹ34ʺ W; Feb. 1989; depth 62 m; RBZ leg.; EP-8902 cruise, stn E22, on board R/V El Puma; UMAR SIPU-002 .

Description ( UMAR-SIPU 129)

(Based on holotype.) Trunk 80 mm in length; pinkish brown body wall, slightly iridescent ( Fig. 15A ). Trunk skin squared; middle trunk with protruding globose skin bodies on each square ( Fig. 15B ), present on approximately half of trunk length; first 35% and last 15% of trunk length free of skin bodies. Glans region on last 8% of trunk length, not distinctly differentiated from trunk, caudal tip with a notch. Introvert ¼ of trunk length, with scattered triangular, rounded tip papillae. Short crenulated tentacles surrounding mouth ( Fig. 15D ).

Longitudinal musculature divided into 35 bands. Four retractor muscles attached to body wall at same level, at 25% of trunk length; ventral pair attached to two muscle bands ( LMB 3–4), dorsal pair attached to three muscle bands ( LMB 12–14). Brain oval, 1 mm in length, wider than long, with main tubular process ( Fig. 15E ). Post-esophageal loop of same length as intestine, reaches glans region. Pair of nephridia 20 mm in length, with granulated surface; nephridiopores open anterior to anus. Anus located at 25% of trunk length; rectum with a pair of wing muscles; single sack-like caecum present, attached to spindle muscle. Spindle muscle well developed, attached anteriorly to rectum, subdivided along entire intestine in various stringy muscles, not attached posteriorly ( Fig. 15C ).

Variations

(Based on 25 specimens from paratype material.) The trunk length of the smallest specimen is 58 mm, while the largest is 115 mm long. The proportion of the body occupied by globose skin bodies is ½ of the trunk length, with a range from ⅓ to ⅔.

Regarding the longitudinal muscle bands ( LMB), the majority (52%) of the specimens have 35, 20% have 36, 16% have 37, one specimen has 33 and one has 34 LMBs. Almost all specimens analyzed have the ventral retractor muscles (RM) attached to two LMBs ( LMB 3–4), but one specimen has the ventral RM attached to three LMBs ( LMB 3–5); in most of the specimens the dorsal RMs are attached to three LMBs ( LMB 12–14), but some specimens have the dorsal RM attached to four LMBs ( LMB 12–15); a few other specimens have the dorsal RM start their attachment to LMB 11–13, resulting in six possible combinations observed: attached to three LMBs (11–13, 12–14 or 13–15) or attached to four LMBs (11–14, 12–15 or 13–16), where the last three combinations are the rarest.

Habitat

Subtidal (54–62 m); in muddy/sandy bottom.

Distribution

Only known from the western coast of Baja California Sur.

Remarks

Specimens of Sipunculus (Sipunculus) bastidai sp. nov. from Baja California Sur resemble S. (S.) phalloides phalloides ( Pallas, 1774) from the island of Granada, Antilles, and S. (S.) phalloides inclusus Sluiter, 1902 from Indonesia by having between 35 and 41 longitudinal muscle bands and by having the origin of the retractor muscles separated. However, specimens of S. (S.) bastidai have a series of morphological characters that are different from those of the two subspecies of S. phalloides . In their descriptions and illustrations ( Pallas 1774; Sluiter 1902), neither of the subspecies of S. phalloides has skin bodies on the trunk, which are clearly observed as globular projections in specimens of the new species; the range of number of longitudinal muscle bands (LMB), regardless of the size of the specimens, is also different: 33–37 in S. (S.) bastidai , 35–41 in S. (S.) phalloides phalloides and 32–39 in S. (S.) phalloides inclusus. Furthermore, according to Cutler & Cutler (1985), who reviewed Sluiter’s type material, S. (S.) phalloides inclusus has LMBs that separate and rejoin each other along the trunk, unlike S. (S.) bastidai , where the LMBs maintain the same number throughout the trunk.

Other morphological features that separate Sipunculus (Sipunculus) bastidai sp. nov. from the subspecies of S. (S.) phalloides are the number and position of the LMBs to which the retractor muscles are attached ( Table 2 ). Stephen & Edmonds (1972) mentioned that both subspecies of S. (S.) phalloides do not have a caecum in the rectum, whereas the species from Baja California Sur does. Due to this set of morphological differences, there is enough evidence to consider S. (S.) bastidai as a valid new species. Regarding molecular analyses, it has been shown in a species of the same genus ( Sipunculus nudus Linnaeus, 1766 ) that there is evidence of multiple genetic clades, invalidating the idea of cosmopolitan species ( Kawauchi & Giribet 2014).

Figures

Fig. 15. Sipunculus (Sipunculus) bastidai sp. nov. (UMAR-SIPU 129). A. Lateral overview, introvert with tentacular crown. B. Close view of mid-trunk papillae. C. Internal anatomy. D. Tentacles; asterisk indicates mouth. E. Cerebral ganglia. Abbreviations: see Material and methods. Scale bars: A, C = 20 mm; B = 3 mm; D = 2 mm.