Phascolosoma (Phascolosoma) azteca, 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 : 205-209

Phascolosoma (Phascolosoma) azteca sp. nov.

urn:lsid:zoobank.org:act:EB807E85-7A40-48D0-9B1B-57D77D1633F5

Fig. 13

Phascolosoma dentigerum (not Selenka & de Man, 1883) – Steinbeck & Ricketts 1941: 345–346. — Fisher 1952: 432–434, pl. 39 figs 4–7 (based on material collected by Ricketts).

Etymology

This species is named after the ancient Mexican culture of the great Tenochtitlan commonly known as the Aztecs. The epithet in a noun in apposition ( ICZN 1999, Art. 31.1).

Material examined

Holotype

MEXICO • Jalisco, Los Arcos Beach ; 22 Jan. 2001; depth 2 m; LIB leg.; in dead coral; EMU-13443 .

Paratypes

MEXICO • 19 specs; same collection data as for holotype; EMU-13444 • 10 specs; same collection data as for holotype; UMAR-SIPU 139 • 7 specs; Sayulita Beach ; 21°01ʹ39ʺ N, 105°16ʹ59ʺ W; 19 Feb. 2000; depth 3 m; EMU-13438 • 8 specs; Punta Raza Beach ; 21°01ʹ59ʺ N, 105°18ʹ51ʺ W; 11 Apr. 1996; EMU-13439 .

Other material

MEXICO – Baja California • 1 spec.; Los Ángeles Bay ; 28°56ʹ55.48ʺ N, 113°33ʹ26.36ʺ W; 25 May 1986; SSV and JLG leg.; ECOSUR-S0272 . – Baja California Sur • 6 specs; La Paz , Tecolote Beach ; 24°20ʹ13.38ʺ N, 110°19ʹ04.7ʺ W; 15 Oct. 1986; SSV and NEG leg.; intertidal; ECOSUR-S0271 • 1 spec.; La Paz , Presidente Beach ; 19 Apr. 1987; RBZ leg.; in dead coral; UMAR-SIPU 140 • 3 specs; La Paz , El Caimancito Beach ; 24°12ʹ10.43ʺ N, 110°18ʹ01.09ʺ W; 10 Oct. 1987; depth 2 m; SSV leg.; in rocks; ECOSUR-S0275 • 1 spec.; Cabo Pulmo ; 1989; in dead coral; UMAR-SIPU 149 • 1 spec.; El Tesoro Beach ; 17 Jul. 1996; UMAR-SIPU 142 • 1 spec.; La Paz, Calerita Beach ; 18 Jul. 1996; intertidal; EMU-13442 • 1 spec.; La Paz , El Caimancito Beach ; 24°12ʹ15.00ʺ N, 110°18ʹ02.96ʺ W; 29 Feb. 2004; depth 1 m; PSS and MTH leg.; inhabiting Porites sp. ; ECOSUR-S0268 • 10 specs; La Paz , Balandra Beach ; 24°19ʹ16.20ʺ N, 110°19ʹ33.54ʺ W; 2 Mar. 2004; depth 1 m; PSS and MTH leg.; on oyster; ECOSUR-S0273 . – Sinaloa • 35 specs; Mazatlán, Pinitos Beach ; 23°12ʹ31.93ʺ N, 106°25ʹ39.77ʺ W; 22 Feb. 2004; depth 2 m; PSS and MTH leg.; on oyster; ECOSUR-S0265 • 3 specs; Mazatlán, Pinitos Beach ; 23°12ʹ28.02ʺ N, 106°25ʹ32.69ʺ W; 23 Feb. 2004; depth 1 m; PSS and MTH leg.; associated with sabellariids; ECOSUR-S0274 • 3 specs; Mazatlán, Cerritos Beach ; 23°17ʹ49.63ʺ N, 106°29ʹ08.51ʺ W; 27 Feb. 2004; PSS and MTH leg.; on oyster with green and red algae; ECOSUR-S0276 . – Nayarit • 5 specs; Cabo Litibu ; 20°47ʹ21ʺ N, 105°31ʹ03ʺ W; 9 Apr. 1996; depth 3 m; UMAR-SIPU 143 • 18 specs; Sayulita Beach ; 20°47ʹ24ʺ N, 105°31ʹ54ʺ W; 10 Apr. 1996; depth 3 m; UMAR-SIPU 144 • 4 specs; Guayabitos Beach ; 21°02ʹ06ʺ N, 105°19ʹ14ʺ W; 11 Apr. 1996; depth 3 m; UMAR-SIPU 145 • 8 specs; Punta Raza Beach ; 21°01ʹ59ʺ N, 105°18ʹ51ʺ W; 19 Feb. 2000; UMAR-SIPU 146 • 1 spec.; Guayabitos Beach , naval base; 22°08ʹ00ʺ N, 105°31ʹ00ʺ W; 19 Feb. 2000; EMU-13441 • 3 specs; Chacala Beach ; 21°09ʹ55ʺ N, 105°13ʹ39ʺ W; 20 Feb. 2002; EMU-13440 • 2 specs; Sayulita Beach ; 20°52ʹ15ʺ N, 105°26ʹ40.4ʺ W; 28 Nov. 2004; depth 1 m; PSS et al. leg.; under rocks; ECOSUR-0267 • 8 specs; Banderas Bay , Manzanilla Beach ; 20°44ʹ25.49ʺ N, 105°23ʹ24.33ʺ W; 29 Nov. 2004; depth 2 m; PSS et al. leg.; in rocks; ECOSUR-0277 . – Jalisco • 21 specs; Los Arcos Beach ; 20°32ʹ30ʺ N, 105°18ʹ24ʺ W; 12 Apr. 1996; UMAR-SIPU 147 • 4 specs; San Patricio Melaque Beach ; 19°13ʹ12.08ʺ N, 104°42ʹ49.95ʺ W; 2 Dec. 2004; depth 3 m; PSS et al. leg.; in rocks; ECOSUR-0266 • 2 specs; Barra de Navidad , Corrales Beach ; 19°11ʹ14.08ʺ N, 104°41ʹ42.84ʺ W; 3 Dec. 2004; depth 4 m; PSS et al. leg.; in rock; ECOSUR-0269 . – Colima • 3 specs; La Audiencia Beach ; 19°06ʹ11ʺ N, 104°21ʹ01ʺ W; 15 May 2006; EMU-13445 • 2 specs; La Audiencia Beach ; 19°06ʹ11ʺ N, 104°21ʹ01ʺ W; 15 May 2006; UMAR-SIPU 148 . – Michoacán • 3 specs; Bucerías Beach ; 19 Dec. 1994; SGM and RBZ leg.; UMAR-SIPU 149 .

Comparative material ( Phascolosoma (Phascolosoma) perlucens Baird, 1868 )

MEXICO – Quintana Roo • 3 specs; Playa del Carmen, Navega docks ; 23 Aug. 2003; MTH leg.; ECOSUR-S0044 .

PANAMA • 2specs; Colón, Portobelo ; 4Jun.2002; depth 1m; JC and SSV leg.; in rocks; ECOSUR-S0056 .

VENEZUELA • 2 specs; Cumana , Turpialito; 22 Feb. 2002; depth 1.5 m; IL leg.; inhabiting Millepora sp. ; ECOSUR-S0057 .

Description (EMU-13443)

Trunk 8 mm in length, pale brown body wall with scattered conical papillae ( Fig. 13A ), larger and denser towards anterior and posterior ends; with pre-anal area of pigmented small, conical papillae ( Fig. 13B ). Introvert twice as long as trunk; 12 small digitiform tentacles, aboral surface with longitudinal dark pigmented band ( Fig. 13C ), arranged in arc surrounding nuchal organ, dorsal to mouth; nuchal organ rounded and bilobed. Hooks curved ( Fig. 13D–E ), 52 µm long, with small secondary tooth, curved streak present, internal triangle separate from streak; hooks arranged in 15 complete rings. Longitudinal dorsal reddish band on posterior 80% of introvert towards anus. Dorsal conical papillae, posteriorly directed, on posterior half of introvert.

Longitudinal musculature in 18 anastomosing bands. Four retractor muscles attached at 50% of trunk length, ventral pair attached to six bands of longitudinal musculature ( LMB 2–7), dorsal pair attached to two bands ( LMB 6–7), anterior to ventral pair. Paired nephridia approximately 50% of trunk length; nephridiopores open anterior to anus. Spindle muscle attaches intestine to rectum anteriorly and to caudal region posteriorly ( Fig. 13F ).

Variations

Based on 20 paratypes and the extra material examined, the number of hook rings varies according to the size of the specimen, a specimen with a trunk length of 6 mm having 12 hook rings and a specimen with a trunk length of 10 mm having 20 complete rings. The number of tentacles also varies according to the size of the specimen from 10 to 14.

The Caribbean specimens ( Fig. 14 ) have a greater trunk length, 13 mm long with 12–16 tentacles.

Habitat

Intertidal to subtidal (12 m); inhabiting Porites sp. , in rocks, associated with sabellariid tubes, algae and oyster shells.

Distribution

Mexican Pacific: present along the central and northwestern Mexican Pacific coast, from Baja California to Michoacán.

Remarks

Specimens of Phascolosoma (Phascolosoma) azteca sp. nov. are morphologically close to P. (P.) perlucens Baird, 1868 . For comparative purposes some specimens of P. (P.) perlucens from the Venezuelan coast were examined, and these specimens were consistent with the descriptions and redescriptions of that species ( Baird 1868; Rice & Stephen 1970).

Morphological differences were found between specimens from the Caribbean and those from the central and northwestern Mexican Pacific. Specimens of Phascolosoma (Phascolosoma) perlucens are larger and have 12–16 tentacles, whereas P. (P.) azteca sp. nov. has 10–14. Moreover, P. (P.) perlucens has more longitudinal muscle bands, 20–22, while P. (P.) azteca has 17–20. Furthermore, the ventral retractor muscles are attached to six longitudinal muscle bands (LMB 2–7) in P. (P.) azteca and to five (LBM 2–6) in P. (P.) perlucens .

Phascolosoma (Phascolosoma) perlucens has pre-anal pigmented papillae on 10–20% of the posterior introvert ( Fig. 14B ), while in P. (P.) azteca sp. nov. they are restricted to 5% of the posterior introvert ( Fig 13B ). Finally, the hooks of P. (P.) perlucens have a principal tooth that is slightly straight and the secondary tooth is somewhat like a hump ( Fig. 14D–E ), whereas in P. (P.) azteca the hooks have a more curved principal tooth and the inner margin is concave, making the secondary tooth look more projected and slightly acute, rather than like a hump ( Fig. 13D–E ).

Since the morphology of Phascolosoma (Phascolosoma) azteca sp. nov. resembles that of P. (P.) perlucens , the newly described species belongs to the P. (P.) perlucens species complex, for which, as mentioned by Kawauchi & Giribet (2010), there is evidence of multiple genetic clades, and some morphological differences can be shown between the populations as well. However, the morphological differences listed above indicate that P. (P.) azteca from the northwestern Mexican Pacific is a valid species, distinct from P. (P.) perlucens from the Caribbean.

Figures

Fig. 13. Phascolosoma (Phascolosoma) azteca sp. nov. (EMU-13443). A. Lateral overview, introvert contracted. B. Close-up of introvert base and anal area. C. Tentacles. D. Mid-posterior hook; asterisk indicates bubble inside clear streak. E. Illustration of hook. F. Internal anatomy. Abbreviations: see Material and methods. Scale bars: A, F = 2 mm; B–C = 0.5 mm; D–E = 20 µm.

Fig. 14. Phascolosoma (Phascolosoma) perlucens Baird, 1868 (ECOSUR S0044). A. Lateral overview, introvert contracted. B. Close-up of introvert base and anal area. C. Tentacles; asterisk indicates position of mouth. D. Mid-posterior hook; asterisk indicates bubble inside clear streak. E. Illustration of hook. F. Internal anatomy. Abbreviations: see Material and methods. Scale bars: A, F = 4 mm; B = 2 mm; C = 0.7 mm; D = 20 µm.