Phascolosoma ( Phascolosoma ) azteca, Gómez-Vásquez, 2024

Phascolosoma ( Phascolosoma) azteca sp. nov.

urn:lsid:zoobank.org:act:

Fig. 13 View Fig

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 GoogleMaps • 8 specs; Punta Raza Beach ; 21°01ʹ59ʺ N, 105°18ʹ51ʺ W; 11 Apr. 1996; EMU-13439 GoogleMaps .

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 GoogleMaps . – 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 GoogleMaps • 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 GoogleMaps • 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 GoogleMaps • 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 . GoogleMaps – 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 GoogleMaps • 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 GoogleMaps • 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 . GoogleMaps – Nayarit • 5 specs; Cabo Litibu ; 20°47ʹ21ʺ N, 105°31ʹ03ʺ W; 9 Apr. 1996; depth 3 m; UMAR-SIPU 143 GoogleMaps • 18 specs; Sayulita Beach ; 20°47ʹ24ʺ N, 105°31ʹ54ʺ W; 10 Apr. 1996; depth 3 m; UMAR-SIPU 144 GoogleMaps • 4 specs; Guayabitos Beach ; 21°02ʹ06ʺ N, 105°19ʹ14ʺ W; 11 Apr. 1996; depth 3 m; UMAR-SIPU 145 GoogleMaps • 8 specs; Punta Raza Beach ; 21°01ʹ59ʺ N, 105°18ʹ51ʺ W; 19 Feb. 2000; UMAR-SIPU 146 GoogleMaps • 1 spec.; Guayabitos Beach , naval base; 22°08ʹ00ʺ N, 105°31ʹ00ʺ W; 19 Feb. 2000; EMU-13441 GoogleMaps • 3 specs; Chacala Beach ; 21°09ʹ55ʺ N, 105°13ʹ39ʺ W; 20 Feb. 2002; EMU-13440 GoogleMaps • 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 GoogleMaps • 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 . GoogleMaps – Jalisco • 21 specs; Los Arcos Beach ; 20°32ʹ30ʺ N, 105°18ʹ24ʺ W; 12 Apr. 1996; UMAR-SIPU 147 GoogleMaps • 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 GoogleMaps • 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 . GoogleMaps – Colima • 3 specs; La Audiencia Beach ; 19°06ʹ11ʺ N, 104°21ʹ01ʺ W; 15 May 2006; EMU-13445 GoogleMaps • 2 specs; La Audiencia Beach ; 19°06ʹ11ʺ N, 104°21ʹ01ʺ W; 15 May 2006; UMAR-SIPU 148 . GoogleMaps – Michoacán • 3 specs; Bucerías Beach ; 19 Dec. 1994; SGM and RBZ leg.; UMAR-SIPU 149 GoogleMaps .

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 View Fig ), larger and denser towards anterior and posterior ends; with pre-anal area of pigmented small, conical papillae ( Fig. 13B View Fig ). Introvert twice as long as trunk; 12 small digitiform tentacles, aboral surface with longitudinal dark pigmented band ( Fig. 13C View Fig ), arranged in arc surrounding nuchal organ, dorsal to mouth; nuchal organ rounded and bilobed. Hooks curved ( Fig. 13D–E View Fig ), 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 View Fig ).

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 View Fig ) 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 View Fig ), while in P. ( P.) azteca sp. nov. they are restricted to 5% of the posterior introvert ( Fig 13B View Fig ). 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 View Fig ), 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 View Fig ).

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.