Mulinia edulis ( King & Broderip, 1832 )

Signorelli, Javier H. & Pastorino, Guido, 2011, Revision of the Magellanic Mactridae Lamarck, 1809 (Bivalvia: Heterodonta), Zootaxa 2757, pp. 47-67 : 55-58

Mulinia edulis ( King & Broderip, 1832)

( Figures 8–10 )

Mactra edulis King & Broderip, 1832: 335 ; Potiez & Michaud, 1844: 248, pl. 65, fig.5; d´Orbigny, 1846: 510; Reeve, 1854: pl. 7, fig. 32; Hupé in Gay, 1854: 348; Martinez y Saez, 1869: 12, pl. 3, fig.8; Mabille & Rochebrune, 1889: 106.

Mulinia typicus Gray, 1837: 375 ; Hanley, 1843: 34.

Mulinia edulis Gray, 1837: 376 ; Hanley, 1843: 35; Adams & Adams, 1856: 379, pl. 100, fig. 3; Dall, 1909: 274; Carcelles, 1950: 81, pl. 5 fig. 89; Carcelles & Williamson, 1951: 343; Bernard, 1983: 40

Mactra marcida Gould, 1850: 216 ; 1852: 392, pl. 33, figs. 505 a–b; 1862: 76; Mabille & Rochebrune, 1889: 106.

Mulinia typica Gray, 1853: 42 ; Adams & Adams, 1856: 380.

Mactra typica Reeve, 1854 : pl. 11, fig. 45; Philippi, 1893: 8, pl. 1, fig. 1.

Mulinea typica Conrad, 1868: 31 .

Mulinea edulis Conrad, 1868: 31 .

Mactra coquimbana Philippi, 1893: 10 , pl.2, fig. 7; Bernard, 1983: 40.

Mactra (Mulinia) typical Gray, Philippi, 1893: 8 , pl. 1, fig. 1.

Diagnosis. Shell trigonal to subcircular, inflated, periostracum reddish brown; escutcheon defined by posterior line from umbo to posterior margin; lateral teeth elongated but close to the cardinals.

Description. Shell trigonal, subcircular, strong; external surface smooth, with reddish brown periostracum; umbos slightly inflated, prosogyrous; posterior dorsal margin rounded from umbo to posterior end; anterior dorsal margin straight; ventral edge curved without sharp angles. Pallial sinus separated from ventral edge, U-shaped, horizontal, approximately half of shell length ( Fig. 8 C–D). Right valve hinge with small, short lateral teeth; cardinal teeth unfused ( Fig. 9 A), left valve with V-shaped cardinal teeth composed of two simple, divergent cardinals; one anterior and one posterior lateral tooth present ( Fig.9 B); ultrastructure of shell as in other species analyzed ( Fig. 9 C–D).

Mantle cavity organs. Siphons fused; apertural area of incurrent characterized by presence of tentacles in two rings; internal ring with two sizes of tentacles, external ring with only one. Excurrent siphon with subequal tentacles ( Fig. 10 G–H). Ctenidial demibranchs fused posteriorly; inner demibranchs with well-defined food grooves at distal edges ( Fig. 10 A–C). External and internal demibranchs similar in size and shape; of ctenidial type C(1) of Atkins (1937). Ctenidia fused with labial palps anteriorly, elongated, trigonal, with internal surfaces plicate facilitating food transport to mouth ( Fig. 10 D). Heart with two ventral auricles and one large ventricle; intestine passing through ventricle ( Fig. 10 E–F).

Type material. [ M. edulis ] NHM 1837.1.12.1168-9 and 196325, three syntypes (figs. 8A–D); [ M. marcida ] USNM 5892, holotype from Orange Bay and ANSP 51364, one paratype (figs. 8E–H); [ M. typicus ] NHM (unnumbered), one specimen from Patagonia (figs. 8G–H); [ M. coquimbana ] MNHNC (unnumbered), holotype from Coquimbo, Chile (figs. 8I –K).

Type locality. Puerto El Hambre, Magellanic Strait, Chile.

Other material examined. Ecuador. Guayaquil ( ANSP 51335). Peru. Lima ( USNM 593115); Peru ( AMNH 34751); Callao ( USNM 13432). Chile. Atacama ( AMNH 132942); Chile ( MZUSP 13071; USNM 212597, 212598; AMNH 34042); Valparaíso ( USNM 159384); Coquimbo ( USNM 128354; NHM 1898.7.29.20; MORG 18971); Talcahuano ( MNRJ 1300); Valdivia ( MLP 9381); Puerto Montt ( MLP 1853); Chiloe ( MZUSP 66341); Gulf Elefantes, XI Region (NHM 1999.02.02); Magellanic Strait ( MZUSP 13066, 13069, 13072, 13073, 13075). Argentina. Tierra del Fuego ( USNM 568263); Orange Harbor (NHM 1962.10.93); Ushuaia ( MLP 2239; MACN 19826, coll. in 1931, 5 valves; 13559, 12 valves, coll. by Carcelles in 1923).

Distribution. From Guayaquil, Ecuador, to Ushuaia, Argentina.

Remarks. The analysis of the type specimens of Mulinia typica housed at NHM confirms it as a synonym of M. edulis ( Fig. 8 G–H). The material of Mactra marcida collected by the U. S. Exploring Expedition from Orange Harbor (USNM and ANSP) revealed its synonymy ( Fig. 8 E–F). Finally, the type material of Mactra coquimbana described from Coquimbo, Chile (MNHNC) is the same that M. edulis ( Fig. 8 I–K).

Bernard (1983) mentioned the species Mactra cuneola Gould, 1850 as a synonym of M. edulis . However, the Gould species, described from Callao, Peru, is more trigonal with a rounded posterior end and the anterior straight ( Fig. 8 L–M). In addition, the pallial sinus is shorter and the lateral teeth more elongated. The type material of Mulinia antarctica Dunker, 1850 , cited by Paetel (1883: 201) from Chiloe Island, Chile, was not found at the ZMB collection. Neither was the original description found in the literature, only the citation of Paetel. For these reasons, we conclude that this name should be considered a nomen nudum.

Other nominal species, i.e., Mactra calbucana Philippi, 1893 ; Mactra epidermia Philippi, 1893 ; Mactra fuegiensis Smith, 1905 ; Mactra lotensis Philippi, 1893 ; Mactra pencana Philippi, 1893 ; Mulinia jousseaumi Mabille & Rochebrune, 1889 ; and Mulinia levicardo Smith, 1881 , were incorrectly given by Bernard (1983) as synonyms of M. edulis .

Figures

FIGURE 8. Mulinia edulis, A – D: Syntypes of Mulinia edulis King & Broderip, 1832 (NHM 1837.1.12.1168); E – F: Holotype of Mactra marcida Gould, 1850 (USNM 5892); G – H: Specimen labeled by Gray, possible Holotype of Mulinia typica Gray (NHM unnumbered); I – K: Holotype of Mactra coquimbana Philippi, 1893; L – M: Holotype of Mactra cuneola Gould, Holotype (USNM 5891), scale bar = 1 cm.

FIGURE 9. Mulinia edulis, A – B: hinge description according to the nomenclature developed by Bernard and Munier Chalmas, Scale bar = 1 cm; C – D: Ultrastructure of the shell, C: outer layer showing cross lamellar structure; D: inner layer with the cross lamellar complex, scale bar = 50 µm.

FIGURE 10. Mulinia edulis, A – C: SEM picture of Ctenidia, A. internal view of the outer demibranch (oh) and inner demibranch (ih), B – C: food groove (fg) in the ventral margin, scale bar A = 1000 µm, B = 100 µm and C = 20 µm.; D: inner labial palp (ilp) with the inner surface plicate, scale bar = 2000 µm; E – F: SEM picture of the heart, E: dorsal view showing the ventricle (vt), F: ventral view showing the auricles (au), scale bar E = 500 µm, F = 200 µm; G – H: SEM picture of siphons, G: general aspect of the incurrent (in) and excurrent (ex) siphons, H: detail of the tentacles, scale bars: G = 2 mm, H = 1 mm.