Mactrellona alata ( Spengler, 1802 )

Signorelli, Javier H. & Pastorino, Guido, 2012, Taxonomic revision of Brazilian Mactridae Lamarck, 1809 (Bivalvia: Cardiida), Zootaxa 3245, pp. 30-53 : 36-37

Mactrellona alata ( Spengler, 1802)

Figures 4 A–G, 5A–D

Mactra alata Spengler, 1802: 99 — Reeve, 1854: pl. 8, fig. 29; Carpenter, 1855, in Carpenter, 1855 –57: 50; Krebs, 1864: 105; Mörch, 1870: 122; Gundlach, 1883b: 482; Olsson, 1935: 105; Rios, 1970: 195.

Mactra laevigata Schumacher, 1817: 167 .

Mactra carinata Lamarck, 1818 , in 1815–1822: 473; Bory de Saint Vincent, 1827 [in Bruguière et al. (1791–1827)]: 151; Deshayes & Milne-Edwards, 1835: 98; Chenu, 1843 in 1842–54: pl. 2, figs. 2–2b; 1859–62: 55, fig. 227–228; Conrad, 1868: 34; Weinkauff, 1884: 5, pl. 1, fig. 2; Dall, 1894b: 26; Lamy, 1914: 128.

Mactra concentrica Valenciennes in Bory de Saint Vincent, 1827 [in Bruguière et al. (1791–1827)]: 151.

Mactra (Mactrella) alata Adams & Adams, 1856 in 1853–1858: 377— Carpenter, 1864: 668; Conrad, 1868: 34; Dall, 1894b: 26; 1901: 142; 1915: 62; Lamy, 1917: 264; Cauquoin, 1969a: 1026.

Mactrella carinata Chenu, 1862: 55 , figs. 227–228.

Mactra (Mactrella) subalata Mörch, 1861: 180 .

Mactrella subalata, Dall, 1894c: 42 .

Mactrellona alata ( Spengler, 1802) — Olsson, 1961: 327, pl. 56, fig. 4; Rios, 1975: 236, pl. 75, fig. 1132; 1985: 243, pl. 86, fig. 1214; 1994: 266, pl. 91, fig. 1296; 2009: 537, fig. 1490.

Diagnosis. Shell up to 120 mm in length; short lateral teeth close to the cardinals, very conspicuous keel at the posterior end.

Description. Shell trigonal, inflated, inequilateral; external surface smooth; greyish, thin periostracum, anterior end rounded, ventral margin convex; umbones prominent, prosogyrous; posterior area typically defined by a keel-like ridge ( Fig. 4 A–B); internally white, left hinge with the diagnostic V-shaped cardinal tooth (2a–b) and short anterior and posterior lateral teeth (AII & PII) ( Fig. 5 B); right hinge with two anterior and two posterior lateral teeth (AI, AIII, PI & PIII), dorsal one smaller, cardinal teeth unfused in this valve (3a & 3b) ( Fig. 5 A); chondrophore well developed, flanked dorsally by a shell ridge which separates the external ligament from the resilium; valves slightly gaping at the posterior end. Microstructure consisting of an outer crossed-lamellar and an inner complex crossed-lamellar structure ( Figs. 5 C–D).

Type material. [ M. alata ] ZMUC unnumbered, holotype, a complete specimen, one smaller paratype; [ Mactra carinata ] MNHN unnumbered, two syntypes; [ M. (Mactrella) subalata ] ZMUC N° 235, holotype, one RV from Realejo , Nicaragua .

Type locality. “South America ”.

Other material examined. Mexico — Acapulco ( AMNH 309307 , 131830) . Central America—Nicaragua ( USNM 181844 ; 462394, 462390, 253129) ; Panama, Chiriqui lagoon ( USNM 169859 ) ; Darien gulf ( ANSP 52691 ; USNM 618727 ) ; Pedro Gonzalez Island ( AMNH 158848 ) ; Guatemala ( MZUSP 13040 ) ; Honduras ( USNM 215588 , 364571) ; Costa Rica ( USNM 54353 ) ; Jamaica ( USNM 24941 , 619068) ; Puerto Rico, Humacao beach ( USNM 523626 , 464242) ; Haiti ( USNM 439246 , 440241, 442572) ; Dominican Republic ( AMNH 44641 , 44103 10–40 m) ; Santo Domingo ( ANSP 173266 ; USNM 462395 ) ; Tortola, Virgin Islands ( ANSP 51414 ) . Colombia— West Columbia (MACN-In 11428) ; Santa Marta ( AMNH 34737 ) ; Cartagena ( ANSP 51404 ; USNM 364329 ) . Ven-ezuela—Margarita Island ( AMNH 158817 ; ANSP 51410 ) ; Macuto beach ( ANSP 175308 ); Brazil—Fortaleza ( MZUSP 16260 ) ; Rio Grande do Norte ( ANSP 300282 , 300230; MZUSP 40123 ); Natal ( FURG 15243 ); Ilha de Itamaracá ( FURG 6453 ); Pernambuco ( MZUSP 41377 , 41388); Recife ( MZUSP 14819 ); Praia de Pirambu (MACN-In 5047); Maceio ( MZUSP 22405 , 62826; FURG 34344 , 831); Jaraguá ( FURG 7542 ); Bahía ( MZUSP 81424 , ANSP 263465 , USNM 337297 ); Caravela ( MZUSP 26276 ); Praia de Santa Mónica, Guarapari ( AMNH 248027 ); Espírito Santo ( MZUSP 70679 ; AMNH 248028 ; FURG 14485 , 11814; ANSP 343904 ); Itaparica ( FURG 11001 ); Peruíbe ( FURG 31418 ; MZUSP 22415 ); São Paulo ( FURG 7301 ; USNM 681990 ; MZUSP 301 , 661, 14969, 15143, 15155; 15404, 15815, 22407, 22408, 22410, 22412, 22413, 22416, 22417, 22418, 43380; 43488, 44965, 44966, 44970, 44972, 44974, 44979, 56640, 62787, 62791, 62793; 62794, 62795, 79931, 80161; MACN-In 1819); Ubatuba ( MZUSP 22409 , 22411, 22414; MACN-In 1818); Paraná ( MZUSP 22420 , 22419; AMNH 199215 ); Camboriú ( FURG 16075 ); Porto Belo ( FURG 18124 ); Santa Catarina state ( MZUSP 300 , 15063; AMNH 278721 ; FURG 5175 ).

Distribution. From Gulf of México to Santa Catarina, Brazil, and from Nicaragua to Ecuador in the Pacific Ocean.

Remarks. The genus Mactrellona , introduced by Marks (1951), groups three species: M. alata ( Spengler, 1802) , M. exoleta ( Gray, 1837) and M. clisia ( Dall, 1915) . The three species were originally included in the genus Mactrella Gray ( Chenu, 1862; Conrad, 1868; Dall, 1915; Lamy, 1917; among others). They erroneously considered M. alata Spengler as the type species of Mactrella ,. However, when Gray (1853) introduced Mactrella , he assigned Mactra striatula Linnaeus, 1767 , as type species. The error could be due to the diagnosis of Mactrella given by Gray, which fits more adequately to M. alata than to M. striatula . This problem was treated by Marks (1951) who accepted the designation of M. striatula as genotype of Mactrella .

Mactrellona alata is a valid species, very common in the Gulf of Mexico and Brazilian coast. The presence of this species in the Pacific Ocean was reported by Olsson (1961). Later, Rios (1985) reported shell differences between Atlantic and Pacific specimens. However, the specimens examined by us do not suggest the presence of two distinguishable species. The synonymous species checked here are Mactra subalata Mörch, 1861 ( Figs. 4 F– G), described from Realejo, Nicaragua, and Mactra carinata Lamarck, 1818 ( Figs. 4 H–I). Mactra concentrica Valenciennes in Bory de Saint Vincent, 1827 [in Bruguière et al. (1791–1827)] and Mactra laevigata Schumacher, 1817 , are two nominal species that were based on the plates previously published by Bruguière (1797, pl. 251, fig. 2a–b, pl. 252, fig. 2b) [in Bruguière et al. (1791–1827)]. The original illustrations of Bruguière coincide with the shell morphology of the type material of M. alata . In conclusion, both species are added to the synonymy of Spengler´s species.

Figures

FIGURE 4. Mactrellona alata (Spengler, 1802). A – E: holotype (ZMUC unnumbered), A: RV, B: LV; F – G: Mactra (Mactrella) subalata Mörch, 1861, holotype (ZMUC N ° 235); H – I: Mactra carinata Lamarck, 1818, syntype (MNHN unnumbered), scale bar = 1 cm.

FIGURE 5. Mactrellona alata (Spengler, 1802), A – B: hinge description according to the nomenclature developed by Bernard & Munier Chalmas, A: RV, B: LV, scale bar = 1 cm; C – D: SEM picture of ultrastructure of the shell, C general aspect, ol: outer layer, il: inner layer, scale bar = 100 µm; D: detail of the outer layer with the cross lamellar structure, scale bar = 50 µm.