Barnea (Anchomasa) lamellosa (d'Orbigny, 1841)

Delfino, Marina & Signorelli, Javier H., 2021, Fig. 13 in Fig. 12. Majella pristis n in Periclimenaeus djiboutensis Bruce 1970, Zoological Studies 60 (28), pp. 1-20 : 3-4

Barnea (Anchomasa) lamellosa (d'Orbigy, 1841

in 1834–1847)

( Figs. 2A–C , 3 )

Pholas lamellosa – d'Orbigny 1841 in 1834–1847: 498, pl. 77, figs. 20, 21; Dall 1908: 289.

Barnea lamellosa – Ihering 1907: 329; Castellanos 1970: 258, pl. 26, figs. 1–2; Figueiras and Sicardi 1970: 412, pl. 5, fig. 80; Scarabino 1977: 215; Bernard 1983: 60; Scarabino 2003: 242; Dias Passos and Magalhães 2011: 148; Scarabino et al. 2016: 10.

Barnea (Anchomasa) subtruncata lamellosa – Lamy 1925: 82; Carcelles 1944: 295, pl. 14, figs. 108–109; Carcelles 1950: 82.

Barnea subtruncata lamellosa – Barattini 1951: 256; Barattini and Ureta 1961: 184.

Barnea (Anchomasa) lamellosa – Turner 1954: 25, pl. 8 and 10; Figueiras 1962: 64; Olazarri 1962: 51; Klappenbach 1967: 164; Rios 2009: 591, fig. 1630; Huber 2010: 474.

Type material: NHMUK 1854.12.4.655, two syntypes, an articulated specimen and a single valve.

Type locality: “Patagonie, au sud du Rio Negro”, Rio Negro Province, Argentina.

Description: Shell: fragile, pellucid, equivalve, moderately elongated, inequilateral; shell length up to 50 mm; anterior end pointed, forward projected; posterior end rounded ( Fig. 3A–B ); umbos prosogyrate, subcentral; umbonal reflection totally free, well developed on the anterior side of the umbo; apophysis prominent, long, narrow, curved and ventrally projected inside each valve, dorso-posterior margin curved; ventral margin almost straight, slightly rounded; external surface with concentric sculpture defined by spines, more conspicuous on the anterior side of the shell ( Fig. 3A ); internal surface white; hinge plate rudimentary; pallial sinus broad and deep; adductor muscle scars moderately marked ( Fig. 3B ). Dorso-anterior area with a calcareous protoplax, strongly keeled, rhomboid and narrow ( Fig. 3E ); valves not completely closed over the ventral edge; pedal gape rounded.

Mantle cavity organs: siphons totally fused, very elongated, twice shell length, with mud and sand particles attached to the external surface ( Fig. 3C, FG ); incurrent siphon wider than excurrent, with a ring of white and single tentacles, equal in size and length; space between tentacles brownish; excurrent siphon without tentacles; two demibranchs at each sides of the body, equal in length, food groove present over the ventral edge of inner and outer demibranch ( Fig. 3H– I ); labial palps trigonal with the outer surface smooth and inner plicate ( Fig. 3J ); visceral mass white; on the posterior area with a collecting membrane, trigonal, inflate, well developed; foot large, tubular; pedal gape disc-like; dimyarian, adductor muscles lenticular.

Material examined: Uruguay ─ Departamento de Rocha ( MACN 14790); Argentina ─ Santa Clara del Mar ( MLP 7781), Mar del Plata ( MACN 10745, MACN 11991), Miramar ( MACN 15636), Monte Hermoso ( MACN 6619, MLP 7780), Bahía Blanca ( MACN 38385), Punta Alta ( MACN 11171), San Blas Bay ( MACN 20213), Rio Negro mouth ( MLP 2510), San José gulf, Punta Tehuelche ( CNP-INV 2910, 2911, 2912), Puerto San Julián ( CNP-INV 2908, 2909).

Distribution: Santa Catarina, Brazil to the Malvinas / Falkland Islands ( Rios 2009). In this work specimens from Rocha, Uruguay, to Puerto San Julián in Santa Cruz province were revised.

Remarks: Barnea lamellosa has been recorded boring horizontal consolidated mud substrates in the intertidal zone, usually covered with a layer of sand. The sampled specimens were found in a very low density. Although Tryon (1868) and Carcelles (1944) mentioned Barnea (Anchomasa) lamellosa (d'Orbigy, 1841 in 1834–1847) as synonym of B. (Anchomasa) subtruncata , type material examination confirmed that both species are valid. Barnea subtruncata ( Fig. 2GJ ) is distributed along the Pacific coasts of America, from USA to northern Chile, whereas B. lamellosa ( Fig. 2A–C ) inhabits the coasts of Argentina and Uruguay ( Coan and Valentich-Scott 2012; Scarabino et al. 2016; Zelaya 2016). No additional synonym of B. lamellosa were found in the literature. Barnea lamellosa differs from the eastern Pacific B. subtruncata in being shorter, with a less elongated posterior end and by having a shallowest pallial sinus. Kellog (1915) described the collecting membrane for B. costata and B. subtruncata (as B. pacifica ). The morphology of this character has taxonomic value. Atkins (1937) and Purchon (1955) described this membrane in other Pholadidae highlighting size differences between species. In B. lamellosa the collecting membrane is wider than in B. costata and B. subtruncata ( Fig. 3H ). The collecting membrane of the visceral mass, is posteriorly oriented and projected to the mantle cavity. It is a retractile and ciliated organ related to cleaning functions that prevent the entrance of sediment into the mantle cavity at low tide (Kellog 1915).

Figures

Fig. 2. A−C, Barnea (Anchomasa) lamellosa (d'Orbigy, 1841 in 1834–1847), NHMUK 1854.12.4.655, syntypes. D−F, Barnea (Anchomasa) truncata (Say, 1822), MACN 38385 from Bahía Blanca. G−J, Barnea (Anchomasa) subtruncata (G. B. Sowerby I, 1834, in 1821−1834), material collected by d'Orbigny in Payta, Perú, NHMUK 1854.12.4.656. The specimens of B. (A.) lamellosa and B. (A.) subtruncata with the apophysis broken. Scale bar = 1 cm.

Fig. 3. Barnea (Anchomasa) lamellosa. A, external view right valve. B, internal view right valve. C, external view of living specimen. D, anterior view showing pedal gape and foot. E, detail of calcareous protoplax. F−G, detail of siphons. H, general aspect of mantle cavity organs. I, detail of food groove over the distal edge of the outer demibranch. J, detail of left labial palps and apophysis. Scale bars: A−B, D−E, H−J = 5 mm; C = 1 cm; F−G: 2.5 mm.