Fimbria Mühlfeld, 1811

Glover, Emily A. & Taylor, John D., 2007, Diversity of chemosymbiotic bivalves on coral reefs: Lucinidae (Mollusca, Bivalvia) of New Caledonia and Lifou, Zoosystema 29 (1), pp. 109-181 : 172-175

Genus Fimbria Mühlfeld, 1811

Fimbria Mühlfeld, 1811: 52 .

TYPE SPECIES. — Fimbria magna Mühlfeld, 1811 (junior synonym of Venus fimbriata Linnaeus, 1758 ). (monotypy).

DIAGNOSIS. — Shell large, thick, ovate, anteriorly extended, inflated. Umbones low. Sculpture of radial ribs crossed by closely spaced, rounded commarginal lamellae. Lunule short, lanceolate. Ligament set in shallow groove. Hinge massive, with 2 cardinal teeth in each valve, a single, large anterior lateral tooth close to cardinals, with smaller posterior lateral located above posterior adductor scar. Anterior adductor muscle scar short, broad, reniform in outline, slightly deviating from the pallial line. Pallial line entire. Interior shell margin strongly denticulate.

REMARKS

Although often separated as a distinct family Fimbriidae (e.g., Chavan 1969), recent molecular analysis of Fimbria fimbriata indicates that it groups within a monophyletic Lucinidae ( Williams et al. 2004) .

Fimbria fimbriata ( Linnaeus, 1758) ( Fig. 42 )

Venus fimbriata Linnaeus, 1758: 687 .

Fimbria fimbriata – Nicol 1950: 83, figs 1, 2, 4, 6, 7.

MATERIAL EXAMINED. — Koumac. 10 stn, 0-15 m, 29 v, 26 live.

Touho. 5 stn, 0-8 m, 8 v, 11 live.

Lifou. 10 stn, 0-45 m, 30 v, 14 live.

Chesterfield Islands. 14 stn, depth range 25- 69 m.

Other New Caledonia. LAGON, 21 stn, from intertidal zone to 48 m. Loyalty Islands. MUSORSTOM 6, stn DW 430, 20°21’S, 166°07’E, 30 m, 3 v. — Stn DW 435, 20°21’S, 166°08’E, 32 m, 1 v ; Ouvéa lagoon, 5 sh.

DISTRIBUTION. — Central IWP: Andaman Islands to Marshall Islands, Fiji and Tonga (see Nicol 1950: fig. 9).

DESCRIPTION

As generic diagnosis. L to 106 mm, H to 89 mm, commarginal lamellae closely spaced, often sinuous and dividing. Radial ribs more prominent to anterior and posterior. Juvenile shells ( Fig. 42C ) are generally longer than high and have more prominent commarginal lamellae and posterior sulcus.

SUMMARY OF DISTRIBUTION

OF LUCINIDS AT KOUMAC, TOUHO AND LIFOU

A range habitats were sampled, from intertidal mangroves, seagrass beds and sands to reef fronts, lagoon sands and deeper passes between the reefs. Full details of the distribution of lucinids at the stations sampled are available on files deposited in MNHN (Malacologie) and NHM (Mollusca Section) and only a brief summary is given below. At the three intensively sampled sites around 75% of stations yielded lucinids, Touho (74%), Koumac (81%) and Lifou (72%).

Inshore sandy habitats from the intertidal to about 5 m were characterised by a lucinid fauna of Codakia species , Ctena bella , Anodontia ovum , and Wallucina fijiensis while in deeper sandy lagoon bottoms Liralucina sperabilis n. comb. and Pillucina copiosa n. sp. were most typical. Sand deposits in coral-dominated habitats and reef slopes contained abundant Funafutia levukana . Deeper channels and reef passes with muddy substrates had a distinctive fauna dominated by Leucosphaera diaphana n. sp. and Myrtina porcata n. gen., n. sp. At the Baie du Santal, Lifou, habitats were less varied, comprising coarse, bioclastic sands with no fine sand or mud, and the lucinids were more uniformly distributed. Notable, however, was the higher abundance of Anodontia hawaiensis and Solelucina koumacia n. gen., n. sp. at this more oceanic site.

Of the 34 species of Lucinidae recognised, only three were not present at the three intensively sampled sites ( Table 2). Twenty-nine species were recorded from Touho (26 species) and Koumac (21 species) sites. Of these, 18 occurred at both sites (62% overlap), eight species were found only at Touho and another three recorded only at Koumac. Another five species that did not occur either at Touho or Koumac were recorded at other sites around New Caledonia. For the Lifou stations, a total of 18 species of Lucinidae was recognised, with only two unique species, and 89% of the species were shared with the Touho and Koumac sites.

In terms of species abundance the three sites differed considerably ( Table 3). At Touho and Koumac many species were quite rare with 40% and 38% occurring at three stations or less, while at Lifou only 22% of species occurred at less than three stations. At Touho the most abundant taxa were Liralucina sperabilis n. comb. (c. 20% of valves), Anodontia ovum (20%), Wallucina fijiensis (16%) and Leuocosphaera diaphana n. sp. (10%). While at Koumac, Pillucina copiosa n. sp. (26%), Liralucina sperabilis n. comb. (22%), Chavania striata (10%) and Funafutia levukana (9%) were dominant. By contrast, at Lifou, 39% of the valves consisted of Ctena bella and 33% Funafutia levukana . Species varied considerably in distributional range ( Table 4); at Touho the most widespread species was Ctena bella occurring at 45% of the 29 stations with lucinids, followed by Liralucina sperabilis n. comb. (41%) and Pillucina copiosa n. sp. (35%). At Koumac, Pillucina copiosa n. sp. occurred at 56% of stations with lucinids, followed by Ctena bella (41%) and Liralucina sperabilis n. comb. (36%). At Lifou, the lucinid fauna was much more uniformly distributed and from the 47 stations at which lucinids were recorded, Ctena bella occurred at 79%, Funafutia levukana at 70% and Anodontia hawaiensis at 47% of sites.

Figures

FIG. 42. — Fimbria fimbriata (Linnaeus, 1758): A, B, exterior of right valve and interior of left valve, Touho, stn 1242, New Caledonia (MNHN); C, juvenile, left valve, Koumac, stn 1286 (MNHN). Scale bars: A, B, 10 mm; C, 5 mm.