Anadara consociata (E.A. Smith, 1885 )

Tudu, Prasad Chandra, Yennawar, Prasanna & Mohapatra, Anil, 2019, First report of two ark shells, Anadara consociata (E. A. Smith, 1885) and A. troscheli (Dunker, 1882) (Arcidae: Anadarinae) from Indian waters with notes on morpho-taxonomy of some related species from east coast of India, Records of the Zoological Survey of India 119 (1) : -

2. Anadara consociata (E.A. Smith, 1885) ( Fig. 2 ; c - e)

1885. Arca consociata E.A. Smith , 19

1998. Anadara (Mabellarca) consociata : Evseev and Lutaenko, 8

Material Examined: 38ex, Rameswaram (09°16.867’N and 079°18.879’E), 7-IX-2014, coll. P.C. Tudu, ( MARC / ZSI M4140 ) .

Description: Shell medium in size (L up to 34mm and H up to 23.4mm), equivalve, elongate ovate; ventral margin smoothly arcuated and widely rounded towards the anterior and posterior sides. Umbones somewhat inflated, situated rather forwards, cardinal area narrow and elongate. Radial ribs not wide, flattened, squarish or somewhat concave in cross-section in adults, and narrow, triangular in cross section, ornamented in top with closely situated and well-rounded nodules in both juvenile and adults; number of ribs 21-27; there are fine regular ridges in interspaces of the ribs and width of interspaces smaller than width of ribs. Ligamental area narrow, with shorter and wider anterior side compared to posterior side; ligament opisthodetic, however its narrow strip continues anteriorly before area border, with 1-2 chevron grooves. Beak prosogyrate, shifted anteriorly; tooth plate divided in two series a little posterior in beak, the anterior series twice as short as posterior series. Periostracum brown or dark brown, finely rugulated on the interspaces of ribs at certain interval which is visible under microscope only. Outside of shell grey white or cheesy white in colour and inner with whitish colour.

Distribution: In India: Tamil Nadu (present report); Elsewhere: Arafura Sea (Northern Australia) ( Smith, 1885), China Sea, widely distributed in Vietnam ( Evseev and Lutaenko, 1998).

Remarks: This species is the first ever report from Indian waters, from Tamil Nadu (Rameswaram). This species is quite similar with A. ehrenbergi (Dunker, 1868) in general appearance and in number of radial ribs but radial ribs of A. consociata contains rounded nodules and ribs are triangular in cross section; in compared to the radial ribs of A. ehrenbergi having regular ridges and squarish in cross section of ribs.

Figures

Figure 2. a-b,Anadara antiquata (Linnaeus, 1758); a- exterior of right valve, b- interior of right valve; c-e, A. consociata (E.A. Smith, 1885), c- exterior of left valve, d- interior of left valve & e- dorsal view of umbo; f-g, A.eherenbergi (Dunker, 1868), f- exterior of left valve, g- interior of left valve.