Common Names: Boring or Crocus Clam, Crocea clam
Colour: Tridacna crocea is probably the most colourful member of this genus. Colours can include various mixtures of blue, purple, yellow, green, brown, gold, and orange in a variety of patterns. The mantle usually has numerous iridescent blue, yellow or green blotches, small spots or lines.
Figure 12.1 Tridacna crocea
Upper and lateral view of shell.
Below: Map with geographical distribution of the clam. After Lucas 1988.
Distinguishing Characteristics: Large, wide byssus gland opening; normally smooth shell with closely placed scutes restricted to the upper margin; almost symmetrical shape; small size; frequently brightly coloured and; the incurrent aperture has very small, fine tentacles (Lucas, 1988; pers. obs.). Cultured clams will have scutes along the entire body of the shell, as they have not yet ground them down through their burrowing habits. Max. Length: 19 cm (9 in.).
Similar Species: This species is often confused with T. maxima, especially by those who rely on colour pattern alone. The shells of these two species, however, are easily distinguished.
Sometimes it is difficult to distinguish between T. crocea and T. maxima on the basis of mantle colouration alone. This beauty is a good example. It is probably T. crocea, but without viewing the shell it is hard to be certain. J.C. Delbeek.
Tridacna maxima usually has a more elongated shell; at times the shell can be 3x longer than it is broad. Although both species have rows of scutes on the outside of the shell, those in T. maxima are more pronounced and cover the majority of the shell, while those of T. crocea are usually worn away and are generally restricted to the upper margin of the shell. Finally, T. crocea has a very7 long, wide byssus gland opening, extending almost to the edge of the shell.
Right: This clam imbedded in a coral head could be either T. crocea or T. maxima. S.W. Michael.
Natural Habitat: Tridacna crocea is commonly found in shallow areas near shore and on the interior reef flat (Crawford and Nash, 1986). As its common name indicates, these clams actively burrow deep into boulders and coral heads by contraction and relaxation
Above: The typical habitat of T. crocea, bored into old coral rock in the intertidal zone. Note shell of a dead clam still in the bored hole. J. Sprung.
of their byssal muscles. As a result only the top edges of the shell and mantle are visible. Once embedded they use their byssal
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