Bistolida stolida kwajaleinensis (Martin & Senders, 1983)
Stolid cowry, 17-36mm

The form of Bistolida stolida found at Kwajalein is unique. Throughout most of its Indo-Pacific range, B. stolida’s shell has a dark brown blotch on a blue-gray background. Those from Kwajalein tend to be distinctly smaller and have a reddish brown blotch on a light reddish brown background. This variety has been given its own subspecific name, Bistolida stolida kwajaleinensis. The “ensis” suffix on scientific names is generally used to indicate a place for which the species is named. This subspecies may be restricted to Kwajalein; most specimens of Bistolida stolida from nearby Enewetak Atoll have the typical blue-gray background, although a few were observed that tended toward the kwajaleinsis form. This species is mostly a lagoon dweller, living on subtidal interisland reefs or algae patches such as those in the lee of Ebwaj and North Loi at depths ranging from about 2 to 30m. Specimens can also be found on some near-shore lagoon pinnacles such as those east of the Mar Fill end of Kwajalein. Occasionally, specimens have been found on shipwrecks, such as the ones near G-Buoy and off the edge of the reef at North Loi. Some have suggested that the reddish brown color might be due to incorporation of rust from Kwajalein Atoll's shipwrecks, but this is certainly not the case. Other cowries occasionally do have rust embedded in the shell, but only a few specimens found directly on the wrecks, and not even all of those, show this blotchy rust color. In Bistolida stolida kwajaleinensis, all shells have a very smooth, consistent reddish brown color whether or not they were found anywhere near shipwrecks. Various forms of Bistolida stolida are known throughout the Indo-Pacific with the exception of the Hawaiian Islands.

The mantle and foot of Bistolida stolida kwajaleinensis is mostly yellow, and the animal seems to feed on a yellow sponge living beneath rocks.

The dark blotch can occasionally extend across most of the shell.

Pattern varies.

The stretched-out foot of the next specimen is protecting its egg mass.

A slightly young specimen lacks the blotch entirely. This shell nearly has its adult structure, so the dark dorsal blotch must be laid down on the shell late in development.

A very young thin specimen is nearly hidden by its yellow mantle.

Adult shells from Enewetak Atoll were generally larger than those from Kwajalein, and they varied in color from similar in color to Bistolida stolida kwajaleinensis to the more blue background of the more widespread variety, Bistolida stolida stolida. The Enewetak specimen below has a dark brown blotch (less reddish than those from Kwajalein) and the background is a very light tan. The Enewetak specimen in the two photos immediately below has a more typical bluish gray background.

This Enewetak specimen was considerably more rostrate, with its anterior and posterior ends a bit puckered and turned up, than is typical of this species. This specimen was found inside a concrete barge aground on an Enewetak lagoon pinnacle, just into the lagoon from an east reef deepwater pass.

Created 1 April 2008
Updated 24 February 2012

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