(above, ~3x) A fatal hole in a Honey Cowry (left, enlarged)

There is—in Hawaii, at least—one major cause of a puka, or hole, in a cowry shell and that is the he'e, or octopus. With its buccal bulb and single tooth, it can soften and dig away a small, usually triangular, hole in a cowry shell. It is almost always on the posterior, columellar sector of the cowry's shell; that's a vital spot beyond which the cowry cannot withdraw. Once the shell has been breached, the he'e injects venom into its prey. I estimate that about one-fifth to one-fourth of all dead-collected shells in my database have a hole similar to those shown here. However, it would be difficult to say what portion of preyed-upon cowries fall to the he'e. The Textile and Banded Marble cone shells leave—like Mac the Knife—no trace of their deed. Spotted Eagle rays are unlikely to encounter cowries while feeding; sand-dwelling shells like the Cones, Augers, Miters and Harps are much more at hazard from these big 'crushers.'

Fatal hole #2 (left, ~3x life size) (below, a closer view)

Cowry shells are also subject to damage from crabs [see related item in HSN]. A crab will usually find a place for its claw at opposing spots on the shell's dorsum and the cowry's aperture and then apply crushing force—with a fatal effect on the animal within. Very few cowries, it seems, escape with survivable damage. Rather, the victims look like the several fragments shown below. If a worker/collector happens upon the remains relatively soon afterward, the pieces can be reassembled and that shell's data obtained. Otherwise, one gets whatever can be found. A complete labial section can hold the length and tooth count information, two worthwhile tidbits.

The pieces of a cowry mentioned in a Hawaiian Shell News article, March of 1991. Note the damage in the center of the dorsum; other parts cracked instead. The damage (below) still occurred even though the top did not yield. Several of its layers flaked away before other sections of the shell cracked.

Point of collapse on the dorsum of a Cypraea leviathan. Notice how the inside layers gave way more than those directly under the claw. Part of the claw's contact area is shown by the arc in the middle of the dorsum (below).

Below, all I got of a C. carneola shell. Above, the damaged nacre by the break. Crabs often scuttle into a hole after exposing an animal's flesh. Other creatures may try to rob it after it's done the hard part of gaining access to its meal.

In all of the above instances, which are very typical of a crab's method, the crushing pressure comes down onto the dorsum and up into the aperture. The damage caused on the dorsum is similar to a bee-bee gun's mark on a plate glass window; the force leaves a smaller hole on the side it impacts and leaves a larger, cone-shaped void on the inside. That is an important characteristic of this type of destruction.

A shell found in 1988; ~10 meters of water, 100+ meters offshore. Length = 0.757 inch (~19¼ mm) Below, close-up views of its posterior and anterior holes, respectively.

Now for the main point of this quickly assembled article... While curating my sample of more than 3,200 Cypraea helvola Linné, 1758, I came across a shell with two curious holes,... but neither of them in the dorsum or the posterior, columellar area. Astonishingly enough, both are near the labial callus, one near the anterior end and the other near the posterior. These are good locations for threading the shell onto a thin strip of leather for, possibly, a hanging adornment with its colorful dorsum outward. I spent some time musing about how a shell like this got into this 'pocket' off the Makua shore, but was unable to visualize just how such an artifact might have ended up where I had found it (and in relatively good condition, too). By examining the holes with a magnifying glass, it appeared an artisan might have punched them from the outside, just as a crab would. However, crabs don't have any noted tendency to idly punch holes in shells; all those that I've seen only had the idea of eating whatever it sensed was in the shell. Later, I found some time at work to use one of many binocular zoom microscopes and closely examined this curiosity. That combination of fine optics, a specialty light source and human sight revealed several new bits of information, some of which proved too difficult to image effectively with my modest digital camera and commercial-grade optics.

I was struck by the irregular shapes of the holes since I felt that if these had been made by drilling with a sharp stone, or enlarged by reaming out the initial holes, they would have been more circular, and they should have been slightly larger on the outside, tapering to a smaller diameter on the inner surface of the shell. However, as can be seen in the close-up images above, no noticeable effects of a worker's tool(s) can seen. In fact, the posterior hole plainly shows the expected shape of a hole made by strong pressure from the outer surface. (One subtle bit of curious, though unrelated, information which did not photograph well can almost be seen in the photo of that posterior hole. Where the full thickness of the shell's dorsum is viewable, there is a sharp division, at virtually the halfway point, where the inner material is pure white and the outer material—except for the few layers of color which create the pattern—is a shade of purple that very nearly matches the anterior and posterior tips of this species.)

Telltale damage on the aperture of this freak C. helvola.

Once I had spent some time viewing the specimen under a microscope, I was forced to accept that this shell was a freak of the Forces of Nature, not a hand-worked remnant of the Hawaiian folk. Particularly convincing was the aperture of the shell under the posterior hole; the image at the right gives a hint of something plainly visible to microscope-aided human eyes. A two-tooth portion of the labium is cracked—and nearly broken off—by the pincher pressure which did puncture the dorsum just above it. I have added crude arrows to bring attention to part of the cracked shell (left) and a damaged labial tooth which has part of its ridge missing (right). Lesser damage—no surprise, yet too difficult to image well—also exists on the seventh labial tooth back from the anterior end of the shell, just below the anterior hole in the dorsum.

I was perplexed for a while as to how and when these two holes might have been made,... both at the same time, or first one and then the other later. Since the shell shows evidence that—again, very tough to image effectively—the two outermost layers of nacre had been worn away by wave-powered sand abrasion, I suspect this shell was punctured after it had rolled about in swell-driven sand on the floor of this large and ancient sinkhole which has, for the present, become a submerged 'pocket.' As for the timing that goes with them, a guess—based, as it is, on years of underwater experience—will have to suffice.

One crab with two claws probably made these holes in an attempt to devour some small 'morsel' which had used this shell as protection against just such an eventuality. Yet, there was the troubling puzzle of how it could have clutched this shell and applied enough force at these off-center points to penetrate it. My surmise is that there was a third pressure point involved,... the rock (or coral) substrate to which the crab would have been clinging. With six strong legs to lock itself down, it could have used that surface as a 'backstop' of sorts as it maneuvered the shell in its claws.

Why wasn't this shell crushed to pieces like the C. caputserpentis shown above? There might have been any one of several events which could have arrived at this outcome: 1.) As the shell began to give way, its occupant may have panicked and tried to flee, only to be consumed by the crab, or 2.) The tiny critter did get away and the crab dropped the shell to pursue it or find a new potential meal, or 3.) In repositioning the shell to complete its destruction, it lost its hold and the shell fell too far away for the crab to deem it worth retaking.

There could easily be some other, more complex series of events which culminated in a small cowry shell with holes suitable for a string to pass through, but I've many more of this species to curate before continuing with a prior research project.

fin.