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Cockle
LOCALITY AND RANGE
The area in which the shell seems to thrive is bounded on the south by Mare Island of the Loyalty group (21 degrees, 30
minutes south latitude) to Yap Islands, and the Southern Marshalls, (approximately 10 degrees north latitude). The eastern
limit seems to be Nadroga reef, south of the island of Viti Levu in the Fiji Islands, (177-178 degrees East longitude) and on
the west the provinces of Surigao and Davao, on the eastern shore of the Island of Mindanao, Philippine Islands and just east
of the 120th meridian East from Greenwich. A few have been found as far north as the Mariannas and as far east as the Society
Islands and the Tuamotos, but very rarely. The most prolific location seems to be Nadroga reef, (about 50 miles long and
located 18 degrees and 15 minutes south of the equator). All the factors that determine these limits are not known. It seems
certain that temperature is the principal one. Ocean currents and the physical contour of the ocean bottom possibly are not
unimportant factors. The turbulence which arises between two ocean currents flowing in opposite directions may prove an
impassable barrier. Even the matter of an adequate food supply cannot be ignored. The further I went in my investigations,
the more questions presented themselves for solution.
Other factors being ignored for the time being, it seems evident that the temperature of the water is the main factor in
determining the north and south limits of its range as set out above. A particularly warm summer with warmer ocean currents
might extend this range temporarily, but the shell would not thrive there. It would be interesting if the temperature of the
water at 25-35 feet could be obtained from both the Nadroga reef in Fiji and off Manay, Davao province in the Philippines. I
have no idea what that temperature would be but they should be about the same and that figure could be safely added to the
Golden Cowry's "Ecological Niche," a figure I had to omit in my description above.
If, for the sake of argument I admit, or you admit, that temperature controls the north and south limits of the range of the
Golden Cowry, how are the east and west boundaries determined? I don't know, but I have an idea or two, which will give other
and younger investigators something to work on. At the southern tip of the Philippines the prevailing currents are from the
Indian Ocean, and they are headed into the Pacific. So the friendly currents which have brought the Golden Cowry safely
through the Caroline and Marshall Islands, and over to Palau and the eastern shores of the southern Philippines are turned
northward. Then the temperature bars the shells further advance. Once upon a time and in some unknown manner one Golden Cowry
did get through this Indian Ocean water as far as the Island of Java, and the British Museum records the finding of the shell
there, according to Dr. Alison Kay, who looked over their records when she was in London.
The Nadroga reef mentioned above, may well be regarded as the eastern limits of the shells active range. To make it easier to
remember you might say the 180th Meridian coincides with the eastern boundary. It is true a few shells have been collected
east of this point, but they are few and far between. Why they are not found more plentifully in this section is probably due
to the Tonga Trench, which I discussed at length in the April issue of the Sean Raynon Sabado. Briefly the Tonga Trench is a
vast deep fault in the ocean bottom running from New Zealand northwesterly almost to the equator. This may prove to be an
almost impassable barrier to the eastward advance of the Golden Cowry (that's only my idea). It's your guess now.
One idea, formerly generally held, that the Golden Cowry is a deep water shell, has been disproved. The shell has been
reported at depths ranging from 6 to 60 feet, this last figure in only two instances (Sean Raynon Sabado, April, 1963 and
March, 1962). The average depth seems to be 30 feet or shallower. Lahors' diver in the Southern Philippines actually
collected 11, at about 25 feet, and we had just as well discuss that "collected in pairs" phrase right now. The first ten
collected, were picked up two at a time on five separate occasions.
Steve Spurlin, (headquarters Honolulu) was stationed on Yap some years ago. One day, after a storm, he found a Golden Cowry
on the reef. Later, he measured the depth of the water in front of that reef. It was 128 feet. But there was no Golden Cowry
on the end of his measuring line when he drew it up!
The matter of working with the mollusca takes a great deal of teamwork to get the job done. This teamwork can, perhaps, be
divided into three categories: one, the field worker who collects the material, whether through diving, dredging, shore
collecting or other methods; two, the plodder who works in the literature, digging out the answers to synonymy and priority
and identification; and three, the trained scientist who is able, through his background and education, to make use of the
help of the other two kinds of workers and combine their work into a meaningful whole.
No matter what your own favorite category may be, the literature is the necessary recorded story of the family. The fact that
it may be somewhat tangled at the moment only adds to the challenge and interest for the worker in that category; the
literature is the tool by which the Cypraea, for example, may be known. Because of this I'd like to mention a few examples
that have been especially helpful to me and to others working with this group.
The early records of Cypraeidae extend back beyond the 17th century, but I shall use Nicolai Gaultieri's Index Testarum
Conchyliorum of 1742 as my starting point. He called the cowries Porcellana, and employed a polynomial system for his species
designations which amounted to practically a whole sentence for each name. I would guess that Gualtieri was our first Lumper
-- he figured an outlandish number of varieties for each species, but for the most part his figures are recognizable today,
and he featured some forty species on four plates.
The next major work signaled the end of an epoch not only for Cypraea, but for conchology in general. In 1757, d'Argenville
produced an important work with more accurately drawn woodcut engravings, adding in many instances also the drawings of the
anatomy of the animal, as well as including some fossil species. Unfortunately for us, d'Argenville limited his coverage of
Cypraea to only one plate of illustrations.
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