|
|
Heishe pokalet
From radula studies it would appear that bregeriana is a subspecies of walkeri after all, and not a separate species as I
always believed. However, it is open to doubt if radula comparisons are the only criterion in deciding a shell's specific
identity. Besides, bregeriana and walkeri are closely allied, and no large differences were to be expected. It is Dr.
Schilder's opinion, that there are no constant differences in radula between the species allied to arabica, and only few
species of Erosaria have peculiar characteristics. On the other hand, among 20 C. stolida from Shimoni, six showed distinct
central denticles in the middle of the median tooth, yet fourteen specimens showed no trace and the difference was not due to
sexual differences. Such a difference according to Dr. Schilder could be treated as generic almost and the difference in
radula of C. bicolor sometimes exceed usual subgeneric differences. It appears that the radula of a species is as variable as
the shell itself, and it seems to me, that the live animal's colour of foot, mantle, papillae and tentacles are more constant
than both radula and shell. Out of over 2000 Cypraea specimens I collected in Fiji for radula studies, only 6 specimens
showed a gross colour difference from the usual colouring of the species.
We can therefore regard bregeriana as a very good subspecies of walkeri, one that is in the transition stage of becoming a
species.
of Comparative Zoology at Harvard. Thus Richard Johnson in 1949 was able to select neo-holotypes for C. semiplota and C.
unifasciata and a lectotype for C. insecta.
1 Johnson, R.I., 1949. Jesse Wedgewood Mighels with a Bibliography and a Catalogue of his Species. "Occ. Pap. on Mollusks," 1
(14).
The "Ecological Niche" Of The Golden Cowry
Before you read this article, let's explain what it's all about. The "Ecological Niche" is a rhetorical expression understood
by most scientists and all malacologists. To the uninitiated, here is a homemade definition. It is not really a "niche" in
the generally understood meaning of the word. Instead, in Malacological lore, it is a description of a hypothetical location
where, if all the factors entering into the ideal conditions of living were present, that shell, and that shell only would be
found there. And that shell in this case is Cypraea aurantium Gmelin, 1791, which is referred to as the Golden Cowry.
The "Ecological Niche" of the Golden Cowry, or to put it in other words, the conditions under which it thrives, may be
described as follows: It is found only in the tropical Pacific Ocean, in the caves and crevices on volcanically formed land;
on the seaward side of reefs in water of maximum salinity at average depths of 25 to 35 feet; it is herbivorous living on
algae; it is nocturnal in its feeding habits; mature specimens average in length about three and a half inches, or around 90
millimeters. Width is around two and a half inches and the height is generally more than two inches; in color it ranges from
deep to lighter shades of orange. It is almost always found in pairs, and its natural enemies are sharks and violent storms.
The writer's theory is that the shell originated in the Solomon Islands.
Some amplification and discussion of the various items in the above paragraph may prove of interest.
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!
heishe pokalet,hearshell,shells bracelets,shell madebelts,lambis milladeda,capis shell,conus virgo,cyprea talpa,blacklip,heishe pokalet
Heishe pokalet brown conus painted capis sigay shells shell pendants puka capis hanging lamp tiger cowry blacktab black lip brown lip shell-madebelts distrosioanus shelltiles wallets lampshade ovula ovum brown-lip shell heishe shell inlay.
heishe pokalet
Shells
Jewellery
|
