All cowry shells belong to the family Cypraeidae and various members of this family have been utilized down through the centuries by many tribes, nations and countries as having a monetary value. Trading in them has been traced back over 40,000 years.
Fossilized examples date back to over 140,000,000 years and today there are around 200 species inhabiting world seas. The majority of these are tropical of origin and inhabit the Indo-Pacific region.
Belts of Money Cowries Monetaria moneta were used as currency throughout the Indo-Pacific for many thousands of years before the coming of Europeans, this practice still exists for trading in some places, even today. ( photo: Neville Coleman)
The basic shell is highly polished and generally high-domed with individual colour patterns for each species. It is the very shiny shell and beautiful colours and patterns that have intrigued humans for thousands of years. In some cultures a rare species has been given high status to be used as adornments by chiefs and people of high status .( eg: Golden Cowry and Fijian Chieftains)
The Prince Cowry Leporiccypraea valentia was first discovered by hard – hat pearl shell divers in the Torres Straights area of Northern Australia and for many years the few available shells were worth thousands of dollars each. In recent times scuba divers have found them at night when diving the harbour drop – offs at Rabaul, Papua New Guinea. (photo/ Copyright: Roger Steene)
Modern day collectors have been known to pay thousands of dollars for just one shell of a very rare species.
The advent of scuba diving provided access to a number of these rare species and once their nocturnal habits and habitats were discovered many rarer ones have now fallen in price on the world markets.
The popularity of shell collecting in Australia has faded away due to many species being over collected and younger generations of humans realizing that there is far more to nature than just killing everything and sticking it on a mantelpiece.
However, even as these molluscs were pursued even more earnestly than whales for thousands of years by millions of people there is precious little natural history on the living forms. (The exception to this is Dr. Barry Wilsons monumental studies and publications on the Western Australian temperate water species)
Even though the dead shell specimens have all been described, little comparative work has been done on tropical forms to enable species to be recognized by their mantles, although those with red mantles appear easier than most.
Found across the Indo-Pacific, the Sieve Cowry Cribarula cribaria has a very individual pattern on its shell and a bright orange mantle. Due to its decorative shell it has been very popular with collectors of the past.( photo: Neville Coleman)
One of my ideas in my book 2002 SEA SHELLS was to provide the first references to living animals pictured with identified comparisons of their named dead shells. Although this provided a basic comparison to some species, there is still a long way to go before we can recognize them all in the wild.
The majority of species inhabit tropical regions around the equator and they are far more prevalent in the Indo-Pacific than they are anywhere else on the planet. The fossil history shows that there is evidence that many distributions have changed considerably over the last 120,000 years.
Cowry molluscs can be found in most major marine habitats, though coral reefs , rocky reefs and rubble areas support the most species. They occur from the intertidal area down to at least 460 metres, though most species are found between the littoral zone and 60 metres. Some smaller species spend their entire lifetime within a few square metres and may live under the same rock for most of their lives. Other larger kinds forage over bigger areas in search of food and mates.
Unlike most other species the shell of the Pustulose Cowry Staphylaea staphylea is covered in small pearly pustulations. Its mantle is wine coloured with lots of papillae.( photo: Neville Coleman)
The most important function of an external shell is to protect the animal from the elements of its habitat and attacks by predators.
Similar to the components used by other molluscs to construct their shells, the shell of a cowry is built from the combination of calcium carbonate crystals and an organic material consisting mostly of fibrous protein. Most adult cowry shells are very strong and the shiny surface makes it difficult for some predators to actually hang onto the shell while trying to extract the animal. However, strong-jawed fish like the larger wrasses and ground sharks have no trouble in crushing the shells of even the largest cowries.
Prized by collectors for hundreds of years the endemic West Australian Cowry Zoila venusta lives in caves and on reefs, generally in the vicinity of an encrusting karki sponge that it feeds on. ( photo: Neville Coleman)
Most species have a series of teeth along the edges of the aperture ( apertural teeth) and the numbers of teeth present were used by taxonomists to determine the identity of similarly patterned species. Unfortunately the teeth are only fully developed in adults, so in earlier years some immature forms were once thought to be new species because their teeth were under developed. The reason for these apertural teeth is not known, but might be some form of defensive formation that further protects the animal from attacks by predators.
The bi-lobed mantle (which lays down the shell secretions and colours) expands from each side of the aperture and covers the entire shell. Although many species have their mantles withdrawn during the day, all cowries have their mantles expanded at night.
Unlike many other species who have their mantles fully extended at night, the easily recognized shell spots of the Tiger Cowry Cypreaea tigris can be seen through the mantle.( photo: Neville Coleman)
Superficially similar to the Pustulose Cowry, the File Cowry Staphylaea limacina has a wine-red coloured mantle which is heavily adorned with masses of long papillae.( photo: Neville Coleman)
The mantle itself is a very highly complex organ and may be smooth and clear on one species, covered in pustules in another, or brightly coloured with long branching papillae in others. Although experts admit that nothing is known about the function of the papillae on the mantle it would appear to have two main functions. (1) It is sensory and (2) it affords (at least in some species)a brilliant camouflage when the mollusc is moving around searching for food at night. Yet in most cases the colour pattern of the shell and the colour and texture of the mantle have little in common.
The siphon is located at the front end of the mollusc and through this water is drawn in for respiration. There is a long sensory tentacle on each side of the head and although the eyes do not have lenses they are thought to be well – developed.
A common shallow water species the Milk Spot Cowry Lyncina vitellus distributed
throughout the Indo -Pacific and extends south even to New Zealand. As common as it might be little is known about its natural history. ( photo: Neville Coleman)
The prehensile proboscis is located between the two tentacles and similar to most univalves there is a well - developed radular that is used to scrape off morsels of algae and other prey. In general there are about 200 rows of teeth with seven teeth to a row in most radula ribbons of cowries. As old teeth become worn, new ones are being continually formed at the other end.
Cowries exude a tremendous amount of slime and have a wide, strong, extendible foot that enable some to move along at a surprising speed for a snail -like creature.
Feeding exclusively on sponges this was the first published 'in habitat' image (1974) of the once very rare Rossell's Cowry Zoila rosselli and was taken at 30 metres at Rottnest Island, Fremantle, WA. Since those early days professional shell divers have found hundreds of these gems and made them available to collectors all over the world. Some forms have sold for over $1000.00 each. ( photo: Neville Coleman)
Although we do know that some species of temperate water Cowries feed almost exclusively on sponges and bryozoans, tropical ones may have a diet of algae
and others feed on sponges. Until such time as we can be sure what they each feed on in the wild they can be considered as omnivores.
This female Mole Cowry Talparia talpa is brooding a large batch of white egg capsules with up to 50 eggs in each. When they hatch, the veligers move up into the water column and are distributed along with the currents until they settle down on another reef sometime later as juveniles.( photo: Neville Coleman)
Cowry molluscs have separate sexes with the females being larger than the males (sexual dimorphism) After internal fertilization the female lays a batch of eggs and sits on them untill they hatch. Most tropical species have planktonic larval dispersal. By comparison many temperate water species reproduce by direct development.
Donated to the Western Australian Museum to aid the continuing research of Dr. Barry Wilson (who completed a Phd on the study of Western Australia's southern cowry's) these were the first egg capsules of Zoila rosselli known to science . (197l) Direct development.( photo: Neville Coleman)
In contrast with the tropical species, the Southern Australian Black Cowry Zoila friendii thersites lays eggs capsules in which only a single egg is fertilized. When the fertilized egg hatches, the veliger feeds on the other eggs ( called nurse eggs) until it is time to hatch out of the capsule as a fully formed juvenile.( Direct development) ( photo: Neville Coleman)
In 2002 SEA SHELLS I have done my best to change attitudes towards what I now know to be incredible life forms . I would like to think we can advance our understanding of the roles that molluscs have in the overall health of our oceans and learn to respect their presesence without exploiting them as much as has been done in the past.
With digital underwater cameras, divers everywhere can now collect images of living creatures and record information of incredible behaviours and share them with like - minded persons. It must be realized that life has far more value to each of us than a few dead skeleton trophies gathering dust.
Copyright Neville Coleman