With well over 30,000 species of sea shells known to exist through the Indo-Pacific, Neville Coleman has found and photographed several thousand species, including thousands of images of ovulids.
The Australasian area has one of the most impressive molluscan faunas in the world. Every year more and more records are discovered, distributions extended and new species described.
The recording of knowledge is a continuous process and due to the efforts of early explorers, and conchologists, marine shells are amongst the most well documented of all marine phyla.
Today, with the emphasis on photographic recording rather than collecting the shells themselves, divers are faced with a mammoth task of finding molluscs, where they live and in having adequate reference material to identify them.
With so many species and so few professional taxonomists and malacologists working on molluscan natural history there is still an amazing array of species of which nothing is known. The opportunity for the interested diver, snorkeller, underwater naturalist, and photographer to extend his or her expertise towards filling some of the immense gaps in the natural history of these fascinating and beautiful animals has never been more important, nor as opportune.
In many areas of the Indo-Pacific over-zealous collecting of shells has resulted in many species being reduced to remnant populations, especially on the intertidal and shallow water reefs. However, some groups remain hidden to most divers...
Left: Found in many areas of the Indo-Pacific, the costellate egg cowry Ovula costellata grows to 50mm and ranges in depth from low tide down to 30 metres or more. The shells are pure white with pink inside the aperture. The mantle is very characteristic and doesn't appear to vary over its entire range. Males are smaller than females and in Australian waters they are known to feed on the soft coral Cladiella sp. Juveniles resemble opisthobranchs with bulbous pustules on the mantle. Recorded from Africa, to Japan and out into the South Pacific to Tonga, Lord Howe Island and as far south as Cronulla on the southern coast of
New South Wales.( Photo: Neville Coleman)
Right: A very well known species which ranges from Japan to Papua New Guinea, south to Vanuatu and Sydney Harbour, New South Wales, the Wilson egg cowry Prionovolva wilsoniana is found on the spiky soft corals Dendronephthya spp. The mollusc's mantle has a very characteristic pattern and the adult shell itself has four or five deep indentations on the outer lip. Like all ovulids this species lays its eggs directly onto its host, usually in summer. The species is quite common in Moreton Bay, Queensland and Port Stephens, New South Wales.( Photo: Neville Coleman)
Above: Far easier to recognise than to find the tiger egg cowry Primovula tigris represents an enigma in the family Ovulidae. Whereas almost all ovulids mimic their host and blend in with their micro-habitat, this species presents the opposite form of survival, by mimicking bad-tasting opisthobranchs with bright coloured, highly contrasting mantle patterns that stand out. The tiger egg cowry ranges from Japan to Indonesia and to at least Coff's Harbour on the New South Wales north coast. It lives exclusively on the sea fan (gorgonian) Euplexaura sp. where there may be several individuals living on the same small fan. Interestingly enough each mantle pattern appears to be distinctive to each individual living on the same fan.( photo: Neville Coleman)
THE OVULIDS
In the 29 years since "What is Shell is That?" was written there has been a great deal of information, discovery and scientific work produced on the allied cowries (Ovulidae) yet so much remains a mystery in regard to the lifestyles and natural histories of the living animals. Most published photographs of live molluscs have been from dredged specimens in aquaria and while some of these are excellent in their display, the molluscs are rarely shown from several attitudes, nor is there any reference to whether the mollusc is male or female. Many of the shell photographs and their early descriptions are difficult to compare due to inconsistencies between different author's terms. In some cases it is apparent that shells, types, photographs and descriptions have at times got mixed up.
Left: Dondan's egg cowry Serratovolva dondani has been recorded from Japan, the Philippines and Bali, Indonesia. This species has one of the most beautifully marked and distinctive mantle patterns and although the extent of lines may alter with individuals the shape is very distinctive. This mollusc occurs on the spiky soft coral Dendronephthya sp. at around 20 metres. It grows to 18mm and females lay their eggs in November on the branches (near a fork) of the soft coral host. ( photo: Neville Coleman)
Right: One of the most uniquely patterned mantles is on the long-beaked spindle cowry Phenacovolva longirostrata. This species grows to 40mm and has been recorded from Arab Emirates to Japan and Loloata Island in Papua New Guinea where it lives on the sea fan Astrogorgia sp. There is no doubt this mollusc would live at other localities and its rareness in the Pacific is only due to its habit of living at deeper depths (38m plus) than generally frequented by recreational scuba divers. ( photo: Neville Coleman)
Because many studies are carried out by specialist conchologist taxonomists whose material and information is supplied by second, third or fourth parties, thousands of kilometres away it is often difficult to determine what is correct. In this way, learned and well-respected taxonomists and malacologists have published facts passed on by collectors which are misleading. As much as I appreciate the difficulties and respect the work done by professional malacologists, we are all subject to limitations. A lot of confusion stems from the various species of shells having few distinctive features to describe. The normal variations in shell characteristics, effects of wide-ranging distribution, depth, range, male, female and juvenile shell dimorphism, host or habitat variation, genetics etc. play an important part in the shape, size, thickness, and features of each shell and few of these are ever known or referred to due to the lack of available comparative material.
In general, male shells are smaller than female shells. They may also be slimmer and have thicker shells with more well-developed features. In some cases, females breed and lay eggs while their shell remains in what is termed a "juvenile" form where the aperture lip has not been completely formed. However, in the genus Phenacovolva some species are always found in sexually dimorphic pairs with eggs, while a pair of another species my be seen with eggs, yet the parent shells are of similar sizes.
Representing the first living photographs taken of the species in situ this female recurved spindle cowry Phenacovolva recurva was discovered at 40 metres at Bali, Indonesia. The species grows to 22mm and lives on small sea fans of the genus Euplexaura sp. on steep slopes. The mantle pattern is unique and has no resemblance to any other species. It has been dredged at 300 metres in Japan and appears to be a deep water mollusc.
(photo: Neville Coleman)
Blending into its living habitat Angas's spindle cowry Phenacovolva angasi lives on its host sea fan Melithaea sp. in tropical areas of the Pacific region. In southern waters it lives on the sea fan Mopsella sp. ( photo: Neville Coleman)
All species belonging to the family: Ovulidae are associated with colonial organisms belonging to the class: Alcyonaria (soft corals, sea fans, sea whips, sea pens) or the class: Ceriantipatharia (black corals, bushes, trees, whips).
As far as can be ascertained many ovulid species are host specific, while others may be found on up to six different hosts over their wide range of distribution.
The majority of species live out their lives on the same host they land on when they settle out of the plankton. A few, such as Ovula ovum, Ovula costellata, Volva volva move around in search of prey and mates. In many cases, the eggs are laid on the grazed surface area of a host's skeletal surface (gorgonians) or around the base of a branch on soft corals.
Giant sea fans Melithaea sp. growing beneath caves drop offs and swim throughs in moderate current make for excellent living conditions for egg and spindle cowries.
(photo: Neville Coleman)
Eggs are generally laid in winter or spring. Most ovulids lay their eggs on their specific host. In this way it is thought that the young hatchling veligers are programmed with the odour of their food host enabling them to detect it and land on their preferred host when they settle out of the water column. As great as the chemoreceptive host-finding mechanism must be, there seems to be an indication that ovulids are more likely to select, or be found on isolated colonies of their respective hosts than in the middle of a sea fan forest made up of many species.
Although this golden shelled form of the spotted egg cowry Pseudosimnia punctata has only been recorded from Loloata Island, Papua New Guinea where it lives on the spiky soft coral Dendronephthya sp. the species occurs over a wide area.(photo: Neville Coleman)
Mostly found on the soft coral Lobophytum sp. the toe-nail egg cowry Calpurnus verrucosus has black spots on its mantle which are thought to mimic the withdrawn polyp holes of its found source. This form from Milne Bay Papua New Guinea has extremely well developed mantle pattern. (photo: Neville Coleman)
Left: Egg cowries Ovula ovum are found throughout the entire Indo-Pacific regio where they feed on soft corals Sarcophyton sp. Lobophytum sp. and Sinularia sp. Egg capsules are white and laid directly on the host soft coral.
( photo: Neville Coleman)
Right: Found on the spikey soft coral Dendronephthya sp. ridged Egg Cowry Pseudosimnia culmen grows to 12mm and is distributed across the Indo-Pacific. The mantle pattern is distinct, though the mantle papillae may vary in length.
( photo: Neville Coleman)
SIMPLE EXPERIMENTS
In 1965 to 1967 I conducted a number of experiments with Prosimnia semperi to try and determine how they recognised their own host Mopsella ellisi. I brought up three different coloured (yellow, red, orange) sea fans with their respectively coloured shells, set them all up in an aquarium, then removed all the shells to the other end of the aquarium and left them overnight. When I checked them in the morning, all the specifically coloured shells were on their same colour sea fan, all managed by "smell" as their eyes have no focussing lens to actually see things. Next I removed the red and orange sea fans and left the yellow and then repeated the experiment. Within two days all the orange, red and yellow shells were on the yellow gorgonian.
Several days later I moved all the shells across the aquarium, removed the sea fan and substituted another species of sea fan they were never found on in the wild. In the aquarium they all eventually ended up on the non-preferred sea fan because there was no other substrate they could relate to. Because they crawl on a species of gorgonian in an aquaria it does not necessarily prove that they live on it in the wild.
Tokio's Spindle Cowry Phenacovolva tokioi may be found on a number of different species of sea whips and gorgonians sea fans and it's mantle pattern is very variable. ( photo: Neville Coleman)
PRESENT THOUGHTS
My original interest had concluded that each species would have a distinctive pattern to its mantle even if the colour was similar to other species. After 30 years and thousands of pictures I must admit to it not being quite that simple. In regard to photographic recording of living animals, the mantle pattern can be different on each side and appear different again from a dorsal aspect. In some cases the male mantle pattern can be similar, but not the same as the female.
However, although mantle colour patterns may appear different within a species there is some evidence to suggest that the basic design is maintained within each species and in males and females. Conversely it appears as though several described species have the same or very similar mantle colour, pattern, and expanded mantle papillae when recorded alive and cross-referenced.
There is also marked variation in the colour, pattern, papillae distribution and shape depending on whether the papillae are withdrawn (smooth) bulbous (half-extended) or fully expanded (polyplike tentacles, or other genetically controlled features designed to mimic the host's Alcyonarian or Anthipatharian.
So even when one has access to a lot of information and comparative, accurately maintained specimens and photographic records, sorting out the living ovulids is not as easy as I had once presumed.
With such a range of variable shell characteristics, less than ideal type photographs, missing type species, ambiguous type localities and general difficulties amongst confusing nomenclature my efforts to complete these findings were delayed as several more expeditions were required to try and get back-up material and photographs. Some expeditions were successful, some were not.
Almost all my scientific collections are now housed in State museums. Now this book is published there will be no reason to hold onto the specimens held for reference and photography and they will also be relegated to more auspicious surroundings.
My childhood hobby has led to a lifetime of adventure and realisations beyond my wildest dreams. I did not find many so-called "valuable" shells but I hope my endeavours in the pursuit of knowledge will contribute to the wealth of human nature and show that sometimes the spirit can overcome childhood adversity and put "abuse" to good use.
Copyright Neville Coleman
Credits:
Photographs are from my book 2002 Sea Shells which presents marine molluscs in a visual appreciation of nature, combining specimen shells and living specimens displaying the magnitude of molluscan biodiversity.
Many of the species displayed have never been published in living colour (2400 pictures) and a large number are unique to that publication.