Erronea errones (Linnaeus, 1758)
Wandering Cowrie
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Erronea errones with its mantle extended, covering the shell (left) and with the mantle retracted exposing the glossy shell (right). (Photo credit: Ria Tan)[1]

[1] What is this....

Erronea errones (Linnaeus, 1758), better known as the 'Wandering Cowrie'[2] or 'Erroneous Cowrie' is a species of marine snails that are very common to the shores of Singapore. They belong to the mollusk gastropod family of Cypraeidae that includes all the other cowries. Members of this species, are on the average 20-24mm in length and may grow up to 45mm. This is smaller, compared to other cowries found in Singapore like the Arabian Cowry, that can grow up to twice that size. Erronea errones can vary greatly on the dorsum of the shell with variable spots, patches or transversal bands (see above, right) on top of the usual of pale brownish or greenish base.

[2] I have never seen a cowrie before!

This is quite an impossible statement especially if one resides in Singapore. Other than being the most common cowrie seen on the shores of Singapore, you would have probably seen it here as well...
Specimen note.png
Singapore $10 currency of the Portrait series notes released in September 1999. The cowrie,E. errones can be found on the circled area.
The Portrait series notes' obverse have different cowries printed in the background. Take a closer look and you will see them. The table below shows the various cowries that can be found on the different denominations of the series.
Value
Specimen Note
Type of cowries printed on the obverse
$2
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Monetaria moneta_1.PNG
Money Cowrie (Monetaria moneta)
$5
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Annulus cowrie.PNG
Gold-ringed Cowrie (Monetaria annulus)
$10
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Erronea errones money sample.PNG
Wandering Cowrie (Erronea errones)
$50
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Cypraea Cylindrical.PNG
Cylindrical Cowrie (Erronea cylindrica)
$100
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Hirundo.PNG
Swallow Cowrie (Bistolida hirundo)
$1000
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Pulchra cowrie.PNG
Beautiful Cowrie (Luria pulchra)
$10,000
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Onyx cowrie.PNG
Onyx Cowrie (Erronea onyx)
Table of the Portrait series note printed in September 1999
(Image credit: Monetary Authority of Singapore[3] )
Photos of the cowries printed on Singapore Dollar Notes
(Photo credit: Philipp Rosenkranz)

2.1 Why cowries?

Shells, were used as a form of currency in the past, as a medium to exchange for goods. Shell money can be found all over the world, on every continent and the most frequently used are the cowries, being a more charismatic and beautiful looking shell. Among them, money cowries (Monetaria moneta) were probably the most frequently adopted medium of exchange.
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'Barter. Couries used as Money' (Photo credit: Permission granted from Science & Society Picture Library)
Here, we shall delve deeper into this prize-worthy shell E. errones, learning more about the morphological, biological and phylogenetic characteristics.

[3] What do I call it?

Nomenclature

Scientific (binomial) Name:
Erronea errones

Original Combination:
Cypraea errones

Common Name:
Wandering Cowrie or Erroneous Cowrie

Etymology (origins of name):
The common name comes from the latin translation of the word 'erroneus' which refers to a wanderer
The sub-genus Erronea was first separated from the Linnaeus' parent genus Cypraea by Troschel in 1863, C. errones being given as the type.

[4] How do I know a shell belongs to E. errones?

Erronea errones azurea.png
bimulcuta.png
Errones.png
From left to right :Erronea errones azurea, Erronea errones bimaculata, Erronea errones errones (Photos credit: Philipp Rosenkranz)
The shells above look so different yet they are all grouped under the same species Erronea errones. Various attempts have been made by shell experts to elevate the variants of E. errones to subspecies status. However, as of now there are only E. errones azurea and E. errones errones recognized as subspecies, according to World Register of Marine Species (WoRMs)[4] . Erronea errones bimaculata it is still under taxon inquirendum because experts are still bearing differing views on its whether it could be officially considered as a subspecies.

Lets have a look at all the subspecies and variations of our wandering cowrie![5]
Erronea
errones errones
errones azurea
errones "bimaculata"
errones "coxi"
errones "caerulescens"
Status
errones1.png
Subspecies
azurea1.png
Subspecies
bimulcuta2.png
Variant
coxi.png
Variant
caerulescence.png
Variant
Shape
Cylindrical
Oval
Elongate oval
Oval pyriform (Pear-shaped)
Oval
Dorsal color; blotch
Pale green-blue/ brown;
indistinct
Blue,banded;
no dorsal pattern
Dark-green;
distinct when present
Dark bluish;
distinct when present
Light brownish;
distinct when present
Columellar teeth
Strong
Rather fine
Strong, slightly outstanding
Rather fine
Rather fine
Base color;
Aperture
Pale cream;
Narrow to wide
Plain white;
Rather wide
Tanned orange;
Rather narrow
White to tanned;
Rather wide
Thin translucent;
Narrow to wide

If you are not sure of which are the parts of shell we are referring to above, click here to jump to morphology section!

Varieties in E. errones are mostly obscured by ecological influenced modification (e.g what are the available shell-making minerals, their diet). This is why they are rarely elevated to species or subspecies level, and remain as a variant.

So how exactly do we describe this species with such a variety of visual differences?

4.1 Going back to the original description by Linnaeus 1758...


Erronea errones Original description.png
Original description of E. errones under Cypraea errones by Linnaeus (1758) in Systema naturae[6] .
In the original description by Linnaeus, you can probably see that it is brief and not very helpful with the following statement:
"C. tefta umbilicata: macula teftacea aequali"
According to Dodge[7] (1955) it only tells us that the shell is umbilicate (having a central depression) and showed a spot, assumed to be the one on the dorsum. He also mentions that the phrase "macula testacea aequali" cannot be comprehensively translated. Individually, the word "testacea'"is often utilized by Linnaeus to refer to "shell-colored". Not only is this vague, but it is also incorrect as we can see from the specimens above that coloration ranges greatly. "Aequali" word can be interpreted as "symmetrical" likely referring to the dorsal maculation, which is also inconsistent across the complex organism associated with this species name.

The only useful information perhaps is given in the subdescription:
"Differt a C. stolida macula una, nec pluribus."
Which basically means that the color pattern of the E. errones shell varies intraspecifically.

There is no locality or geographical information included in this diagnosis as well.

4.2 A clue through taxonavigation?

This species of cowrie was derived from the following classification :
Kingdom
Animalia
Phylum

Mollusca
Class


Gastropoda
Order



Littorinimorpha
Superfamily




Cypraeoidea
Family





Cypraeidae
Genus






Erronea
Species







errones
Certain morphology of the wandering cowrie are characteristics features of the higher classification they belong to. So click to learn more about the higher taxonomic rankings of E. errones.

4.3 Morphology of E. errones

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Diagrammatic comparison of a cowrie morphology (Photo credit: Smithsonian National Musem of Natural History[8] , Ria Tan, Edited by Zong Rui Tan)
Errones Shell morphology_1.jpg
Shell morphology (Photo credit: Zong Rui Tan)
Gastropods from the superfamily Cypraeoidae generally have smooth shells which is often due to them enclosing it in their mantle. This prevents against abrasion and growth of other organisms like algae or barnacles. The mantle also serves to repair the shells when it is damaged.

Extending from the mantle are the tentacles, at the base of which the eyes can be found, along with the siphon that is modified for breathing and sensing chemical cues. These are important biological features for the cowries to detect changes in the environment.
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E. errones with mantle covering the shell (Photo credits: Ria Tan)
Erronea errones also lack an operculum and have a narrow aperture (opening of the shell). The aperture is lined with teeth.

Erronea errones belongs to the large taxonomic subclass prosobranchia which translate literally to 'gills in front' [of the heart]. In addition, the mantle cavity and anus is also situated in front as well. This subclass was dismissed from the actual taxonomy when it was found to contain lineages of multiple descent (polyphyly), and became more of an anatomically descriptive term for a taxa.

4.4 Could this be...

The Ovum Cowrie (Erronea ovum) is often mistaken for our E. errones. Let us put what we have learnt about their morphology to the test and try telling them apart!
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Wandering cowrie
Erronea errones
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Ovum Cowrie
Erronea ovum
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Cylindrical shell
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Pear-shaped shell
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Does not have coloured teeth
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Teeth that have a tinge of orange or yellow
Differentiating Ovum and Wandering cowrie (Photo credits: Ria Tan)
Just remember that you should avoid identifying the two shells based on the colour pattern seen on the dorsum. The wandering cowrie varies with a great range of patterns, many of which may bear resemblance to the ovum cowrie.

[5] Where can we find this awesome looking shell?

Cowries typically can live in shallow to deep water habitats. In Singapore, they can be commonly found in shallower waters of the coral rubles, coral reefs, near sponges or even on open rocky shores. Adult E. errones are benthic creatures, thus they can only be found crawling on the shores with corals or rocks. Have a look at the few places where the wandering cowrie have been spotted on Singapore's shores!


The next map will show the areas which each subspecies and variant of E. errones have been found globally.[9] Being a tropical or subtropical dweller of the cowrie family, E. errones can be found distributed across the East Indian Ocean and West Pacific Ocean. As their shell morphology can vary due to environment, many of the variants can be found clustered in certain parts of the world.
Environmental ranges[10]
Depth range (m)
0.5 - 70
Temperature range (°C)
23.011 - 28.488
Salinity (PPS)
33.691 -34.975
Oxygen (ml/l)
4.336-4.754
Go ahead and click on each color tag below to find out where each variant or subspecies in located worldwide!


[6] What do they feed on?

Known as the grazers of the sea, wandering cowries feed by scraping algae off substrates. Its herbivorous diet is pretty befitting of its moniker, as it practically feeds like a sheep.

Like many other animals, the diet of gastropods is dependent on their denture, known as radula. For E. errones, it possess a typical taenioglossan radula (below) that consist of seven teeth on each row: one middle tooth, flanked on each side by one lateral and two marginal teeth, giving the 2+1+R+1+2 formula.

Erronea errones mouth and radula.png
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Left to right: E. errones feeding; Radula of E. errones observed under a microscope
(Photo credit: Zong Rui Tan)
SEM image of the Taenioglossan radula of
E. errones
(Photo credit: Florida Museum of Natural History)[11]
This set of "teeth"—a diagnostic characteristic of subclass Caenogastropoda that E. errones belongs to, operates like a "rake" to scrap algae and detritus off the substratum.

[7] What about mating and reproduction?

As a member of the previously used order Neotaenioglossa (subsequently placed into Littorinimorpha), the cowrie is likely have separate sexes - male and female (gonochoric). They are also broadcast spawners, releasing sperms and eggs into the open waters.
Cowries, including E. errones pictured below, are brood-protecting animals[12] . Thus cowries can often be found perching over their eggs on corals, boulders or rocks where they have laid their eggs. Their foot will be fully extended to cover the egg masses which are horny, glossy and pale yellow in color[13] .


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Erronea Errones resting on a boulder, the left most one perching on its eggs. (Photo credit: Ria Tan)
When disturbed during brooding, they display restlessness.
So next time, do the mother-cowrie a favour, if you ever see a cowrie perched on a boulder, do NOT remove it as you might separate the mother from her eggs!

Once hatched, the juvenile snail would be in the form of a trochophore larvae and rapidly develop into a veliger larva. It will already possess a shell with reticulate markings and pale brownish in color. A typical character of a veliger larvae is the velum, which is bi-lobed and colorless, with long cilia that helps to gather food towards its mouth.
veliger.png
Erronea errones Veliger and trocophore larvae.png
Drawings of the egg capsules and veliger larvae
of E. errones
(Photo credit: Natarajan )
Left to right: Photo of a trochophore larvae (first stage); veliger larvae (second stage).
Iridescence is due to usage of polarised light.
(Photo credit: Mary Janna Grove[14] , edited by: Zong Rui Tan)
An interesting aspect of their growth, is that they can "adult" their shells. Upon reaching sexual maturity, they will in-fold the lips and thicken their shell. This results in the formation of the two shell-like features which is, in fact one continuous shell.
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Broken shell of a cowrie, exposing the "dwarf shell" in the interior (Photo credit: Ria Tan)

[8] How does the wandering cowrie defend itself?

As mentioned earlier, the mantle of the cowrie keeps this shells smooth, making it hard for the predators to have a good grip over it. Moreover, the snail will protect itself by retracting back into its hard shells, which is difficult to fish the flesh out of. In addition, the mantle has many tiny protrusions and dull colouring, allowing it to blend into its surroundings and camouflage the shell.

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Blending into the surrounding with the mantle extended. (Photo credit: Ria Tan)
Even though the narrow aperture of the cowrie shell is difficult for many predators to reach into, there are still some natural predators of the
E. errones.
These includes some of the crustaceans (e.g crabs, prawns) that are able to break the shells and reach in for the flesh.

With the whole shell intact, they can also be preyed on by the cone snails, which inject venom into the cowrie flesh before reaching in to feed and ingest the soft tissue of the cowrie.
Conus feeding on Erronea errones.PNG
From left to right: Cone snail (Conus marmoreus)detecting its prey(Mole cowrie) with its siphon; Once deem edible it will extend venomous harpoon (circled) to stun the prey. (Photo credit: Jeanette Johnson[15] , edited by Zong Rui Tan)

[9] It's so pretty! Can I bring one home?

That is highly not recommended. Despite being the more common cowries on our shore and their pretty appearances, cowries are often over-collected for several reasons.
Firstly for the shell collectors, they tend to collect a wide variety of shells, leading to a bustling shell trade online.
Shells trade.png
Erronea errones being traded online alongside other shells. (Screen shot edited by: Zong Rui Tan)
The shells are priced based on their rarity, finishing and completeness. Among the E. errones, e. azurea is the more highly sought-after shell because of its attractive colouration. Most of the shells are hand picked and not collected with nets. This decreases the likelihood of damaging the shell and increase the chances of collecting rarer ones.

Similarly, they are also collected for the aquarium trade, to beautify the tank as well as to clean up the tank, by scraping off the algae on the glass.
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Photo taken of a cowrie snail in an aquarium tank. (Photo credit: Wally B.)
Cowries are also collected and made into accessories for similar reasons.
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Cowrie necklaces (Photo credit: batiksarong.com)
Furthermore, in Singapore, due to land reclamation and other anthropogenic activities, there is constant habitat loss for our shelled friend.

9.1 Then aren't they at risk of being depleted?

Fortunately for us, E. errones is widely distributed and many variants are common on our shores. Therefore, it is neither listed in ICUN Red List of Threatened Species, nor in the Singapore Red Data Book of Endangered Animals.

E. errones is determined as an Evolutionarily Significant Unit (ESU). ESU refers to a population that is considered distinct for conservation purposes which could be based on either phenotypic, phylogenetic or geographical differences. Even then, it is not covered by the Endangered Species Act practiced by the United States, due its healthy population.

[10] What else does this snail do?

Through a study done by Anand & Edward (2002)[16] , wandering cowries actually possess some antimicrobial activity. It was tested on 5 different members of the Erronea genus which the author still refers them under the Cypraea genus.

Antimicrobial activities.png
Published results of study conducted by Anand & Edward (2002), showing microbial activities of Cypaea errones (E. errones)
They also tested on Didemnum psammathodes which is an ascidian part of the diet of the wandering cowrie to ensure that the antimicrobial activities are not dietary derived. Although the snail has been successfully proven to have antibacterial activity, the result in turn showed that the ascidian is a much promising source of antibacterial compound.

[11] If I don't see them on the shores, where can else can I find them?

Cowries (Cypraeidae) are one of the most well studied molluscan members. While many of the specimens may be lost due over time due to reasons like war, misplacement and such, we are fortunate that The Linnean Society of London still holds on to majority of the specimens collected and diagnosed by Linnaeus himself.


Linnaeus collection 2.pngLinnaeus collection_1.png
Cypraea errones from the original Linnaean collection (Photo credit: The Linaean Society of London[17] )
For the other variants and subspecies there are countless specimens stored all over the world in various museum, of which most Natural History Museums will possess at least one sample specimen of it.
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Cypraea errones chrysophaea holotype specimen from National Museum of Wales, from the Mevill-Tomlin Collection (1888). (Photo credit: Museum of Wales)
Natural History Museum of Rotterdam
Museum Victoria

Just drop by to any nearby Natural History Museum (for Singapore: Lee Kong Chian Natural History Museum) and find our lovely shells there!

[12] Still can't tell the difference in morphology? Try molecular data!

As we progress technologically, many of the species are identified through the use of molecular data information (e.g DNA, nucleotide sequences, protein).Convergent evolution has led to many similar characteristics in separate species that make it hard to differentiate them based on visual appearances. This is apparent in many of the invertebrates that live in the same environment[18] .
Molecular data grant us the ability to identify cryptic species that may appear identical morphologically to each other, and might trick the eyes of experts.
Common cowrie_after alignment.png
Top: CO1 sequences of the common cowries in Singapore, aligned with Muscle and viewed in Aliview.
Bottom: The same set of sequence translated into amino acid sequences.
E. errones, E. ovum. E.cylindrica molecular data is obtained from Singapore specimens. (Photo credit Zong Rui Tan)
Eclogavena quadrimaculata appears to mismatch here due to a longer sequence used.
Using programs like Aliview and Mega allows quick alignment of the sequences available and presents the analytical work that needs to be done. Comparisons can be made across large numbers of specimens to find out how alike they are for a particular set of genes. From there on, the user then can choose what they want to do with the data, or what percentage differences do they want to use to delimit a species (usually at 10%, derived from empirical studies conducted).

You can also try it out by using sequences from National Center for Biotechnology Information (NCBI)

12.1 What is this CO1 and why is it used?

CO1 is an essential gene that codes for a protein in cellular respiration pathway in the mitochondria.
Actually, any set of genes can be used in this sequencing process, however this gene is more "ideal" than the others due to the reasons below:
1)It is present in most eukaryotes (cells with membrane bound organelles).
2) It is a highly conserved gene, thus, the change in the gene sequence is slow enough to identify with same species but fast enough to differentiate separate species.
3) Cells have many copies of it which increases likelihood of extracting sufficient amount for analysis.

12.2 OK, so what can I do with all these ATCGs?

Many projects are working towards constructing a comprehensive phylogeny at appropriate levels for diversification of the taxa that are being studied.
It depends a lot on the ESU mentioned previously in the conservation section which sometimes is known as operational taxonomic unit (OTU).

In the study conducted by Meyer (2004)[19] , other than being monophyly, when delineating the significant units in cowries, they have to meet at least 2 of the 3 criteria:
1) Geographical distinction or allopatry
2) Significant difference in the genetic distance such that pairwise distance comparison yields pairwise yield a bimodal distribution (2 different modes)
3) Taxonomic recognition by previous works

Most OTUs that satisfy all 3 criteria are considered as ESUs.
The results are then expressed into phylogenetic trees showing evolutionary relationships through cladogram or phylograms.

Genus.png
Results of phylogenetic study done by Meyer (2004), using CO1 and 16s sequences
Here we can see that within the Cypraeidae, Erronea is actually closer related to Bistolida (genus of swallow cowrie) and Eclogavena than Monetaria (genus of money cowrie) and Annepona. These coincides with the the results we obtained previously using the sequences available on NCBI!

Now let us take a closer look at the species level.
Phylogenetic tree species.png
Cladogram (Left) and Phylogram (Right) derived based on likelihood distance using GTR+I+G model of sequence evolution. (Meyer, 2004)
Here, we can have a closer look at how closely related are the members of the Erronea genus, including E. onyx (Onyx cowrie), E. cylindrica (Cylindical cowrie) and E. Ovum (Ovum Cowrie) which were discussed previously.

In order for us to obtain such trees a Maximum Likelihood (ML) algorithm is adopted and requires a model of evolution (in this case: GTR + I +G). This ensures the complexity of the model so that more parameters can be covered. Results from a sufficiently complex model can then be trusted. Here Meyer used the General Time Reversible (GTR), proportion of Invariable site (I) and Gamma distribution (G) models, which are more commonly used.

Therefore with such modern technology, we are able to grasp a clearer picture of the relationship of our E. errones alongside other cowries, tracing back to the last common ancestors!

[13] Give me more!

If you are still not satisfied with what you have learnt here, go to these websites and enter the world of shells!
Wikipedia
Wildsingapore
Tidechaser
Gastropods.com
Cypraea.eu


[14] References


  1. ^ Tan, R., 2012. Wandering cowrie (Erronea errones) on the Shores of Singapore. Wild Singapore.
    http://www.wildsingapore.com/wildfacts/mollusca/gastropoda/cypraeidae/errones.htm. (Accessed November 2015).
  2. ^

    Allan, J., 1950. Australian Shells: with related animals living in the sea, in freshwater and on the land. Georgian House, Melbourne. xix 470 pp..
  3. ^ Monetary Authority of Singapore, 2013. Know your money - notes.
    http://www.mas.gov.sg/Currency/Learn-About-Currency/Know-Your-Money.aspx. (Accessed November 2015)
  4. ^

    Rosenberg, G., 2015. Erronea errones (Linnaeus, 1758). In: MolluscaBase (2015). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=216859. (Accessed November 2015)
  5. ^

    Lorenz, F., & Hubert, A.,1993a. A guide to worldwide cowries. Hemmen. 106-109 pp.
  6. ^

    Linnaeus, C., 1758. Systema Naturae, Ed. 10, Vol. 1. 824 pp. Salvii, Holmiae.
  7. ^

    Dodge, H., 1995. "A historical review of the mollusks of Linnaeus. Part 2. The Class Cephalapoda and Genera Conus and Cypraea of the Class Gastropoda." Bull. Am. Mus. Nat. Hist 103.1 : 93 pp.
  8. ^

    Smithsonian Museum of Natural History, 2014. Morphological Variation in the Tiger Cowrie Shell, Cypraea tigris Linnaeus, 1758
    http://invertebrates.si.edu/Features/stories/cowrie.html (Accessed November 2015)
  9. ^

    Lorenz, F., & Hubert, A.,1993b. A guide to worldwide cowries. Hemmen. 106-109 pp.
  10. ^

    Encyclopedia of Life (EOL). Erronea errones,Detail - Ecology.
    http://www.eol.org/pages/4854054/details (Accessed November 2015)
  11. ^ Florida Museum of Natural History, 1995. Cowrie Genetic Database Project, 2005. Erronea errones (Linnaeus, 1758), radulae
    https://www.flmnh.ufl.edu/cowries/errones.htm (Accessed November 2015)
  12. ^

    Lo Bianco S.,1899. Mitt. Zool. Stat. Nexpel. 13., 448pp
  13. ^ Natarajan, A. V., 1954. On the breeding habits of the cowry Erronea errones (Linne). Current Science, 23(7), 225-226.
  14. ^

    Grove M. J., 2011. Invertebrate embryology. Veliger larvae of mollusc.
    http://invert-embryo.blogspot.sg/2011/05/veliger-larvae-of-molluscs.html
  15. ^

    Johnson J., 2009. Kwajalein Underwater Conus marmoreous (Linnaeus, 1758)
    http://www.underwaterkwaj.com/shell/cone/Conus-marmoreus.htm (Accessed November 2015)
  16. ^

    Anand, T. P., & Edward, J. K. P., 2002. Antimicrobial activity in the tissue extracts of five species of cowries Cypraea spp.(Mollusca: Gastropoda) and an ascidian Didemnum psammathodes (Tunicata: Didemnidae). Indian journal of marine sciences, 31(3), 239-242
  17. ^

    The Linnean Society of London. Cypraea errones (Linnaeus, 1758) .Online Collection. http://linnean-online.org/16986/ (Accessed November 2015)
  18. ^

    Moore, J., & Willmer, P.,1997. Convergent evolution in invertebrates.Biological Reviews of the Cambridge Philosophical Society, 72(01), 1-60.
  19. ^

    Meyer, C. P., 2004. Toward comprehensiveness: Increased molecular sampling within Cypraeidae and its phylogenetic implications. MALACOLOGIA-PHILADELPHIA-, 46(1), 127-156.