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You are here:   OldClasses > 2012 > Erosaria erosa | Bartholomew Woodham

 

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Erosaria erosa

Eroded Cowry

Bartholomew Woodham (2012)


 

 

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Summary


Physical Description


Ecology


Life History & Behaviour


Anatomy & Physiology


Evolution & Systematics


Biogeographic Distribution


Conservation & Threats


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Anatomy & Physiology

Torsion

A defining characteristic of all gastropods is a developmental process know as torsion. This process results in the visceral mass of the organism being twisted 180 degrees. This results in the anus being positioned on the same end of the animal as the organism's mouth (Ruppert et al., 2004).

Radula

The radula is the hard rasping structure that cowries use to remove food from surfaces and process the food item before it enters the digestive tract. The radula, in gastropods, is specialised to the mode of food acquisition that that species uses (Ruppert et al., 2004). Cone shells are well know for their ability to 'dart' prey, the radula in this case is modified into a piecing structure for predation. In cowries the radulais ideal for removing food items from tough substrates.

Shell development

Juvenile cowries look extremely similar to other gastropod molluscs in that their shell superficially resembles those of ordinary snails, this makes identification to species level extremely difficult in juveniles (Wilson, 1985). As the shell grows, and just prior to becoming an adult, the shell wraps around on itself and totally encloses the previous whorls, it is this that gives cowries their oddly shaped shell. As the cowrie grows the shell is absorbed on the inner surface and the mantle deposits shell on the external surface, resulting in more volume of the shell without growing extra whorls.

Papillae

The papillae of E. erona are extremely large when compared to other species of cowrie. Below is a picture showing the branching and colouration of individual papillae. The function of papillae is debated but there have been suggestions that they are used in a sensory capacity, other functions may include: camouflage, respiration or predator deterrents. The protrusions and their mottled colouration do break up the outline of the shell when it is attached to the substrate. The large surface area would allow significant amounts of gas exchange across the membrane but this has not been examined. It is possible that the papillae contain substances that prove unpalatable to predators but, again, this has not been examined.



Attempts to dissect and section papillae at Heron Island Research Station were unsuccessful. When observed under a dissecting microscope there did appear to be an inner tube-like structure surrounded by an external sheath, possibly hinting at a fluid transport mechanism; no conclusions should be drawn from this however as proper investigation would be required.

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Classification

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