External Morphology
Shell and Mantle
The external features of L vitellus is characterised by its calcium carbonate shell and protective mantle. Observations in L. vitellus show no clear correlations between sediment colour and shell colour (Savazzi, 1998). The mantle and its associated papillae may have a camouflage function that also reflects feeding type (Savazzi, 1998). The lack of crypsis displayed by the shell may be instead used to 'advertise' these organisms, making them easily recognizable by predators and thus learning to avoid them (Savazzi, 1998). In some cases, the colourful shell pattern in Cypraeans can be confused for a nudibranch which carry nematocysts, or other organisms that live in the same environment (Savazzi, 1998). Different colour patterns displayed in both the mantle and shell may also cause confusion in predators when the sudden withdrawal from an attack exposes a shell that is different in appearance (Savazzi, 1998).
Papillae
Papillae size, structure and colouration has been observed to be species-specific and is associated with the ecology and habitat of the animal. However, the exact function of the papillae remains unknown, as mentioned in the Australian literature. Sections were made at the University of Queensland to gain an insight into their structure and subsequent physiology.
Analysis of papillae sections in L. vitellus.
By Chelsea Waters
As a whole, the individual papillae are lined by an epithelium which provides a number of functions (namely secretion, selective absorption, protection, and detection of sensation). Attached to the epithelium are microscopic hair-like structures called cilia (Ciliopathy Alliance, 2010). They may either play a role in respiration (motile cilia) or as a sensory system (non-motile cilia), receiving signals from their surroundings (Ciliopathy Alliance, 2010). Upon closer inspection, goblet cells can be seen between the epithelium. Goblet cells are membrane bound secretory granules filled with mucus (Specian et.al, 1991). Secretion of mucus from goblet cells is elicited primarily by irritating stimuli rather than in response to hormones (Bowen, 1998). Cilia play an important role in detecting these irritations (Ciliopathy Alliance, 2010).
Ciliated epithelium and goblet cells seen in L. vitellus.
The dermis of the papillae contain abundant Meissner’s corpuscle; touch receptors which consist of a number of flattened cell layers, each with an elongated nucleus (Histology, 2005). Distortion of the corpuscle due to pressure stimulates the nerve endings, registering the sensation of touch (Histology, 2005). This may be associated with the triggering of mucus in the goblet cells. However, closer inspections need to made to determine whether it is Meissner’s corpuscle, or merely connective tissue.
Longitudinal section of L. vitellus papillae (Microscope: 10x0.3).
Interior of the papillae (Microscope: 20x0.5)
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