Are there sexual differences in the chemical composition of the secretion from the hypobranchial gland of the purple snail Plicopurpura pansa (Gould, 1853)? a preliminary study

The majority, if not all, of the marine snails from the family Muricidae produce in the hypobranchial (mucous) gland a secretion, which turns on exposure to air and light to “Tyrian purple”. The “milk” of the “Pacific Purple Snail” Plicopurpura pansa (Gould, 1853) can be obtained by milking periodically the animals without harm­ing them, in contrast to the Mediterranean muricids which have to be killed to obtain “Tyrian purple”. In this study the “milk” from Plicopurpura pansa was obtained from snails collected from rocky shores of the Pacific and from snails cultured over many years in the laboratory at CICIMAR, and the sex of the snails was de­termined. We collected the “milk” in the laboratory from snails fed daily with squid: four snails of unknown sex, two female and two male snails, and from the “wild” six of unknown sex, one female and one male were collected. At University College Dublin a small amount of deep-frozen and subsequently freeze-dried snail “milk” sample (~1-5 mg) was silylated prior to injection into the gas chromatograph-mass spectrometer (GC-MS). Compounds with the expected mass spectra of tyrindoxyl and tyrindoleninone were detected in all samples, except from those collected from laboratory male snails, in which only tyrindoxyl was detected. In the samples taken from wild snails other compounds, as yet unidentified, were detected that had the cha­racteristic isotope pattern of bromination. The chromatograms of the wild male and female snail milk were very similar.