Plicopurpura pansa from the Pacific Coast of Mexico and Central America: a traditional source of Tyrian Purple

Journal of Shellfisheries Research, April, 2004 by Ludwig C.A. Naegel

ABSTRACT Most marine snails of the families Muricidae and Thaididae, which make up the genera Murex, Thais, and Plicopurpura, produce in the hypobranchial gland (mucus gland) a viscous liquid secretion. The secretion contains, besides mucus and biologically active compounds, minute amounts of chromogens, which develop enzymatically and under the influence of light and oxygen into a purple pigment known as "Tyrian purple," "Royal purple," or "Shellfish purple." Throughout history, humans have used the pigment for various purposes. On the Pacific Coast of Mexico and Central America. for at least 500 y, the dyeing properties of the "snail's ink" have been known and the pigments used for ceremonial and funeral garments. Here, the muricid Plicopurpura pansa (Gould, 1853) is the most exploited, and rarely the thaid Thais kiosquiformis. T. kiosquiformis has to be killed to obtain a few drops of the secretion from the hypobranchial gland, in contrast to P. pansa, which can be "milked" periodically without harming the animal to obtain a few milliliters of mucus containing the "Tyrian purple" precursors, In contrast to the Mediterranean region, where the use of purple from marine snails has long been forgotten and the craft of dyeing today cannot exactly be reconstructed, in remote Pacific regions of Mexico (in the states of Oaxaca and Michoacan) and in the Indian community of the Borucas in Costa Rica, its use continues until the present day on a small scale and represents the survival of a knowledge of considerable antiquity. However, it is feared that this old tradition will be lost in the near future. The scarcity of the snails, the time, patience, and labor required for collecting them: and the great numbers of them required to dye a small piece of material are the main reasons why cheap, synthetic pigments are today used for dyeing traditional dresses.

KEY WORDS: Plicopurpura pansa, purple snail, Tyrian purple

INTRODUCTION

A large number of publications exist about the use of shellfish purple as a dye, mainly describing the source from Mediterranean snail species. Recently described was the source and chemistry of Tyrian purple from the west Pacific marine snail species Plicopurpura pansa (Naegel & Cooksey 2002). General references about the use of Shellfish purple are the books by Schweppe (1993) and Cardon (2003).

The majority of purple-producing marine snails belong to the family of Muricidae and most, if not all, produce a colorless secretion in the hypobranchial gland (also called mucus gland), which turns purple on exposure to air and light (Fretter & Graham 1994). giving what is known as "Tyrian purple," "Royal purple," or "Shellfish purple." Mollusk purple as such does not occur in the live animal, but is formed during a sequence of chemical reactions in the presence of oxygen and light from the secretions produced by the animal. As in antiquity in the Old World, the use of muricids for dyeing led also on the Pacific Coast of the Americas to a product of high economic value. However, in contrast to the Mediterranean region, where the use of purple from marine snails has long been forgotten and the craft of dyeing today cannot exactly be reconstructed, in remote Pacific regions of Mexico (in the states of Oaxaca and Michoacan) and in the Indian community of the Borucas in Costa Rica, its use on a small-scale continues until today and represents the survival of a knowledge of considerable age (Turok 1999). As in the Old World, the conservative Indian communities in Mexico are convinced that Tyrian purple possesses properties that cannot be duplicated, apart from the practical advantage that material dyed with purple does not bleach. Cheap and fast synthetic dyes of purple color are today available, but the communities still prefer the expensive snail purple. The garlic-like smell of material dyed with snail purple, which aroma fades only after several washings, is valued as a proof of authenticity (Gerhard 1962). Additionally, in various parts of the Americas, shellfish purple has long been used in the bridal dress of Indian women. Here, we may have an explanation for the great esteem in which shellfish coloring has been held on this continent, and consequently an analogy with the Old World belief that the purple from snails helps a woman to become prolific. There is also the possibility of a similar early idea that dye mollusks give protection from evil spirits or that shellfish colors are in some long-forgotten way connected with power, royalty, and religion (Gerhard 1962, Yoshioka 1974).

The use of muricids for dyeing cotton on the Pacific Coasts of Mexico and of Central America dates at least from Columbian times. Here, mainly Plicopurpura pansa (Gould, 1853) is exploited for Tyrian purple production. The carnivorous, gonochoristic marine snail inhabits intertidal rocks exposed to the open sea with high impact waves. The range of P. pansa extends at the Pacific from the northwest coast of Mexico (Baja California Sur) (Clench 1947; Keen 1971) to northern Peru (Pena 1970, Paredes et al. 1999). At low tides the mollusk is relatively easily gathered, and it ejects its dye-producing liquid in such a quantity that there is no need to kill the animal to obtain the purple. Furthermore, the dye-producing hypobranchial gland is so active that the snails can be "milked" periodically. The secretion is a milky-white liquid. which turns on exposure to air and light, at first yellow, then greenish, bluish, and finally purple ("Tyrian purple").