Type locality: “Ad insulam Owaihee lectum communicavit Chamisso” (Agardh 1821: pl. XIX)
Taxonomy: Rhodophyta: Eurhodophytina: Floridophyceae: Gigartinales: Phyllophoraceae: Mastocarpus papillatus
Mastocarpus papillatus can be found in the lower intertidal zone, where it is typically attached to a rock substrate by a discoid holdfast. The thallus can be identified by its dichotomous branching pattern that extends to the edge of the blade and its dull, reddish-brown color, exhibited in Figures one and two, even with a wide array of morphologies. The thallus (of the specimens found on the Monterey Peninsula) may extend up to fifteen centimeters in length, though specimens found in the area of San Juan Island have mostly been much shorter (Smith, 1944).
Mastocarpus papillatus has been mostly recorded in North America, along with Northeast Asia (Russia), and along the coast of Chile. This species has multiple stages in its life history, two of which are crustose, and one as a gametophyte that takes the form of the thallus that’s most frequently associated with the genus and species. The species has been observed at several locations in the area around San Juan Island, including Botany Beach (B.C.) and Mar Vista.
A few specimens of Mastocarpus have been pressed for preservation in the herbarium at Friday Harbor Laboratories, though there has been only one specimen of papillatus pressed recently, with the alternate PHYKOS identification tag JLS 190. There was also a cross section made, seen here.
Mastocarpus papillatus goes through three stages during its life cycle: a dominant gametophyte generation, a sporophyte generation, and a carposporophyte generation (Searles, 1980). It may occasionally be difficult to tell the difference between the tetrasporophyte and gametophyte generations, as the plant forms may be isomorphic in their alternation of generations. It’s also possible for the species to exhibit a heteromorphic alternation of generations. The alternation of generations follows a circular path starting at the gametophyte stage, during which the plant’s gametes are released and fertilized so the species can spread or be sustained, continuing with the new tetrasporophyte generation, which will release tetrasporangia into the water column (which the species is dependent upon for gamete movement) and complete the cycle. During the heteromorphic alternation of generations, the tetrasporpohyte, contrary to the gametophyte, will assume a crustose form known as a Petrocelis phase (Cole and Sheath, 1990). From this phase, tetrasporangia are generated and released into the water column for germination (and the completion of the cycle).
This species is also useful for cooking in island-based cultures. M. papillatus, along with members of other genera such as Ulva and Porphyra can be used to prepare a variety of dishes, such as noodles, crackers, soup, and more. One such recipe details how to create “milk jellies” with fresh members of Mastocarpus, with the firmness of the jelly created dependent upon the amount of seaweed used and the carrageenan levels present.
Outside of cooking the entire plant, the carrageenans present in the thallus are also widely used in the food industry, for purposes including thickening of various products (particularly plant milk products, such as some ice cream) and adding viscosity to gel-based foods. In addition, carrageenans have a wide range of applications outside the food industry. For instance, they can be used as toothpaste stablilizers (and can help keep the toothpaste material from breaking “uncleanly”, i.e. keeping it from becoming stringy and such), enabling transport of solid materials in a “slurry” state of semi-solid form (particularly transition metals), and as a component of anti-icing material used on aircraft that regularly cruise at high altitudes (Tye, 1988).
Cole, Adam and Sheath, Robert. 1990. Biology of the Red Algae. Cambridge University Press, Cambridge.
Searles, Richard B. 1980. The Strategy of the Red Algal Life History. The American Naturalist, 115(1): 113-120.
Smith, G. 1944. Marine Algae of the Monterey Peninsula. Standford: Stanford University Press.
Tye, R. J. 1989. Industrial and non-food uses for carrageenan. Carbohydrate Polymers, 10 (4): 259-280.
Molecular data: http://www.ncbi.nlm.nih.gov/nuccore/?term=Mastocarpus%20papillatus
John Luke Schaefer is an undergraduate student at the University of Washington.