ABSTRACT
The genus Codium is characterized by extremely high intrageneric diversity in thallus form, including species with prostrate, globose, procumbent, cylindrical, rope-like, erect and flattened, and erect and dichotomously branching thalli (Silva 1954, 1992). C. fragile (Fig. 1A), the topic of this review, is a large branching species (up to ~ 1 m long, 3.5kg ww). The alga has up to ten orders of dichotomous branching; the cylindrical or terete branches are 3-10 (-14) mm in diameter (Silva 1951, 1955, Wood 1962, Scagel 1966, Boraso & Piriz 1975, Stegenga et al. 1997). One to many fronds arise either out of the holdfast-a broad, spongy basal disk (Lund 1940, Silva 1951, 1955, Scagel 1966, Meiling & Tseng 1984, Oh et al. 1987)—or from a vaucherioid mat (sensu Silva & Irvine 1960). When submerged, the spongy, uncalcified thalli are buoyant due to gas trapped within the thallus (Moeller 1969, Dromgoole 1982). The composition of the gas (by weight) for ssp. tomentosoides is 94.3% nitrogen, 4.1% oxygen, 1.6% argon, and sometimes carbon dioxide (Moeller 1969).
