Cladophora columbiana and detail of filament arrangement (right).
Green Seaweeds | 57
Identifying Pacific Seaweeds
descends until enough oxygen is produced to lift it again. In Japan, where the species is known as Marimo, people were so captivated by this activity that they imprisoned virtually all the wild Aegagropila balls in their private pools. Emperor Hirohito recognized the danger to the species and, upon releasing his Aega-gropila balls, decreed that the species be protected. A Japanese postage stamp commemorates this event, and A. linnaei has the distinction of being the only species protected by Imperial decree.
Habitat & Distribution
Cladophora is found in high tide pools as well as on lower exposed surfaces of the mid- and low intertidal regions from Alaska to Mexico.
Derbesia Green sea grape
Above: Derbesia marina (filamentous phase). Photo by Gary Saunders
Right: Derbesia marina (arrow shows spherical phase) atop a crustose coralline-encrusted limpet. Photo by Russ Norberg
58 | Filaments
Pacific Seaweeds
Class Ulvophyceae Order Bryopsidales Family Derbesiaceae
Number of Species
Derbesia (after Alphonse Derbes, a French phycologist) is locally represented by D. marina, one of the approximately 20 species found worldwide.
Description
Derbesia marina has a life cycle that consists of two different morphologies: an inconspicuous branched filamentous phase lacking normal cross-walls, alternating with a unicellular spherical (up to 1 cm/0.4 in in diameter) phase. The filamentous plants form fuzzy tufts with branches up to 1.5 cm (0.6 in) long.
The spherical phase produces sexually fusing gametes fortnightly. These gametes fuse, initiating the spore-producing filamentous stage. Spheres with dark patches produce female-like swimming gametes, and spheres with pale, yellowish patches produce male-like swimming gametes. These patches explode, deflating the spherical cell and releasing the gametes. The gametes fuse in the surf zone (no small feat!), settle out and develop into the filamentous phase. Over the following two weeks, the sphere is repaired and re-inflated, and more gametes are produced. These observations were first made by G.M. Smith (Stanford University) in 1930. Professor Smith produced the first popular flora for our coasts: Marine Algae of the Monterey Peninsula (1940). This flora, with its exquiste drawings, has morphed into the compre-hensive Marine Algae of California (1976).
Habitat & Distribution
Both phases of D. marina may be found on rock or crustose coralline sea-weeds in the low intertidal and subtidal zones of wave-swept shores. The filamentous phase may also be found on sand. It is commonly distributed from Alaska to southern California.
Bryopsis Green sea fern
Class Ulvophyceae Order Bryopsidales Family Bryopsidaceae
Number of Species
Bryopsis (Greek=moss-like) is represented by three species in our area, B. corticulans, B. plumosa and B. hypnoides, of the more than 50 species known worldwide.
Green Seaweeds | 59
Identifying Pacific Seaweeds
Description
The typical feather-like branched filament lacks normal cross-walls and is essentially unicellular. Thus, a typical plant represents one cell up to 15 cm (6 in) long and is branched. These giant cells could “bleed” to death if they broke. Bryopsis overcomes this problem by taking protein bodies from throughout the cell and moving them quickly to the point of break in order to seal the rupture. Scientists have exploited these giant cells by conducting unique hybridization experiments. The pro-cedure is to squeeze the protoplasm from each of two differ-ent morphological forms and mix them together. The resulting plant (a hybrid) contains nuclei representing the different morphologies in the same cell. The form taken by this engineered plant will reveal which morphology is gen-etically dominant, or if neither is dominant, which would result in an intermediate morphology.
Habitat & Distribution
Plants are found on rocks, shells and wood in the lower intertidal region from BC to Mexico.
Bryopsis sp.
Bryopsis corticulans and detail of a large cell (left).
60 | Blades
Pacific Seaweeds
Blades
The blade morphology is common among the major seaweed groups. In the green seaweeds, the blades are usually one or two cells thick. The blade’s thickness as well as its other dimensions are determined by the pattern of cell division. A game biologists play is to arrange species on the basis of morphological criteria. For example, one could establish a simple-to-complex lineage for some of the common green seaweeds. Imagine the green seaweed cell as being a cube. In an unbranched filament, this cube can divide in one plane only, resulting in a longer filament (Rhizoclonium, p. 52). In branched forms, the cube can occasionally divide in a second plane, giving rise to branches (Cladophora, p. 56). More or less equal cell divisions in two planes would result in a blade one cell thick (Prasiola, p. 61). Cell division limited to once in one plane, accompanied by equal and many cell divisions in two planes, would result in a blade two cells thick (bladed Ulva, p. 62). In some forms the two cell layers become disconnected, resulting in a hollow tube or sac (cylindrical Ulva, p. 66). Finally, the sac