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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.