Codium species consist of long cells (some cells are up to 30 cm/12 in long)
Codium fragile.
Codium fragile and detail (right) of surface cells with gamete-bearing cells (g) as observed in cross-section.
Green Seaweeds | 69
Identifying Pacific Seaweeds
that branch near the plant surface. There they differentiate into a beautiful scale-like “skin,” which can be viewed with the aid of a magnifying glass. These long cells, lacking regular cross-walls, are packed with chloroplast and other cellular components. The sea slug Alesia sucks the chloroplasts from Codium and houses them in a special gland. Here the chloroplasts photosynthesize and produce a slime the animal uses to lubricate its path.
Codium fragile had a unique introduction to the Mediterranean. According to Professor Jean Feldmann (University of Paris), this species was imported from California to the Banyuls-sur-Mer marine station for research purposes prior to World War II. Care was taken to secure these plants in the laboratory, but all for naught. Allied bombers liberated Codium and it has persisted as a noxious weed on local swimming beaches ever since.
Habitat & Distribution
Both forms of Codium are found in the low intertidal zone from Alaska to Mexico.
Close-up of Codium fragile branchlet.
70 | Unicellular forms
Pacific Seaweeds
Unicellular forms
Unicellular green algae are found in two settings on our coasts: those capable of swimming, or motile, and non-motile forms found inside seaweeds and invertebrates. Motile forms are found in tide pools high in the splash zone above the normal high tide level.
Tetraselmis p. 71
Elliptochloris p. 71
‘Codiolum’ / ‘Chlorochytrium’ p. 72
A shell stained green by the presence of many ‘Codiolum’ or ‘Chlorochytrium’ unicells.
Green Seaweeds | 71
Identifying Pacific Seaweeds
Tetraselmis
Class Prasinophyceae Order Chlorodendrales Family Chlorodendraceae
Number of Species
Tetraselmis (Greek=four branches; refers to presence of four flagella, cellu-lar swimming appendages) consists of six species locally, the most common and easily distinguished being T. ascus and T. marina.
Description
Tetraselmis shifts between two unicellular life stages: a swim-ming form and a sedentary form attached to rock by a long clear filament. Both stages are microscopic. In the filamentous stage, Tetraselmis ascus may form colonies of short profuse branches with pigmented cells at the tips, whereas T. marina colonies are typically of long and sparse branches.
Habitat & Distribution
Swimming unicells of Tetraselmis normally inhabit tide pools above the direct influence of the tides. These pools accumu-late salt from ocean spray and are subjected to rain and severe evaporation, resulting in drastic ranges in temperature and salinity—to the point of being a totally dry salt cake! An inhabited pool will resemble pea soup. Tetraselmis is found from BC to central California.
Elliptochloris
Class Trebouxiophyceae Order Prasiolales Family status uncertain
Number of Species
There are six species in the symbiotic green algal genus Elliptochloris, of which only the species E. marina is found as a symbiont within the tissues of sea anemones.
Description
The common Pacific intertidal sea anemones Anthopleura elegantissima and Anthopleura xanthogrammica house microscopic unicellular algae of two types: dinoflagellates and green algae. In this symbiotic relationship, the anemone gains extra nourishment from algal photosynthesis, while the algae gain protection from herbivores and a place to live.
Tetraselmis.
72 | Unicellular forms
Pacific Seaweeds
Molly Letsch (Le Moyne College) used genetic analysis during her doc-toral studies to determine that the green algal symbionts, formerly referred to as “Chlorella-like” (Greek=green and small), were a new species, which she named Elliptochloris marina.
Habitat & Distribution
Species of anemones in the genus Anthopleura are abundant on rocks, in tide pools or crevices and on pier pilings. They are characteristic of the mid-dle intertidal zones of semi-protected rocky shores of both bays and outer coasts. Distribution is from Alaska to Mexico.
‘Codiolum’ / ‘Chlorochytrium’
Class Chlorophyta Order variable Family variable
Number of Species
‘Codiolum’ (Greek=little ball) and ‘Chlorochytrium’ (Greek=little green fungus) are two unicellular forms once considered to be distinct