Enteromorpha: now Ulva
See Eur. J. Phycol. (August 2003) 38: 277-294. Linnaeus was right all along: Ulva and Enteromorpha are not distinct species.
When Enteromorpha first begins growing, it
forms a single row of cells, this structure is monosiphonous. Soon
after the monosiphonous filament is formed, longitudinal division of
cells creates a two layered filament. Eventually, after more cell division
the two cell layers separate to form a tube, forming the adult morphology.
The thallus of Enteromorpha is tubular with
the wall of the tube a single cell layer thick. The thallus can be
branched or unbranched, and there is a wide variety of forms within
the genus. Enteromorpha is attached to the substrate by a
disc-like holdfast. The holdfast is formed by the basal cell dividing
into three or four holdfast cells which elongate and undergo further
The cells in Enteromorpha can vary in size
and shape from species to species, and sometimes they will form regular
linear series in a frond, while other times there is an irregular arrangement
of the cells. Each cell contains a single chloroplast, varying in size
depending on the size of the cell.
There is a variety of differences in the morphology
of Enteromorpha, some of which are illustrated in the following
A single thallus of Enteromorpha. Note how
the tube becomes more compressed at the top of the frond. To see a
larger image, click on the image or click
Three separate thalli, all of these are of the species E.
intestinalis. To see a larger image, click the image, or click
Another example of the spiral shape of the thallus
in some species.
Enteromorpha growing on a rock in the intertidal
zone in Stillwater Cove, at Pebble Beach, CA
More Enteromorpha, also in Stillwater Cove
at Pebble Beach, CA.
A view of partially submerged Enteromorpha in
Stillwater Cove at Pebble Beach, CA. This is some of the same Enteromorpha that
was used to take pictures in the lab and under the microscope.
A different species of Enteromorpha, this
picture was taken by Judith
Connor at Elkhorn Slough. This is most likely E. prolifera,
which is widespread in Elkhorn Slough and other sheltered habitats.
More E. prolifera, this picture was also
taken by Judith Connor at
Elkhorn Slough. The white algae in this picture is also Enteromorpha,
it is just drying out, and turning white as it does so.