Bryopsis plumosa
Any sunny location in a marina is a good place for algae to grow, but the south-facing sides are particularly ideal for a variety of green, red, and brown algae (see Provincetown sidebar photo entitled "Public Dock, South View"). If you are looking for species of green aglae or trying to assess species diversity, it usually means sorting through the vegetation along the water line and on the sides of docks. The usual subjects include the more commonly observed Ulva, Enteromorpha, and filamentous green algae.
Another common green alga seen on floating docks is Bryopsis plumosa, a branched alga with feather-shaped plumes that arise from a rhizoidal holdfast. The growing tip sends out side branches which give the branch a pennate structure. The distinguishing feature of this alga is that it belongs to a group of organisms composed of multinucleated cells referred to as coenocytes. A coenocyte is a multinucleated cell which can result from multiple nuclear divisions without accompanying cell division, in contrast to a syncytium which results from cellular aggregation followed by dissolution of the cell membranes inside the mass. Several groups of fungi and green algae, including the Bryopsid species, are coenocytic. When a Bryopsis branch is damaged or broken, the membrane is punctured and "clotting factors" (specific proteins, organelles and chloroplasts) aggregate at the site of the wound and plug it up. WIthin 15-20 minutes, a gelatinous envelope composed of polysaccharides and lipids develops around the aggregate. A cell membrane and cell wall are subsequently formed around the aggregate as well.
Bryopsis has a two phase life cycle that alternates between the familiar, macroscopic gametophyte and an inconspicuous, microscopic sporophyte. This cycle is distinct from many other green algae, such as Ulva, whose gametophyte and sporophyte look identical. The gametophyte of Bryopsis is coenocytic, but the gametes, spores, and sporophyte are uni-nuclear. The gametes are biflagellated. In addition to reproduction from gametes and spores, Bryopsis is also capable of reproduction from algal fragments or extruded protoplasm that lacks a cell wall. When the multinucleated cells of Bryopsis are injured, the protoplasm that is extruded from the cells can generate new cells. The coencyte's cell organelles aggregate and secrete a gelatinous envelope and then a cell wall around themselves. Hundreds of cells can be generated from a broken branch, many of which can develop into new plants.
Bryopsis has a two phase life cycle that alternates between the familiar, macroscopic gametophyte and an inconspicuous, microscopic sporophyte. This cycle is distinct from many other green algae, such as Ulva, whose gametophyte and sporophyte look identical. The gametophyte of Bryopsis is coenocytic, but the gametes, spores, and sporophyte are uni-nuclear. The gametes are biflagellated. In addition to reproduction from gametes and spores, Bryopsis is also capable of reproduction from algal fragments or extruded protoplasm that lacks a cell wall. When the multinucleated cells of Bryopsis are injured, the protoplasm that is extruded from the cells can generate new cells. The coencyte's cell organelles aggregate and secrete a gelatinous envelope and then a cell wall around themselves. Hundreds of cells can be generated from a broken branch, many of which can develop into new plants.
Bushy Green Algae Bryopsis plumosa
Image of Bryopsis from the North Western Pacific, Siberia, Russia, March, 2012.
A Single Plume of Bryopsis plumosa
A Single Plume of Bryopsis plumosa
The entire plume is a giant multinucleated cell. Side branches can also branch into a feather-like structure. Collected from floating docks at MacMillan Wharf in Provincetown, September, 2012.
The Growing Tip of Bryopsis plumosa
Photomicroscopic image of the the tip and outer branches of Bryopsis plumosa collected in Provincetown, September, 2012. Stereozoom 1 x 10x objective
Coenocytic Branches off the Main Branch of Bryopsis plumosa
Branches have a homogeneous green appearance that narrows at the junction with the main branch, giving the side branches greater flexibility. Collected in Provincetown, September, 2012. Stereozoom 4 x 10x objective
Life Cycle of the Biphasic Green Alga Bryopsis
The life cycle of Bryopsis involves the alternation of two heterothallic stages: the familiar, macroscopic gametophyte and the inconspiruous, microscopic sporophyte. Bryopsis can also reproduce by fragmentation of microthalli.
PUBLICATIONS AND LINKS:
MarLIN: The Marine Life Information Network, Biodiversity & Conservation. Descriptions of major taxonomic groups. The life cycle of homothallic green algae such as Ulva is contrasted to Bryopsis.
The life cycle of green algae such as Ulva or Enteromorpha involves the alternation of two homothallic stages: the gametophyte and the sporophyte. Both forms look alike.
Burr, FA, JA West. Light and electron microscope observations on the vegetative and reproductive structures of Bryopsis hypnoides. Phycologia 9: 17-37, 1970.
Abstract (excerpt): "The vegetative system of the coenocytic alga Bryopsis hypnoides has a large central vacuole which extends throughout the body of the plant. This vacuole occupies most of the volume of the thallus, leaving only a thin layer of cytoplasm appressed to the cell wall. Numerous evaginations of the vacuole penetrate the cytoplasm. In the mature parts of the thallus the cytoplasm is divided into two definite layers: the outer layer adjacent to the cell wall contains most of the organelles excluding only the chloroplasts, which are present in the inner layer next to the vacuole."
Kim, GH, TA Klotchkova, YM Kang. Life without a cell membrane: regeneration of protoplasts from disintegrated cells of the marine green alga Bryopsis plumosa. J Cell Sci 114: 2009-2014, 2001.
Regeneration of protoplasts from a broken branch.
Takahashi, F, K Yamaguchi, T Hishinuma, H Kataoka. Mitosis and mitotic wave propagation in the coenocytic alga, Vaucheria terrestris sensu Goetz. J Plant Res 116: 381–387, 2003. (Images of the morphology of coenocytic nuclei and microtubules during the different stages of mitosis in a green alga completely unrelated to Bryopsis)
Coenocytic nuclei in the growing tip of Vaucheria terrestris sensu Goetz, another coenocytic alga. a) photomicrograph of a growing tip and b) nuclei in the same region stained with a blue dye.
Monterey Bay Aquarium Research Institute: Marine Botany. Bryopsis morphology.
Algaebase. Bryopsis. Description of the genus.
Algaebase. Bryopsis plumosa. Database on the species.
The Reef Tank: Marine Benthic Macro-Algae (MaBMA) Catalogue. Bryopsis. Description of species and life cycle.
University of Hamburg Biology Website: Morphological Diversity within the Algae. Descriptions of the structure of coenocytic algae like Bryopsis and parenchymatous algae like Ulva or Enteromorpha.
Queen's University Belfast Biology Website: Morphogenesis in the Green Algae. Ulva and Enteromorpha.
Growth of parenchymatous green algae from a single progenitor cells by cell division into multicellular sheet or tube.
Gulf of Mexico Integrated Science: Tampa Bay Reports. Characterization of Epiphytes on Seagrass in Tampa Bay.
Enteromorpha showing 1) macroscopic structure, 2) cross section showing single cells, and 3) surface view.
Algaebase. Description of Ulva species: Ulva rigida.
Microscopic section through an Ulva species showing 2 cellular layers
containing chloroplasts
Marevita - Algues et Plantes Marines - Chlorophyta: Bryopsis plumosa.
WoRMS: World Registry of Marine Species. Bryopsis plumosa (Hudson) C. Agardh, 1823.
