These algae are usually brought into an aquarium on live rock. They grow best when kept in shallow water aquariums of one foot or less in depth, with good deep sand beds and very intense lighting. They reproduce sexually by releasing cysts that in turn produce gametes (drifting sperm or eggs that are capable of participating in fertilization), and asexually by division at the base of their stalks.
Cups - Acetabularia sp.
With the fine ribbed cup, umbrella, or dish shaped caps that the Acetabularia sp. grow on their stalks, they are commonly referred to as the Mermaid's Wineglass or Parasol. Acetabularia grows abundantly in brightly lit shallow waters of the Florida Keys and are commercially available for sale. Growing as one giant single-celled organism, the caps can reach up to 3/4 of an inch in diameter.
A. crenulata is pale white in color with branched flower-like caps giving it the appearance of having a rough, jagged toothed edge, while A. calyculus is much greener in color and has smooth edged caps. A. mediterranea and A. acetabulum also have smooth edged caps. Polyphysa polyphysoides is another similar species to Acetabularia. It grows much smaller than the Mermaid's Wineglass and is intensely white from its high calcium or lime content.
Brushes - Penicillus & Rhipocephalus sp.
Penicillus are known as the Mermaid's Shaving Brush because of their brush or bristle-like tops. They anchor deep into sand beds by means of a very complex structure of root-like filaments. P. capitatus grows two to four inches tall with a long slender stalk, P. pyrifrmis has a shorter stalk with a flat top and grows to about four inches in height, and P. dumetosus grows very tall at about six inches in height and has a stubby base with a rounded top. Rhipidosiphon javensis is another similar brush-like bristled calcified algae.
Rhipocephalus phoenix is referred to as the False Shaving Brush or Ripweed. This calcified algae grows layered plates instead of brush-like bristles, has a very thick stalk and can grow quite tall. R. phoenix is one of the single species found in Florida, growing to about six inches in height.
In Part 6 of this series we discuss Fans and Fingers found in the green algae phylum Chlorophyta.