Stream macroalgae of Hawai`i: an identification guide - Hawaii.gov

Hildenbrandia
Classification: Rhodophyta (Family
Hildenbrandiaceae)
General habit: a crustose red alga that appears as
pink to dark red splotches on rocks, usually grows
in shadier areas of streams, can be small patches
under 1cm in diameter up to expanses of 10’s of cm
Species in Hawai‘i: H. angolensis
Island distribution: Kaua‘i, O‘ahu, Maui, Hawai‘i
Distinguishing features: this alga should be
checked using a microscope since Hawaiian streams
often contain crusts of various algae that can easily
be confused with Hildenbrandia at the macroscopic
level; Hildenbrandia is a filamentous alga that is
composed of a series of branched vertical files of
cells, cells have a “honeycomb” appearance from the
surface of the crust
Compare with: periphyton growths, cyanobacterial
crusts
A. Surface of a rock in a stream with patches of
Hildenbrandia. Scale bar = 4cm. B. A piece of
Hildenbrandia crust viewed with a dissecting microscope.
Scale bar = 0.5cm. C. A surface view of the
40
crust viewed with a compound microscope. Scale
bar = 20µm. D. A cross section through a piece of
crust illustrating the vertical files of cells. Scale
bar = 15µm.