Keyhole Sponge

Orange Keyhole Sponge (Mycale armata)

Mycale armata, Orange Keyhole Sponge

Photo courtesy of DAR


  • Bright orange encrusting sponge (Hawaii Biological Survey, 2001)
  • Can grow up to one meter in diameter (Hawaii Biological Survey, 2001)
  • Firm but compresses and tears easily (Hawaii Biological Survey, 2001)
  • Large oscules spread evenly across body (Hawaii Biological Survey, 2001)


  • Typically found in fouling communities such as floating docks, piers, and jetties (Eldredge & Smith, 2001)
  • Found on shallow patch reefs in Kāne‘ohe (Eldredge & Smith, 2001; Bolick & Coles, 2007)

Impacts & Concern:

  • Overgrow native corals and sponges on patch reefs (Eldredge & Smith, 2001; Bolick & Coles, 2007)


  • First reported in Pearl Harbor in 1996 (Hawaii Biological Survey, 2001)
  • Unintentionally introduced, most likely through hull fouling (Hawaii Biological Survey, 2001)

Distribution in Hawaii:

  • Kauai: Unknown
  • O‘ahu: Pearl Harbor, Honolulu Harbor, Ke‘ehi Lagoon, Barbers Point Harbor, Kāne‘ohe Bay (Hawaii Biological Survey, 2001; Bolick & Coles, 2007)
  • Molokai: Unknown
  • Lanai: Unknown
  • Maui: Kahului Harbor (Hawaii Biological Survey, 2001)
  • Big Island: Unknown


  • Eldredge, L. G., & Smith, C. M. (2001). A guidebook of introduced marine species in Hawaii. Honolulu: Bishop Museum and the Univ. of Hawai’i
  • Bolick, H., & Coles, S. (2007). Invasive introduced sponge Mycale grandis overgrows reef corals in Kāne‘ohe Bay, O‘ahu, Hawai‘i. Retrieved March 22, 2021, from’ohe_Bay_O’ahu_Hawai’i
  • Hawaii Biological Survey (2001). Mycale armata, Introduced marine species of Hawaii Guidebook. Retrieved March 22, 2021, from