Hydatina physis (Linnaeus, 1758)
|Maximum size: 92 mm
(extrapolated from shell length of Leeward Is. animals); main island
animals probably seldom exceed 54 mm.
species has a translucent brown body shading to iridescent
blue-white marginally. The shell is faun marked with fine spiral brown
lines. (Note 1)
Hydatina physis is
a rarely seen nocturnal species that buries itself in sand during the
day. It is found in tide pools and mixed habitats to depths of 1-2 m
(3-6 ft) at
moderately exposed sites. It feeds on polychaete worms (Rudman, 1972) and its egg mass
is similar to that of Hydatina amplustre
(though usually more elongate). (Kay, 1979)
Big Island, Maui, Molokai, Oahu, Kauai, Niihau, Pearl & Hermes Reef
referred to as the "paper bubble shell" in Hoover, 1998 &
2006 and may have been first reported from Hawaii in Pilsbry, 1921 (as Hydatina physis staminea).
Severns: found by CP in Napili Bay tide pool; Sept. 8, 1995.
Observations and comments:
1: Shells of this species show strong red fluorescence under ultraviolet light (395 nM).