Hydatina amplustre (Linnaeus, 1758)
|Maximum size: 50 mm
(extrapolated from shell length); most smaller.
species is easily recognized by its thin, strongly inflated shell
marked with broad flesh-colored bands outlined in black. The animal is
translucent cream. (Note 1)
is a moderately common species in mixed habitats at protected to
moderately exposed sites. The animals are nocturnal, burying themselves
in sand during the day (often under cobbles). It is found from the low
intertidal to depths of 1-2 m (3-6 ft). It feeds on polychaete worms
of the family Cirratulidae (Rudman, 1972) and derives defensive toxins
from it's prey (Gosliner, 2018). It lays a convoluted, cream egg mass
attached by a mucous thread.
The eggs hatch in about eight days in the laboratory (Daniel
Jennings-Kam, pers. com.).
Big Island, Maui, Kahoolawi, Molokai, Oahu, Kauai and French Frigate Shoals:
widely distributed in the
referred to as the "swollen bubble shell" in Hoover, 1998 &
2006. The live photo in Severns, 2011 was flipped, reversing the
apparent direction of coiling. It was probably first reported from
Hawaii in Eydoux & Souleyet, 1852 (as Bulla aplustra). It's listed as Aplustrum amplustre in Quirk & Wolfe (1974), WoRMS and some other sources.
Hekili Point, Maui; Nov. 5, 2002.
Observations and comments:
1: Shells of this species show
strong red fluorescence under ultraviolet light (395 nM). However, it's
confined to the pink bands.