Umbraculum sp. #3
|Maximum size: about 130 mm.|
species with a broad, cap-shaped external shell
covering the center of the notum. The mantle is covered with very large,
cauliflower-like tubercles (though the tubercles may be patchily
irregular in some individuals). Its background color is bright orange
broad, white tips on the tubercles. Young animals may
have less well developed tubercles. Its shells are usually overgrown
with algae and remnants of a hairy
periostracum may be present around their margins. The shell is similar
to the shell of Umbraculum sp. #2 but more heavily calcified than the shell of Umbraculum sp. #1.
Umbraculum sp. #3
is a moderately rare nocturnal species found primarily in Halimeda kanaloana
beds and other sandy habitats. Rarely, it occurs in shallow rocky
habitats and tide pools but usually in more protected areas than Umbraculum sp. #2. It may bury itself in sand during the day. It feeds on sponges and lays a frilly, pink egg mass
(although the color of the egg mass may turn out to be variable). (Note 1)
Big Island, Maui, Oahu and Midway: widely distributed in the
Indo-Pacific. (Note 2)
Taxonomic notes: This species is lumped with Umbraculum sp. #1 and Umbraculum sp. #2 as Umbraculum sinicum in Kay, 1979 and as Umbraculum umbraculum
in Hoover, 1998 & 2006. It's referred to as the "umbrella shell" by
Kay and the "umbrella slug" by Hoover in that context. However,
its distinctive color, large
cauliflower-like tubercles and different habitat suggest that it's
likely to turn out to be a separate species. In Ostergaard, (1950), the egg mass
of U. sinicum
is described as pink but no mention is made of the color or morphology
of the animal. So, if the egg mass color is consistent that source may
also refer to this species. Pilsbry, 1917 states that "Umbraculum sinicum aurantiacum (Pse.) which Mr. Thaanum has taken at Hilo, appears to be sufficiently distinct from U. sinicum by characters of the shell to warrant a subspecific name." The name suggests that it might refer to this species but Umbraculum sp. #1 is also a possibility. (Note 3) The shells labelled U. sinicum in Morris, 1974 and Tinker, 1958 may be this species but their assignment is ambiguous.
Photo: Warren Blum: about 130 mm: Maalaea Bay, Maui; Feb. 28, 2012.
Observations and comments:
1: The two egg masses we've seen
associated with this species were pink. However, orange forms from
elsewhere in the Indo-Pacific have been photographed laying (or in
association with) egg masses ranging from white to pink, perhaps reflecting differences in diet.
Note 2: There is little variation in either background color or pattern throughout its range from Hawaii to East Africa.
This is speculative, of course. But, if future DNA work shows that the
orange and brown forms from the Western Pacific are the same species
(or, even lump with the Atlantic form) then this is the Hawaiian
population that will probably group with them (with Umbraculum sp. #1 and Umbraculum sp #2 remaining as outliers).