young, 3 mm
Diniatys dubius (Schepman, 1913)
|Maximum size: 26 mm.
of this species is transparent to slightly translucent. With
growth, it becomes proportionately more elongate and, in fully mature
animals, the outer lip becomes slightly thickened. Very small shells
(up to 2-3 mm) have fine, evenly spaced axial folds and spiral striae
completely covering their surfaces. In larger shells, that sculpture
restricted to the apex and base. (see photo) The animal is
cream to olive-brown, flecked with white, and a dendritic
network of red-brown lines shows through the shell.
Natural history: Diniatys dubius
moderately rare in mixed habitats and sand channels at protected to
moderately exposed sites where it occurs at depths of as little as 1 m
(3 ft). However, it is one of the most common Hawaiian haminoeids in Halimeda kanaloana beds at depths
of 9-29 m (30-95 ft). Dredged shells
from the Bishop Museum extend the depth range to at least 183 m (600
ft). It appears to be largely nocturnal in habit but mating
and feeding aggregations of up to several dozen animals may remain in the open
during the day in the Halimeda
beds. It probably feeds on a cyanophyte growing on sand around the Halimeda (suggested to be Microcoleus sp. in Gosliner, et. al., 2018). It lays a spherical white egg mass that is more flaccid in
texture than that of most haminoeids. In the field, the egg masses are
usually attached to the tips of Halimeda
branches, decorating them like Christmas tree ornaments when the
population is high. (see photo)
hatch in about four days in the laboratory.
Big Island, Maui, Oahu, Kauai and French Frigate Shoals: widely distributed in the
This species is listed in Gosliner, et. al. (2008), as Haminoea sp. 2. Immature
shells at the
Bishop Museum labeled Atys costulosa
Pease, 1869b appear to be this species as do mature shells labeled "Diniatys monodonta?". It's also probably the species listed as Atys costulosa in Kay, 1979. It was probably first reported from Hawaii in Pease, 1869
(as Atys costulosa). However, the illustration of Atys costulosa in Pilsbry, 1917 and its description in Edmondson, 1946 seem somewhat ambiguous. In many sources it's listed as Diniatys dubia.
Photo: CP: 19
mm: Wahikuli Park, Maui; May 1, 2005.
Observations and comments:
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