young, 5 mm
Stylocheilus(?) sp. #1
|Maximum size: 22 mm.
is a small, translucent-cream sea hare frosted with white and brown
decorated with prominent blue and gold ocelli at all sizes. Although
superficially similar to Stylocheilus striatus, it can
be distinguished from that species by its more prominent blue and gold
ocelli, more elaborate villi and brown flecks that are random rather
than arranged in lines. The ornateness of the villi and amount of white pigment are variable.
Natural history: Stylocheilus(?) sp. #1 is a moderately common
species found in moderately protected to highly exposed rocky habitats
from < 1 to 11 m (< 3 to 36 ft). It may also be found in Halimeda kanaloana beds. It feeds
on cyanobacteria (blue-green algae). As in S. striatus, the blue and gold
ocelli may represent aposematic coloration "advertising" the presence
of toxins concentrated from its food. (Note 1) It lays a tangled, golden-brown
egg string that hatches in six to seven days in the laboratory.
Big Island, Maui, Oahu, Kauai and Pearl & Hermes Reef: may be widely
distributed in the Indo-Pacific (pending further work to determine
whether the Hawaii population is the same as others in
Taxonomic notes: Carlo Cunha (pers. com.) suggested that this species may be a Stylocheilus rather than a Bursatella since the latter genus lacks a shell and the widely distributed Bursatella leachii is much larger. (Note 2) However, further work will be needed to confirm the genus. It was first recorded
in Hawaii from Maliko Bay, Maui by PF in Aug., 1992.
Photo: CP: 16
mm: Ulua Beach, Maui; April 2, 2005.
Observations and comments:
1: This species, Stylocheilus straitus, other ocellate sea hares that aren't present in Hawaii and most of their various mimics such as Aegires
exeches and Scyllae sp. #1
appear highly cryptic from a distance but have very similar blue and
gold ocelli when viewed at close range. Perhaps, they're under
simultaneous selective pressure from two groups of predators with very
different visual systems (maybe, fish and crustaceans such as mantis shrimp?). Together, they seem to represent a large
mimicry complex similar to the "black-and-yellow" terrestrial insects
(associated with stinging bees and wasps) and including both batesian and mullerian components (maybe, with the
sea hares representing the primary models?). As with its terrestrial
analog, there are other species in the complex that combine the colors
in a less precise manner (such as Stylocheilus longicauda, Dendrodoris krusensternii, Miamira sinuata, Odontoglaja sp. #1 and Lobiger viridis). At least three Hawaiian crab species, the prosobranch Sulcerato sandwichensis, several small fish and the urchin Astropyga radiata (another possible model) may also be involved.
Note 2: The largest of 99 animals from
was only 22 mm in length and the few animals seen in the field weren't
noticeably larger. Also, an 11 mm animal laid eggs while held. This contrasts with 150 to 200 mm for large Bursatella leachii.