on food sponge
Aldisa pikokai Bertsch & Johnson, 1982
|Maximum size: about 24 mm.|
orange-red dorid with red gills frosted with white. There are three
crater-like depressions on the notum. The notum is decorated with white
flecks that often form patches flanking the gills and rhinophores. In
young animals, the notum is papillate but in older animals it develops a
network of low, irregular ridges that appear more prominent if the animal is
"flattened out." Papillae in older animals are not limited to the
junctions of the ridges (particularly toward the margins of the notum).
The bottoms of the pits between the ridges are not reticulated with
lighter pigment. It may be distinguished from Aldisa sp. #2 by its low ridges, its less dense white pigment and its lack of reticulated pigment in the pits between the ridges. It may be
distinguished from Aldisa sp. #1 by the presence
of three crater-like depressions on its mid-notum (in contrast to two
in the latter species).
Aldisa pikokai is
a moderately common nocturnal dorid found under rocks at moderately
highly exposed rocky sites. It may occur at depths of 1-24 m (3-80 ft) but photos confirm a minimum range of 4-6 m (13-20 ft).
Scott Johnson reports
it apparently feeding on an orange-red encrusting sponge and we've found it in association with similar sponges in the field. (Note 1)
Big Island, Maui, Oahu and French Frigate Shoals: (Note 2)
Taxonomic notes: This species is listed as Aldisa sp. in Bertsch and Johnson, 1981 (bottom photo). Aldisa sp. #2 was probably lumped with this species in the original description and it's possible that examination of the holotype of A. pikokai will ultimately result in assigning that name to Aldisa
sp. #2, instead. We've opted to provisionally use the name for
this form since it's the one shown in the A. pikokai photo in
Johnson, 1982 (Fig. 6) and the one attributed to the type location in
Bertch & Johnson, 1981. It may have been first reported from Hawaii
& Johnson, 1981.
Photo: CP: about 24 mm: Kapalua Bay, Maui; May 31, 2016.
Observations and comments:
1: Based on available photos,
the sponges associated with this species appear to be lighter in color with
more prominent oscules than the sponges associated with Aldisa sp. #2 (perhaps, indicating niche partitioning based on food species?).
Note 2: Both Aldisa pikokai and Aldisa sp. #2 probably represent widespread Indo-Pacific lineages that tend to mimic each
other in any particular region. Conceivably, both may be composed of
multiple allopatric species. However, determining whether the Hawaiian population of A. pikokai is endemic or also occurs elsewhere will require more work.