Opisthobranch of the Week Data
Halgerda willeyi is a relatively large discodorid, considered uncommon on Okinawa; thirteen individuals have been collected since the first Okinawan specimen was collected on the sixteenth of October, 1984. H. willeyi is one of thirty-five described species of Halgerda, all found within the Indo-Pacific (Fahey & Gosliner, 2001). As of mid-October, 2001, eleven of the thirty-five described species are found in Okinawan waters (H. diaphana and H. onna are unique to the Ryukyu Archipelago*). As of early June, 2016, fourteen described species of Halgerda have been featured on these pages from Okinawa's main island and the Keramas. These fourteen species are:
H. albocristata H. batangas H. brunneomaculata H. carlsoni H. dalanghita H. diaphana H. elegans H. malesso H. okinawa H. onna H. paliensis H. tessellata H. wasinensis H. willeyi - The featured animal above
The above featured animal was found crawling on the upper surface of coral rubble in an area of mixed sand and strewn coral rubble during a mid-morning SCUBA dive. I've not found H. willeyi in association with any prey species; Marshall & Willan (1999) suggest that it probably feeds on siliceous sponges. I've included three additional images, illustrating some of the variation seen in the Okinawan material.
* Okinawa is the largest of approximately seventy-two islands making up the Ryukyu Archipelago which stretches for 600km.