Opisthobranch of the Week Data
The above featured animal, Janolus savinkini, originally appeared in these pages as Janolus sp. 3. The original unknown has now been described as Janolus savinkini by Martynov & Korshunova, 2012. J. savinkini is considered very rare on Okinawa; I've collected a total of three individuals, and all three were simultaneously taken within 20cm of each other. They were found on a 2m vertical hydroid-covered spar, located in open sand approximately 30m from the pier itself. The blue and purple tipped cerata made the initial discovered individual stand out, even among the dense stand of hydroids. I bagged the animal and proceeded to fan by hand the same general area, which resulted in two additional specimens being washed into view from the hydroids. I've added a second page with images of the two additional specimens, collected from the same general area as the featured animal. Other than size, all three of the animals are identical in external appearance. The animal depicted above was deposited as CASIZ * 105312.
Jim Black has several excellent images of Janolus savinkini from Indonesia and the Philippines posted on Mike Miller's Slug Site.
The following description involving the external morphology and coloration of Janolus savinkini are taken from Martynov & Korshunova (2012):
The body is densely covered with numerous large spindle-shaped smooth papillae, often attenuated towards at the top. There are no less than 100 papillae in an adult specimen. Late juvenile specimens have different appearance, including considerably fewer papillae (ca. 30-40). The notum is completely reduced. The digestive gland is strongly branched and penetrates papillae, where it forms a broad basal thickening and several narrow branches spread inside each papilla towards the top. The head is small, bears two short but distinct oral tentacles. Rhinophores are grouped together and bear oblique lamellae. The caruncle (inter-rhinophoral crest) is well defined, comprises of finely branched folds. Up to 20 rhinophoral lamellae are present in an adult specimens and 10-15 in juveniles. Foot is rounded, anteriorly without corners, but strongly bilobed. Anus is placed posteriorly on the right of the dorsal side.
The ground color is creamy, yellow with a light orange hue. The papillae have the same color throughout most of their length, but apically they are cover[sic] with a broad purplish ring and bright, opaque blue apical spot. The rhinophores have similar color pattern to the papillae.
In addition to the above featured animal I've previously featured Janolus toyamensis & J. mirabilis as well as seven unknown Janolus species on these pages. These featured animals are:
*CASIZ: California Academy of Sciences Department of Invertebrate Zoology
J. mirabilis J. savinkini (the above featured animal) J. toyamensis J. sp. 1 J. sp. 2 J. sp. 4 J. sp. 5 J. sp. 6 J. sp. 7 J. sp. 8