419 Dive Log Australasia AUGUST 2026

therefore an active process while fluorescence is a passive consequence. However, just to add a little confusion, some animals use bioluminescence to excite fluorescence. NUDIBRANCH BIOLUMINESCENCE Not too many nudibranchs are known to display bioluminescence but some species of dorid - Plocamopherus and Kaloplocamus of the Triophinae subfamily (Polyceridae family) possess the capacity. The dorid nudibranch species known to emit bioluminescence include: Plocamopherus imperialis, Plocamopherus ceylonicus, Plocamopherus maderae, Plocamopherus tilesii and Kaloplocamus ramosus. This is not to say there are not others of the genera with the capability. Bioluminescence is mostly only observed when elucidated through stimulation whilst in captivity. Observation and recording in the wild due to natural stimulation would be most difficult, if not impossible. It is possible though that all of the Plocamopherus species may possess the

capability because a common and unique feature to that genus is the possession of one or more pair (up to three pair) of distinct globular knobs terminally situated on large lateral papillae. In those species that are known to emit bioluminescence it emanates from those knobs so it is not too great a leap to assume that it may be produced by all species possessing them. Plocamopherus bioluminescence is derived from columnar cell secretions performing the luciferin-luciferase reaction making it extra-cellular bioluminescence. The body wall and smaller papillae can also emit flashes of light but this is of a much lower intensity than that emitted by those globular knobs situated terminally on the largest papillae. Species of Kaloplocamus lack distinctive globes and instead emit the bioluminescence from cells in the lateral body wall, head region and also the tail crest. Kaloplocamus bioluminescence is known to be an intracellular process.

Follow clockwise from upper left: A sequence of images of the cryptobranch dorid Diversidoris sp . showing the progression of gill retraction from fully deployed to eventual full retraction into a pocket beneath the mantle surface for protection. DIVE LOG Australasia #419 August’26 49 www.divelog.net.au