Je vote pour Halgerda willeyi, une espèce très variable.
Gosliner & Fahey (1998) considèrent que H. elegans n'a pas de traits foncés dans la partie médiane. Mais un débat existe sur ce point.
J'ai repris la publication de 2003, si vous arrivez à lire en anglais, vous verrez facilement la différence entre ces 2 espèces :"There are also some external similarities between H. willeyi and H. elegans (see Fig. 7C [from Okinawa
SlugSite and SeaSlug Forum; photo by B. Picton, SeaSlug Forum, March 8, 2000]); both species have dark lines perpendicular to the mantle edge and yellow-orange lines along the ridge crests.
However, the dark marginal lines of H. elegans do not extend to as large a degree from the mantle edge throughout the dorsum and into the ridge concavities as they do with H. willeyi. The dark lines on specimens of H. willeyi are much more numerous, with complex patterns that merge and inter-weave with the yellow or orange lines all over the dorsum. The yellow ridge crests are the most notable feature of H. elegans whereas it is the dark lines with the orange or yellow ridges that are most notable on specimens of H. willeyi.
The gill in these two species is quite different as well. In H. elegans, it is sparse, irregularly pinnate and has dark coloration encircling the top half of each of the leaves; in H. willeyi, is quite bushy, feathered and has a dark line extending the length of each of the leaves.
The rhinophores of the two species also differ in coloration. Those of H. willeyi have dark stripes, those of H. elegans have black subapical coloration. "
Redescription of Halgerda graphica Basedow and Hedley, 1905, with Observations on External Morphological Variation within Selected Species of Halgerda (Mollusca: Nudibranchia). Shireen J. Fahey and Terrence M. Gosliner, 2003.
Bref, tout correspond à H. willeyi...
Pour répondre à Cédric, H. elegans est davantage "Pacifique" que "Indo", mais les animaux se déplacent, naturellement ou aidé par l'homme, et tout est possible.