Nudibranch Similarities
Ceratosoma trilobatum group
Ceratosoma gracillimum can be distinguished externally by the complete absence of the mantle edge between the head and the well-developed lateral lobes on each side.
Ceratosoma trilobatum has the mantle edge, edged in purple, between the head and the lateral lobes. Both species have a similar range of colour variations, as does Ceratosoma tenue, but they differ from each other externally by the lack of a mantle edge in Ceratosoma gracillimum and the extra pair of small lateral lobes in Ceratosoma tenue.
Chromodoris annae group
Author: Nila Murti
Both have elongated bodyform, both have yellowish or orange-ish gills and rhinophones, both have similar mantle colouration and colour variation - pale to bright blue in the middle with black elongated lines bordering the blue area, and faded to bright orange mantle margin.
Chromodoris elisabethina normally has more elongated black lines in the blue area, sometimes a median line, often some broken shorter lines.
Chromodoris annae usually has no or less black lines, but some have been found to have multi black lines like Chromodoris elisabethina.
So what's the telltale difference? Apparently it's the uniformity of the blue colour. If it's smooth and uniformly coloured then it's Chromodoris elisabethina, while if the blue area has tiny dark speckles hence not uniform (zoom your photos to see it!) then it's Chromodoris annae.
Chromodoris coi group
Chromodoris kuniei group
Author: Nila Murti
Both Chromodoris geminus and Chromodoris kuniei have oval body form and wide mantle overlap. Both have purplish or brownish mantle with dark round spots with white haloes in the mantle.
The difference between the two is in Chromodoris kuniei the mantle edge is broad with purple colour followed by a narrow dark ring and an uneven yellow in the innermost band.
In Chromodoris geminus the mantle border consists of four different coloured rings – an outermost white, then faded purple, followed by another white and finally yellow.
Chromodoris lochi group
Author: Nila Murti
With their strikingly similar colours and patterns, it is quite tricky to distinguish Chromodoris willani, Chromodoris lochi, Chromodoris dianae and Chromodoris boucheti. Chromodoris willani is easier to differentiate from the other three.
Apparently Chromodoris lochi and Chromodoris dianae have different number and shape of gills but this isn't always easy to notice by laymen. The 'easier' external characteristic differences to spot are as follows:
Chromodoris willani has translucent translucent rhinophores and gills, with tiny white dots on them.
Chromodoris boucheti has yellow tipped rhinophores, but with a special pattern in the yellow tipped gills: there is a vertical black line in the middle of each gill running from the base up. The mantle of Chromodoris boucheti is uniformly colored and smooth looking, without any white specks.
Chromodoris lochi has a rather elongated body of the Hypselodoris genus. It has pink or yellow tinted rhinophores and gills which are sometimes translucent (but with no white dots like in Chromodoris willani). The mantle of Chromodoris lochi is uniformly colored and smooth looking, without any white specks. Its dark/black elongate band in the mantle is thin and unbroken.
Chromodoris dianae also has pale blue based gills and rhinophores, with orange yellow or deep yellow tips, but has more of an oval body form of true Chromodoris genus. Its mantle has white specks or dots hence not smooth looking. The black band in Chromodoris dianae are thicker and discontinuous, especially around the rhinophores.
