Nudibranch Similarities

Risbecia tryoni group

Author: Nila Murti

Risbecia tryoni has somewhat longish body form compared to Chromodoris leopardus which is more oval like. It also has a reduced mantle overlap, while Chromodoris leopardus has a wide mantle overlap. Both have very narrow purple colour band at the mantle edge. However in Chromodoris leopardus there is a second, broader white border immediately inside.

Perhaps the clearest difference is in the markings on the purplish or brownish mantle; Risbecia tryoni has dark round spots encircled by whites, while in Chromodoris leopardus the white-haloed markings are hollow rings, like in its namesake, the leopard.

Risbecia tryoni from Taka Bonerate, Indonesia
(467 photos)

Tambja affinis group

Author: Dr. Richard C. Willan

Roboastra luteolineata: Feeds voraciously on other nudibranchs; has very large oral tentacles; two pale stripes on the head between the rhinophores, neither of them expanded; no colour band around the rhinophoral sheath.

Tambja affinis or Tambja victoriae: Feeds on bryozoans; has relatively small oral tentacles; one pale stripe on the middle of the head between the rhinophores that is expanded; pale colour band around rhinophoral sheath.

Since they are so similarly coloured overall, perhaps some mimicry is going on.

The ways to separate Tambja affinis, Tambja victoriae and other Tambja species are set out nicely and clearly on Tambja affinis colour group in the Sea Slug Forum

Tambja affinis from Koh Tachai, Thailand
(32 photos)
Tambja gabrielae from Bali, IndonesiaIdentification reviewed by Richard Willan
(66 photos)
Tambja olivaria from Phuket, ThailandIdentification reviewed by Richard Willan
(12 photos)
Tambja victoriae from Queensland, AustraliaIdentification reviewed by Richard Willan
(4 photos)

Thorunna furtiva group

Thorunna daniellae from Bali, Indonesia
(53 photos)
Thorunna furtiva from Piti Channel, Guam
(51 photos)

Triopha maculata group

Rostanga pulchra from California, USAIdentification reviewed by Gary McDonald
(14 photos)
Triopha maculata from California, USAIdentification reviewed by Gary McDonald
(18 photos)

Tritoniopsis elegans group

Author: Dr. Richard Willan

At the present time Tritoniopsis elegans is known from the Red Sea and eastern coast of Africa. It is closely related to Tritoniopsis alba from the tropical western Pacific Ocean. In fact, some people have speculated they may be the same species, in which case the name would have to be Tritoniopsis elegans because it is older. However, until a comparative anatomical study, possibly reinforced with molecular data, has been undertaken and published it is advisable to consider them as separate species.

Tritoniopsis alba from Lailai Rock Fishing Area, Taiwan
(25 photos)