Dear Wilhelm,
I have no personal experience of these species so I am relying on what I can find in publications. As you suggest, at first sight it looks like Janolus capensis, but it could be a colour form of Bonisa nakaza. One major external difference between the two is that Janolus has a large wrinkled ridge (caruncle) between the rhinophores while in Bonisa it is much less prominent. In your photo [see lower right enlargement] there is no sign of the caruncle which I would expect to see even though it is partially obscured. The other major difference is that in Janolus, there is a digestive gland duct in each ceras, while this is absent in Bonisa. I think the reddish-brown colour in the base of the cerata in your photo is the colour of the body fluids rather than an indication of a digestive gland duct. If you look at your separate photo of Janolus capensis [message #14114] you will see the similarly coloured branch of the digestive gland is much narrower, not filling all the space in the ceras. I suspect therefore that your animal is most probably a form of Bonisa nakaza. I would appreciate a comment from Terry Gosliner.

In Terry Gosliner's publication on these animals he identifies the food bryozoans of both these species. Janolus capensis is reported to feed on Menipea triseriata and Onchoporella buskii and Bonisa on Tubucellaria levinseni. I therefore sent your photos to Dennis Gordon, a bryozoologist in New Zealand to see if he could identify the bryozoans, and he sent them on to Wayne Florence, an expert in Sth Africa, who has identified the bryozoan in the photo alongside as a soon to be named new species of Thalamoporella. So when we confirm this animal's identification we have a possible new food identification as well. As I will mention in your separate message [#14113], the typical Bonisa nakaza is on another species of bryozoan.
Best wishes,
Bill Rudman

Dear Wilhelm,
Thanks for these. You will se in the close-up of the cerata that there is no digestive gland duct visible in the cerata. This is how the cerata look in your mystery animal [#14092] suggesting it is also Bonisa. As seen in your other message [#14114], the digestive gland ducts are very obvious in Janolus.

It would be interesting to know whether the white line on the 'tail' is always present in this species and absent in Janolus capensis. It might turn out to be a useful distinguishing feature in the field. As I mentioned elsewhere [#14092], Wayne Florence has identified the bryozoan in your photo as Gigantopora polymorpha.
Best wishes,
Bill Rudman

Dear Sakkie,
Both the animals in the top photo are Bonisa nakasa and those in the bottom one Janolus capensis. I understand that B. nakasa is quite variable in colour but you'll note that in Janolus capensis the white pigment on the cerata covers most of the outer side and only the tip of the inner side while in Bonisa nakasa, the white, if present, only occurs at the tip. More importantly, Janolus has a large inter-rhinophoral crest [caruncle] as you can see in an earlier photo [#11177] and there is no sign of it in the paler animal.

It is also unlikely that you will find them together because they feed on different bryozoans. It is of course possible that you might have a mixed growth of bryozoans, but on the balance of probabilities I think they are both Bonisa. Concerning the lower photo - as you subtly suggest, the upper two animals are mating.

Best wishes
Bill Rudman

Dear Rudolph,
Certainly the lower photo looks like the animal in one of your earlier messages which I identified as Bonisa nakasa. The upper two photos are more problematic. They could be the same species, or they may be Janolus capensis. Unfortunately I can't see enough detail to be sure. Species of Bonisa differ from Janolus in lacking a branch of the digestive gland up into the cerata on their backs. In colour the lower photo is of Bonisa, but the other two photos could be either, and I can't see clearly through the ceratal wall to determine whether there is any digestive gland htere or not.
Best wishes,
Bill Rudman

Dear Rudolph,
In your other message I said we all learn from the identification process and this is a good example. Your other photos were of the yellow and blue form of Bonisa nakaza. I think this photo is also of Bonisa nakaza but a colour form which lacks the blue pigment and has the yellow restricted to the ceratal tips. I have never seen this colour form so I will be interested in having it confirmed by Terry Gosliner, who named this species.
Best wishes,
Bill Rudman

Dear Rudolph,
These photos are both of Bonisa nakaza, a beautiful species known only from the Cape Region of South Africa. Like all zephyrinid nudibranchs, it feeds on colonial bryozoans.

Concerning difficulties in identifying species on the Forum. I am in the process of adding a couple of keys to the Forum which should help. One will be a simple database query system where you will be able to ask for all the nudibranchs on the Forum with red spots, or all the chromodorids with yellow spots, and you will be rewarded with a page of thumbnail photos to choose from or browse. The other resource will be an interactive 'key' which hopefully will enable you to identify your mystery to any level from species to order.

However, one point of the Forum is to share finds and problems, so I think we would lose if the Forum to become a total 'self-service' identification centre, because we would lose all the new and interesting records that are at present posted for all to share. So don't hesitate to send in your queries - we all learn from the experience.
Best wishes,
Bill Rudman

Thanks Valda,
Concerning its name. In Terry Gosliner's description he writes:
Bonisa = ".. is named for my wife Bonnie Isabel ...."
nakaza = ".. is a Zulu word meaning 'to adorn with beautiful colours', and the name is based on the bright coloration typical of this species."

Best wishes,
Bill Rudman

Dear Erwin,
This is another zephyrinid, Bonisa nakaza. Species of Bonisa differ from species of Janolus in not having branches of the digestive gland extending into the cerata.
Best wishes,
Bill Rudman