Tom Trott Leandro Capurro Sudhanshu Dixit Peter Striplin

Hi Rodrigo,

Thank you for adding these photographs. This animal does not appear to be dorso-ventrally flattened as most nemerteans (mentioned by Leandro) and flatworms mentioned by Sudhanshu) are. For example, check out " New records of ribbon worms (Nemertea) from Ceará, Northeast Brazil" on researchgate. Given you were collecting on a beach, your guess that it may be an echiuran is very possible. My guess of what is the head end may be a very small section of the proboscis while the posterior end could show part of the alimentary canal extruded through injury caused during accidental collection. A wild guess, since that could be the proboscis as Leandro first mentioned.

Normally echiurans (and nemerteans) are infaunal and need to be dug up. Since you were collecting macroalgae on the beach, perhaps sampling required moving a few rocks with holdfasts and this animal was accidentally uncovered. This is a guess, of course. Also, if you have access to AMOR, A. 1971. Echiura del Brasil. Physis 81(3):521-538, that paper might supply a few more clues as to what animal you have collected. Unfortunately, I don't have access to that publication at this time. Knowing the approximate size of this specimen will be very helpful.

My hope is that anyone reading this will realize I am guessing about what this animal might be and take what I have said with "a grain of salt." I am very curious about what this animal is and am eager to read the opinions of others.

--Kind regards to all, Tom

It appears to be a member of Echiuridae family and I agree with Tom Trott . Did you observe the proboscis to extend equal to more than its standard length? If it retracted the proboscis then there is good chance for the specimen to be a sipunculan worm also as echiurans are unable to completely retract their probosces. The presence of setae in echiurans and their absence in sipunculans also confirm their status.

Regards,

Abhishek

Thank you for your answers. I am glad to read your opinions and agree with them. Although I could not see the same thing as Tom regarding the animal's posterior end. To me, this part seems considerably well preserved and the cup-like structure appears more like some kind of attachment sucker rather than an injured part. It's just a terrible guess and pardon me if I am completely wrong. Considering Tom's opinion, is it possible to identify this animal even if it's harmed? Or this possible injury would make the id at species level impossible?

Abhishek Mukherjee That's a great idea. Unfortunetaly, I couldn´t see the animal alive. I didn´t find any setae either, but I am not a taxonomist yet and maybe I will need a better stereo microscope.

I have found lots of nemertean in algae and when they are fixed they have that form, anyway i have seen freshwater nemerteans so i don't know how often it happens in marine nemerteans. One thing you can do is looking at it at the microscope because if it is a nemertean sometimes you can see the ryncocele, that is a cavity exclusive of this phyla. Otherwise it is posible to apreciate others estructures as ocelli or even gonades that are darker than others tissue.

In nemertea ocelli are very small so you have to look for them with a 40x at microscope o a very good magnifying glass.

Hi Rodrigo, all great ideas mentioned by everyone here. Might you please indicate the size of this specimen? Thank you, Tom

It's about 0.5 cm long

HI Rodrigo, Just to rule out other possibilities, have you ever collected insect larvae with your algae samples at this sample site? I often collect insect larvae when sampling certain rocky/sandy intertidal areas. ~Tom

Yes, I have found a few larvae and a couple of adult dipterans, but nothing similar to this animal.

This seems a nemertean to me, the body seems swollen a typical artifact after fixation. This seems an ideal work for the expert Juan Junoy, any idea on the family, genus..?

For exploring the possibility that this is a nermertean, you might also try to ask @Helena Matthews-Cascon at Universidade Federal do Ceará, located in the same region as your sample site. Helena was second author on the paper I recommended. Good luck!

That's a good idea, Tom. I'll see what I can do now. Thank you for your support!

Hi Rodrigo, If you find out what this specimen is or some helpful information for its identification, might you please post it here? I'm very interested in knowing what this organism is. Thank you, Tom

Dear Rodrigo.

I think that is a sipunculan worm,but I´m not sure;so like say Tom you can get the paper of Analia Amor (1971).

The collection journals of Physis are in my ex-laboratory because I´m pensioner,so I send you the mail of boss of that laboratory ([email protected]).You do the contact with Dr.Acuña and told him if it is possible send you the paper of Amor. When you writte to Acuña say him I mentioned to him.

Dr.Analia Amor was my colleague during a long time until she died.

Good luck.

MYSTERY SOLVED (?)

Dear all, according to the specialist Cecili Mendes (University of São Paulo), the animal is a nemertean, indeed. The species is called Evelineus tigrilus, and she also told me about its current taxonomical uncertainty, since this species can be a synonymous of another species belonging to a different genus (Lineus).

I truly appreciate everyone's effort here, specially @Tom Trott's, and I hope we can keep sharing useful information like this inspired by our own curiosity.

Wonderful! Rodrigo. Mystery solved. I'm happy Dr. Mendes was able to help you and perhaps be of help in the future. What a colorful nemertean! All of the Lineids in my part of the world (New England) are milky white or tinged with red or dark green - nothing with pattern like tropical nemerteans have.

It was my great pleasure to participate in such an amicable chain of responses to your original question. Boa sorte, Tom