Ophiactis is correct but they are definitely not similar to savignyi in any way. They are pentamerous and the radial shields are small. I cannot identify the species but O. balli shouldn't occur in India if that is where you collected it. There seems to be a wide, axe-shaped oral papilla. Possible species include definita and perplexa (which may be synonyms) but there are several species in the Indo-Pacific that I haven't examined. Hope this helps a little.

I would only suggest Ophiactis sp.

 Thank you sir. I welcome further suggestions..

Hello,

This ofiurideos are very similar to those belonging to the species Ophiactis savignyi (Müller & Troschel, 1842). However, it is not possible to be sure that through photography is here. I advise you to identify how

Ophiactis sp. as said the colleague in the previous message, Dmitry Telnov!

try someone at the California academy of Sciences.  they might be able to help.

Ophiactis is correct but they are definitely not similar to savignyi in any way. They are pentamerous and the radial shields are small. I cannot identify the species but O. balli shouldn't occur in India if that is where you collected it. There seems to be a wide, axe-shaped oral papilla. Possible species include definita and perplexa (which may be synonyms) but there are several species in the Indo-Pacific that I haven't examined. Hope this helps a little.

Forward your pictures to Jennifer Olbers at olbersj@ukznwildlife. She is not on Researchgate but is our local ophiuroid specialist

Thank you so much for helping me. Lately I understood that, specimens in the photographs might be a juvenile of adult Ophiactis sp. Would pigmentation/ other dorsal scale development cause identification?. Because, the doubtful specimen had black dots at the base of each radial shield.

Difficult to say without a sizing scale. It is quite well developed. Pigmentation is sometimes reliable, in many species it is not. I recommend that you read the original descriptions of O. definita, flexuosa, perplexa, perhaps picteti and some others. I'm not sure exactly which ones are hexamerous in India but there are savignyi, plana, lymani, macrolepidota, profundi, brachyura, modesta. This is not one of those and it is also not abyssicola or balli. You can find a complete list of valid species and references in WoRMS http://www.marinespecies.org/ophiuroidea/index.php

Usha, conferta and maculosa are synonyms of savignyi. This specimen has only 5 arms and its radial shields are too small for savignyi. quadrispina is not documented from the Indian Ocean or Indo-Pacific. modesta is six-armed as I said above.

Sorry I did not give further details in my previous answer. Obviously I should have added the detail O. savigny to compare the differences.

Regards,

Thank you all for better suggestions. As Dr. Sabin Stoehr suggestion, I have gone through the definitions given for O. definita but I guess, this specimen may not be O. definita because it has different dorsal interradius as well as minimal scale patterns between CPS and RC. For better clarification, I will attach some more closer view of dorsal and ventral disc. This specimen was associated with the Gastropod egg mass taken from Chennai coast, Bay of Bengal.

These 6 (Ophiactis brachyura, O. definita, O. delagoa, O. macrolepidota,O. modesta, O. picteti and O. savignyi) are the valid species reported from Indian waters. I have verified my specimens with these 6 but non are matching. Again as per Dr. Sabin's suggestion, I will follow the other species for better clarification.

I still suspect that it is a small/young O. definita/flexuosa. I can see the axe-shaped oral papilla on your images. I don't know the acronyms CPS and RC. What is the disc diameter of your specimen? definita grows to about 7-8 mm dd.

That was typographical error. The acronyms are Central primary plate and Radial shield. The dd of given specimen is 3.5mm. Again I will check with O. flexuosa and O. definita. Thank you mam.

Hello mam.. I again rechecked the characters with O. definita and O. flexuosa. The specimen has affinities with O. definita than the O. flexuosa. But still it has some controversial key characters as described for O. definita. e.g No disc spine; presence of imbricated scales in O. definita but the present specimen has all these.

Will environmental conditions/ geographial areas cause this kind of variation in same species? or is this other species? Should I go for any molecular work further?

Suggestion please.

Hi Chami

These animals are a real mess. I suspect there are a lot of cryptic species. If it were six-armed I would have said it was O. macrolepidota. But you do get rare five armed specimens of species with six-arms. The dorsal arm plates don't quite look like O. modesta unless yours is just a juvenile. I would think it is not O. definita or perplexa. These are deep water species (below 200 m) and yours looks too colourful to be that deep. Sorry to be not more exact. These questions will only be sorted out using DNA. 

Tim

Thank you Timothy sir. I have collected some juveniles of that same species but all are having 5 arms none is with 6. I hope molecular analysis is the only way to identify the exact species.