I think that they are spawning masses of nudibranchs, but I don't know what species.

I think you meant Siphonaria (Heterosiphonaria) maura Sowerby, 1835. I am not familiar with a Fissurella maura from the Panamic Province. It has been a while since I work with marine species, but what you show looks like a Siphonaria (pulmonate), not a Fissurella (a much more primitive group). Very good picture but there is no scale and you don't give a size.

They look more like Siphonaria (H.) gigas Sowerby, 1825 than to S. maura. S. maura usually doesn't have as pronounced ribs (but they all are very variable!) and reach only around ~20-25 mm in length. S. gigas usually has the strong ribs as in the picture, and do reach 50-60 mm in length. 

thanks for answers, it was my mistake, it's Siphonaria maura, not fisurella. But I'm asking about the ones around Siphonaria.

I'll correct that detail

Hola Damián:

Aquí en España se encuentran puestas similares y por la forma son de algún nudibranquio supongo que de la familia Dorididae. No conozco las especies que hay en Ecuador, por lo tanto, no puedo darte más detalles. Te sugiero que contactes con Ángel Valdés, compatriota mío que está dando clases en la Universidad de Pomona (California, USA) y gran especialista en nudibranquios, que quizás pueda darte alguna indicación más.

Muchas gracias por su ayuda, la especie de nudibranquio que hemos encontrado en la zona es dolabrifera dolabrifera, ahora procederse a revisar literatura y consultar con el profesor Valdés.

Hi Damián,

They are spawing mases of nudibranchs. If difficult to know the species but you can infer that with yours observations in the field.  

Best regards,

Hi Damian,

I would take a closer look to the spawning masses. Those of Siphonaria are usually much less organized in extreme south-Atlantic species. They are just like a cloud of eggs in a jelly matrix. However S. gigas masses from the northern hemisphere look much alike.

Hello Sir,

They are spawing mases of pulmonate like Siphonaria. I have similar samples collected from Saurashtra Coastline (INDIA).

Regards,

Bhavik