Hi,

Although some mention there is an homologous of the SCN in fish, there is no clear-cut functional and anatomical evidence for it in my opinion. There are nuclei in the corresponding fish preoptic area  that might function as SCN neurons... Perhaps you could ask to Prof. Jose Antonio Muñoz Cueto, from the university of Cadiz (Spain) who is a specialist of the fish brain anatomy.

Thank you so much Sir.

Hi,

Now I am enjoying my Christmas holidays. As soon as I come back to the lab I will answer you in detail.

Best regards

Jose

Its ok Sir.

Chiqui: Me gustaría que me incluyas en la respuesta!!!!!!

Sir,

Please written in English.

Dear Saurav,

Be careful with stating that the SCN drives circadian rhythms in all vertebrates. In birds, it seems that the SCN might not be that important, while the pineal is more the central pacemaker. Pineal and SCN together probably comprise the circadian pacemaker in birds, but lesion studies in birds (Mike Menakers early work) show that the pineal is essential. Also it is not entirely clear that we can talk about an SCN in bird neuroanatomy. I am mainly a rodent neurobiologist, so the bird people may correct me on this....Therefore, considering the evolutionary phylogeny, I would guess that the pineal is also essential in fish and, if there is an SCN like structure in the fish brain, it might be of lesser importance for circadian rhythms than in mammals/rodents. If you want to find it, I would presume that it also receives massive input by the retina. Because it needs to synchronize with the pineal, I would also expect high density of melatonin receptors. A melatoninreceptor staining (perhaps fluorescent melatonin binding or radioactive iMel binding) combined with an anterograde tracing in the eyes should give you a good indication of the SCN-like structure in fish, perhaps. But, as I said, I am not a fish biologists, so there must be much better knowledge out there....

greetings,

Roelof Hut.

Thank you so much for your valuable suggestion. 

Regards,

Dear Saurav

First, I apologize for the delay in answering. 

Concerning your question, I agree with Jack and Roelof concerning the controversy in the homology of mammalian SCN with fish SCN. In fish, no central pacemaker appears to be present, and pineal and retina seem to represent the main neural structures driving circadian rhythms. However, I do not agree completely with this consideration. I mean that although a master clock as mammalian SCN do not appear to operate in fish, this do not exclude that some central structures from fish brain could represent a clock. The question is if there is a single clock (master clock as SCN from mammals) governing circadian rhythmicity or there is a constellation of coordinated cells masses/structures that might represent a less hierarchical and complex central clock.

In this context, we have identified in the European sea bass (a perciform teleost) a cell mass in the caudal preoptic area that we have named SCN (Cerdá-Reverter, J.M, Zanuy, S. y Muñoz-Cueto, J.A. A cytoarchitectonic study of the brain of a perciform species, the sea bass (Dicentrarchus labrax). II. The diencephalon. Journal of Morphology. 2001. 247: 229-251), which is recipient from retinal projections (Servili and Muñoz Cueto, unpublished) and express melatonin receptors (53. Herrera-Pérez, P., Rendón, M.C., Besseau, L., Sauzet, S., Falcón, J., Muñoz-Cueto, J.A. 2010. Melatonin receptors in the brain of the European sea bass: an in situ hybridization and autoradiographic study. Journal of Comparative Neurology. 518: 3495-3511). Now, we are analyzing if this cells mass expresses clock genes, but it is certainly a candidate to be a part of a central clock (if present in fish!!!).

I attach you both papers, which can help you for recognizing this putative homologue of mammalian SCN. 

Warm regards

Thank you so much.

With regards,

Saurav saha i am also working on on the same field i also tried to find SCN in eel fish (Macrognathus pancalus) but could not locate it i have shown its anatomy and NPY distribution in its fore brain (Paper attached)Regarding cat fish brain you can study the papers of NK subedhar etal.