Black/Brown Dot on the Stomach of Stingrays?

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I have to weigh in on the other side of the fence on this one. I do not think the pigmentation that some rays exhibit on the bellies have anything to do with the yolk sac. Not all rays have them, but all rays have yolk sacs. The location of the belly spot also is not always in the same location and the yolk sac remnant on every pup I have ever seen is in the same place. You might expect some type of scar- which we do not see- but not a dark pigmented spot. Also, you do not see any type of yolk sac scarring on any other rays or sharks to the best of my knowledge, not to mention reptiles that also are nourished through a yolk sac.

I think it is just pigment. Rays have spots on the top of their discs, why can't they on the underside.
 
amazongirl;1425844; said:
I have to weigh in on the other side of the fence on this one. I do not think the pigmentation that some rays exhibit on the bellies have anything to do with the yolk sac. Not all rays have them, but all rays have yolk sacs. The location of the belly spot also is not always in the same location and the yolk sac remnant on every pup I have ever seen is in the same place. You might expect some type of scar- which we do not see- but not a dark pigmented spot. Also, you do not see any type of yolk sac scarring on any other rays or sharks to the best of my knowledge, not to mention reptiles that also are nourished through a yolk sac.

I think it is just pigment. Rays have spots on the top of their discs, why can't they on the underside.
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I agree with all of that.. more great info. I have seen many differentiated underside patterns in rays as well..

Do you think that this pigmentation has any practical purpose beyond just being a dot? Breeding distinctions? Genetics? Collection zones?

Just curious of opinions..
 
Miles;1427748; said:
I agree with all of that.. more great info. I have seen many differentiated underside patterns in rays as well..

Do you think that this pigmentation has any practical purpose beyond just being a dot? Breeding distinctions? Genetics? Collection zones?

Just curious of opinions..
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Who know's why it is there. It hardly seems like it could be useful since they spend most of their time on the bottom, but to occur a trait really just needs to not be detrimental. Why do people have birthmarks? There has got to be a lot of genetic variation for pattern.
 
I noticed that when my pup was born, she had the remnants of a yolk sac. It was about 5 mm long, and the diameter of a large pencil lead. At that time, there was no dark mark on her belly. The sac was absorbed after about a week. She now has a typical dark spot on her belly where the sac was located.
 
Can you say..

"Birth Mark"..

????

Maybe like a belly button.. some have innies and some have outties..
 
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