Black/Brown Dot on the Stomach of Stingrays?

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I dont think rays have umbillical cords as it is placental mammilian trait. Like other live bearing eslambranchs I assume FW rays will have the yolk sack in untero and pretty much be free 'swimming' in the female organ that I guess one could consider a uterus though Im not sure if it is called that.

Has anyone seen video of the tiger shark pups in-utero 'swimming' around and eating each other? That is what I envision minus the cannabilisim rays are like.
 
maybe diffrent rays are born diffrent but i dont think so

just take a look at the p14 giveing birth on franks site the exact same as mine no yolk sack their :confused:
 
Yolk saks could be absorbed by the mother I would think possibly just prior to birth or just after. And even in a sak they would still have something attatching them to their nutritional source.
 
Hi,

some info on the development of Potamotrygon embryos (this is from the website of K. Birkett):

"The embryos obtain nourishment from their yolk sacs early in their development. During the later stages of pregnancy, small, filamentous appendages called trophonemata develop within the uterus and penetrate the spiracle of the embryo (Nikolskii, 1961), supplying it with a nutrient-rich fluid called histotrophe that feeds it until it is born (Charvet-Almeida et al., 2005)."

Sometimes the pups are born with a small rest of the yolk sac, sometimes the yolk sac is absorbed. And the dark marking in the center of the belly is exact where the yolk sac is located. But I don't know why some rays have this dark marking while others have none. This is a mystery to me too.
 
rayman;1423379; said:
Hi,

some info on the development of Potamotrygon embryos (this is from the website of K. Birkett):

"The embryos obtain nourishment from their yolk sacs early in their development. During the later stages of pregnancy, small, filamentous appendages called trophonemata develop within the uterus and penetrate the spiracle of the embryo (Nikolskii, 1961), supplying it with a nutrient-rich fluid called histotrophe that feeds it until it is born (Charvet-Almeida et al., 2005)."

Sometimes the pups are born with a small rest of the yolk sac, sometimes the yolk sac is absorbed. And the dark marking in the center of the belly is exact where the yolk sac is located. But I don't know why some rays have this dark marking while others have none. This is a mystery to me too.
Click to expand...

Ah thank you! I was just about to read thoroughly through that article by Charvet-Almeida.. great info!
 
learn somthing new every day :D
 
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