egg capsule

Mermaids purse

All the different specie in this family have their eggs enclosed in a square leather-like capsule with spines sticking out of each corner known as a Mermaids Purse. The capsule always contains only one egg. Small holes are present on the corners of the capsule to enable the circulation of water through the capsule. The different specie of rays and skates lay their eggs on the bottom at different times of the year. A female thornback ray can lay between 15-20 egg capsules, and one egg capsule can take as long as one day to lay.
  The length of the egg capsule except for the spines varies between the different specie, the thornback ray egg capsules are between 6,3 - 9 cm in length, the common skate 25 cm and the starry ray between 4,2 - 6,6 cm. Egg capsules from the common skate are noticably larger than the other specie that are found in scandinavian waters. The starry rays egg capsule is smaller than the thornback rays, but have longer spines, up to 9 cm. They are keeled along the edges and strewn with small fibres. It is the starry ray egg capsule that is pictured in Aquascope.
  When the eggs hatch, the young break through the wall of the capsule, usually along one of the shorter sides.The young are roughly the same length as the capsule, sometimes a little longer.

A starry or possibly a thornback ray

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Swedish rays and skates


Mermaids purse

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Bo Johannesson | Martin Larsvik | Lars-Ove Loo | Helena Samuelsson