Bamboo Shark Lays Viable Eggs After 45-Month Seclusion From Males

Posted on January 8, 2015

Brownbanded Bamboo Shark pup at the California Academy of Sciences' Steinhart Aquarium

A brownbanded bamboo shark at the California Academy of Sciences aquarium dropped a viable egg case following a 45-month seclusion from males. A healthy pup that emerged from one of the eggs is pictured above. The scientists say this is the longest-ever case of sperm storage in sharks.

Scientists say they were very surprised with the egg case resulted in a healthy pup after the female ways isolated from males for nearly four years. The scientists say it is some potentially good news for wild sharks threatened by overfishing and habitat loss.

Dr. Luiz Rocha, Academy Curator of Ichthyology, says in a statement, "Long-term sperm storage--where a female can delay fertilization for months or even years after mating--is a remarkable adaptation that helps promote genetic diversity. In contrast, asexual reproduction produces offspring with very little genetic variation. Exploring the bamboo shark's ability to store sperm gives us hope that wild sharks can help protect their population's genetic diversity when mates are scarce and serious threats arise."

The researchers say many sharks are known to produce unfertilized eggs. A curious biologist decided to test egg cases found in the aquarium's Shark Lagoon exhibit. They transferred several brownish egg cases to an incubator and two of the eggs showed signs of development. One of the eggs did not hatch while the other produced the healthy shark pup pictured above. The scientists say some female sharks can store sperm in the tubules near their oviduct. Long-term sperm storage has also been observed in other animals, including marsupials, insects, and frogs.

A research paper on the long-term storage in the brownbanded bamboo shark was published here in the Journal of Fish Biology.

Photo: California Academy of Sciences