Fast Facts: The Recent Progression of Shark Artificial Insemination
LONG BEACH— The Aquarium of the Pacific in Long Beach has shown a progression in science with its research on the artificial insemination of sharks. The Aquarium of the Pacific’s Veterinarian, Dr. Lance Adams, was the lead author of a new paper published in the journal Frontiers in Marine Science. The paper, Artificial Insemination and Parthenogenesis in the Zebra Shark Stegostoma tigrinum, describes a study of artificial insemination of zebra sharks to reproduce this species at an aquarium.
The new paper detailed the methods used in the study and animal care, genetics, efficacy of artificial insemination, and other affiliated variables. Among a population of zebra sharks consisting of three females and one male, reproduction failed despite the constant male presence with two of the females. To determine if assisted techniques could be used to recover sexual reproduction, artificial insemination was performed on a single female twice over three years using freshly collected samples. In addition, hatching success for eggs laid by all three females was monitored to compare natural and artificial insemination modes.
Some things have changed in the procedure as the Aquarium has gained more experience through the artificial insemination trials, and there are still many questions and variables to explore. Still, so far, the insemination steps are largely the same.
According to the Director of Public Relations for the Aquarium of the Pacific, Marilyn Padilla, different sample collection methods have been explored, the evaluation of the semen for quality has improved, and the Aquarium has learned about the storage limits of refrigerated samples and improved shipping methods. Most importantly, the Aquarium is trying to figure out how to determine when the most appropriate time is to inseminate the females during the reproductive cycle to be the most successful.
According to Padilla, the Aquarium of the Pacific is believed to be the first Aquarium to perform a successful shark artificial insemination in the United States, which took place in 2009. The outcomes from this research could also be used to help recover endangered sharks in the wild. Dr. Adams began looking into artificial insemination to breed sharks in the early 2000s when the Aquarium opened its Shark Lagoon site. Successfully breeding sharks using artificial insemination would help make reproducing sharks safer in an aquarium setting, eliminate the need to transport male and female sharks to the same location, and help create a self-sustaining aquarium population.
During the study, the Aquarium compared artificial insemination with natural reproduction by housing a male zebra shark with two reproductively active females, but no sexually produced offspring resulted. As a result of the study’s two artificial insemination procedures, the Aquarium became the first to successfully reproduce zebra sharks via artificial insemination when the facility’s female Fern laid fertile eggs that hatched in 2014. This was also the first successful reproduction of a large shark species through artificial insemination.
“Like all veterinary procedures conducted at the Aquarium, shark artificial insemination is performed in accordance with the Aquarium’s animal welfare policy to ensure the health, safety, wellbeing, and humane treatment of the animal,” said Padilla. “First, the Aquarium’s shark aquarists help guide the shark into a stretcher using a process the animal is trained to do through positive reinforcement. Once in the stretcher, the aquarists roll the shark into a belly-up position that induces tonic immobility, a relaxed state in which the shark’s muscles relax, and heart rate slows naturally. Dr. Adams performs an ultrasound to see if there are any eggs present in the shark’s oviducts, which would indicate whether the shark is ovulating and if it is a good time for a successful insemination. Next, he inserts a speculum into the shark’s cloaca, draws the semen sample into a catheter, and deposits the sample. The shark is then rolled back over and released from the stretcher and swims out.”
Two offspring resulted from this action, one of which still lives at the Aquarium in the Tropical Reef Habitat. This female, Gatsby, is now partaking in additional artificial insemination studies as a reproductive adult. The other shark was relocated to another Association of Zoos and Aquariums institution as part of the Species Survival Plan for zebra sharks.
The results of this study are now available to other zoo and aquarium professionals and scientists, allowing them to replicate Dr. Adams’ approaches and produce further data about artificial shark insemination. This is a growing area of interest in the industry and can help stimulate shark conservation. Dr. Adams continues studying artificial insemination with zebra sharks and other shark and ray species at the Aquarium.
This study specifically focused on egg-laying sharks. However, successful artificial insemination has been previously reported in other marine animals such as bottlenose dolphins, white sided dolphins, orcas, and penguins and has been attempted in polar bears and walrus. In addition, artificial or induced spawning has been performed for some marine fish and invertebrate species.
In aquarium populations, female zebra sharks can lay approximately 150-300 eggs per year. Even if they have not been mated before, most eggs do not mature or survive until hatching. In this study, two eggs laid after one insemination procedure made it to hatching and were genetically confirmed to be from artificial insemination. As the sharks mature and grow, they may remain at the Aquarium of the Pacific or be transferred to another AZA-accredited zoo or Aquarium.
Zebra sharks are listed as endangered by the International Union for Conservation of Nature’s Red List of Threatened Species.
With further evolution, artificial insemination could represent an effective tool that could be used for maintaining genetic diversity for animals housed in aquaria and conservation-based breeding programs for elasmobranchs.