With Mother’s Day quickly approaching, it’s a great time to show your appreciation for the wonderful women in your life—as well as the plentiful moms of the Bay’s ecosystems.
Swell shark’s egg cases are rubbery in consistency and have wiry tendrils attached to the ends designed to look like kelp in order to stay camouflaged from hungry predators. Photo courtesy of Aquarium of the Bay
By Mallory Johnson
Published: May, 2013
With Mother’s Day quickly approaching, it’s a great time to show your appreciation for the wonderful women in your life—as well as the plentiful moms of the Bay’s ecosystems.
At Aquarium of the Bay, biologists and educators are also taking a closer look at the relationships between moms of the Bay and their offspring, because the San Francisco Bay-Delta Estuary is a nursery and is home to many water-dwelling moms. It provides an important habitat in the life cycle of many animals because it is sheltered by the ocean and provides a quiet, shallow habitat for babies to grow in. On average, the Bay is only about 16 feet deep, keeping smaller, younger animals safe from larger threats.
Just like our moms have different parenting styles, so do moms of the Bay. Some may seem a little overbearing, while others prefer to take a bit less of a hands-on approach. Let’s start with differences in reproductive traits. Not surprisingly, many of the animals in the Bay lay eggs. Some egg-laying moms are very protective of their offspring, while others give their eggs a bit more space.
Take the giant Pacific octopus, for example. This mom may be the most dedicated of them all, literally giving her life for her offspring. Giant Pacific octopuses are terminal spawners, which only gives them one chance to reproduce. But what a chance—the octopus will lay anywhere from 18,000 to 74,000 eggs. Once she lays the eggs, the mother octopus does not leave their side. She sits and guards her eggs at all times for the six months it takes them to hatch, not even leaving to eat. Then, the mother typically dies shortly after her babies hatch.
Then there’s the swell shark. Swell sharks lay green, flattened egg cases that are rubbery in consistency and have wiry tendrils attached to the ends. These cases are also commonly known as mermaid purses and are designed to look like kelp in order to stay camouflaged from hungry predators. After the eggs are laid, the swell shark mother uses the tendrils to anchor the egg cases in rocky, algae-covered habitats where they will be protected until they hatch, about 10-12 months later.
Not all animals in the Bay are egg-layers. Some animals, such as the sevengill shark, are ovoviviparous, meaning that they have live births. Also the Bay’s largest predator, sevengills are typically found in the deeper pockets of the Bay, but female sevengills will move to more shallow waters to give birth. Once they are born, the pups stay in the shallow waters until they grow large enough to move on to deeper water. San Francisco Bay may be the primary pupping ground on the West Coast for sevengill sharks.
One of the consistencies you will see in moms of the Bay is that while many of them may spend plenty of time and care guarding and nurturing their eggs or offspring, once the babies are born or hatched, the maternal relationship typically ends. Babies of the Bay are almost instantly left to take care of themselves.
You can learn more about moms and babies of the Bay this Mother’s Day, when Aquarium of the Bay will be offering free admission for all moms and grandmothers. There will be special presentations highlighting more moms of the Bay, and visitors can even see some egg cases out on display. For more information, visit www.aquariumofthebay.org.
