Mommy, Where Do Babies Come From?

We’ve been busy in the hatchery during the past few weeks growing and caring for some 14-day old oyster larvae. But first, let me back track and tell the story of how it all begins…

The act of spawning is simple…yet complicated. The idea of reproducing oysters merely consists of mixing some eggs and sperm together; however getting them to do it is the tricky part. In nature, when the water reaches a warm temperature, oysters let go their eggs and sperm into the water and the magic happens on its own. In a lab setting we mimic this exact process, called thermal spawning. After conditioning the oysters for about 4 weeks with heavy algae, the gonads are plump and ripe, ready for spawning. We place the oysters in a shallow tank of warm salt water (about 85° F) which begins to “set the mood” for our handsome devils. We feed them some algae, dim the lights, and put on some Barry Manilow. The waiting process can take some time, but oysters are able to sense when the others are spawning so once one goes the others aren’t far behind. Once spawning occurs, its important to separate males and females in order to avoid polyspermy. Polyspermy is when more than one sperm attack an egg and that egg becomes deformed. In our hatchery we then separate the individuals by sex into dishes where they can continue to spawn. So how can you tell males from females? Looking at oysters you cannot tell the sex but once they begin to spawn the difference is immediate.

In the photo above, the top left is a male clam releasing a milky white stream of sperm. Eggs and sperm look the same for both clams and oysters! There is a female on the bottom left puffing out clouds of tiny microscopic white balls, which are the eggs. Once the oysters are spent and have spawned out, we collect all of the eggs in buckets and use the sperm to fertilize them properly, avoiding polyspermy. We then can count how many eggs the oysters produced by simply counting how many are in 1 milliliter and do some math from there.

These eggs are so tiny they cannot be seen individually to the naked human eye, but all together they look like a pile of pink-colored fine sand. Under a microscope you can actually see each oyster and see right through their shells to their digestive system. In the photo above on the right, 2-day old oysters are seen under the microscope, and they are entering a stage called “D-stage” as their bodies form little D’s with a straight edge on the backs of their shells. These larvae will soon transition to become “young adults” within the next week or so!

 

★ Hannah Pearson runs our hatchery. She is from a small island on the East Coast of North America known as Rhode Island. She owns a lot of NCAA apparel from various schools. ★