12,000 babies!

The last few times I brought goodies from the beach home for my hermit crabs, a flatworm has come along, possibly among the barnacles. They would eat the barnacles, but then, so would the trophon snails, so I decided to let them sort it out among themselves, and added the flatworms to the aquarium. But the pump inhaled them and tore them up; it's a stronger pump than I used to have when flatworms roamed the walls before.

The next one went into the auxiliary tank, the amphipod and hydroid breeding tank, which has no pump, just the bubbler. There, it did just fine.

This last collection included the largest flatworm I have ever seen; up to 2 inches long when it's travelling. Again, we debated whether to add it to the tank; what would it eat that I wanted to keep? But there are plenty of barnacles and mussels, and a whole shopping list of worms there. The flatworm fits in fine.

"Stretch", resting, underside against the glass. The brown splotches are algae on the glass.

Three days later, "Stretch" had found the small flatworm already in the tank, and they were travelling together. The next afternoon, I found them, still together, with two patches of eggs they'd laid on the wall. A day later, there was another patch, larger, about an inch long.

Day 2. The third patch is not as densely packed as the first two.

Zooming in on the second day's eggs. The eggs are glued in a single layer on the glass.

Zooming in more. First day's eggs, near the top. Background cleaned up.

This afternoon, Day 4, with the microscope I can see, inside each egg, a swirling mass of points, with usually one darker spot.

What I can't really show you is the frantic activity around, under, and over the eggs. They are surrounded by a snowstorm of copepods, amphipods, worms; transparent hair-like worms, stretched ovals sliding and curving about like scale worms, two-tentacled tube worms and feather duster worms on the sand directly beneath them, busy mites, a pair of mud shrimp, and hundreds of things moving too fast, and too small besides, to identify.

One of the mites.

Shadow and feet of an amphipod on the far side of the layer of eggs.

Feather-duster worm with catch. Something tentacley, something blobby, something leggy.

There seemed to be an enormous number of eggs, so I had to count them. The lazy way; I cropped a square approximately 20 eggs on a side, and measured it against the total area.

About 20 x 30 = 600 eggs.

This was about 1/20 of the total area, and about mid-density. Multiplying 600 by 20, I get around 12,000 eggs in that mass. Could be more; some areas are quite dense.

Even after the onslaught of all those opportunists, I think there are enough so that some may possibly hatch.

The flatworms are hermaphrodites, with both male and female reproductive systems in each individual. In some species, one acts as the male, impregnating the other, who then lays eggs. In this case, it seemed that both flatworms were laying eggs; this is also a strategy of some species of flatworms.

The young may hatch as plankton, swimming about for a few days before they settle, or they may emerge as tiny worms with the adult shape. I couldn't find any information on our local species, which are notoriously difficult to identify, in any case. I'll just have to wait and see.

I hope some do make it.