Friday, April 27, 2018

Maternity ward

Shore crabs are busy little critters. They dig holes under rocks and shells, lifting huge (for them) rocks aside in the process. They re-arrange the landscaping in my aquarium. They pester the anemones and roll the hermits out of their way. Occasionally, they go jogging.

I had taken a big male back to the beach, exiled because he was bullying everyone else in the tank. And then the female, left alone, went mad. She ran around and around the aquarium, scraping at the walls as if she were trying to find an exit. She tried to climb the walls, standing on tiptoe and reaching, reaching for the top. She never gave up. Day after day, she ran.

I found a small male at the beach and brought him home. She attacked him on sight. I realized why a couple of days later when he came up to my light at the wall and I saw his purple polka-dotted pincers. He's a purple shore crab; she's a green.

I found a green male and brought him home. She settled down immediately and went back to weight-lifting oysters and barnacled rocks; normal crab behaviour.

And then one day last week, she came to the glass to show off her new brood. She was carrying a belly-full of eggs.

"Look what I've got!" Photo taken the 24th; it took a few days to catch her in a decent light.

Showing off.

This is why female crabs have wide abdominal plates. They need to provide housing for thousands of babies. The males' abdominal plates are narrow and pointed.

The structures at the sides, the feathery pleopods, serve as anchor points and safety gates.

She grooms these babies constantly, opening and shutting her abdomen to provide a scrubbing current, picking away at them with those giant chelipeds, clearing out debris. Motherhood is hard work!

They're getting quite big already.

The female's rounded abdominal flap can carry more than 10,000 eggs at once. (Biodiversity of the Central Coast)

Yesterday, the night of the 25th, she came to the glass wall again.


And now the eggs have eyes!

Looking out at the world from the shelter of Mommy's tummy.

Zooming in ...

Tiny cuties!

This morning, Ma crab greeted me when I turned on the lights. She's slim again. The babies are gone, out swimming in the current.

I don't expect to have 10,000 crabs in the tank. Many will get lost in the filter, others will be eaten quickly. The anemones all looked quite perky this morning, after their crabby breakfast.

Maybe one or two will escape the voracious filter and the reaching anemones, hide under the sand, or on the backside of one of the seaweeds, and show up one of these days, a pinhead crab on her way to adulthood.

1 comment:

  1. You teach me something new in every post. Love it. - Margy


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