Posts Tagged ‘shrimp’

The Post – How Long Do Fiddler Crabs Stay Pregnant?

February 23, 2008

I spotted this question on a Google search and decided to follow up on it. It has been the question in our house – Scarlett O’Hara seems to get bigger every day with the larval crabs she’s carrying. How long will she carry them? What will she do with them? I’ve learned that female fiddler crabs usually like to hang on to the babies until the right set of tides and conditions so that their babies will be carried out to the open ocean. Apparently they do this because the larval crabs stand a better chance of finding food, and of not becoming someone else’s food, out in the open ocean. That gives them the best chances for reaching adulthood.

The question in our minds here is: we have no outgoing ocean tides in the “aquarium estuary” so when will she release them?

We’ve noticed she keeps hanging out on top of the water filter. In fact yesterday she was deep down INSIDE the water filter. She’s also been ripping the filter backing apart and eating whatever she’s pulling off the fibers. Since fiddler crabs like to eat a lot of microscopic algae, I assume that’s what she’s found. I keep wondering though, is she going to release her babies in the “currents of the water filter?” If so, I wonder how she will decide which currents are “outgoing tide” to that imaginary open ocean we don’t have. 🙂

Anyway, two good articles I came across in my search:

1) When ‘in a pinch’ won’t do: Ultra-picky female fiddler crab cited in UCSD (Univ of California at San Diego) study.

Apparently the female California fiddler crabs are VERY picky about their mates and have REALLY high standards for what kind of “house” the male is offering them. On average the female passes up 23 offers before finally selecting a male. In one case a female passed up 106 offers before choosing her mate. Now…I don’t know who to be more impressed with – the female fiddler crab who passed on 106 males before choosing one? Or the human researcher who followed this female fiddler crab around and kept track of how many males she turned down before choosing? In any event, an interesting article on the life cycle habits of the California fiddler crab.

2) The SC and C FAQ Database: it has a large number of questions and answers about crabs, shrimp, and crayfish. Question # 16 is about 3 pregnant female fiddler crabs and how long their gestation period lasts. Apparently in an aquarium, the female will release the eggs in about a week. We shall see. …Also it has information on what to feed the newly released babies, which might actually let them survive in an aquarium and grow to adults. Hmmmm 100,000 grandchildren. Needless to say my husband is thrilled with the news we might actually be able to help the babies survive in a tank! 🙂 Now all I need to do is find micro-plankton, like Infusoria, to feed to them…..

The Post – and finally, Admiral Byrd

February 2, 2008

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To round out the fiddler crab trio in our household, I give you the sole male in the tank, Admiral Byrd. He is fearless, commands the tank, explored every inch of it the moment he first entered the tank, and so he deserved a name fitting for a courageous explorer.

The first picture shows Admiral Byrd under less than optimal circumstances. In one of the first blogs about the crabs I mentioned the problem of getting the salinity level right in the water. Being brackish water crabs, they like lower salinity. Not knowing this, I had made the water the same as regular sea water. That drove Admiral Byrd literally out of the water, up the gravel hill, and as seen here, climbing the walls of the tank to get out. I quickly diluted the water, thus calming him down and convincing him to stay.

The second picture seems to sum up Admiral Byrd’s standard pose: “Stand back! I have a claw and I’m not afraid to use it!”

The third picture shows Admiral Byrd trying to get closer to the ladies by nestling in against the live rock while they were sleeping inside. (He was too big to fit inside). I guess he figured if he slept outside their front door, they’d have to run into him sooner or later. Admiral Byrd may be brave, but he is not too smart. The ladies just exited the live rock by the side entrance.

The last shows dinnertime. Admiral Byrd is chewing on a shrimp pellet clasped in his smaller front claw.

That’s the crew.

In another post, I will talk about a couple of ways this photo project helps my writing.