Posts Tagged ‘currents’

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 – Scarlett O’Hara and her molted ghost

January 31, 2008

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Well, I’ve been promising pictures of the fiddler family members so let’s start with Scarlett O’Hara and her recent molt.

The first picture shows her just after she molted, climbing down the side of the water filter. I love how they can have their eyestalks going in two directions as they move about. If you look closely, the right eyestalk is vertical, while the left one is scanning in a horizontal direction. Off to the right in the picture, her whitish “ghost” sits, discarded. With the water currents waving the legs and claws back and forth, the discarded shell looked eerily alive.

The second one shows her nestled safely under the water filter and behind her old self (fuzzy part in front), where she rested for some time. It is not unusual for newly molted crabs to hide. Their new shells are soft at this point and they feel vulnerable. So they hide to give themselves protection as their new shell hardens.

The third picture though a bit dark, gives you a close-up view of the ghost version. You can see the empty leg, claw and eyestalk casings. I will add that the “ghost of Scarlett O’Hara” no longer exists. Admiral Byrd ate it. Perhaps he is getting ready to molt. Crabs often eat discarded shells to reclaim the calcium the shells contain.

Last picture shows Scarlett O’Hara when she finally emerged from under the water filter. Still a bit tentative, she sought shelter under an overhang on the Live Rock.

These were all from Saturday, the 26th. Today she was back to her old self, running around the tank and eating. Maybe I can get a lighter picture of her now that she’s out and about. I need to work on “lighting” issues for these, but still, not bad considering no flash and long exposure times.

Soon to come, Admiral Byrd and Melanie Hamilton!!!