Suspicious Mite and Random Scab?

[Cumba]

Hi! I hoped I would never have to post on here, but here we are I'm not sure just HOW urgent this is, but if this is an emergency I need to act fast.

1. What kind of substrate is used in your tank and how deep is it?
Eco earth and sand mix, about 8 inched.

2. Do you have gauges in the tank to measure temperature and humidity? If so, where are they located and what temperature and humidity do they usually read?
Yes, upper left side, not touching heater or light. Heat is 80F and humidity is 81%.

3. Is a heat source used in the tank? If so, what?
Yes, two large UTHs on the side of the tank.

4. What types of water are available (fresh or salt) and how is the water treated (what brands of dechlorinator or salt mix and what ratio is used to mix it)?
Fresh and saltwater. I treat two gallons with prime, and then add 1/2 cup of instant ocean to one of them.

5. What kinds of food do you feed and how often is it replaced?
I have dried veggie and fruit mixes which I rehydrate and change every few days. The crabs will have some protein every night, and if I gave fresh food I'll change it the next day.

6. How long have you had the crab and what species is it, if known?
A PP, had him for about 5-6 years.

7. Has your crab molted, and how long ago did it happen?
Yes, they both molt about twice a year (sometimes for months!) and he came up about two months ago.

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
They are kept in a 29 gallon with a glass lid.

9. How many crabs are in the tank and about how large are they?
2 PP, I would consider them "large" on the sizing chart.

10. How many extra shells are usually kept in the tank, if any?
About 10.

11. Have there been any fumes or chemicals near the crabitat recently?
No.

12. How often do you clean the tank and how?
Usually about every other month I take everything out and wipe it down with water. I take out the soiled substrate, mix in some new stuff, and turn it all over.

13. Are sponges used in the water dish? If so, how are they cleaned?
No.

14. Has anything new been added to your crabitat recently?
No.

15. Is there any other information you would like to share that might be helpful (anything that is regularly part of your crab care, playtime, bathing, etc.)?
No.

16. Please describe the emergency situation in detail.
I have had my two crabs in their new 29 gallon for about 6 months now with no issues. They have been climbing, acting fine, eating tons. Today I noticed a small bug in the crabitat. I've seen little bugs like this before, but they were never on the crabs. I reviewed the mites information sheet and the ones I've seen in the past seemed to be harmless food mites. The mite I saw seemed to be larger, but not too different. I then noticed a "wound" on one of the joints of one of my crab's legs. I couldn't snap a good picture (I'll try to get one soon) but it just looked like a scab on the joints on one of his legs. I don't know what is going on! Are these two things related?
I bathed the crab in question and he was acting fine - extra peppy, actually. I GENTLY flushed the scab with some dechlorinated water, but nothing happened. Could this be an injury from falling or a fight with his friend? In the six years I have had my crabs, I have never seen anything like this. Any help would be appreciated. I'll get a picture up ASAP.

[JoeHermits]

I’m guessing an injury of some sort, which will most likely heal with the next molt.

Parasitic mites can only be introduced by infected crabs, so considering you’ve had healthy crabs for a while I don’t think mites are an issue.

A picture would be helpful for confirmation, though.


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[wodesorel]

They can scrape their knees up sometimes while moulting, and it will look like a scab after. The food mites will also crawl all over anything in their path, including the crabs. I think like motör that it's coincidence, but we can review a photo to be sure!

[Cumba]

Thank you for your responses, I appreciate them!

Today I went to see my crabs and get some pictures of the wound.
I took out my crab, snapped a few pictures, but then noticed that his scab was beginning to peel. After took a few pictures, some of the scab fell off. It began to ooze clear/grey pus. He didn't seem bothered at all. I gently placed him back in the tank.
I don't know what to do, maybe a bath to clean it out?
I still can't figure out how to get a picture on here, I will soon! Sorry!

[Cumba]

Figured it out, finally!

Here is the "scab" (upper leftmost leg):


Here is it oozing:

[wodesorel]

I wouldn't mess with it unless it seems to be spreading. They don't scab over and heal like we do, because they can only regrow their hard exoskeleton during a moult. What happens instead is that any exposed flesh from under the exo will harden and blacken, and create a temporary and much weaker seal to prevent infection and foreign bodies from getting into the hole. It's not perfect. If it loosened and leaked then you probably saw it bleeding, which will be slightly bluish.

The wound is in an odd location but it doesn't seem bad. Another crab may have clipped it, or it may have moulted funny. I've had them get old exo stuck around joints before and cause problems.

[Cumba]

Thanks so much! I'm so glad it's not a huge problem. Here I was all ready to do a complete change and quarantine. It's so helpful to have this forum.