Tidbits of info gleaned from scientific journals

[Guest]

I'm a newbie to hermit crabs and after reading the various websites and forums (Jedi Master Thrash's posts rock) I decided to hit the scientific journal articles to see if I could fill in some knowledge gaps. I've mostly been disappointed - not much is published on hermit crabs (lots of recent work on interactions with ants).One interesting article I found though discussed the different abilities of crabs to detect various chemical cues in the air. Lets jump right to the findings:- Coenobita rugosus (ruggies) are not good at smelling food but very good at sensing fresh vs salt water.- C. cavipes could not smell the difference between salt and fresh water- C. brevimanus (Indos) can sense salt vs fresh water- C. perlatus (straw) can not detect the difference between salt and fresh water. Also it is noted the straws are the least terrestrial of the species.So this had me wondering what the experienced crabbers here thought about the straws' apparent inability to detect the difference between fresh and salt water (-by odor-). Could this be one of the factors causing crabbers difficulty in keeping these? Does it matter, since they could tell as soon as they taste the water?Some other items of note straws seem to prefer higher temperatures in the wild relative to things like PPs (~90F optimum).And some scientists at the smithsonian research station in panama describe rearing baby E's in captivity in some detail and make it sound easy (all the other species have been described as well - E's were the last to be reported).Edited version of methods: quote:Several ovigerous (carrying eggs) C. compressus (E's) were intercepted just above the surf zone on Culebra Beach, Naos Island, Panama, shortly before high tide on evenings from March through May, 1997. Each crab was kept inside a round plastic washtub partly filled with damp sand into which was placed a 300-ml Pyrex dish filled with filtered sea water. Tubs were checked every 2 or 3 hours until at least one female had shed zoeae into its water dish.These larvae were placed five to a compartment in larger plastic boxes holding 75 ml (1/3 cup) of filtered sea water.The larvae were reared on a 12/12 L/D light cycle at 26°C (79F). Zoeae were transferred to clean compartments and fed Artemia nauplii (Brine shrimp) daily; newly hatched Artemia were consumed for the first two weeks of development, after which they fed upon larger 1- or 2-day-old Artemia. When larvae metamorphosed into megalopae they were moved to small plastic containers holding about 4 ml of sea water. Each container was sunk into damp sand in the larger compartmentalized boxes, so that individual megalopae had the opportunity to leave the sea water. Megalopae were fed fish flake food daily and provided small vacant gastropod shells (Nerita modesta). (Total time from hatch to metamorphosis: 21-33 days) Has anyone been trying to breed these in captivity or at least harvest eggs rather than crabs? It bothers me that all these crabs are taken from the wild.

[Jedediah]

I always wondered about the breeding artivle, they do make it sound easy. But they don't mention how many larvae died (I think) and they had everything prepared. Until now, people were surprised when their crabs layed eggs and the larvae died after two weeks at the most - no-one had a cycled saltwater tank ready. I suspect that sometimes the females keep the eggs too long because they cannot find the ocean and when they drop them in the water dish, it's just too late. Crabs have successfully mated in captivity before, but until now the larvae always died. I hope that someone will succeed in breeding them, though.

[Guest]

Welcome, Ambitious!quote:- C. perlatus (straw) can not detect the difference between salt and fresh water. Also it is noted the straws are the least terrestrial of the species. Do you have access to the full scientific article from which this appeared? I searched around on coenobita.org but couldn't find a reference. I'd like to read more of this.----------My experience with Straws, until recent months, was not good. I lost many, all to either PPS or bad molts. Every time one died, I swore off ever getting them again. But, I can't resist their beautiful colors and active lifestyles.A year ago I bought two new Straws. Due to practices I found successful with PPs, the only crabs I used to be able to get, I misted the tank only one a week (but maintained a humid environment with moist substrate), fed primarily FMR foods with a few fresh fruit treats, maintained a salt water tub for dipping, and that was about it. Once I purchased the two Straws, I misted daily (I have a pump that sprays rainfall), changed my food variety, and cleaned the salt tank often. Of course, I kept out fresh water, but they are not deep enough for the Straws to submerge themselves. The Straws haven't died yet--and, stragely, haven't molted yet, either.I bought two other Straws over a month ago, and they are still kicking. All four can never decide if they want to bury themselves or run amok, tearing up my tank.My belief was always that Straws, shipped from Australia or a nearby area, spent quite a while between harvest and my crabitat without proper access to the right foods, the right humidity, a low stress level and without any competition for shells or water--which was probably not of the proper salinity if seawater was provided at all. While I'm giving the best care I know to the Straws when they get home, I can't control their travel and mostly summed up their deaths to bad luck. But, then again, I misted daily and put more variety in their foods, but I didn't think this was the absolute cause. Perhaps the salt water bowls built up too much ammonia or something, but I don't know.I've seen my Straws in the salt bath, and then immediately come out and sip fresh water. I've seen them take water dripping off my climbing nets or plastic plants after a mist. I believe they're creating a balance somehow, if not in their shellwater but in their digestive systems. My tank, for all intents and purposes, is primarily providing saltwater most and freshwater second, so perhaps the Straws in this case can be better drawn to the saltwater if they can't dip in the fresh, especially, if the study is correct, they can't tell the difference when navigating to it.My PPs never, ever, ever get near the saltwater bowl or go inside. I believe they can tell the difference... they have no problem with the freshwater bowls.

[Guest]

quote:Originally posted by bpbatch:Do you have access to the full scientific article from which this appeared? I searched around on coenobita.org but couldn't find a reference. I'd like to read more of this. The article is:Vannini M, Ferretti JChemoreception in two species of terrestrial hermit crabs (Decapoda: Coenobitidae) JOURNAL OF CRUSTACEAN BIOLOGY 17 (1): 33-37 FEB 1997 I just read the abstract since an electronic version isn't available and I didn't feel like going to the library. I suspect I am misrepresenting the data a bit though based on the responses. This just means they can smell it and use that smell to navigate to it, or use it to orient themselves. It doesn't mean they can't sit right in front of it and not tell the difference.I'm a total newbie to hermit crabs, but from reading what people have said here I can't help but wonder if the main issue is people keep the straws too cold. In the discussions here talking about lighting for heat one person indicated that her straw sit directly below it in 100+F temperatures. Its been noted that straws are the least terrestrial of the land hermit crabs and higher temperatures increase gas exchange across the gills and abdominal lung so perhaps temperature, humidity, and access to salt water are just much more critical for this species. Adding your thoughts to the problem, this means straws will experience even greater stress during the collection/shipping/pet store experience. Another study talked about how the larger crabs are less susceptible to desiccation, so maybe the best bet is to pick the largest crabs. I find the breeding of these in captivity the most interesting though. From what I have read online it sounds like most crabbers try putting the larvae in an aquarium. The scientists basically put them individually (or in small groups up to 5) in tiny cups of seawater. They then feed them the absolute tiniest brine shrimp possible (fresh hatched) and rather than trying to circulate or filter the water they just replace it with fresh on a daily basis. 88 survived in the first batch in the study (this is from eggs from 3-10 crabs), and only 9 survived metamorphosis into crabs. It sounds like they made a lot of changes as things progress (probably quickly changing things for the better - this happens often when you are at a field research station. This was in 1997 so I imagine they have it down better now - especially since I see further studies using megalopae. A lot of the scientists there are based out of the smithsonian research institute in Fort Pierce Florida so if any of the florida based crabbers were really interested I bet they could get a tour and some tips from the true experts.

[JediMasterThrash]

Wow that's interesting.I've never had the luck of getting a female with eggs. I wonder what percentage survive in the wild, I bet it's probably a small percentage, so 8 out of 88 or so might not be that far off.Temp is definitely more important than we used to think. I remember we used to say 70o was acceptable. But that's like winter in the tropics.