HCA: Hermit Crab Association

how do crabs like dairy, or is it just plain bad for them?

i haven't been giving my crabs any, but i am wondering if it would be ok for them.

That's a really good question. My food group is doing trials of various dairy-derived foods. We've established that crabs CAN eat live-culture organic yogurt -- the live bacteria in the yogurt help digest it. Certain types of cheese such as hard ripened cheeses like cheddar, can also be eaten.

One person is doing a feeding trial of whole milk but I haven't got the report back on it yet, so I wouldn't suggest trying it. I'm going to give it a go this week and see what happens. But since this person has been feeding it for months with no ill effect, I think it might turn out to be safe in the end.

A great many aquaculture diets for captive raised crustaceans are based on casein, which is the protein found in milk.

So, for now, unless you have some live-culture yogurt or some sharp cheddar you want to offer your crabs, I'd wait on the dairy. Once I've finally made a determination about the truth or falsehood of the idea they can't eat dairy, I'll make a global announcement.

any ideas on cream cheese? it seems soft which would be easy for them eat.

The only safe ones right now are the ones I already mentioned. Leave the cream cheese out until we know more about the whole milk trial.

It was always my understanding that any non-mammal doesn’t have the enzyme lactase, which is necessary to break down the sugar lactose into glucose, which can then be digested and used as energy. The lack of lactase makes it impossible for any non-mammal to use lactose for any benefit.

The live cultures in some yogurts and cottage cheeses can create some lactase in humans, although there’s no way of knowing if the amount produced will really be enough for any use in a completely lactase-deficient crustacean or if it’s creation in the crustacean digestive system will work in the same way. Nevertheless, they stand the best chance of actually being digested. Perhaps it’s work asking a crustacean expert.

Given what we already know about lactose digestion, feeding trials of dairy products without live cultures don’t seem like a good idea. Even if it doesn’t somehow make the crabs ill, they will get no benefits from consuming it.

From the trials we've been doing, the lactose/lactase thing is not applicable to crabs. I just heard back from the woman doing the whole milk trial. She has been feeding it weekly since May with absolutely no ill effects or mysterious deaths. I am going to reproduce her trial this month and I fully expect at the end of this time to clear dairy as a crab food.

Crab biology is so very different from mammalian biology that it's not wise to compare them, or to hold traits of one to the other.

Her crabs, especially the perlatus, really love milk. She says they've slowed down on it a bit since she first started offering it, but that there are still crabs that drink it regularly.

One little aside on the subject of arthropods and dairy: the cheese mite:

Cheese mites can also live in corn, flour, etc., but they are best known for their occurrence in cheese, in which they gnaw small holes. These cosmopolitan mites are common in stored food, damp flour, old honeycombs, and insect collections. A ripe, mite-infested cheese will be more or less covered with a grey powder, which consists of the mites themselves and their moulted skin and faeces. Cheese mites can live at low temperatures but not in the refrigerator. For many cheeses the presence of mites is highly undesirable, but there are some cheeses in which a culture of cheese mites is introduced for example to Altenburger cheese to impart a characteristic "piquant" taste. When the cheese is covered with a greyish powder, consisting of enormous numbers of living and dead mites, cast skins, and faeces, it is considered by some people to be "ripe" and particularly delectable. Cheese can be protected by a thin layer of paraffin wax.

The cheese mite, known to cause dermatitis, is larger than both the grain mite and the mould mite. It has stout, well-tanned, faintly-wrinkled legs (obviously been on holiday) and tanned mouthparts. Males and females are similar except that females are larger. The life cycle requires 15 to 18 days at the ideal temperature of 73°F and an Relative Humidity of 87%. Unlike the grain mite the hypopus stage does not occur in the cheese mite.

http://www.the-piedpiper.co.uk/th7g.htm

I saw a show about these in Britain once. Ew.

Julia_Crab wrote:From the trials we've been doing, the lactose/lactase thing is not applicable to crabs. I just heard back from the woman doing the whole milk trial. She has been feeding it weekly since May with absolutely no ill effects or mysterious deaths. I am going to reproduce her trial this month and I fully expect at the end of this time to clear dairy as a crab food.

Crab biology is so very different from mammalian biology that it's not wise to compare them, or to hold traits of one to the other.

Fair enough, but I wasn’t comparing crabs to humans, I was comparing lactose to lactose, which is the same substance regardless of who’s digesting it. Every creature has to have the ability to break down whatever it digests into nutrients. All animals, including crustaceans, use digestive enzymes to do that. As far as I know, lactase is the only kind of digestive enzyme that can break down lactose, and only mammals have it. Is there another enzyme that crustaceans have that can break down lactose?

It could be that the lactose just goes in one end and out the other and they still have ways of extracting what they need from the rest of the item they're eating. If mites can eat cheese, there must be some biological mechanism.

There is no concern over the salt in the cheese? What if the cheese contains regular table salt?

I'm kinda with Laura. Milk and dairy are made by mammals for mammals. Why would a crab want milk or milk products? Do people feed reptiles or turtles milk products?

While it may not harm the crabs wouldn't it result in them eating something and filling up on something that won't benefit them? Should every meal count?

This is all just opinions. If you fell uncomfortable feeding cheese, then don't do it. If you don't want to try the milk, then don't do it.

If people are going to try and see a benefit in it, then they can try.

I look at it from the author's view. I trust the people who have done research. Just like when it was thought that citrus was bad, then we found out it's ok. So we hear dairy is bad, then we find out well some dairy isn't. Again it's totally up to the the person to try it. I haven't tried cheese, but I might. Just don't have any in the house atm

A great many things are fed to captive crabs that aren't found in their native environment with great results: hemp seed, rooibos, roses all come to mind.

The thing that bothers me is that people come up with this "common knowledge" about a food -- dairy and previously (my biggest headache before this one) citrus -- that is not based on any scientific evidence one way or the other. But people stick to the information though it's not based on any fact, just conjecture.

If arthropods cannot digest "dairy" please explain the cheese mites to me. Also why casein, a milk protein, is 96% digestible by farmed crustaceans.

If you don't like the idea of feeding dairy, then don't. But don't jump on the witch hunt bandwagon and go baying like hounds after those of us who are willing to do actual scientific research and who risk their own crabs doing food experiments, because we are attempting to advance the knowledge of crustacean nutrition. It really does get old.

Thanks.

Whoa. Since when did questioning something become participating in a witch hunt? Sure, crabbers can do whatever they want with their own crabs but when someone posts information on this forum that I have questions about why can’t I ask them, for my benefit and for the benefit of other crabbers? If people are comfortable with feeding dairy, rock on, but there’s no harm in sharing questions with others.

I feel like my concerns about dairy were based on more than conjecture, unlike the citrus myth. There is absolutely no logical reason why crustaceans can’t digest citrus other than the fact it had been said before; it was never based on anything (and I’ll note that I questioned that myth on these forums since the day I joined). However, I feel that the question about what enzyme crabs use to digest dairy, since they don’t have lactase, was a legitimate one. If it had an obvious answer someone would have answered it. Lactase breaks down lactose, that’s not conjecture, that’s fact. Crabs don’t have lactase, that also seems to be a fact, at least I haven’t been able to find any information saying otherwise. So how are my questions not based in fact?

Cheese mites and land hermit crabs have many differences; arthropods are an extremely diverse group. Although I don’t know how the mites digest dairy, I want to find out given the possibility that these mites have a digestive enzyme or bacteria that crabs lack or have in common (in which case we’re good to go). The fact that the mites can digest dairy and are arthropods is not, in itself, proof that crabs can. Termites are arthropods and can digest heaps of wood due to special bacteria in their intestines. Butterflies are also arthropods, but lack the bacteria that would make it possible for them to eat heaps of wood like termites (thank goodness, because I’d hate to see a swarm of house-devouring monarchs). The mite question can point us in the right direction though, which is why I’d like to look into it further.

Casein would be no problem because, unless the manufacturing process is flawed, it doesn’t contain lactose. It’s the other milk protein, whey, that has lactose coming out the wazzoo. If casein has many of the benefits of dairy maybe we should look into feeding that.

Another possibility if we really want to feed cheeses before we figure out the whole lactose thing is to feed those with low lactose content. There’s a list of lactose content in different dairy foods here:
Link to List

In regards to feeding tests, they can be an indicator or the most toxic foods but we can’t look to them as scientific research. The sample sizes are too small, there’s no control group and they’re fairly short term. I think they tell us a lot and I think we should keep doing them (I have been for years now), but we need to recognize that they have limitations and are not beyond reproach. A feeding test can tell us if something is toxic, but not if it causes more long-term health effects and not if it’s actually beneficial to crabs. We need other information to make those assessments.

In pursuing that other information, I’m trying to contact some biologists to find out their feelings on the dairy matter. I may be totally wrong and I’m completely open to that possibility, but I don’t feel like there’s ever anything wrong with asking questions that are based in fact. That’s all I was doing, asking questions, and I feel a little like I’m being berated for it. If anyone can show me that my lactose concerns aren’t a problem, please do so. The more variety in crab diet the better. But I’m going to get my questions answered, either by this forum or on my own, before I stop asking them. If expressing concerns is offensive to people they’ll just have to deal in the meantime. Or, if people really want to shut me up, they can help me find answers.

The test is underway:







Lined up waiting their turn three deep.

Julia, is that a bowl of milk they are all waiting around? I wish your crabs good luck with their test diet. Maybe there is something in the milk and cheese that will benefit them, calcium maybe?