Tropical Fish Keeping - Aquarium fish care and resources

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fish_4_all 07-25-2007 08:00 PM

Snail poisoning by Hydra?
I was curious if anyone could tell me wether or not it was even possible?
I have a lot of them, and I mean a lot of Hydra and I have noticed that every time my snails are moving along the glass and touch one they do react if it is a mouth part that hits them. The foot seems almost impervious to them but the mouth parts almost always react.

Could they be getting stung enough that it is actually poisoning them?

Lupin 07-25-2007 09:15 PM

Re: Snail poisoning by Hydra?
From this site...

To capture these minute forms of life and to defend itself from larger animals, hydra are equipped with poison-containing structures in the ectodermal layer called nematocysts, the most complex cellular organs in the animal kingdom. Judging from its incredible potency and speed of paralysis and death, the poison is believed to be a nerve toxin. They have four different types of nematocysts, some stinging and paralysing the prey, whilst others discharge threads which coil round the prey and hold it. Small animals paralysed by the stinging cells are brought to the digestive centre by the tentacles and devoured. The mouth of the hydra is located at the centre of the tentacles. The body is hollow and the inner layer of cells digests the food by engulfing it. With prey almost as large as itself, the hydra stretches so thin in getting its digestive gut around it that the prey animal appears to be covered with a thin transparent film; only the tentacles tell you that you are looking at a hydra, although they generally keep their tentacles coiled up. A hydra that has recently fed will be shorter and more rounded than one that is hungry.

Trishfish 07-25-2007 09:31 PM

I would regard them as harmless. Your snails will be fine. Don't overfeed your tank.

daisycutter 07-29-2007 11:35 PM

i had my pomeca snails actully eat hydras on purpose eating them not just randon grazing

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