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The sea sponge is scientifically classified as an animal, therefore maybe it would be considered unkosher, as seafood. On the other hand, it seems much more similar to a vegetable of some kind, so would be kosher to eat.

So, are sponges kosher?

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Fascinating! This forces us to examine the halachic definition of "animal" and see whether it matches up with the biological definition. ( – Isaac Moses Nov 4 '10 at 19:29
I have nothing to add, other than compliments on a very creative question. But are sponges edible, anyway? – Seth J Nov 5 '10 at 1:47
And what about Anemones? – Seth J Nov 5 '10 at 14:38
You should just eat lulavim instead. Because with fronds like these, who needs anemones? :) – Alex Nov 5 '10 at 15:01
Can one eat a Venus Fly Trap (before it eats you?) – Yehoshua Mar 7 '13 at 20:06

3 Answers 3

up vote 23 down vote accepted

The Yerushalmi (Shabbos 7:2) mentions sponges (ספוג) in a group of items where cutting them causes them to grow back even more, and therefore declares that someone who does so has performed two categories of work, "reaping" and "planting." These melachos refer to plants, not animals, so I would think that indicates that the sponge is viewed as a plant (probably because it doesn't move around).

That said, I haven't found this Yerushalmi cited as halachah.

Another possible data point, though, might be that in the course of explaining when a sponge may or may not be used on Shabbos, Shulchan Aruch (Orach Chaim 320:18) cites Aruch, who explains that the sponge sits atop the head of a large fish (a whale, maybe?) and covers its eyes when it sticks its head out of the water, so that it doesn't see ships and wreck them. Mishnah Berurah there (320:45) alternately describes a sponge as "a wool-like material found on beaches." Both of these descriptions suggest that they saw sponges as inanimate or vegetable matter rather than an independent life-form.

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The Yerushalmi holds that one who pulls a fish out of the water is חייב משום עוקר דבר מגידולו, so apparently the Yerushalmi holds that something does not have to be a plant for there to be קוצר. – wfb May 19 '13 at 2:51
@Alex Sponges are 100% animals. Growing back doesn't prove anything (for a more obvious example, pull the lizard off a tail, it'll grow back). It's just sponges are so primitive at the level of their cellular organization that being partially "reaped" doesn't kill them. They have animal cells. They consume food (are not autotrophs like plants). They reproduce like some other marine animal species. Eating them is eating a non-kosher animal, whether or not it seems like a plant. Then again who in their right mind would even eat one, so it probably isn't a practical issue anyway. – A L Jul 19 '13 at 4:28
@AL: we find that the Gemara considers coral to be a kind of tree (Rosh Hashanah 23a), even though it's actually also a type of marine animal (or rather, an accretion of them). So it's conceivable that halachah says the same about sponges; the key difference might be whether they stay in one place (corals and most sponges) or not (some types of sponges). – Alex Jul 19 '13 at 13:46
@Alex I would remind you that the Gemara often based itself on the science of the time. Fifty years ago, we even thought they were plants. Just because the Gemara said it was a tree as was common knowledge, doesn't necessarily mean that when we've discovered it's an animal (an animal that grows in one spot) that it can still be as kosher as any plant. – A L Jul 19 '13 at 17:18
Can they be Tevel if in Israeli water? – Double AA Jul 29 '13 at 18:51

Although this does not answer the question, I came across the following quote from R. Yosef Albo, Sefer ha-Ikkarim 3:1:

Coral is intermediate between inanimate matter and plants. We also find the sea sponge, which only has the sense of touch, and is an intermediate between plant and animal stages. We also find the monkey to be intermediate between animals and man.

This idea is repeated, for example by R. Moshe Isserles (the Rema) in his commentary מחיר יין, on מגילת אסתר, א:ו, and is ultimately based on Aristotle's classifications.

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Of course we know today coral and sponges are 100% animal. Until they were examined more carefully fairly recently (perhaps until some time in the 20th century, not sure exactly), people had misconceptions about that, which I presume is what informed R. Albo's statement; nevertheless it is incorrect. And as animals without kosher signs, they are not kosher. – A L Jul 19 '13 at 4:23
Their scientific classification as members of the animal kingdom is not obviously relevant to their halakhic status. As it happens, R. Yosef Albo is repeating Aristotle's classification, which is also not of clear halakhic relevance. – wfb Jul 21 '13 at 1:53

Assuming the key halachik distinction is that which underlies the difference between tolesh and netilas neshama in hilchos shabbos, as seems plausible, that should depend on whether sponges display some form of sentience (at least basic percepts of pain and/or pleasure, as distinct from the automated motions of machines and plants) . To some degree, modern "science" is somewhat unreliable in this analysis since contemporary scientists' materialistic dogmas interfere with their ability to classify sentience, or even to clearly ascribe it to humans, let alone lower lifeforms. Still, it does seem plausible that some form of centralized nervous system or even a brain should be necessary to say something is alive (חי) in the classical sense (or some comparable system that would mediate some low level of sentient perception). Though according to the Ri Albo cited by WFB, it should qualify as safek treif in the same sense that a koy is a safek chaya safek behema. In sum, tzarich iyun.

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