From the Super Mario Wiki
A Preying Mantas is a Jellyfish found underwater in Super Mario World 2: Yoshi's Island and its remake Yoshi's Island: Super Mario Advance 3. Their name is a pun on praying mantis, which is a kind of insect, and manta ray, a kind of stingray, while enemy itself is designed after jellyfish. Preying Mantas move up and down in a small area, and therefore do not pose much of a threat to the Yoshis. The Yoshis can simply defeat them by shooting a torpedo at them in their Yoshi Submarine forms. They appear again as enemies in Yoshi's New Island.
Preying Mantases also appear in Super Mario Galaxy in the Deep Dark Galaxy and the Bigmouth Galaxy. They are found in groups of four swimming around, hurting Mario if he touches them. They can be defeated with a Spin or a Koopa Shell and give one Coin when defeated. They also appear in Super Mario Galaxy 2 in the Cosmic Cove Galaxy, although the Prima Official Game Guide for the game calls them Jammyfish.
It is possible that the Preying Mantases are related to the salt-water dwelling Jellyfish from Yoshi's Story.
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