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Suckermouth

Additionally many other fish of the order Cypriniformes have developed a sucking ability to a lesser or greater extent:

• The Hillstream loaches (family Balitoridae) have modified fins to attach themselves to a surface and a ventrally located mouth.
• The sucker fish (family Catostomidae) also have a modified mouth.

In general many benthic dwelling or feeding fish will have a suckermouth feature. Many of these fishes originate from fast-moving waters, where the sucker allows the fish to 'stick' itself down without too much difficulty.

Whilst all these fish have a limited sucking ability – they are able to swallow their food – it is not necessarily correct to assume that they can attach themselves to a submerged object by suction; though their behaviour may give that impression, the orientation of their fins and a flow of water can give sufficient downward force to temporarily attach themselves to an object.

• Lamprey – Uses teeth to attach itself to a host. The sucker-like mouth is generally termed as an "oral disk."
• Remora – Sometimes known as 'suckerfish', remora use a modified dorsal fin to stick onto objects and other animals.
• Leech – The anterior portion (not the mouth) of this animal is modified to attach itself to a host.