Once you find that special someone, it’s hard to let go. The same is true for animals that literally attach themselves to their mates—some just briefly, and some for hours, or even for life.

In the animal kingdom, these specialized “clingy” behaviors help to increase reproductive success. From romantic amphibian embraces to deep-ocean dwellers that aptly demonstrate the phrase “two become one,” here’s a breakdown of the animal kingdom’s most clingy lovers in honor of Valentine's Day.

When you live in dark ocean depths up to a mile below the surface, finding a mate can be tricky. That’s why a male anglerfish has a somewhat unorthodox technique for keeping a lover: biting her and latching on.

Eventually the bodies of the