The Economic Times

In 2012, researchers found one of the Animal Kingdom's costliest parenting jobs belonged to snail dads

Snail dads: Male marine whelks, Solenosteira macrospira, undertake demanding parental roles by carrying eggs. These fathers protect hundreds of developing eggs on their shells for about a month. DNA analysis revealed males carried offspring fathered by many other males. Carrying the egg capsules imposed a significant burden, causing weight loss in the snails.