Traits

Sometimes pores in a leech's neck will develop a transparent skin over them, expanding and fleshing out into pockets for storage. 

Leeches featuring this trait will use them to show and display things that they're fond of collecting, whether it be physical objects, blood, or other foods. They tend to have much bulkier necks as well, both to have space for the neck cavities and strength to hold things stored inside.
It's extremely popular with luxuries and pets to have this combined with blush cheeks.