Cheapest priced copy (Ravnica: Clue Edition): $0.35 at Card Kingdom, near mint, their price list as of .
Scuttlegator 
Creature — Crab Turtle Crocodile · 6/6 · Common · Ravnica Allegiance · #218
Defender
{6}{G/U}{G/U}: Adapt 3. (If this creature has no +1/+1 counters on it, put three +1/+1 counters on it.)
As long as this creature has a +1/+1 counter on it, it can attack as though it didn't have defender.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ravnica: Clue Edition | 206 | Common | $0.35 | — |
| Ravnica Allegiance | 218 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 25 January 2019You can always activate an ability that will cause a creature to adapt. As that ability resolves, if the creature has a +1/+1 counter on it for any reason, you simply won’t put any +1/+1 counters on it.
- 25 January 2019If a creature somehow loses all of its +1/+1 counters, it can adapt again and get more +1/+1 counters.