Regenerate

If the creature is reduced to 0 Wounds place the model on its side. The creature can still be fired at or hit in close combat. If the creature suffers any more hits while on its side make saving throws as normal and place extra wound markers with the creatures if it suffers them.

In the rally phase in the next Tyranid turn roll to regenerate each Wound marker the creature has suffered. Roll a D6 for each marker: on a 4+ the wound marker is removed. If the number of wound markers the creature has left is equal to or greater than its number of wounds the creature dies. If the creature has fewer wound markers than its number of wounds it stands back up and may act normally in the next turn.