The upcoming Battlefleet Gothic Armada 2 will introduce a number of playable factions/races which includes The Necrons and even Tyranids. I don't have much knowledge of the space combat side of 40k. I can say for sure in this scene a Necron fleet was attacked, but by what exactly? Tyranid?
Above is an image of a Tyranid Hive ship from the game Dawn of War 2. The wiki says these ships form the heart of a Tyranid Hive fleet and are incredibly Massive, even by the standards of 40k, it easily dwarfs an imperial BattleBarge. Clearly large enough to swallow ships whole, though I can't make out a mouth if there is any.