Board Thread:Warhammer 40k General Discussion/@comment-25618639-20150406151006/@comment-6078851-20150412153646

you do know about tyranids, right? they can create any type of bioform for any type of situation, within hours of encountering a situation (it's one of the things that makes them such a daunting entity) - a spore-bioform could simply be a genestealer with spore glands. if it was a ship it doesn't need to be big (it could be relatively tiny, like the size of a car - basically a spore-delivery missile). as for sustenance... uhhm... intergalactic travelers? i think they have that base covered :) and tyranid ships, even the biggest of them, are undetectable besides visual confirmation and the shadow in the warp, but the shadow only comes into play with the numbers present in a hive fleet.

as for saving hassle: genestealers draw hive ships, hive ships then wage war... hassle. if a world is seeded with spores then within the space of a day there would be a colossul tyranid army, amongst which are more spore-bioforms, or even regular breeder-bioforms, so by the time a hive fleet reaches the world all it has to do is slurp up all that gooy goodness, hassle-free :)

the more i think on this though the more i think that orkoid life is different from anything tyranids may have encountered/eaten: tyranids make immediate use of new genetic patterns and there is definitely a benefit to be had from their spore reproduction, if improved upon. but while tyranids are the undisputed masters of bio-engineering the old ones will always be 2nd (or 1st amongst the milky way's native life), and maybe the orkoid genome is so sturdy, and alien even to tyranids, that tyranids are having trouble assimilating it - squigs having tyranid dna and yet remaining orkoid could be indicative of such.

but, as always, it's just my opinion :)