i thought i'd see some responses from at least one person who's worked in the trade. guess at this point i'm the only one. someone at another board told me i should write this stuff up and publish it. i thought lots of folks knew how stuff gets from here to there.
in any event, here goes...
first: do not use ziplocs, they will not be able to withstand the drop in pressure and very likely will burst.
*get fishbags and bands from the local, you shouldn't require O2 for these guys.
*before you do any bagging you need to "prep" the bags - take two bags and a piece of newsprint (folded so it goes all the way around and meets at the bottom) sandwiched in between.
*be sure that the bags allow a "buffer zone", about 2"-3" (i use that as a minimum) around to prevent bumping in transit. fill with no more than 2/3 - 1/2 water (in the shipping biz lbs=$$).
*depending on the species, you can tie the frags to a piece of styro - some use rubberbands others like old stockings - so they will always be submerged in the water.
*then, trap as much air as possible in the bag and twist tightly the top 4"-6" of the bag.
(this is THE MOST IMPORTANT part of packing for ship!)
then loop the band tightly at the base of the twist, using about 1/3 - 1/2 the band.
now, keeping tightly twisted, you must bring the end of the bag down so that you've created a loop, much like tying a one-armed bow. ideally you'll have about 1"-2" hanging off the end of this loop once you've finished tying off with the rubberband, looping each loop tightly and securely.*
second: for anything you think can be shipped "dry", use newsprint and shredded sponge to keep moist.
third:use chemical heat pax to keep your specimens warm. these are just the same thing as what skiers use, you ought to be able to find them at any sports supply.
fourth: always use styros! they've got the best combination of insulation and softness. you should always box styros inside a carboard box, but if you can carry this stuff on you might be able to get past this.
fifth: use bags of air to cushion and to fill in any empty spaces around the bagged specimens.
hope this helps, it's basically the same method used by every shipper i've worked for.