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Field Collection and Transport of Tissue Samples

MVZ Handbook > MVZ Tissue Guidelines
Frozen vs. non-frozen preservation

Although preservation of frozen tissues may not always be possible (e.g., in foreign field work), we strongly encourage preservation of frozen tissues (versus ethanol, buffer) whenever possible for the following reasons:

  • the long-term viability of non-frozen tissues is an open question
  • frozen tissues are much better for long-range PCR and genomics applications (R. Macey, Joint Genome Institute, pers. comm.)
  • only frozen tissues can be used in certain types of studies, e.g., allozyme electrophoresis

A second back-up vial in 95% ethanol should be preserved in situations where potential loss of frozen tissues is an issue.


The MVZ provides vials and other supplies for collection of tissues that will be deposited into its collections. Liquid nitrogen (LN2) is supplied by Praxair and can be ordered through the administrative office. Curators and research staff have nitrogen tanks and dry shippers of various sizes that may be borrowed upon request. Ted Papenfuss also has two portable –20oC freezers (different sizes) that he is willing to loan upon request. (Excel file of LN2 tanks and portable freezers in the MVZ, with policies on use).

Tissues should be put into standard Nalgene vials to enable easy cataloguing into the collection. Two types of vials are available:

  • 2 mL sterile cryogenic vials for frozen tissues (purchased in bulk, 1000 vials per case)
  • 1.5 mL sterile vials with a gasket for non-frozen tissues (purchased pre-packaged, 25 vials per bag)
Labeling vials

All tissue vials should be labeled with the collector’s (or preparator’s) initials and personal catalog number, and with the taxonomic identification of the specimen. Specimens that cannot be identified fully should be labeled with the best possible identification (e.g., generic name, family, etc.).

Collector numbers should be written twice, either on the vial or with one number written on a cleared-and-stained tag put inside the vial. VWR pens (available from MVZ) are preferred for writing on vials – especially those storing etoh tissues because they are alcohol resistant. Permanent ink pens (e.g., rapidograph) should be used for writing on tags inside vials.

Notations in field catalog

If tissue is saved for a specimen, this should be indicated in the field catalog along with other data. The number of vials per specimen (if > 1) and the type of tissue preservation also should be noted, e.g., “frozen tissue” and/or “tissue in 95% etoh.” If preservation method is not indicated, the default is assumed to be frozen. It is also important to note tissue type if non- standard tissues (muscle, liver, kidney, and/or heart) are saved, e.g., “tail tip,” “toe clip,” “scale,” “blood,” etc.

Data for samples that are non-vouchered, either because a voucher is not saved or because it is left elsewhere for disposition, should be recorded in a field catalog in the same manner as vouchered material. Non-vouchered samples should be given a field number in sequence with other material, as if a traditional specimen were saved and catalogued by the collector, and all relevant data (locality, date, ecological or behavioral information, etc.) should be noted. Disposition of the voucher also should be recorded, e.g., “specimen discarded,” “animal released,” “voucher left in Mexico at UNAM,” etc. Again, it is important to note tissue type if non-standard tissues are saved, e.g., “blood only,” “tail tip only,” etc.

Animals that are brought to the Museum alive for later preparation should be given a collector number in sequence with other material, with the annotation that the “specimen” is alive. Data on specimen preparation and tissue preservation should be added at the time that the animal is killed and preserved. However, if a piece of tissue (e.g., tail tip) is saved when the animal is initially collected, that should be noted in the field catalog.

International Transport of Tissues

Individual researchers are responsible for getting information on rules and regulations for international transport of tissues and associated equipment/supplies on commercial airlines. However, we can provide the following guidelines. Permits for importation of tissues are covered in a separate document.

LN2 is not permitted on commercial airlines. After completing a field trip during which frozen tissues have been collected, we recommend the following procedures:

  • empty the tank right before departure
  • pour some of the LN2 over “blue ice” to freezer them at ultracold temperatures
  • put the tissues along with frozen “blue ice” in a soft-sided, insulated cooler that can be purchased at a sporting goods, hardware, or drug store. The cooler can be hand-carried as baggage if it fits the size requirements

Alternatively, the tissues can remain in the emptied tank. If the tank is in good condition, the tissues should remain frozen for at least 24 hours. One tip is to add vials half-filled with water into the tank before the nitrogen is emptied; these act as ultracold “ice cubes.”

Both the empty tank and cooler can be transported as baggage. However, it is a good idea to check with the airlines to make sure that they do not have any special regulations. It is also a good idea to declare your tank, stating simply that it is an empty cooler for scientific samples.

Ethanol is considered a dangerous good in certain quantities and concentrations; thus, shipping and/or transportation must follow the regulations. Vials with ethanol should be well-sealed to prevent leaking (e.g., with parafilm, in a plastic bag or box). Ethanol- or buffer-preserved tissues should be packed with baggage, and not hand-carried.

Be aware of possible regulations on transport of collecting equipment (especially sharp objects, firearms). Firearms (“long guns,” i.e., shotguns and rifles) may be taken as baggage but they must be declared at the air ticket counter. The basic rules are:

  • firearms must be broken down and transported in a locked, hard gun case
  • ammunition must be packed separately from the firearm(s)
  • ammunition must be in its original container
  • ammunition is limited to a certain weight

Always check with the airline re: transportation of such items before your trip. Certain countries also require special permits for importation of firearms (permits for “long guns” may be different from other firearms).

The MVZ has drafted a letter that should be carried during international field work. This letter certifies that the carrier is a researcher with the MVZ and is conducting legitimate international scientific research. A copy of the letter is available from curatorial staff, and should be shown to agents upon request.

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