Specimens for morphological study are
typically preserved by immersion in 70% ethanol. Larger specimens are
fixed by injecting them with 95% ethanol. Kahle’s fixative, otherwise
known as FAA (a mixture of formalin/acetic acid/alcohol in a ratio 18:1:1, with
5% glycerol added to keep the specimens from becoming brittle), can also be used
to fix specimens, although it renders them unsuitable for DNA extraction.
Whichever method of fixation is used, the chelicerae should be opened to
facilitate future study and illustration. Once fixed, the specimens should
be transferred to 70-80% ethanol or isopropanol for permanent storage (ethanol
is preferred, as it is better at preserving color). The alcohol should be
replaced fairly soon after the initial preservation, and again as necessary if
it continues to discolor. It may be possible to temporarily transfer
specimens into propylene glycol (found in some antifreezes) for shipment or transportation on airplanes,
although with airline restrictions subject to frequent change, the acceptability
of this practice should be verified first. Be sure NOT to use ethylene
glycol as a preservative if DNA extraction is intended.
Solifuges that are to be used for DNA
extraction may be fixed by injecting them and storing them in 95-100% ethanol,
flash-freezing them in liquid nitrogen, or storing them in RNAlater®. The
choice of method for preservation may depend on whether one is in the field or
in the lab, and upon restrictions in the transportation of reagents. Live
specimens collected during short field trips or obtained from colleagues are
preferably brought back to the laboratory alive for tissue fixation at
Specimens fixed by freezing alive in 95–100%
ethanol must be retained at low temperature for at least 7–10
days to ensure adequate fixation, after which the ethanol (now diluted) must be
replaced before the samples are dispatched or processed for DNA extraction.
This method has been found to significantly increase the yield of high molecular
presumably because low temperatures retard degradation of the tissues during the
period when fixation occurs.
(dry-shippers), which employ a double vacuum wall to absorb liquid nitrogen,
freeze specimens in vapor and will retain a temperature of -150°C
for up to three weeks. These can be used in the field when available.
Because there is no residual liquid, they may be transported on airplanes.
specimens that are stored in 95% or 100% ethanol typically must be shipped
through a courier service, as they are not permitted on airplanes.
When collecting trips extend for more than three weeks and/or refrigeration
facilities are unavailable, tissues will have to be fixed at ambient
is more difficult from specimens sacrificed by immersion in ethanol at
ambient temperature, especially during hot weather, so any available means
of keeping the specimens cool (such as ice chests or 12-volt refrigerators
designed for use in vehicles) should be employed.
ethanol into the specimen may be
insufficient to guarantee adequate preservation of high molecular weight
DNA, particularly in large solifuges, as the ethanol is unable to
diffuse through the specimen before the soft tissues have degraded through
autolysis (a process that occurs within a very short period of time, usually
a matter of hours). In
such cases, it may be necessary to make an incision in the opisthosoma or
remove a pedipalp and/or legs from one side of the specimen, to allow the
ethanol to diffuse more rapidly into the internal tissues. A sterile
scalpel and dissecting tray (e.g. a petri dish) should used for each
dissection to avoid contaminating one specimen with tissues from the
preceding specimen(s). It is also important
to use a high ratio of ethanol to tissue volume for each specimen or
specimen-lot because fixation will be inadequate if insufficient ethanol is
present. Ethanol should be replaced 24
to 48 hours after the specimen has been prepared, and as often
as necessary thereafter if it continues to
Well-preserved specimens are readily recognized because articulatory
membranes and internal muscle tissues turn white in color.
accurate collection data should be associated with each preserved specimen
or lot. This should include, at minimum, an accurate record of the
geographic location where the specimen was found, along with the date of
collection and the name of the collector.