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REHYDRATION OF DRIED-OUT SPECIMENS: A NEW
APPROACH
F. NEISSKENWIRTH
Conservation and restoration of natural history collections, Bruchstr. 94, 45468 Mülheim an der
Ruhr, Germany
info@naturhistorische-konservierung.de
Abstract.—Different procedures are proposed in the literature for the rehydration of dried-out spec-
imens. These procedures vary greatly in their efciency and application. This work describes a new pro-
cedure that is inspired by the literature but that avoids heating the specimens. This method was applied
to reconditioning dried-out specimens from a historical collection (Swiss freshwater shes, bird brains,
and bird eyes), stored at the Naturhistorisches Museum Bern in Switzerland. The procedure consists of
ve steps. The rst step is the softening of hardened soft tissue with benzaldehyde and demineralized
water. The second step is an indirect rehydration with water vapor. The third step is a chemicallyinduced
direct hydration using a trisodium phosphate solution that allows the specimen to swell in size before
being washed with water to remove all additives. Finally, the rehydrated specimen is transferred into new
preserving uid. Because the dehydrating properties of ethanol as a preservative are problematic, this
paper presents the results of an experimental case study using a glycerol solution as a preservation uid.
Key words.—Fluid preservation, rehydration, dried-out specimens, cherry laurel, benzaldehyde.
INTRODUCTION
In November 2017, the Naturhistorisches Museum Bern (NMBE) received the private re-
search collection of Paul Steinmann (1888–1953), a well-known Swiss hydrobiologist. His
research on Swiss whitesh (Coregoninae) is presented in two of his most important works:
Schweizerische Fischkunde (Steinmann 1948) and Monographie der Schweizerischen Korego-
nen (Steinmann 1950). These two publications are important for the well-known Handbook
of European Freshwater Fishes (Kottelat and Freyhof 2007). Paul Steinmann’s ichthyoloical
collection is of high historical and scientic value. It includes a large number of specimens
of freshwater sh, including one holotype, numerous paratypes, and many extinct species
of Coregonus. The collection also contains eggs, developmental states, gonads, ns, scales,
and parasites of sh specimens.
The value of this collection lies in its signicance for Swiss cultural heritage, as it also
includes older material from past pedagogical collections of institutions like the Swiss Fed-
eral Institute of Technology in Zürich and various sh specimens that date back to 1870.
Therefore, any conservation treatment must take into consideration the collections histor-
ical value (see also Mulder 1997).
A typical challenge of natural history wet collections is the loss of preservation uids.
This can progress so far that most of the uid has evaporated, leaving a dried-out spec-
imen. Fluid loss happens especially due to poor-quality specimen containers that do not
seal correctly in collections that are not properly monitored over time.
This was the case with Steinmann’s collection. The collection was deposited for many
years in a storage container outside the research facility of the Swiss Federal Institute of
Aquatic Science and Technology (EAWAG), where it had been exposed to temperature
changes (cold winters and hot summers) and where there had been no monitoring of uid
levels.
The reconditioning project of the Steinmann collection was intended to restore the sh
specimens for further scientic study. In order to achieve this goal, the dried-out specimens
had to be treated with a nondestructive but efcient rehydration method.
Collection Forum 2020; 34(1):73–86
© 2020 Society for the Preservation of Natural History Collections
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74 COLLECTION FORUM Vol. 34(1)
It is of great importance to note that the decision to rehydrate dried-out specimens is
an irreversible intervention requiring reection. A dehydrated specimen will likely be sta-
ble over decades (Simmons 2014) but is signicantly less useful for morphological studies.
Rehydrating may enable further studies but may also compromise the specimens condition.
In this particular case, such risk was considered as acceptable.
It was decided to research rehydration methods that would be suitable for Steinmanns
ichthyological collection. Several case studies describing rehydration processes are reported
in the literature, most of which involved rehydration of small invertebrates. The procedures
include soaking specimens in alkaline solutions (Van Cleve and Ross 1947, Vogt 2001),
using a vacuum to facilitate exchange of the softening uid and air trapped inside the
specimen (Jeppesen 1988) and/or using heated surfactants to shorten the rehydration time
(Banks and Williams 1972, Waterhouse and Graner 2009). All of these methods are listed in
Simmons (2014: table 22). In all the above-mentioned procedures, the specimens are placed
directly in the rehydrating uid.
Wechsler et al. (2001) explain the importance and the most effective method of softening
dried-out soft tissue before the specimen is reimmersed in any kind of uid. The authors
propose that the specimens rst be placed in chopped cherry laurel leaves (Prunus lauro-
cerasus) and afterward rehydrated in a 1% aqueous solution of trisodium phosphate. The
treatment with cherry laurel leaves is often used in taxidermy as a means to soften skin on
old mounts. This publication is complemented by Wennerstrand (2015), who studied the
use of cherry laurel as a softening agent for archaeological leather objects in more depth.
Wennerstrand (2015) claims that the active compounds in the leaves are benzaldehyde fumes
and water vapor that are released when the leaves are crushed. An alternative treatment is
presented by Wennerstrand (2015) that involves the use of pure benzaldehyde and water
instead of cherry laurel leaves. The author argues that this method is not only less toxic
but also much faster and less contaminating for the treated objects. However, this proce-
dure was proposed and tested for the purpose of softening archaeological leather and not
specimens from natural history collections.
Another idea, proposed by Singer (2014), consists of using an indirect hydration with
water vapor to reverse the drying process. Specimens are not placed directly in a uid but
instead absorb water moisture in a closed environment. Because of its noninvasive prop-
erties and the lack of any chemicals, this method became the starting point for further
experimentation presented in this study.
Review of the previous studies described above led to the development of the following
hypotheses:
rThe rehydration of dried-out specimens is a process that requires time. Heat speeds up
the procedure but can damage specimens.
rTo rehydrate a dried-out specimen, it appears important to rst soften the soft tissue so
it can absorb water.
rSoftened soft tissue should be rehydrated gradually by using water moisture.
rTo overcome wrinkles and ll the soft tissue with uid, the already rehydrated cells
should be hydrated with either an alkaline solution or a surfactant.
rRexation of the specimen for its nal conservation helps the specimen to remain in its
regained rehydrated shape.
The present study aimed to take the best methods from the above-mentioned studies in
order to propose a complete rehydration treatment for the whole Steinmann collection.
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2020 NEISSKENWIRTH—REHYDRATION OF DRIED-OUT SPECIMENS 75
MATERIALS AND METHODS
Three collections of the NMBE were used in this study: the Steinmann collection
(see above), a discarded EAWAG collection, and mounted anatomical specimens from
the collection of Walter Küenzi (NMBE director from 1952 to 1964). An inventory
was carried out of this material, including photo documentation. The original Stein-
mann sh collection consisted of a total of 1,012 jars and other receptacles. The in-
ventory showed that 56% of the jars contained well-preserved specimens, but the rest
were in need of reconditioning (Neisskenwirth 2019). Of the total of 450 jars that
needed reconditioning, 70 jars contained numerous specimens that had completely dried
out.
The EAWAG collection consisted of 17 jars of dried-out sh specimens. It was deposited
together with the Steinmann collection in the previously mentioned storage container out-
side the research facility. The EAWAG collection was used as experimental material for the
Steinmann collection. The knowledge gained from the sh specimens of both collections
was applied to the dried-out mounts of the Küenzi collection. The anatomical specimens
collected by Walter Küenzi make up 13 dried-out mounts of bird brains and eyes. It dates
back to 1917 with formaldehyde as original preservative uid, similar to the Steinmann
collection.
A series of uid analyses and the documentation of the Steinmann collection showed
that most of the sh specimens were stored in a 4% aqueous formaldehyde solution. An
important goal of the reconditioning project of the Steinmann collection was to transfer
all the specimens from their formaldehyde solution into ethanol, part of the new policy of
the NMBE to avoid the use of hazardous preservatives and ensure the safety of staff and
students doing research on the specimens from their collection. Therefore, it was necessary
to nd a uid that enables the preservation of rehydrated specimens. Macleod and Van
Dam (2011) successfully used glycerol solution as a preservative uid. Because ethanol has
a strong dehydrating effect and formaldehyde is a health hazard, glycerin was used in this
study.
For the experiments in this study, a solution of trisodium phosphate was used based
on Wechsler et al. (2001), who recommended a concentration of 1%. Van Cleve and Ross
(1947) used a 0.5% or 0.25% solution, explaining that it would be less harmful to the treated
specimens. This was tested on later applications and showed equally successful results. As
such, a dosage of 0.5% trisodium phosphate was used for further treatments.
Chemicals used in this study included formaldehyde 37% solution, benzaldehyde
for synthesis, disodium hydrogen phosphate anhydrous for analysis (EMSURE®;
Sigma-Aldrich through Grogg Chemie) and sodium dihydrogen phosphate for analysis
(EMSURE), trisodium phosphate dodecahydrate ࣙ98%, TECHNICAL and glycerol 85%
(VWR through Grogg Chemie), thymol crystals (Grogg Chemie), and 99.8% absolute
ethanol (Alcosuisse). All dilutions were performed with demineralized water obtained from
the NMBE desalination plant.
Other materials used included pieces of polyethylene doormat “tropic green” from
Siena Home (subsequently referred to as the “spacer”) and a bath mat (subsequently
referred to as the “perforated rubber platform”), both purchased at a local hard-
ware store. Glassware included a microwave dish from Duran Consumer Glass (subse-
quently referred to as the “borosilicate container”). Notes, photos, and measurements
of weight during each step of the procedure helped to document changes and other
observations.
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76 COLLECTION FORUM Vol. 34(1)
Description of the Method
Softening the soft tissue.—The use of benzaldehyde was preferred over cherry laurel for
several reasons. First, cutting and collecting leaves is time consuming. Second, choosing
pure chemical products limits the number of hazardous fumes released during leaf chop-
ping (Dierks 2016) and possible contamination with other substances contained in the
leaves. Third, as the cherry laurel is required to be in direct contact with the specimens,
undesirable chopped leaf residue could accumulate in small orices and cavities of the
specimens.
Specimens to be processed were placed in a borosilicate container with an airtight lid
(see Fig. S1). It is important not to use plastic materials, as benzaldehyde will soften plas-
tics. Furthermore, the container should be large enough to hold two Petri dishes and the
specimen. One Petri dish was lled with 20 ml of concentrated benzaldehyde and the other
with 20 ml of demineralized water. The container was closed and left for 24 hours at a
room temperature of 20–24°C (it was observed that if the room was too cold, processing
time was much longer). During this process, benzaldehyde slowly oxidizes to benzoic acid,
a white crystalline substance. It should be noted that this substance is very dangerous to the
respiratory system. To avoid exposure to possible suspended particles of the benzoic acid
crystallization, a fume hood and personal protective equipment, including safety glasses,
gloves, and a dust mask, are mandatory.
After 24 hours, the container was opened and checked for crystallization of benzoic
acid (Fig. 1a). The specimens were turned over to expose the other side, and the container
was closed for another 24 hours. The specimens were then taken out of the container and
checked carefully for exibility.
If the crystallization process expanded in the container and threatened to contact the
specimen (Fig. 1b), the container was cleaned, and both the benzaldehyde and the water
were replaced. The procedure was repeated until the specimen showed a notable exibility.
The duration and repetition of this treatment depend on the scale and skin thickness and
size of the specimen and the length of time it has been dehydrated. Specimens smaller than
30 mm may skip this treatment because the steps that follow are able to soften the skin of
small specimens without exposing them to unnecessary chemical reactions.
Rehydration with suspension over water (100% relative humidity).—The specimen was
placed in a clean airtight container (as used in the previous step) on the perforated rubber
surface, resting on spacers to avoid contact with the water (Fig. S2). The container was
lled with demineralized water to a level dependent on the size of the container and height
of the perforated rubber platform and spacers. To prevent fungal growth, thymol crystals
were added to the water. The container was closed and set aside to allow the specimen to
absorb water moisture for at least a week. A constant room temperature of 20–24°Cwas
crucial, as a colder room can slow down the rehydration process. After this procedure, the
specimen gained considerable weight and regained more of its original appearance (Fig. 2).
Specimen swelling.—To ensure that the rehydrated specimen swells in the next treatment,
it must rst be tested to determine whether it oats or sinks in demineralized water. If it
oats, the specimen must again be treated with the previous step to absorb more water. If
this is due to air trapped inside of the specimen, a vacuum pump can be used to remove
the trapped air. For this, a container containing the specimen is lled with demineralized
water and placed in the desiccator. The pump is activated until the vacuum gauge achieves
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2020 NEISSKENWIRTH—REHYDRATION OF DRIED-OUT SPECIMENS 77
Figure 1. (a) Benzoic acid crystallization on Petri dishes after 24 hours of treatment. (b) Extreme benzoic acid
crystallization after 4 days of exposure in a test of growth speed without specimens (© NMBE, F. Neisskenwirth).
−0.6 bar. The desiccator is then opened to equalize the pressure inside the specimen (Jeppe-
sen 1988). This procedure can be repeated several times.
The rehydrated specimen was then immersed in an aqueous solution of 0.5% trisodium
phosphate (Na3PO4) to induce swelling. The swelling process must be carried out with cau-
tion, as excessive swelling of the soft tissue is irreversible and may cause structural damage.
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78 COLLECTION FORUM Vol. 34(1)
Figure 2. Specimen of juvenile Salmo trutta before (left) and after hydration through moisture (right). The rst
step was skipped because of the small size of the specimen (© NMBE, F. Neisskenwirth).
This damage typically happened only after the swelling process, and it was assumed that it
was caused by the alkaline solution. If dried-out specimens already exhibit cracks, swelling
is not recommended, as such treatment can lead to even greater damage to the specimens
(Fig. 3). Delicate membranes are also very susceptible to the swelling process, and, as such,
the swelling should be done under constant monitoring. Here again, a constant room tem-
perature of 20–24°C is essential. If the temperature is too high, swelling will be much faster
and may not be adequately controlled. During the present study, a doubling of the rate of
swelling on a hot summer day of 27°C was noted.
Swelling in small specimens is usually complete after a few hours, but, in the case of
larger specimens, this may take a few days. The eyes of sh specimens tend to bulge but
will return to their normal shape after nal storage (Fig. 4). Alkaline conditions can cause
clearing of soft tissues, as proteins and lipids are leached from the specimens. Because of
this, it is likely that the specimen will lose some of its original coloration, appearing more
translucent.
After this nal step, the specimen should be fully rehydrated and should have attained
its desired shape. At this stage, it should be possible to stretch and articulate ns, tail, and
jaw of treated sh specimens (Fig. 4).
Rinsing of additives with water.—It is important to rinse all the residual alkaline
trisodium phosphate solution from the specimen to prevent further swelling and possible
pH changes in the nal preservation uid. Specimens should be immersed in a water bath
lled with demineralized water for 20–30 hours. The contaminated water should be changed
twice during the process to extract all of the residual trisodium phosphate.
Transfer into preservative uid.—One of the most difcult part of the process is keeping
the rehydrated specimens shape in the nal preservative solution. Ethanol has the negative
effect of shrinking the specimen back into a dehydrated state because of its hydroscopic
properties (Fig. 5). Experiments attempting different transfer steps into ethanol for two
different species of dried-out sh specimens (Telestes soufa with softer skin and Gymno-
cephalus cernua with harder skin) resulted in visible dehydration through weight loss and
shrinkage of the specimens after all transfer attempts. To overcome this, J. Simmons and S.
Moore (pers. comm. 2018) recommend re-xing the specimen in a 3.7% solution of aque-
ous buffered formaldehyde for one to three days, as this process will return the specimen to
a more “balanced” state. To avoid decalcication and other possible damage caused by the
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2020 NEISSKENWIRTH—REHYDRATION OF DRIED-OUT SPECIMENS 79
Figure 3. Damaged specimen of Salmo trutta before and after swelling (© NMBE, F. Neisskenwirth).
formaldehyde, a buffer of disodium hydrogen phosphate and sodium dihydrogen phosphate
was added to the solution (subsequently referred to as “buffered formaldehyde”).
Afterward, the treated specimen was transferred from formaldehyde into ethanol us-
ing gradually increasing concentrations of 5–10% (e.g., 20–30–40–50–60–70–75% ethanol)
with at least 1 day in each solution. The specimens rexed and transferred to ethanol in
this way kept their shape better than those without rexing and with just three increasing
ethanol transfers (Fig. S3).
Better results were obtained when ethanol was avoided, and the specimen was transferred
directly into buffered formaldehyde. This because this preservative has no hydroscopic re-
action with the specimens. The sh specimen was monitored for at least a week to see if any
unwanted structural changes appeared.
An alternative method involves the use of glycerol solution as the nal preservative (see
A. van Dam, this volume). The specimen was transferred through three increasing glycerol
solutions, 30–50–70%, and nally into 65% glycerol solution for nal storage. The result of
this method was notably better than transfer into ethanol. A negative impact on specimen
shape was not observed in the present study after the transfer into glycerol. A side effect of
this method was the light transparency of the specimens skin due to the alkaline swelling
bath and the refractive index of glycerol (Fig. 6).
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80 COLLECTION FORUM Vol. 34(1)
Figure 4. (a) Dried-out specimens of Leucos aula and (b) the same specimens after rehydration and swelling in a
0.5% trisodium phosphate solution. (© NMBE, F. Neisskenwirth).
Application of the Method to Other Vertebrates
The rehydration method described above on the Steinmann collection was tested with
specimens from the Küenzi collection in order to determine the protocols effectiveness on
other vertebrates (bird brains and eyes).
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2020 NEISSKENWIRTH—REHYDRATION OF DRIED-OUT SPECIMENS 81
Figure 5. Juvenile Salmo trutta specimen. Dried-out specimen (left), swollen up (middle), and after the trans-
fer into a solution of 75% ethanol using gradually increasing concentrations of 40–60–75% (right) (© NMBE, F.
Neisskenwirth).
Certain specimens in the Küenzi collection had suffered a substantial loss of uid due to
leaking jar seals, leaving some of the specimens completely dried out. As these were voucher
specimens from the dissertation of Dr. Küenzi, it was decided to keep the collection in its
original buffered formaldehyde preservation uid. Given this decision, it was possible to
rehydrate the specimens without fear of water loss. A remarkable outcome of this exper-
iment was that the veins of the brain surface reappeared after the rehydration. There was
also a signicant increase in weight and a return of the original color of the anatomical
specimens (Fig. 7).
DISCUSSION AND CONCLUSIONS
Simmons (2014) emphasizes that the results of rehydration methods obtained from cer-
tain vertebrate and invertebrate species could not be transferred to other groups. He points
out that blind transfer of the methodology could fail and cause irreparable damage to the
treated specimens.
Indeed, a key nding of the present study is that the specic characteristics of the soft
tissues of different sh species and of the avian anatomical specimens have a signicant
inuence on the effectiveness of rehydration and on the duration of this procedure. Based
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82 COLLECTION FORUM Vol. 34(1)
Figure 6. Rehydrated Cobitis taenia specimens transferred in a 65% glycerol solution 4 months after the applica-
tion of the method (© NMBE, F. Neisskenwirth).
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2020 NEISSKENWIRTH—REHYDRATION OF DRIED-OUT SPECIMENS 83
Figure 7. Dried-out mount of eyes and brain of Podiceps cristatus (left), after the rehydration (middle), and after
treatment and ready to be sealed for storage (right) (© NMBE, F. Neisskenwirth).
on the present study, it appears that large dried-out specimens can take much longer to
rehydrate than smaller ones. The same is true for specimens with overly hardened soft tissue.
Wechsler et al. (2001) state that the method of preservation—preserved with ethanol or
xed with buffered formaldehyde—also affects the treatment time. In the present study,
this could not be demonstrated due to a lack of information on the original uid in the
dried-out jars.
Another observation of the present study is that partially dried-out sh specimens did not
respond as successfully as completely dried-out sh specimens to the rehydration method.
In these cases, gradual rehydration is recommended (Singer 2014). However, it was possible
to transfer partially dried-out sh specimens directly into their nal preservative (ethanol,
glycerol, or buffered formaldehyde) without rehydration, depending on the state of dehy-
dration of the specimens.
Further research on the methodology presented here is needed with respect to the interac-
tion between preservative uids and the weight loss of specimens associated with shrinkage.
The weight loss of specimens after the swelling process in the present study was irreversible,
even if the specimen was rexed with buffered formaldehyde immediately after successful
swelling. The most signicant weight loss and shrinkage in this study was caused by trans-
fer into ethanol, while rehydrated specimens stored in glycerol showed the least weight loss
after nal transfer. In the limited ndings of this study, glycerol and buffered formalde-
hyde solutions showed the best results. Glycerol has a much lower health risk than buffered
formaldehyde solutions and therefore is considered the most suitable of all three preserva-
tion uids used in this present study.
The method presented in this study was successful in achieving the desired exibility of
soft tissue in treated specimens for both sh and anatomical bird specimens. In addition to
the improvement in the sh specimens of the Steinmann collection for morphological study,
a substantial aesthetic enhancement was accomplished in the bird specimens in the Küenzi
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84 COLLECTION FORUM Vol. 34(1)
collection. Although color changes occurred during the rehydration of the specimens, many
of the anatomical details were visible or even restored to their original state.
ACKNOWLEDGMENTS
The author would like to thank Dr. Lukas Rüber, curator of the ichthyology collection of the NMBE, as well as
Prof. Dr. Ole Seehausen, department head of sh ecology and evolution of the EAWAG, for making the acquisition
of the Steinmann collection possible. Thanks also to Martin Troxler and Constantin Latt of the taxidermy depart-
ment of the NMBE for their extensive support during the research and experimentation of this study. Thanks also
to taxidermists Christoph Meier and Klaus Wechsler for sharing their valuable experience on uid collections and
the application of cherry laurel leaves and to Andries van Dam from the Leiden University Medical Centre for giv-
ing advice on how to transfer specimens into glycerol. The manuscript beneted from the critical comments from
Daria Kuzak, fellow student at the Cologne Institute of Conservation Sciences (Germany); Reto Hagmann, collec-
tion manager of the vertebrate collection of the NMBE; and especially Dr. Achim Reisdorf, curator of the natural
history collections of the Ruhr Museum Essen, to whom the author is deeply thankful for the intense amount of
time spent in the review. Last but not least, thanks to the whole pfc 2018 scientic committee for giving life to
the conference and this special issue of Collection Forum and especially to Andew Bentely, ichthyology collection
manager, University of Kansas, and the anonymous reviewers for their remarkable work correctingthis manuscript.
Résumé.—Différents protocoles sont proposés dans la littérature pour la réhydratation
des spécimens desséchés. Leur efcacité et leur mise en oeuvre sont très variables. Ce tra-
vail vise à dénir une nouvelle procédure qui sinspire de la littérature tout en évitant de
réchauffer les spécimens. Celle-ci a été testée pour sur des spécimens desséchés dune col-
lection historique (poissons deau douce, cervelles et yeux doiseaux), du Naturhistorisches
Museum Bern en Suisse (NMBE). La procédure se déroule en cinq étapes. Premièrement,
lassouplissement des tissus mous avec du benzaldéhyde et de leau déminéralisée. La deux-
ième étape est une réhydratation indirecte avec de la vapeur deau. Lors de la troisième étape,
léchantillon est regoné très délicatement grâce à une solution de phosphate trisodique,
puis lavé à leau pour enlever les additifs. Enn, le spécimen réhydraté est transféré dans un
nouveau liquide de conservation. Les propriétés déshydratantes de léthanol étant problé-
matiques, des tests utilisant du glycérol comme uide de conservation ont été lancés.
Zusammenfassung.—Die verschiedenen in der Literatur beschriebenen Rehy-
drierungsverfahren für trockengefallene Präparate unterscheiden sich sehr stark in
ihrer Efzienz und Anwendung. Die Verfahren wurden meist für spezische Tierarten en-
twickelt und sind daher nicht für alle Weichgewebe anwendbar. Ziel dieser Arbeit ist es, ein
neues Verfahren vorzustellen, welches sich zwar an der bereits existierenden Literatur ori-
entiert, gleichzeitig aber eine Erwärmung der Präparate vermeidet. Das Verfahren wurde
für die Aufarbeitung ausgetrockneter Exemplare aus einer historischen Fischsamm-
lung aus Schweizer Seen angewandt, welche sich im Naturhistorischen Museum Bern
bendet. Das vorzustellende Verfahren besteht aus fünf Phasen: Die Aufweichung des
Weichgewebes mit Benzaldehyd und Wasser. Einer indirekten Rehydrierung mit Wasser-
feuchtigkeit. Aufquellen der Probe in einer Trinatriumphosphatlösung mit anschliessender
Wässerung zum Auswaschen aller Zusätze. Überführung des rehydrierten Präparates in
neue Konservierungsüssigkeit. Da die wasserentziehenden Eigenschaften von Ethanol
in der Umsetzung problematisch waren, wurde eine experimentelle Fallstudie mit einer
Glyzerinlösung als Konservierungsüssigkeit durchgeführt, die ebenfalls in dieser Studie
vorgestellt wird.
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APPENDIX
Figure S1. Implementation of the specimen softening step. (© NMBE F. Neisskenwirth).
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Figure S2. Example of used materials to suspend specimens over water (left). Closed container with specimen
depicted in Fig.1 (right). (© NMBE F. Neisskenwirth).
Figure S3. Rehydrated specimens of Telestes soufa and Gymnocephalus cernua before and after the transfer in
ethanol 75%. (© NMBE F. Neisskenwirth).
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