Molluscan Research: Techniques for collecting, handling, preparing ...

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Introduction
The majority of biodiversity to be discovered and described
is of small to minute size (e.g., Bouchet et al. 2002). For
molluscs, that number is in the range of at least a hundred
thousand (Steitz and Stengel 1984; Brusca and Brusca 2003).
Bouchet et al. (2002) found that the modal size of molluscs
from New Caledonia is only 3 mm in the most diverse size
class of 1.9–4.1 mm, which contains a quarter of all
specimens sampled. As investigators working on small sized
molluscs, we have developed and assessed various
collecting, sorting and handling techniques that facilitate
their study. To our knowledge, there is no previous detailed
and comprehensive account of working methods for
micromolluscs, other than a few very general discussions
(e.g., Robertson 1961; McLean 1984; Kurtz 2005).
We give here a summary of our joint experiences, while
acknowledging that further refinement will inevitably be
needed. The notes given here arise from trial and error
experimentation by the authors over more than a century of
professional working years. While the observations reported
do not stem from controlled experiments, they provide
important observational data and a starting point for future
experimentation and improvements. Thus the methods
presented are neither exhaustive nor foolproof. In part, our
intention is also to provide guidelines that should assist
others to find the most efficient methods for them and to
avoid known problems. For that reason, we include
discussions of failed methods and remarks on some of the
problems encountered. There rarely is a single ‘best’
technique for any given procedure and the techniques used
by any given practitioner reflect personal preference and
individual modification to some degree. Although most of
the techniques described have been applied by us in marine
or freshwater settings with shelled molluscs, many if not
most of the techniques described here could also be applied
to terrestrial shelled molluscs. However, different techniques
to those given here may be necessary with shell-less species,
specifically those relating to collection and narcotisation. We
do not deal with methods relating to histology or
transmission electron microscopy as these are well covered
elsewhere. While we describe suitable equipment that can be
used for dissection of micromolluscs, we do not elaborate on
dissection methods and techniques.
A mollusc is here considered small if the largest
dimension of the animal or last whorl of the shell (if a
gastropod – even if tall spired) is less than 5 mm in size. The
smallest molluscs reach around 0.6 mm in adult size, but
many larval or juvenile stages are smaller. While we use the
term ‘micromolluscs’ for species that are less than 5 mm in
maximum dimension as adults, this is clearly arbitrary.
Figures 1–3 show some of the diversity of micromolluscs.
Institutional Abbreviations
AMS—Australian Museum Sydney, New South Wales,
Australia
BMNH—The Natural History Museum, London, Great
GEIGER ET AL. (2007) MOLLUSCAN RESEARCH, VOL. 27
Britain
GNM—Natural History Museum, Gotenburg, Sweden
LACM—Natural History Museum of Los Angeles County,
California, USA
NHMB—Naturhistorisches Museum Berlin, Germany
NMNZ—Museum of New Zealand Te Papa Tongarewa,
Wellington, New Zealand
NSMT—National Science Museum, Tokyo, Japan
SMNH—Swedish Museum of Natural History, Stockholm,
Sweden
USNM—United States National Museum, Smithsonian
Institution, Washington (DC), USA
ZMO—The Zoological Museum, University of Oslo,
Norway
ZMUC—The Zoological Museum, University of
Copenhagen, Denmark.
Other abbreviations
CPD—critical point dried.
FST—Fine Science Tools (supplier of microtools).
HCl—Hydrochloric acid.
HMDS—Hexamethyldisilizane.
KOH—Potassium hydroxide.
MORIA—Microtool brand.
NaOH—Sodium hydroxide.
LaB 6 —Lanthanium hexaborite.
LCD—Liquid crystal display.
LED—Light emitting diode.
OsO 4 —Osmium tetroxide.
PVA—Polyvinyl acetate.
PVC—Polyvinyl chloride.
SCUBA—Self Contained Underwater Breathing Apparatus.
SDS—Sodium lauryl sulphate.
SEM—Scanning electron microscope, - microscopy, -
micrograph.
TEM—Transmission electron microscope, - microscopy, -
micrograph.
VPSE—Variable pressure secondary electron detector.
The workspace
Work with small molluscs is greatly facilitated by the use of
proper tools. It is perhaps not as important to use exactly one
model of something for a certain kind of work, but rather to
be familiar with a range of tools so some alternative options
are available.
When working with small objects, the timing of various
steps in a procedure is critical. Therefore, it is important that
tools and the workspace are clean and well organised. Also,
as in most laboratory situations, suitable precautions should
be taken when working with chemicals that are noxious,
toxic, flammable and corrosive (e.g., ethanol, formalin, HCl,
KOH, OsO 4 , HMDS: see Appendix, manufacturers’ Material
Safety Data Sheets). In respect of these concerns, a fume
hood with an extractor fan is an essential part of any
laboratory space.