Innovative Methods for Zoological Collections
Museum specimens are compared morphometrically at the Molecular Imaging North Competence Center (MOIN CC) and the working group Functional Imaging Deutsches Primatenzentrum (DPZ) using high-resolution three-dimensional magnetic resonance imaging (MRI) and micro-computed tomography (μCT). These techniques allow completely new insights into the anatomy and, in combination with 3D reconstructions, also into biomechanical functions, which are nearly impossible with standard histological sectioning methods.
MRI analyses allows the non-destructive three-dimensional visualization, especially of soft tissues, with a high resolution of few micrometers. This technique is particularly well-suited to reconstruct the inner organs of invaluable type specimens, or old and rare specimens, without destroying them. The outstanding contrast between different tissue types allows the detailed reconstruction of important organ systems, such as muscles, hepatopancreas and sperm storage organs. These analyses are complemented by μCT analyses, which visualizes the radiopaque structures such as the exoskeleton of crustaceans. These complementing datasets can be joined using computer programs, which provides important information, e.g. on the interaction of muscles and exoskeleton. Similarly, the fusion of these techniques can be used to visualize the accumulation of radiopaque structures (e.g. heavy metals, minerals) in the hepatopancreas or food particles in the digestive tract. The application of these methods to time series of museum specimens quantifies the morphological diversity of a species, providing a better understanding of adaptive processes, and the continuity or discontinuity of morphological evolution. Moreover, the three-dimensional reconstruction of moving body parts allows biomechanical analyses. The investigations focus on the following organ systems:
- Digestive tract (e.g. adaptations due to changed food availability)
- Reproductive organs (size, reproductive cycles, functionality)
- Muscles (locomotion as a possible example of fast evolution)
- Nervous system (nerve connections as a possible example of slow evolution).
The μCT analyses are carried out with a research μCT (Viva CT 80, Scanco Medical) at MOIN CC. MRI analyses will be conducted with a 7T-Kleintierforschungs-MRI at the MOIN CC and with a 9,4T-Kleintierforschungs-MRI in the working group Functional Imaging. Large specimens can be analyzed in a 3T Ganzkörper-MRI. The necessary computer programs and analysis tools are available through the working group Functional Imaging. Extensive preliminary studies showed that high-resolution, three-dimensional imaging of historical museum specimens is feasible.
Ancient DNA (aDNA) is of low quantity and quality, often degraded and chemically modified. These properties are also often characteristic for DNA of museum specimens. The ancient DNA laboratory at the Institute of Clinical Molecular Biology (IKMB) in Kiel developed specific DNA extraction protocols and set up ultra-clean rooms, which meet the required high standards with regard to cleanliness, technical equipment and molecular Know-how, to obtain genetic information from aDNA samples. In addition, bioinformatics pipelines and enzymatic repair mechanisms have been established to confirm the authenticity of the aDNA. Protocols are available to enrich aDNA for whole genomes or specific gene. ADNA can be extracted from organic samples of various origins (e.g. teeth, bones, soil, museum specimens). The analysis of aDNA in combination with high-throughput sequencing allows a direct look into formative episodes of the evolutionary history of domesticated and extinct animals, and population genetic changes in museum specimens.