Hejnol Group
Comparative Developmental Biology of Animals

Hejnol Group January 2013

Our group studies a broad range of animal taxa using morphological and molecular tools to unravel the evolution and development of animal organ systems.

To understand the evolution of the biodiversity seen on planet earth is one of the major goals in biology. How animals explored new habitats from only being confined to the marine environment and the how the forms diversified is still one of the most tremendous questions to be answered.

In the “genomic age” with its novel and advanced molecular tools one is able to study the connection between the genotype and the phenotype and how the interaction of genes and cells lead to the formation of a fertile adult, that is able to reproduce and thus assure the survival of its species. The “translation” of the genomic information into a living individual is realized during the process of development. Studying the development of an organism in which a single fertilized cell gives rise to a complex animal is not only fascinating, but is also one of the key processes to study to understand the evolution of animal diversity.

To understand the evolution of animal diversity one has to study the development of a broad range of diverse animal groups using the comparative approach. Our team applies modern descriptive and molecular techniques to gain this information from a broad range of animal taxa using animals that can be kept in the laboratory but also collected from the local marine biota.

Beside established morphological methods like confocal microscopy we are using 3D timelapse microscopy (4D-microscopy) and single blastomere injections of cell tracers to study the cell lineage of embryos of mainly marine invertebrates.

Molecular approaches include the study of gene expression patterns and experimental methods to unravel the genetic framework underlying the formation of different organ systems, such as the CNS, the alimentary canal and other organs. Large scale sequencing approaches are used for gene discovery and are also used for the phylogenetic placement of the specific species.

The research focus on the description of the development regarding cell lineage and gene expression includes understudied taxa such as local bryozoans, brachiopods, nematomorphs, aplacophoran molluscs, platyhelminthes, priapulids, polyclad flatworms etc.

Molecular functional approaches are used to study the development of acoels, rotifers and gastrotrichs.

Further collaborative approaches address the use phylogenomics to resolve metazoan phylogeny.

acoel Convolutriloba macropyga and the rotifer Adineta vaga
Figure 1:
Model systems we use for a functional genomic approach: a) the acoel Convolutriloba macropyga. b) the rotifer Adineta vaga.
(photo: left, Tom Shannon, right, Andreas Hejnol)



Cell lineage of the embry of the rotifer Philodina roseola
Figure 2:
Cell lineage of the embryo of the rotifer Philodina roseola. a) DIC image of the 25 cell stage b) 3 dimensional arrangement of the blastomeres in the 200 cell stage (3D reconstruction with SIMIBioCell. c) Cell lineage of embryo shown in b)



Animal phylogeny

Figure 3:
Animal phylogeny on the basis of 1495 genes used in a phylogenomic approach
(Hejnol et al 2009).

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