Systematic Zoology

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Master Thesis

Pseudo-4D reconstruction of the head region of Engraulis encrasicolus (Engraulididae, Teleostei)

The technology of computer-aided 3D-reconstruction of semi-thin section series (here: surface rendering) most recently allows for a visualization and analysis of complex interwoven organ systems. The individual components cannot only be examined in any combination and perspective concerning their shape, constellation and correlation with the original sections, but also be quantified volumetrically. For example one can gain a novel “4D” insight into the ontogeny of the head region of a species by comparing selected developmental stages.

The heads of six larval stages of the European anchovy (Engraulis encrasicolus, SL 3 -20 mm) were fixed, embedded in Epon, serially sectioned (400 – 2000 sections at 2 µm), stained with Richardson´s reagent and photographed (Olympus dotSlide System, 10x objective). Using Amira® software, these digital image stacks were aligned, segmented, rendered, volume measured and, if necessary, smoothed.

Digital surface models of the following organ systems were generated after individually labeling the organs at a spatial resolution of 0.6 µm x 0.6 µm x 4 µm on each section: chondrocranium, osteocranium, masticatory muscles, brain, eyes, retinae, lenses, optical nerves, eye muscles, and the vestibular system.

The comparison of selected organ systems (3D) of successive developmental stages allows for the understanding of the changes of shape and volume during their development (i.e. pseudo 4D) and for recognizing the mutual influences of directly adjacent organs. Based on this data the modifications of the complex head region during the larval-period can be modeled almost seamlessly (morphing).