Ancient eyes under the microscope
To understand more about the biology, ecology and behavior of ancient organisms, Johan Gren, paleontologist at the Department of Geology, has during his PhD studies made advanced analyses of a variety of fossil tissues from all over the world.
Using microscopy and histology (the study of the microscopic anatomy of cells and tissues) he could establish information about the teeth of for example Mosasaurs - huge, now extinct marine reptiles. Like now living reptiles they had their teeth replaced in cycles. The formation of dentine, which is a bony bulk tooth tissue beneath the enamel, was found to be at higher rate in the larger taxa of mosasaurs than the smaller ones, which reveals that they could have their teeth replaced faster.
In eyes, skin and feather remnants from many fossils, Johan Gren and colleagues found accumulations of small micrometer-sized, round to elongated shaped structures. Similar microbodies have earlier been described as either melanosomes or fossilized bacteria. Melanosomes are animal cell organelles that contain light absorbing pigments, and have a function in coloring and photo protection in animal tissues. Hence, preserved melanosomes could potentially contain brand new information about biology and ecology of animals in prehistoric life.
To find out what the aggregated structures in this case was, the researchers made several analyses and found that the structures here most certainly are melanosomes indeed. To move on from there is however not a straight way forward. The researcher community in this type of paleontology is currently not in consensus on how to map the origin of melanosomes.
Johan Gren will defend his thesis on January 19, in auditorium Pangea, Geoloy Dept, Lund University.