Unlikely intrigue of tissues

By Michelle Wille

Most of us here at the Zoonotic Ecology and Epidemiology group have an interest in birds. Some of us are bird encyclopedias with an expansive knowledge of species names, identification, calls, etc, while others have a passing interest in identifying the species that inhabit our gardens. Those of us working on flu are rather focused on Mallard, which is our study species. At our study site, Ottenby, there are Mallard individuals that are resident, those that are migratory from the Baltic states, and those that come from father afield (ie. Russia). Most of our interactions with these birds are rather brief – weight, ring, swab sample, and maybe a blood sample. Regardless of the number of Mallards I have had the opportunity to handle, I often marvel at their beauty, especially the males. The iridescent green/blue feathers shine in sunlight, and the little twirl on the tail feather is rather endearing.

Envisioning the beauty of a dead Mallard is a different story – ew, gross; blood and guts and gore. It is hard for most of us to image the cellular structure of the insides of Mallard; indeed there are few reasons (or opportunities) to have a look at tissues under the microscope. I had an interesting opportunity to dissect a number of apparently healthy ducks with influenza A infections, and while I was supposed to be focused on the presence of influenza antigens, I couldn’t help but marvel at the beauty and intricacies of the inside of Mallards.

One of my favourite structures was the nasal concha – these spiral structures are found within the nasal cavities (ie inside the bill between the nares/nostrils and base of the skull), and have an important function in airflow, humidification, heating, and filtering of air inhaled through the nares. The walls of the nasal cavity, and the nasal concha, are lined with respiratory epithelium – tall rectangular cells, goblet cells (tall rectangular cells that secrete mucous), and cillia (or little “hairs” which move around the mucous or dirt). Below this layer, there are large mucous glands.

While learning about cellular structure and tissue anatomy, I was often captivated by sections that were “not normal”. Often these anomalies could be attributed to parasite infections. For example, one of the ducks had Capillaria (a nematode) eggs embedded in the epithelium of the oesophagus. The oesophagus is the tube that moves food down to the crop, and thus is highly muscular, contains innervations, and an abundance mucous glands for lubrication. This infection was probably unpleasant for the duck due to inflammation. Capillaria infection has not been recorded in wild Mallard oesophagus prior to this, but this is likely due to limited opportunity to examine tissues from wild birds.

A great misconception of scientists is that they take the beauty out of everything and try to analyze it. The contrasting reality is that most scientists find beauty in everything – from the study of charismatic megafauna, cellular structure, the colour and shape of bacterial colonies, to the sequences of genes and genomes. Though, from time to time it is important to remember to stop and smell the roses…

– Michelle Wille

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