This image is of a pectoral fin of an undescribed loach, Petruichthys sp., from Myanmar. The image was taken on the Tescan Vega SEM. This is high magnification SEM of turbercles (conical, multi-cellular aggregations of keratin produced by epidermal cells) on the surface of the pectoral fin in a mature male specimen of Petruichthys sp., an undescribed species of loach from Myanmar (commonly known as the “Rosy Loach” in the aquarium hobby). This horny (keratinous) patch of tubercles is one of many male-specific (sexually dimorphic) traits of this small-bodied species of freshwater fish. Each individual tubercle is ~20μm tall and the SEM shows ~80 organized into a series of regular rows. The image was taken and submitted by Dr. Kevin W. Conway in the department of Ecology and Conservation Biology.