A Fascinating Frustule from Italy - Observation of the Week, 1/17/23

Our Observation of the Week is this diatom (potentially Cymbella peraspera), seen in Italy by @dgborin! 

“I'd say I'm addicted to nature,” said Davide G. Borin. “I really need a walk in the wood or a hike in the mountains at least once a week, and if I can't do it, my mood suffers.” And while Davide did end up going to a technical high school, he said his second choice would have been biology. 

Part of Davide’s interest in nature was sparked by a toy microscope he received in middle school. 

I liked it so much that in high school, as soon as I earned enough money, I purchased a good quality one that I used for decades. I still own it, but after a long hiatus, in 2016 my interest renewed, so I purchased a 1960/70 Carl Zeiss Jena Amplival microscope, a lot of objectives and accessories, and last year a semi-professional USB camera. I'm still improving my photomicrography skills.

While out on walks, Davide likes to collect water samples to put under his microscope, and these Cymbella diatoms were collected while he was out and about, and he made the image you see above through a pretty involved process.

I took the photomicrographs with 3 different objectives: Planapo 25x/0.65, Planapo 40x/0.95 and Planapo 100x/1.3, with oblique illumination and monochrome green light (frustules are colorless and monochrome light avoids chromatic aberrations). I used a pancratic (zoom) condenser set to N.A. 0.9 (25x and 40x) and N.A. 1.4 with double glycerine immersion (100x). I connected the USB camera through a 2.5x correction projection eyepiece, took the shots as 16 bit monochrome TIFFs and post-processed them with DarkTable, a free RAW processing software I use for all my photos.

I honestly don’t understand too much of that process, but the resulting images are undeniably compelling. Diatoms are tiny, single-celled brown algae that have a silica-based outer shell or frustule. Frustules have tiny pores for waste removal (they actually do go through urea cycle) and other functions, and come in many amazing shapes. 

“[On hikes] I take my DSLR equipped with a macro lens (usually a 150 mm) and wear camouflage clothes, to better blend in the environment 😅,” says Davide (above, in his outdoor gear).

I discovered iNaturalist about a year ago thanks to an advertisement in the local natural history museum. I subscribed immediately, but I started to upload observations only this last summer, so I'm still new…

iNaturalist is really helping me to learn about nature in a fun way: I didn't expect to find such a variety of species in a heavily anthropogenic environment such as the Padan Plane, where I live. I also like the idea to be able to contribute to science, even if only for a tiny bit.

- There’s a lot of great info about diatoms at diatoms.org. Did you know that diatoms produce about 20-30% of the oxygen we breathe?

- There are over 23k observations of diatoms on iNat, check them out!

Posted on January 18, 2023 12:14 AM by tiwane