Hawaiian Umihotaru ("Sea Fireflies")

This is another entry from a few months ago, which I am now adding to my public journal because I believe this observation requires a bit of additional explanation.

While looking for lesser brown scorpions and introduced gecko species at night in Kaanapali, I noticed some tiny, luminescent specks which would appear and rapidly fade with each wave that crashed on the shore. They were so small and scattered that I initially believed they were merely some form of visual noise (i.e. the Ganzfeld effect), however upon closer inspection, and confirmation from my younger brother that there were, in fact, transient, glowing objects appearing on the sand, I realized I was looking at some form of bioluminescence.

Up close, the specks could be seen to flash a pure neon-blue, and slowly dissipate. Eventually, we managed to collect an individual while still bright enough to detect (The organism itself was smaller than many grains of sand on the beach, and transparent) and I began to try to photograph it. I had with me the Canon EF-S 60mm 1:1 macro lens, which was sufficient to capture sand-grain sized objects in reasonable detail. I was excited to find that each speck had discernible eyes and organs, and the recognizable, Hello Kitty-like form of an ostracod. However, taking a picture of the subject proved to be more of a challenge than capturing it in the first place. Focusing at 1:1 in the dark was slightly difficult feat to begin with. The dimness of the glowing substance made it impossible to photograph at any reasonable shutter speed, even at the highest ISO and widest aperture settings, and without a tripod, any image I took either drowned out the luminescence with the flash or was nothing more than a blue smear in the darkness. In addition, each specimen lasted only a few minutes before going completely dark and fading back into the sand, adding a narrow time constraint to each attempt.

Eventually, I realized I could create an image showing both the glowing luciferin and the ostracod itself using the flash on a long-exposure shot. The photos in this observation are not "compound" images comprised of a shot taken with the flash and a long exposure, but single exposures of a 3-10 seconds for which the non-glowing parts of the image are only illuminated during the flash. This technique is effectively a normal photo and a long exposure in one, "freezing" the subject while allowing the faint glow of the luciferin adequate time to "catch up" with the light of the flash.

The non-macro shots in this observation were taken with the long-exposure feature on an iPhone 12 mini. I typically do not like the way images are processed on recent iPhone models, as it generates wildly inaccurate color and detail in an attempt to replicate the vibrance and subtlety of a higher quality camera (I have no issue with using smartphone cameras for iNat, my iPhone SE worked great for years of observations, I only have a problem with the blatant overcompensation of the newer iPhone software. I could write a whole journal post complaining about Apple's design philosophy when it comes to cameras, but I digress). However, in this case the automatic post-processing was quite useful, and represented the glowing ostracods much better at a distance than my DSLR could, at least without a tripod to take very long exposures. That said, please note that the ostracods appear FAR brighter in these photos than in real life-- the software seemed to designate them some kind of significance (maybe an algorithm intended for photos of starry skies?), and made them more prominent.

After downloading my photos, I did a bit of research into bioluminescent ostracods in hopes of refining my ID. However, I found very little info on their presence in Hawaii, with the majority of studies and sightings being in the Caribbean, Japan, and sometimes the west coast of North America.

Publicado el enero 14, 2024 08:41 TARDE por hsug1747