Polarized light vision and marine crustaceans

This is a real image of a marine amphipod without any fancy photoshop tricks. Understanding these diamond-like patterns will require knowledge about polarized light and the role of polarized vision in marine invertebrates.

   When light reaches our eyes we detect wavelength (color) and wave intensity (brightness) information. That is exactly what the brain needs to build a visual picture of the surrounding world. Yet a lot of other information is left out. UV and infrared parts of the spectrum are the most obvious examples. Well, technically the human retina is sensitive to UV, but the eye lens filters it out. That is why individuals missing eye lens, for example due to cataract surgery, can see UV light. Some parts of infrared waves can be sensed by the skin as heat, which is how we can estimate whether a frying pan is hot or not. These features, however, don’t make up for the limitation of our vision.

   Aside from having a very narrow spectral sensitivity, we can’t detect light wave oscillation direction. This is another parameter of a wave in addition to wavelength and intensity. In the majority of cases each individual wave vibrates in a random orientation in a natural beam of light. But there are many natural exceptions that can be useful. This is why many types of invertebrates, birds, and fish found another visual world by means of enabling themselves to sense additional dimension of light—polarization and its angle.

Back from rainy Great Barrier Reef - some wildlife and macro/micro shots

    The Great Barrier Reef is renowned for amazing underwater sights... but the weather might seriously let you down. I spent most of the two-week long field trip indoors cursing the weather, yet managed to get a few shots.

The field trip took place at Heron island, which is a large coral cay. University of Queensland has a research station there.

Transparent water flea

   Most of small and microscopic invertebrates are transparent and sometimes make you feel that they are made out of glass. That fact makes taking pictures very difficult. In  case of this water flea, which happens to be Simocephalus vetulus, I spent 4 days by Photoshop manually stacking and stitching images and cursing all classes, orders, and families of crustaceans I could recall. No automatic software is capable of accomplishing this insane task. I find the combination of dark backgrounds and polarized light very spectacular for transparent animals in general, and though that at least one object deserved such attention. Hope it was worth it.

Hydras fight for food

   Hydras and daphnias became a "classical" pair of predator and prey model of pond microscopic animals. However, what is often forgotten, hydras tend to aggregate together in high numbers. Usually, the encounter is not like one hydra vs one daphnia. It's a real mess! During warm days it's possible to spot hundreds of these tiny hungry monsters on a single leaf laying underwater. Inevitably, they start competing for food. In this post I'll show how two hydras fight for a single water flea. Unlike in my other posts, the photographs are not made through the microscope. I tried Canon MP-E mounted on 7D for videography purposes, but made lots of stills during my project. May be these pictures will not impress you after previous hydra posts (1,2) but they show natural behavior.

Mysterious Bryozoa

Some pond animals might not look attractive at first glance. The majority of people who encounter a bryozoa colony most likely wouldn't recognize what it is. A hairy warm? A weird hydrozoa? After all, even the mention of words "bryozoa"and "moss animals" alone provokes only one question—"what the heck is that?" The truth is, molecular taxonomists have more or less the same question when approaching this group.

Bryozoa are among the least studied invertebrates. According to phylogeny analysis they are not relatives of cnidaria or, in fact, any known group of invertebrates. Some evidence suggests that they might be related to even less studied group of organisms—Entoprocta. But leaving phylogenetic and taxonomic speculations aside, bryozoa are colonial filter-feeding animals that are really abundant in freshwater and marine habitats. Their polyps are tiny and almost invisible to the naked eyes. Yet their colonies can reach up to several meters is size, although such giants are rare.

Hydra dance

Hydras are awesome dancers. They are very flexible and I could never get tired of taking pictures of all bizarre shapes and forms they take.

Microscopic Zerg invasion

This guy with an alien-like eye is a Moina sp., possible M. micrura, and I appreciate the help of photomacrography.com community in ID help. It has the weirdest eye I've ever seen and it reminds me of Starcraft and Zergs. Though I doubt the designers of this game ever seen pictures of water fleas or their eyes.

The pictures are taken in polarized light and I made it a long time ago (it's a stack of 12), though I thought it was ugly and not worth displaying. The flea has a winter egg developing inside.

Big microscopes

SEM

   When I was posting microscopy pictures I mostly used very basic light microscopes to get my images. Though the scopes I worked with are expensive, science today has bigger scales and modern microscopes can look very impressive even when you simply gaze at them.

   Few months ago I happened to visit a nanotechnology laboratory in Brazil and decided to show some cool gear in this post.

Viable Ancient Choanoflagellates from Siberian Permafrost

  Choanoflagellates are the closest unicellular relatives of the animals (Metazoa).

  They seem like very simple organisms. They have a flagellum and a collar, similarly to sponge choanocytes. They use these structures to capture bacteria. Some species have other external structures, such as basket-looking loricas and thecas.
 
Read more about choanoflagellates here and here.

  Choanoflagellates are very common in freshwater and marine environments and they look very gentle and fragile. Yet they managed to survive for around 28-50 thousand years in one of the most extreme environments on Earth. Part of my research was about studying these amazing protists that we found in the Siberian permafrost.