Which freshwater algae do we see?

In the video you will find some algae found in fens in the ‘Wortel Kolonie’ located in Belgium. The ‘Wortel Kolonie’ is a beautiful protected nature reserve with a complex of buildings that served as an asylum for vagrants long time ago. (Here you will find the information in Dutch, English, French and German).

This nature reserve contains a few shallow fens. On a summer day in July, some water samples were taken from two fens using a trawl net with a mesh size of 30 microns. Without examining these samples in depth, more than fifty different organisms, phyto- and zooplankton, were found. Only a few of them are shown in the video. In one of the algae we see a oogonium.

The names of the organisms in the video are deliberately omitted here, to give hydrobiology enthusiasts the opportunity to identify the organisms themselves.

Vorticella - The fastest bell in the world?

Vorticella is a genus of single celled organisms living in both marine- and freshwater habitats. The members of the vorticella genus are commonly referred to as bell animalcules because of their shape. The thing that makes bell animalcules unique are their long stalks which they use to attach themselves to a substrate, which could be things like rocks, twigs and even small animals. The stalks of vorticella resemble our muscle fibers but are able to contract a lot faster than our muscles are. If the cell gets disturbed, it’s able to contract the stalk with an impressive speed of up to 6 meters per second as a defence mechanism to get away from danger or possibly scare predators away.

One Coleps makes two, cell division

• Alga: Coleps
• Order: Prorodontida Corliss, 1974
• Family:  Colepidae Ehrenberg, 1838
• Genus: Coleps Nitzsch, 1827

Coleps is a barrel-shaped ciliate, notable for its regularly arranged ectoplasmic shields, or platelets, of calcium carbonate. The covering with the scales is sometimes completely or partly absent immediately after an amitotic division (direct cleavage of the nucleus without the formation of mitoses). This is clearly visible in the accompanying video. Cell division took approximately 45 minutes. The color of the cell is usually brown and is less determined by the color of the food consumed than with other ciliates.

Algae Bloom

 

These beautiful golden spheres are single colonies of the golden algae synura. Like all other organisms, synura is able to reproduce and one colony eventually turns into two. But when conditions are right, reproduction happens a lot more frequently and what used to be a few colonies can quickly turn into an enormous algae bloom. Even though each synura colony is microscopic and only measures around 20-30 microns in diameter. Their large numbers in an algae bloom are able to turn the water in their freshwater habitats a yellowish brown color. A bloom of synura like the one in the image usually happens in spring and fall when the water is cold. But not all algae will bloom in cold water.

Family Cochliopodiidae de Saedeleer, 1934

For this Amoeba see the excellent website of the world famous amoeba specialist Ferry Siemensma.

"DIAGNOSIS: Amoebae partially enclosed within a flexible cuticle or wall (tectum) usually covered with microscales (Cochliopodium) or with a dorsal fibrous cell coat without scales (Ovalopodium). The covering is open along the region of attachment to the substratum; with no well-defined aperture.

Amoebae in this family have been classified as testate amoebae by Page (1987b) but are included in this chapter because they resemble euamoebae at the light microscope level. Typically they have a distinct hyaline zone often with short subpseudopodia, and a prominent central granular hump."

Daphnias - Some of the smallest and most common crustaceans

We all know some of the bigger crustaceans like shrimps, lobsters and crabs. But far from all crustaceans are as large as these. Daphnias are some of the smallest crustaceans in the world and can be found in almost all ponds, streams, lakes and other freshwater habitats. Their size ranges from a few hundred microns to around 5 mm for the largest species. Like other crustaceans, daphnias are covered in a hard exoskeleton for protection. Underneath this tough exterior are organs like a heart, a digestive tract, reproductive organs, an eye and a primitive brain. And because daphnias are mostly transparent, it's easy to observe their anatomy on your own.

In the back of the animal is a cavity used for protection of their embryos as they develop. After a few days the babies are fully developed, able to swim and feed, and ready to enter the real world. At some point the mother will lift her foot creating a small opening for the babies to swim out of. In a matter of days, the newborn are ready to reproduce themselves and these animals are therefore able to multiply rapidly when conditions are right.

The embryos on the left are fairly new, but the embryos on the right 

have developed eyes, are able to move and ready to be born

Aeolosoma - The strangest worm in the world?

Aeolosoma is a genus of annelid worms like earthworms. But unlike earthworms, these are much smaller and can be found in different freshwater habitats like ponds and streams in many parts of the world. But it's not just in nature you are able to find these as they also inhabit almost all freshwater aquariums, and probably also a huge part of unchlorinated pools. In aquariums they are introduced with food or plants and can sometimes be found in extremely large numbers.

Which diatoms do we see here?

The Macrofauna Werkgroep Groen Hart Leudal in The Netherlands, found some diatoms in the river Swalm near their clubhouse. It is a challenge to name diatoms if the cell contents are still present in the silica skeleton. The organic content should be removed first with the help of chemicals. Yet an attempt can be made to identify these still living tiny algae, which were caught on video with the help of the Motic inverted microscope AE31E with Motic PlanApo 20X and 40X objectives and the Moticam cameras 1080 and S6.

The Swalm is a small river in Germany and the Netherlands. Its source is in North Rhine-Westphalia, Germany. The Swalm flows into the Meuse across the border with the Netherlands. Its total length is 45 km.

The wetland overgrown with trees and heath/bog areas along the Swalm provide a diverse habitat for fauna and flora. Frogs, dragonflies, damselflies, blue throat, kingfisher and golden oriole are to be found as are water crowfoot, bog myrtle and other rare plants. Brown trout, barbel and chub are at home in the river; along the river banks are also various members of the beaver rat family.

Which diatoms do we see in the video?

Bdelloid rotifers - An entire class of animals with no males

We have previously looked at the microscopic animals called Rotifers in general, but today we are going to take a closer look at a specific class of rotifers called Bdelloidea with quite a unique way of living. Bdelloid rotifers are extremely common all over the world where they can be found in different freshwater habitats like ponds, streams, moss, and garden birdbaths where they can be found in enormous amounts from time to time. These animals are incredibly tiny with a size of only 150 - 700 microns when fully stretched. Like other rotifers they feed on microalgae, bacteria, and single celled organisms. So far they sound just like other rotifers, however they are very different in a few ways.

Synura - The golden algae

When we hear the word algae many of us associate that with the color green. And some algae like desmids, are in fact green. But there are a lot of different kinds of algae, and far from all of them are green. Some are red or red and green like haematococcus, some are blue-green like spirulina, while others are yellowish, brown, or even golden.

Euglena - part plant, part animal

Cells with a nucleus are called true cells, or eukaryotes, which can be further subdivided into kingdoms like plant and animal. Plant cells and animal cells are different in their components and structure, but some organisms does not fit as neatly into these little boxes and can be tricky to place on ‘the tree of life’. One of these is the single celled organism euglena.

Euglena with clearly visible red eyespots

Mysterious crystal growth on tiny crustaceans

Crustaceans form a large group in the animal kingdom, and most are familiar with some of the larger members like crabs, lobsters, and shrimps. But many crustaceans are a lot smaller than those, and make up an important part of the food chain as food for fish and other larger animals. One of these planktonic species is daphnia magna, and with a size of 1.5 to 5 millimeters it is one of the largest in its family and just visible with the naked eye. However, it is not the daphnia itself we will focus on today. But a strange phenomenon that occurs on its body, as well as on a few other tiny crustaceans like it.

Female Daphnia magna carrying the next generation in a cavity.

Eudorina - a colonial algae

Eudorina is a genus of green freshwater algae. Each eudorina are multicellular colonies consisting of 16, 32 or even 64 individual cells held together by a gelatinous substance made of sugary proteins, or glycoproteins to be a bit more scientific. The individual cells in a colony are not much larger than our blood cells, and the entire colony is about the same size as the width of a human hair. The green color is due to the presence of large chloroplasts inside each cell used for energy production through photosynthesis.

Note the gelatinous transparent matrix surrounding each colony.

Hydra - The immortal monster of the micro world

A hydra might look a bit like a miniature octopus, but it is actually a lot closer related to jellyfish. It is relatively common in both tropical and temperate regions where it can be found in slow flowing streams, ponds and other freshwater habitats. At one end the animal has one to 12 tentacles which all have their origin around the mouth. In the opposite end is a ‘foot’ allowing the hydra to attach to a substrate. The body can measure up to 10 mm when fully grown and stretched.

Note the small buddig of a new hydra on the lower side.

Ithytrichia lamellaris: ‘Not observed in a hundred years’

In a little stream in Limburg, the southernmost province in the Netherlands, an apparently unknown animal was unexpectedly found by members of the Macrofauna Workgroup Green Hearth Leudal. During the determination an animal with a very remarkable shape was noticed in a partly transparent tube, which was no larger than 4 mm. The segments of the abdomen of the animal were lobed like bellows of an accordion. In addition, there was a drop-shaped appendix on each lobe. This had to be something very special. Internet gave little to no result. Until an article with a photo attracted attention. In the photo you could see an animal that looked like the captured one. The headline: ‘Not observed in a hundred years’, indicated that something strange might have been caught?

You need a unique sample for your teaching lesson? Have a look into your rain gutter.

It’s real life: Sometimes the good things are closer than expected. Your rain gutter not only disposes the water from your roof, but also collects detritus from its colonizers such as mosses and lichens. It’s an extreme biotope: wet and cold in winter, even freezing, dry and hot in summertime. Only few microorganisms survive this extreme change.

One of them just recently came into spotlight. In April 2019 the Israeli space probe Beresheet* crashed onto the surface of the moon; 585kg of weight caused a small caldera. Aboard there were several thousands of Tardigrada, also known like Water Bears. As they had been transported in dried condition, and apparently no water seems to be available on the moon by fog or rain, the probability of life on the moon in 2020 still is quite low.

No need to travel so far to meet this astonishing group of animals. Take a sample of detritus from your rain gutter, if dry, first let it soak in rainwater. After a few days at room temperature it is time to check the water sample. Tardigrada may be fixed on the surface of moss leaves, so it makes sense to place a moss stem on the glass slide and to strip off the leaves by using two tweezers, one fixing the stem, one stripping off the leaves against the direction of growth.

A dead Tardigrada: Sectoral structure of body clearly visible.

Volvox bloom

Volvox is a popular alga among microscopists because of the beautiful images it produces under the microscope. The volvox in the video was unexpectedly found in a pool in Eindhoven, the Netherlands in early November 2019. There were so many of these species present that one could speak of a bloom.

The green alga Volvox is a colony of cells that have started to work together. Some cells catch the light, others provide movement or reproduction. They have become so dependent on each other that you can speak of a multicellular organism.