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

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.

Nematodes - The most common animal on earth

Around 80% of all animals on the planet are microscopic worms called nematodes, more commonly known as Roundworms. In fact, if you go outside and take a teaspoon of soil you will have caught about 50 of them. However, these tiny organisms are not just present in the soil, but can also be found in aquatic habitats, in moss, on trees and rocks, and almost all other places on the entire planet, from deep oceans, to high mountains.

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.

A common pest

Rosebay willowherb or Fireweed - Chamerion angustifolium - is a very striking and widespread plant species. During flowering it is easy to recognize. The upright plants have a cluster-shaped inflorescence at the top that tapers to a point. The color of the flowers is purple or purple-red. The separate flowers in the cluster are somewhat symmetrical on both sides because the top two petals are somewhat smaller than the bottom two. The scattered leaves are narrow and lanceolate and closely resemble the leaves of Willows.

Some of the smallest crustaceans in the world

Crustaceans are a huge group of animals living all over the world. There are more than 67.000 known species which dramatically vary in size from around 0.1 mm to almost 4 m. Most are aquatic animals, like crabs and shrimp but some are terrestrial like the woodlouse. All crustaceans have a tough exterior called an exoskeleton used to support and protect their body. This armor is mainly made up of long polymers called chitin combined with calcium carbonate to make it hard. Here we will look at a few of the smallest crustaceans you might encounter in a water sample. The first one we take a closer look at is a copepod.

It is covered in symbiotic algae. The copepod is surrounded by 

younger individuals at different stages of development.

Mastocytoma dog

A mast cell tumor* (mastocytoma) is a potentially very malignant tumor of mast cells in the skin. This tumor is the most common skin tumor in dogs. It mainly occurs in the skin but not only there. A mast cell tumor can look very different. The tumor can be in the skin or under the skin. The presentation is usually like a solitary solid (sometimes soft) bump with a diameter of a few mm to as much as 10 cm. The overlaying skin is often alopecia (bald spot), erythematous (abnormal red), sometimes eroded or ulcerated (open wound). One should not squeeze the tumor; histamine granules* can be released (degranulate) This can cause an anaphylactic reaction, which means that the animal can get into shock. As mentioned, the tumor can be red in color, contain extra pigment or have the normal color of the skin.

As with all bumps on the skin, it is never possible to determine on the outside whether there is a tumor and what kind of tumor it is. Therefore, further investigation must also be carried out in the event of a suspicion of a mast cell tumor. This can be done by means of a FNAB (Fine Needle Aspiration Biopsy) or by means of a tissue biopsy. Cells are taken from the bump and these cells are assessed under the microscope (by a cytologist) as in this case. A FNAB gives a correct diagnosis in a large number of cases, but in all cases a tissue biopsy gives a correct and sometimes more extensive diagnosis.

Aeolosoma

Aeolosoma are very small annelid freshwater worms found all over the world. Even though these worms have been known for almost 200 years we do not know much about them. In fact, we know so little that there is still uncertainty on how to spell its name. Some will spell it aeolosoma, while others spell it aelosoma. 

Another mystery yet to be solved is which class of worm it is. Some place it in the same class as earthworms, the oligochaetes. Others place them in the polychaetes with bristle worms, and still others think they belong to their own separate class on the taxonomic tree of life. However it seems like the majority describes them as polychaetes.

Video showing aeolosoma at different magnifications with different microscopy techniques. 

Notice the almost complete clone in the back end of the worm

Image stacking - for increased depth of field

A microscope is not only useful when investigating microscopic specimens. To see the fine details of insects and other larger specimens, a microscope is also extremely handy. However, the depth of field (DOF) is very shallow and only a small portion of the specimen can be in focus at each time. This is not due to bad objectives or microscope, but due to the high magnification. But this problem can easily be overcome by the use of an image processing method called focus stacking.

Illustration of the shallow depth of field.
The focus plane is at the top of the right eye and mouth

Tardigrades - Some of the toughest, and smallest, animals on earth!

Tardigrades are some of the smallest animals on the planet. Most are around 500 microns (half a millimeter), but newly hatched tardigrades can be 10 times smaller than that. And the biggest ones only reach about a 1.5 millimeters. Tardigrades are more commonly known as water bears. This is because of their bear like appearance when they waddle around looking for food. But, unlike a bear, tardigrades have eight legs which all end in several claw-like toes. Most tardigrades are herbivores and eat thing like algae and other plant material. However, not all tardigrades are grazers, some are hunters and eat things like bacteria, single celled organisms, rotifers and even other tardigrades.

Living tardigrade from the genus Ramazzottius.

Tardigrade from the genus Milnesium mounted in hoyer's medium.

Large cattail

Typha latifolia, called ‘large cattail’ in English, is a water plant that is mainly found in eutrophic and acid water, along the shores of ponds, ditches and in swamps. This perennial has an upward and wide-spread growth habit. It is easy proliferating through rhizomes. If planted in a garden pond, locking it in a good pond basket is the message. The leaves are broad, linear and blue-green colored. Large cattail blooms from June to September with double cigar-shaped ears. The male ears are at the top, the female right below. After wind fertilization, the characteristic brown colored ‘cigars' form the female flowers. The seeds of cattail develop from the flowers on the cigars. The seed fluff is normally transported by the wind. The plant is hardy, endures sea breeze, air pollution and has a beautiful winter silhouette.

 

Pollen bring light into the darkness

A way of classifying pollen species is by monitoring auto fluorescence images of pollen grains. Several components of the exine (i.e. the outer layer of the pollen wall) show conspicuous auto fluorescence in the pollen grain.