Many features of living microscopic organisms can only be documented by videos, some activities are even only visible by slo-mo or time-lapse footage. The platform for presenting such observations is here:

The platform for presenting such observations is the YouTube Channel here >>>

The marine Roscoff-worm (Symsagittifera roscoffensis) is a green acoel worm, the color of which is due to the symbiosis with the green alga Tetraselmis convolutae. Like in polyclad flatworms the movement of this animal is accomplished by cilia which cover the whole body. The beating of the cilia results in metachronal waves that are dexioplectic in this species. This can be observed by slow-motion video (12x time-expansion)

See the YT-video here >>>

Tetraselmis sp. is a single-celled green alga with a conspicuous "eyespot" (photoreceptor???) and 4 flagella. The alternating rotation of the cell in clockwise and counter-clockwise direction raises the question, if and/ or how the beat of the 4 flagella is coordinated.

One species of this genus: Tetraselmis convolutae is also living as symbiont in the worm Symsagittifera roscoffensis (Xenacoelomorpha).The remnants of the digested diet are spit out through the mouth, again with the help of the trophi.

See the YT-video here >>>

Asplanchna is a raptorious rotifer living in the plankton of lakes, ponds and water reservoirs. It feeds on other organisms that happen to be in the vicinity of the frontal part of Asplanchna, the so-called apical field. This apical field has some sensory bristles which, when touched by the potential prey, trigger the uptake of the diet by the mastax with the pincer-shaped trophi. The apical field is surrounded by arrays of cilia and bristles (corona), which partly cause the propulsion of the animal, partly help to swallow the diet by beating in characteristic ways. The function of some parts of the cilia arrays is still not understood. The remnants of the digested diet are spit out through the mouth, again with the help of the trophi.

See the YT-video here >>>

As the name "S. longispinata" already suggests, this rotifer has a conspicuous long dorsal spine. This raises of course the question if there is a biological function of ths trait. Although "spiny" rotifers are usually living as plankton forms in lakes or calm waters this is the first time this species was found twice in lotic waters. The video presented here also gives insights how the cilia in the corona work

See the YT-video here >>>

Although the pond near the river Ruhr has been surveyed for microscopic organisms several times in the past 20 years, this is the first time that the predatory Cupelopagis rotifers could be observed here. Maybe again that because of the high temperatures in our area in the last months these rotifers that have probably been imported from tropical regions are now able to survive in this pond.

See also the YouTube-video of the trophi of this rotifer here >>>

Interesting organisms (among others): rotifers: Cephalodella paxi, Kostea wockei, Proales similis, Trichocerca taurocephala, Squatinella longispinata, Synchaeta gyrina, Tetraselmis sp.

Presumably because of the high temperatures in our area in June/July there were many Philodina megalaotrocha-specimens in a plankton sample from a nearby pond. A closer observation showed that this bdelloid rotifer has two tufts of long cilia on the ventral side of the head (arrowhead in right image). This is the only bdelloid species which has such a "goatbeard". The weird thing is that these tufts beat with a frequency of about 120 Hz.

The function of this cilia array and its oscillation is not known.

See also the YouTube-video of this rotifer here >>

In the National Park Unteres Odertal, many paths are constructed using concrete slabs with steel rings, allowing the slabs to be transported and laid using a hook. The steel rings are set into grooves that fill with water during rain. In this habitat with its frequently fluctuating water levels, a unique composition of microorganisms has developed over time, so adapted to these extreme environmental conditions, that some have not been found in any other habitat in this area. Two species of rotifers were found here: the monogonont Encentrum lutra and the bdelloid Abrochtha intermedia. The latter may also be the prey of E. lutra .

Because of the conspicuous red eyespots and the lobed rostrum the monogonont rotifer Dicranophorus hercules is a very distinct species within the genus. Observed for the first time in our area.

Compared to other bdelloids the rotifer Philodinavus paradoxus seems to be rarely recorded. This observation from a slay rock in Wuppertal is only my 3rd encounter with this species in 20 years.

While in the last century the Wupper was one of the most polluted rivers in Europe, where virtually no life was possiblle in the water, the ecological situation now is very much better. This is also true for microscopic organisms like rotifers. The abundant diatoms are the nutrition source for many of the rotifer species like Dicranophorus hauerianus, Encentrum spinosum, Euchlanis lyra, Henoceros falcatus, Notholca foliacea or Proales theodora.

The monogonont rotifer Notholca caudata was found in the lake Baldeney.

Already in 2024 I recieved a dry sample from a lithotelma in Oukamaiden/ Morocco. After being kept dry for 18 months, when soaked, some species of microinvertebrates could be revived, for example bdelloid rotifers like Abrochtha intermedia, Adineta sp.6; Habrotrocha cf bidens and Philodina roseola and a water-bear (Tardigrada) that was feeding on rotifers.

Only after a few days since a long frosty season a plankton sample from a near-by water reservoir Heilenbecker Talsperre showed a number of pelagic rotifers. A rare observation was a Polyarthra specimen without any fins, a so-called "aptera"-form.

In a plankton-sample from the atlantic sea the monogonont rotifers Synchaeta triophthalma and Synchaeta vorax could be observed.

In tidal rockpools Encentrum marinum, Testudinella caeca and Testudinella clypeata were found. In the Aber Ildut-area Notholca bipalium could be documented.

The monogonont rotifer Polyarthra minor has been found in the Haspelmoor in Bavaria.

The monogonont rotifer Keratella serrulata has been found with hair-like structures covering most parts of the lorica.

Are these structures bacteria or excretions from the pores in the integument??

The monogonont rotifer Proalides subtilis has been found in a pond near Augsburg, also the bdelloid Henoceros falcatus was found in a billabong of the river Lech. Updated information for Ploesoma triacanthum and Kellicottia longispina.

Again the microscopy workshop was held again at the "Wildnisschule Teerofenbrücke" at the end of May. As in the years before, a focus was on the study of on the "aufwuchs" on slides that had been exposed a few days earlier in various places of the side arms of the Oder. A heartily "Thank you" to R. and U. Szewzyk for preparing and organizing this workshop!.

The focus of my own observations was the study of (dry) mosses and ephemeral waters for rotifers. Some previously never seen morphotypes were discovered, such as Cephalodella intuta, Monommata aequalis, Monommata maculata. Also the backward movement / swimming of Collotheca mutabilis (and thus the reverse beating of the cilia of the infundibulum) could be documented in a video. Here is a list of some observations.

Bryceella perpusilla is an inconspicuous small rotifer living in moss. Only by high speed videography some details of the corona become visible that even a scanning electron microscope cannot detect. This YT-video shows the movement of the cilia

Updated information on the metachronal movement in the corona of Synchaeta pectinata

A superficial observation of the ventral side suggests a homogenous ciliary field. A closer look reveals several distinct areas of cilia with different functions.

Updated information on the metachronal movement in the corona of Proales fallaciosa .

The metachronal movement can be observed in YT-video that shows the cilia of the corona.

The bdelloid rotifer Henoceros falcatus and the monogonont Encentrum spinosum have been found in the Marscheider Bach, also the Heliozoan Raphidiocystis pallida with parasites. In the nearby Sphagnum-moss-cushions the rotifer Bryceella stylata showed an interesting morphological feature that is new to me.

The monogonont rotifer Parencentrum lutetiae has been found in cyanobacteria mats in a pond in Hattingen.

The "eigenthümliches Organ" is the caption for a drawing that can be found in the treatise “Über den Bau und systematische Stellung der der der Rädertiere” by Franz Leydig (1877)
Incidentally, the rotifers were still classified as “ciliated crustaceans” at that time.

Hudson/Gosse (1886) also depicted the same organ in a drawing of "Stephanoceros Eichhornii" (now: Stephanoceros fimbriatus), where it is referred to as the “ganglion”.  

I do not know of any literature from the 20th century where this organ is mentioned; as far as I know, there is also nothing in the Remane-book (1935).
Although the structure is reminiscent of the unusual retrocerebral organ of Trichocerca similis, the function of this structure probably remains in the dark for the time being.

The bdelloid rotifer Mniobia scarlatina is characterised by unregularly formed protuberances on some parts of the integument. It was found in the liverwort Frullania dilatata, but -in contrast to some other bdelloid rotifers like Mniobia symbiotica or Habrotrocha annulata- never inside the lobules of the liverwort. In this sample most of the specimens were filled with fungal parasites, probably Triacutus subcuticularis. Also the liverwort had been infected by a fungal parasite, the Ascomycete Bryocentria brongniartii.

The bdelloid rotifer Adineta rhomboidea was found in the liverwort Frullania dilatata. Several specimens were filled with fungal parasites, probably Triacutus subcuticularis. Adineta was observed while trying to remove a parasite spore: this "cleaning behavior" could be documented in a YT-video.

The metachronal movement of Campanella umbellaria was found to be dexioplectic.

The peritrich ciliate Vorticella also shows dexioplectic movement of the perioral cilia; and although the direction of the metachronal movement of the telotroch cilia of the swarmer is opposite to this both metachronal movements are dexioplectic.

In the plankton of the "3-Insel-Teich" the rotifer Collotheca pelagica was found. The ciliary beat of this rotifer is different from that of most other rotifers. This pond is one of those rare habitats where Kellicottia bostoniensis can be found.

In the venns of the Hildener Heide the rare rotifer Wierzejskiella velox was found with an unusual stomach content.

The "project" was: to observe the red alga Torularia atra and the organisms that live as epibionts on it and around it. In contrast to the observation in 2022 this time the rotifers Dicranophorus hauerianus and Proales theodora, both species feeding on diatoms were present in large numbers. Also Encentrum grande was found. Also from two creeks which flow into the Wupper samples were taken. Both showed the bdelloid rotifer Henoceros falcatus, which seems to be a common rotifer in many creeks in Germany and France.

Macrotrachela quadricornifera rigida from Hattingen. More on this here >>>

Harringia eupoda. More on this here >>>

The rotifer Dicranophorus edestes, found in a nearby creek, had some conspicuous birefringent crystals in the body. The function of these crystals is unknown. It turned out that a specimen found two years before in france had also such crystals. More on this here >>>.

Dicranophorus luetkeni from NSG Schwalm.

Again there were lots of interesting microscopic organisms in the ditches of this nature reserve. One monogonont rotifer was found that on the first glance looked like a Proales species. However a closer look at the trophi revealed the dicranophorid rotifer Encentrum hofsteni. More on this here >>>

During the annual meeting of European microscopists in Darmstadt/ Germany I was presented a sample frm South Africa which should contain some not yet identified rotifers. It turned out that one of the morphotypes is the bdelloid roitifer Pleuretra brycei. More on this here >>>

Philodina alata is the only bdelloid Philodina-species that is characterised by lateral processes on the trunk. This rotifer was found by the British antarctic expedition (1907-1909) and has been described by James Murray in 1910. Since then this species has been found several times on the same continent. There are no records of this species in any other place of the world, so this species has been regarded as endemic. Now a Philodina morphotype identical to the description of P. alata by Murray has been found in large quantities in several lithotelmata in Central Spain. More on this here >>>

Das Räderorgan der Rädertiere, die Corona, ist einzigartig im Tierreich und somit das Alleinstellungsmerkmal dieser Tiergruppe. Die charakteristischen Cilien als Basiskomponente für die charakteristische Bewegungskoordination lassen sich aber auch in vielen anderen Organismen finden, so z.B. -wie der Name schon sagt- auch in den Ciliaten (Wimper"tieren"), aber ebenso in Vielzellern wie Plattwürmern oder auch bestimmten marinen quallenartigen Lebewesen (Rippenquallen / Ctenophoren).

Erst durch Hochgeschwindigkeitsaufnahmen ist es möglich geworden, die Bewegungsmuster dieser Organismen zu verstehen.

Sowohl die Grundlagen der mikroskopischen VideoTechnik, als auch einige der damit erzielbaren Erkenntnisse werden in dem Vortrag vorgestellt.

Eine Zusammenfassung (pdf) ist hier zu finden.

The bdelloid rotifers Embata hamata and Henoceros falcatus have been found in a creek near the "Kemnader See". Both species seem to be adapted to the sediments in lotic waters like another bdelloid/ philodinavid species Philodinavus paradoxus which had been found there 14 years before. More on this here >>>

The monogonont rotifer Eothinia elongata can be easily confused with other notommatid rotifers or even rotifers from the genus Proales. More on this here >>>

In contrast to the observations of last year, when in July high abundancy of the plankton rotifer Ascomorpha ovalis could be observed in the water reservoir Heilenbecker Talsperre, now in May this species could not be found at all, but instead a rotifer from the same genus: Ascomorpha ecaudis was found in masses. A closer look at the integument reveals that this species has many holes in the integument which at least in part function as openings for sensory cells "lateral antennas". The number of lateral antennas in this species is likely to be more than 4 that can be found in Asplanchna

Still in a sample from the "NSG Unteres Odertal" the monogonont rotifer Asplanchna priodonta with parasites was found. This parasite attacks the integument; only after intensive observation I could find out that it is located on the inner side of the integument. More on this here >>>

After the environmental disaster on the Oder River last year, the question was whether the environmental damage would also be felt in the region of the Teerofenbrücke / WildnisSchule (yet) this May in the waters there. The observation of microorganisms from selected sampling sites now show a great biological diversity. Here is a list of the species found with emphasis on rotifers.

Proales sordida and Testudinella mucronata have been found in this pond.

Bryometopus viridis and a male specimen of Cephalodella forficata have been found in a ditch. Updated information for Cephalodella gracilis

Among others the strange ciliate Spetazoon australiense was found in the natur reserve NSG Recker Moor. Also Cephalodella forficata has been found there

This species has only recently (2009) been described by W. DeSmet and M. Verolet from the Ardèche/ France. Now this species as been found also in NRW/ Germany.

Sinantherina socialis found in a pond in Bochum/ Germany. Also Pelomyxa palustris has been found there.

Der geplante Workshop ist die Folge von einem Vortrag bei der BMG im Jahr 2019, bei dem ich meine Arbeitsweise bei der Mikrofotografie vorgestellt hatte. Prof. Hausmann hatte damals angeregt, dass  die dort vorgestellten Arbeitsschritte mal praktisch nachvollzogen werden sollten.  Hier sind einige Informationen und Materialien zu dem Workshop zu finden.