www.bryozoans.nl - Weblog

Verder in Nederlands



I found Plumatella geimermassardi in my favorite lake. I knew the location for the last few years and had seen bryozoa there, but though them P. fungosa in a different growth form (see 22-6-2006 below).
This time i brought a sample home and put it under a microscope - definitely P. geimermassardi: transparent zooids and tubes which are not densely packed and grow closely together (pictures soon to be added elsewhere in this site). Also the statoblast are as described in [Wood 2003].
Last year P. geimermassardi was found on plastic garbage in a lake in the south of the Netherlands, so this is the second find i am aware of.
I will also go back to the Oostermoersevaart to check if the P. fungosa there is not also P. geimermassardi.


I spent a week of diving around Dahab along the coast of the Gulf of Aquaba in Egypt. This time I spent hunting for bryozoa in this marine environment. This was not really simple. There is barely any literature, the literature there is, is scientific and not so usable for an amateur. After some serious searching in varied places I found several species which are shown here.


After a very busy time finally i found some time for my bryozoans hobby. During the fall i took several species home and observed them through a microscope. Most of the pictures and videos i took are on the site.
I was amazed by all the activities. Polyps move and search the environment looking for food. The mouth actively sucks in food and then swallows it. Tentacles are often moving and can be moved individually as well as be bent individually. The stomach and gut show continuous movement. This is significantly more than retracting and extending the polyp - the only movements that can be observed by the naked eye.


Yesterday evening i went back to the Oostermoersevaart to see how P. magnifica is doing. There were fairly many smallish colonies. Possibly caused by a month of extremely hot weather (July) followed by an extremely wet month (August). I noticed that the colonies grew more on the sides of the substrate and less on the underside (as compared to last year). Also many colonies grew in places where they did not grow last year, places with more exposure to the current. Possibly this is the result of the last two weeks that were warm and dry and therefore low current levels.
P. magnifica seems to have clear preferences for substrate: it grows on stone, metal and wood and avoids polyester and plants.
I have brought a small colony home and put it under the microscope. Result will be on the web-site soon.
The water temperature was 21 C and the sight-depth about 50 cm.
Ecxept P. magnifica i also found C. mucedo with very elongated colonies. I did not find P. fungosa, but did encounter P. repens.


During my last dive i collected a C. mucedo colony and put it under a microscope. This video is the result.
On the Cristatella mucedo picture page (bottom) I have added a microscopic picture.


The last few weeks i have been on holiday out of the country. In that period rain has started falling. When i went back earlier this week to my favorite diving lake the water temperature had dropped to 19 degrees Celsius and the visibility had decreased from 6 meters to 2 to 3 meters.
Consequently (more food) the bryozoans were back. Cristatella could be easily found in many places (between 1.5 and 5 meters). P. fruticosa, P. articulata (very small colonies), F. sultana, P. repens and probably P. emarginata could be found here and there. I have not been to the P. fungosa location yet. I expect the numbers of bryozoans to increase over the coming weeks.
While writing this text i was wondering how the bryozoans do this. It seems to me that in a statoblast it is impossible to discern how much food is available. Is there a 'preprogrammed' delay in germination or is there a large spread in germination delay to prevent that all statoblasts die due to lack of food?


The previous week was hot and dry. The watertemperature has again increased with 2 degrees, the sight depth has increased -> less to eat for bryozoans. The byrozoans have almost completely disappeared. On places that a few weeks ago were packed with Cristatella colonies sometimes one or two can be found and sometimes a few statoblastst.
Looking back at the previous weeks i wonder about the sequence of the Cristatella mucedo development. First a few colonies develop to significant size. Barely any indication of colonies that split up. A few weeks later a massive development of new colonies, small at first, often near previous colonies. There is barely any statoblast formation so multiplication through statoblasts cannot be an explanation. Sexual reproduction? Could be and if that is the case, a larvae apparently takes only a very short time to select a new spot. See Cristatella pictures for an impression.


Yesterday evening, after a trip to Zeeland last weel, I went back to my favorite diving lake. Due to the very warm weather of the past week(s), the water temperature at shallow levels (3,5 m) had risen to 23 C. Below that it was still 17 C.
What came to my notice immediately was that the bryozoans, that were abundant two weeks ago, were strongly reduced in numbers. The Cristatella colonies were full of statoblasts and had become small and thin. On some places the colonies had died and some loose statoblast were all to be found. In deeper water (4 -5 m) i found some well developed Cristatella colonies. The other generally found species, Fredericella sultana, Plumatella repens, Plumatella fruticosa and Paludicella articulata, could only be found here and there after serious searching. By the way, this is a yearly recurring (last two years at the least) phenomenon.
I think the explanation can be found in food scarcity (more than in lack of oxygen due to the warming weather), combined with increased rate of development (and decline) due to the higher water temperature. The food scarcity follows a period of food abundance (spring algae bloom), that has been followed by a strong decline in algae due to a decline in food (all consumed) and due to massive algae consumption by copepodes that had developed to massive numbers.
Now i'll have to wait to September to find more well-developed byrozoans.


The day before yesterday i went back to the same spot as before. Mainly to make pictures as my flashlight had a flat battery early on in the dive. Close inspection during the dive and of the pictures afterwards gave surprising results:
- several C. mucedo colonies growing on loose silt / peat flakes. - the bulbous colonies on the branches i had assumed were P. repens clearly were P. fungosa. A much smaller and closely packed polyp, grey. I had not found P. fungosa before in this location!
- On several places on the walls of the tunnel under the road were P. fungosa colonies. Some flat on the wall and some bulbous where they extended from the wall.
- I found a piece of pipe sticking out of the bottom with significant sized P. fungosa colonies.
- More amazing: on many places on the wall, if not all places not covered in sponge, a bryozoan grew in a creeping fashon whith clearly visible red-brown tubes and here and there a polyp. The polyps looked very similar to the P. fungosa polyps elsewhere on the same wall. Same size, same shape, same color. According to all literature i am familiar with this cannot be P. fungosa as this bryozoan always grows in bulbous form. Still i am convinced it is P. fungosa that has adapted to a circumstances that do not threaten with overloading of silt. Pictures follow as soon as i have time.
- in some places P. articulata grew in small colonies flat against the concrete of the wall.


I just returned from a more in depth survey of a small stream that feeds my favorite dive lake. On 5-6-06 i wrote about P. repens colonies in that stream, so i went for a closer look. I found 8 P. repens colonies on different branches of 2 or 3 trees. All colonies were compact and surrounded the branch completely. At some colony edges kreeping extensions could be seen with the P. repens tubes in plain sight. Some colonies started to grow thicker than the substrate.
The stream goes underneath a road and today i went back in the tunnel the stream goes through. I had seen sponges on the walls before. Last time i was here i also found colonies of P. fungosa. Compact colonies, with a grey shine and small polyps that were closer together and more regularly organized than the P. repens colonies. Due to all the silt that blocks all view at the slightest motion i was very careful in my movements, so i had a good view of the walls. I was absolutely amazed to find that all of the walls were either covered in sponge or in bryozo colonies of clearly one species. In some places the typical P. fungosa dense 'lawn' growth form could be found. In most other places a creeping colony form dominated, with clearly the same polyps. The creeping tubes were rust/dark brown and of approximately the same size as P. articulata that could be seen here and there as well. In some places the 'lawn' type colonies extended creeping tubes. In other places tubes were thick and a 'lawn' type colony started to form. It was very clear that this was not P. repens. I had seen these colonies 10 minutes before and they were much larger, more yellow and less organized.
Although i found it nowhere in the literature, i confess i start to think that P. fungosa, like P. repens, has two colony forms: kreeping and 'lawn'. Depending on the local circumstances and the time the colony has had to grow, one or the other dominates.
I must return very soon for a more in depth study!


Today i went back to the Oostermoersevraart to search for P. magnifica. I found many colonies that, given the water temperature of 21 degrees Celcius, were growing nicely. Small colonies look very much like C. mucedo, which i also found there, but are different in structure. If one looks better the typical P. maginfica pink spot is a good differentiator. Pictures follow soon.
I found a rope hanging at an angle in the water completely overgrown with C. mucedo colonies. All were long, all grew in the length of the rope and they were in 'combat' for attachment space on the rope. Many colonies were hanging partly free in the water due to lack of space.
Last year i overlooked them, but this year P. articulata colonies, small and flat, were everywhere. P. repens grew in several places as well.
P. fungosa that i found in fair abudance last year was not there (yet?) this year.
On the aquatic plants i found very small round colonies. Last year they were there as well and i thought them young P. magnifica colonies. Now i know better (and will remove this picture from the P. magnifica page). What it is, i don't know. More research needed!


Yesterday evening i went diving in a different location. The lake bottom there was covered in fine peat that was so loose a small movement would send it in clouds into the water. To my supprise i found C. mucedo colonies in multiple places that had clearly not been moved there by wave action or so. I had found C. mucedo on ublikely substrates as strings of algae, but these could with some effort be classified as 'fixed substrate'. The loose peat was clearly not 'fixed'. Still C. mucedo colonies flourished.
C. mucedo (eand F. sultana) are still growing to abundance in some locations. If observerd more closely so does P. articulata. P. repens needs more careful searching. Aparently it is still too cold (15 C) for P. fruticosa and P. emarginata. These i found in earlier years in the same location.
I found two nice P. repens colonies on branches of an overhanging treeand possibly P. fungosa below a bridge (more study needed).


Yesterday evening was full of suprises. I thought to know all species, except for C. mucedo, prefer shelter for slib below or at best besides the substrate. So i found several F. sultana kolonies on top of the substrate.
The F. sultana colonies have grown to significant size, and that in three weeks!
P. fruticosa and P. emarginata have not shown up yeat. Possibly they need a rise in water temperature above 16 degrees in stead of the about 14 degrees that is sufficient for F. sultana to start growing.


Today the first observation of Cristatella mucedo this year. As in other years development goes fast. Whether the first small colonies are overlooked by me or the really grow very fast and grow to significant size in one week, i don't know (yet).
What caught my eye today is that most colonies are beside or below the substrate. This is the period of the end of the spring algeal bloom and aparently there is so much sediment in the water, that a sheltered spot is preferred. In other years C. mucedo grows mostly on top of the substrate.
Also found: P. articulata (was already active for a few weeks, colonies are fairly well developed and covered in sediment) and P. sultana (has small and thin colonies that look much luke P. fruticosa.).
Today i tried out a new camera - a Canon A620 - with a much better macro option, but without extra (macro) lenzes. I am not sure yet which camera gives the best results. A combination of this camera and extra lenzes would be ideal. The picture of C. mucedo on the startpage is a cutout of a photo with the new camera.