ClassificationDescriptionRelevant literatureMy observations
Nederlandsclassification
Michiel van der Waaij
Pectinatella magnifica (Leidy 1851)
Nederlands
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Proposal for common name: Magnificent bryozoan or moss animal
Classification
| Class | Family | Genus | Species | First described by |
|---|---|---|---|---|
| Phylactolaemata | Lophopodiae | Pectinatella | P. magnifica | Leidy 1851 |
Synonyms
The following synonyms have been used to indicate Pectinatella magnifica:
- Cristatella magnifica (Leidy 1851)
- Pectinatella magnifica (Allman 1856)
Description
Also see the generic class and genus description in the classification page.
A combination of literature has been used to create this description.
| General | Forms very large colonies, up to two meters in diameter Colonies are always build from clearly recognizable rosettes of zooids |
| Color | White because of tentacles, brownish above water |
| Tentacle crown | Horseshoe shaped tentacle crown with 50 - 80 tentacles. |
| Size | One zooid is ?? long A colony maximum 2 m in diameter |
| Statoblasts | Statoblasts float (floatoblasts) and are saddle shaped with a single row of flattened barbed spines along the side of the annulus |
| Conditions | Can be both attached to several kinds of substrate as free floating in the water. Never in streaming water or at temperatures below 20 C (another source states 16 C) |
| Distribution | Mostly in North America, found in several places in Europe, including in The Netherlands |
| Additional | In 2004 statoblasts have been found for the first time in The Netherlands - in Waterschap Hunze & AA (Groningen & Drente) in the Oostermoersevaart, a slow moving stream that ends in the Zuidlaardermeer. Since then I found P. magnifica every year in this site. In 2009 P. magnifica was found in a pond in the city of Tilburg and in the Piepertkolk in Zwartsluis. |
Relevant literature
To be completed
[Mundy] - A key to the British and European Freshwater Bryozoans
[Wood II] - A new key to the freshwater bryozoans of Britain, Ireland and Continental Europe
My observations
- In 2004 the statoblast are found in The Netherlands for the first time - in 'Waterschap Hunze & AA"
(Groningen & Drente) in the Oostermoersevaart, a slow to moderate flowing subsidary to the
Zuidlaardermeer - 17 september 2005 i found the colonies and photographed them
The water temperature at that moment was 16 C, the day before 18 C.
The sight depth about 25 cm. The 'Oostermoersevaart' the colonies were found has brownish peat water with quite
a lot of suspended particles. The bottom is mainly silt. - Further decline of the water temperature can be handled by the colonies for a short time, as i found alive
colonies a short time later when significant rain had brought further cooling. Many colonies were dying by
then - The biggest colonies i found were about 20 cm below the surface below a bridge and below a small boat. The
colonies grew on and around the edge of a horizontal concrete part of the bridge, but not really on the side of
it.
Small colonies could be found on several places on aquatic plants along the water edge.
On a wooden pole in front of the bridge i found no colonies.
The 1/3 most upstream parts of the bridge also had no colonies. Possibly the current is too strong there. - My first impression was as if a group C. mucedo colonies were growing unusually tightly together. A better
observation showed this was not the case. - The small colonies on the aquatic plants were ball shaped and looked fluffy (see pictures).
- Just like C. mucedo the polypes are not very inclined to retract. Even the significant disturbance is caused
with my photocamera with macro lenze at close range did not induce the polyps to retract. After even more
significant effort from my side i managed to make them retract - see pictures. - A few days later i went for a more extensive search action and found much larger colonies on the underside of a
big flat bottom boat near the bridge. They were more than a meter in diameter. About half the boat was covered
in P. magnifica. Besides that wonderfull branching colonies of sponge (Spongilla fluvatilis) - I also found a ball shaped colony on the stem of a water lily of about 10 cm in diameter.
- The most colonies grew below the bridge, on boats and shallow (20 - 30 cm depth). Some colonies grew up to 1
meter depth on other substrates such as a sunk rowing boat. These were only found where hidden from the
current. - Some colonies were already in decline, most were not. In declining colonies thin whitisch structures developed
sometimes more than 3 times the hight of the colony (see pictures). - I took one of the colonies with me:
The colony feels like a stiff jelly and a bit slimy
The colony smells a bit of fish
The colony base - the jelly mass - is transparent and not really colored - Nearby i also found P. fungosa, c. mucedo and a hydroid polyp i had never seen before.
Besides a lot of sponge(Spongilla fluvatilis). - On 14 october 2005 i went back. Almost all colonies were in decline. Some colonies clearly showed
statoblast formation.
Some colonies were still active. The water temperature was 16 Celsius, but must have been lower than that
(possibly even 14 C), given measurements in a nearby lake. - A week after that friends went for a look and found no colonies at all. The water temperature had dropped
to about 13 Celsius and this is clearly too cold. - I was surprised by the spread in temperature sensitivity, possibly even by zooid or colony.
- Something i also wonder about is that P. magnifica makes very large colonies that apparently grow over a season.
In august no colony had any sign of decline. That implies that the zooid life is a season. This is far beyond
that of other species. C. mucedo for example is usually gone after 6 to 8 weeks and in P. articulata a large
colony has died off for a significant part by the end of the season. Also the literature describes an average '
lifetime per zooid of 6 weeks. At the other hand this implies that the food levels fluctuate less in this
stream than they do in a lake, so constant growth is possible. - I went back for a new inspection on 17 June 2006 .The water temperature was 21 Celsius, the sight depth about
30 cm. As it had not rained for a while there was no current. On several places i found P. magnifica colonies
in various stages of development. The largest were almost hand sized, the smallest were only 2 polyps and had
just emerged from a statoblast. I also found several statoblasts that had not yet germinated. Apparently P.
magnifica has a broad period of time for statoblast germination. Seems to me to be a fine strategy to deal with
uncertainty in temperature and food availability. In my observation C. mucedo is much faster in growing from no
colonies to masses of colonies.
