Cristatella mucedo (Cuvier, 1798)

Verder in Nederlands

  1. More information
  2. Photos
  3. Microscope photos and videos
  4. Statoblasts

Dutch common name (translated): Crawling yellymossanimal

Cristatella mucedo


Class Family Genus Species First described by
Phylactolaemata Cristatellidae Cristatella C. mucedo Cuvier, 1798


The following synonyms have been used to indicate C. mucedo:

  1. Cristatella mucedo (Cuvier 1798)
  2. Cristatella vagans (Lamarck 1816)
  3. Cristatella mirabilis (Dalyell 1834)
  4. Lophpous crystallinus (Dumortier & Van Beneden 1850)
  5. Cristatella idae (Leydy 1858)
  6. Cristatella ophidioidea (Hyatt 1866)
  7. Cristatella lacustris (Potts 1884)
  8. Cristatella mucedo var. idae & var. genuina (Kraepelin 1887)


Also see the generic class and genus description in the classification page.
A combination of literature has been used to create this description.

  1. Cristatella mucedo forms clear, soft, gelatinous colonies
  2. The colony is slug to band formed, also described as a caterpillar
  3. The colony does not branch nor is it lobed
  4. The colony has a convex curved upper side
  5. The zooids extend from the body in parallel or concentric rows
  6. The olders zooids on the inside and younger zooids in 2 to 3 rows on the outside
  7. The colony can move a bit (a few cm/day, and specially young colonies). It is unknown how they do this
  8. The polypide is relatively big and extends far from the cystide aperture.
  9. The central part has no zooids
  10. There is no cuticula
  11. A thin fluid is secreted by cells in the ectoderm on which the colony is presumed to glide. Other sources suggest that muscles in the colony bottom wall could play a role
  12. Separation walls between polypides are reduced to bands at right angles.
  13. Colonies are round if young/small and become elongated in later stage
  14. Big (long) colonies can divide into smaller colonies.
  15. Floating statoblasts (floatoblasts) develop in the colony centre.
  16. The lophofores are relatively low in reaction to external stimuli and seldom retract like other bryozoa do when disturbed
  17. If the polipide retracts it will extend after only a short interval (a few seconds)
Color White to pale yellow
Tentacle crown Tentacle crown is horseshoe shaped with 80 to 100 tentacles.
Size One zo id is about 2 mm long
A colony is up to 20 - 40 cm long and about 0,6 to 2 cm broad
Statoblasts Statoblasts are floating (floatoblasts) and perfectly round
Statoblasts have two rows of barbed round extensions - one with 12-20 extensions on the dorsal side and one with 20-40 extensions on the ventral side
The annulus is connected only on the dorsal side
Habitat On most substrates in standing or lightly streaming water to 2 m depth
Cristatella mucedo lives in lakes, ponds, slow streams and rivers(?)
As the species is small it is easy to overlook.
Area Cristatella mucedo is found in many places around the world (America, England, Norway, Poland, New Zealand and most likely in many other places
In The Netherlands no other Cristatella species are found
  1. It is unknown if a relation exists between food richness of the water and the existence of the species
  2. It is unknown what the oxygen requirements of the species are. It is clear that the species is not found below 2 meters, this may indicate a need for oxygen rich water.
  3. Cristatella mucedo needs a firm substrate, such as wood, rocks, reeds, aquatic plants, glass bottles and alike.
  4. In situations where too much silt lands on the colony it will not survive. In these cases it can usually be found in a sheltered or vertical location.
  5. In the fall (October) when the water temperature falls below about 8 degrees Celsius the colonies will die off and release stored statoblasts.
  6. Cristatella mucedo has a primarily a-sexual reproduction. Each statoblasts potentially forms a new colony.
  7. Statoblasts are moved and spread by water currents, but also by aquatic birds (attached to feet or in the gut system when aquatic plants are eaten that have statoblasts attached) and possibly by vegetarian fish
    Aquatic birds are thought to have a maximum range of dispersing a species of 300 km.
  8. Is not found in strongly eutrophic of polluted waters

Relevant literature

  1. [Allman] - A monograph of the fresh-water polyzoa including all the known species, both British and foreign
  2. [Borg] - Die Tierwelt Deutschlands
  3. [Brauer] - Die S sswasserfauna Deutschlands
  4. [Geimer&Massard] - Les Bryozoaires du Grand-Duch de Luxembourg et des R gions limitrophes
  5. [Grabow] - Farbatlas S wasserfauna Wirbellose
  6. [Lacourt I] - a monograph of the freshwater Bryozoa
  7. [Lacourt II] - Bryozoa of the Netherlands
  8. [Mundy] - A key to the British and European Freshwater Bryozoans
  9. [Pennak] - Fresh-water invertebrates of the United States
  10. [Streble] - Das Leben im Wassertropfen
  11. [Wood II] - A new key to the freshwater bryozoans of Britain, Ireland and Continental Europe
  12. [Woss] - Moostiere (bryozoa)

My observations

  1. C. mucedo is often found on the upper side of a substrate, but also at the underside. This in complete opposite to all other species that seem to prefer the underside.
  2. Aparently C. mucedo can handle descending silt fairly well. Although surrounding substrate is covered in silt, the colony will be clean.
  3. It seems to me that the way the zooids are grouped in a colony should aid in creating a water current that keeps the colony clean of silt. Much better at least than most other (branching) colonies such as F. sultana.
  4. I have found C. mucedo several times around 5 meter depth and even up to 8 meter depth. These colonies were clearly in good condition and attached to some substrate and clearly not swept away from shallower regions.
    I think C. mucedo is warmth loving and can handle moderate to low oxygen saturation. This because 8 meters is below the summer thermoclyne and oxygen levels drop during summer below the thermoclyne. It may have helped that the colonies grew on aquatic plants so local oxygen levels may have been sufficient.
  5. I have found C. mucedo at 20 - 50 cm depth, in sheltered areas with low wave action and current.
  6. C. mucedo can be found hanging, for instance from a branch, attached to the substrate only by a small part of the colony. Apparently it is well able to cling or stick to the substrate. However a small current is enough to dislodge the colony.
  7. C. mucedo becomes active later in spring than many other species, once the water temperature rises above 15 - 16 ° C (beginning of May). There are four generations in a year:
    1. A few colonies arise from statoblasts (i assume)
    2. A few weeks later large numbers of colonies grow in the direct environment of the initial colonies. I think this is due to sexual reproduction. The result is densly packed colonies that form statoblasts and die towards the end of June.
    3. A low-number mid summer generation that often looks smallish and also forms statoblasts and dies mid - end of August
    4. A fall generation (September - October), that looks more healthy, forms statoblasts an dies as the water temperature drops
      I have an observation that indicates that the fall generation also sexually reproduces. In a lake I was diving mid October 2009 a few locations showed significant numbers of small colonies closely together.
  8. Shortly after a colony develops (1-2 weeks) the first statoblasts can be seen
  9. Colonies die after about 6 weeks
  10. C. mucedo dies off as soon as the water temperature falls below 9 - 10 degrees Celsius (end of October, beginning of November)
  11. I found more than 10 active Cristatella colonies between 1 and 6 m depth on 27-12-2009 at 3 °C. The colonies were fairly full of statoblasts, but all had multiple active polyps! This find was in the Veenmeer (Tynaarlo, NL) which is not my normal place to go. In the Piccardthofplas (Groningen, NL) there are a few colony sacs, packed with statoblasts, but without active polyps. These have died weeks ago.
    I have two ideas why Cristatella may endure this long and this cold:
    1. The cold came fast, water temperatures dropping with a degree C per day and the decay goes slowly at these low temperatures.
    2. The water is significantly less eutrophic than in the other regional lakes (sight depth > 5 meters versus 2 meters elsewhere). This may cause the Cristatella colonies to need longer to finish making statoblasts forcing them to endure longer.

    Any how these are far lower temperatures than found in the literature i know.
  12. C. mucedo will successfully compete against cyanobacterya and algal mats; i have never seen an overgrown colony and have seen thousands of colonies. This might indicate some form of chemical warfare?
  13. Colonies are fairly loosely attached to the substrate and can be swept off the substrate by a moderate current, such as one generate by a too abrupt movement of a hand. This is completely different from all other byrozoa.
    This seems to me as a good explanation of why C. mucedo is not found in regions with too much current and/or wave action
  14. I have found C. mucedo colonies on top of loose silt and attached to a few strands of algae. So the perception that C. mucedo needs a solid substrate is invalid
  15. I have not found C. mucedo in food rich (eutrophic) waters.
  16. The C. mucedo statoblasts have a skirt around them that is likely to be supported by the spikes extending from the statoblast. This is possibly to use the surface tension of the water surface to enhance the floating ability or extend the time the statoblast floats. Opposite tof what is described in literature it is unlikely that the hooks on the spokes are used to attach to for example bird feathers to enhance the area C. mucedo is spread to.
  17. A colony i kept in a small petridish for observation moved in 12 - 16 hours from the center to the edge - 3 to 4 centimeters.