Plumatella repens

Proposal for common name: Creeping bryozoan or moss animal

Classification

Class	Family	Genus	Species	First described by
Phylactolaemata	Plumatellidae	Plumatella	P. repens	Linnaeus 1758

The following synonyms have been used to indicate P. repens:

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

General	Colony has different shapes, dependent on local circumstances and substrate, creeping ('repens') across the substrate Colony often branching, specially young colonies Sometimes zooids are tightly packed (not unlike P. fungosa) into a lawn or fungoid shape Even in this fungoid form zooids never closely align. Non unlike an unkempt lawn (as opposed to the well-kept lawn of P. fungosa) Fungoid (tightly packed) colonies are irregular in shape, showing lobes and/or branches, possibly some creeping extensions at a border (also unlike P. fungosa) There are no separations (septa) between zooids
Color	Cystid translucent to dark, sometimes a chitinous shine
Tentacle crown	Horseshoe shaped tentacle crown with 40 to 70 tentacles.
Size	One zooid is 1 - 5 mm long A colony maximum 10 cm (?) in diameter
Statoblasts	Statoblasts in floating form (floatoblasts) are produced massively; they are short-oval to round and evenly broad The floating ring does not extend far beyond the capsule Statoblast capsule is covered with tubercles There are multiple statoblasts per zooid
Conditions	Plankton rich shadow rich water. On most substrates, specially aquatic plants
Distribution	No information found in literature
Additional	No information found in 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

I have found P. repens almost exclusively beneath wooden sheets or submerged trees and branches and only once on rocks (underside).
I have never found P. repens beyond 5 meters of depth. The colonies always grow on a place sheltered for silt that could suffocate them. The only exception was a colony on a submerged branch of a tree in a shallow (30 cm) spot in moderately streaming water; i expect the water flow washes of any silt.
The maximum depth is possibly induced by the thermoclyne that develops in lakes, beyond which the oxygen level drops during summer.
I have seen a P. repens colony overgrown with a freshwater sponge (Spongilla lacustris) that not only over grew the zooid tubes but also the tentacle crowns.
I found small colonies of a few dozens or hundreds of zooids, but also colonies that spread out creeping over several square decimeters of substrate area. So the 10 centimeter colony size falls short of reality.
Discerning P. repens in fungoid form from P. fungosa is not really easy when finding them in their habitat. Some pointers are:
- P. repens looks like a lawn that has not had any care for some time, P. fungosa is much more smooth
- P. repens has a shoddy colony border, forming lobes or extending creeping tubes while P. fungosa colonies have smooth edges
- P. repens looks yellowish, P. fungosa more greyish
- P. repens has bigger tentacle crowns than P. fungosa

Below two images are presented to compare the species: P. fungosa (left) and P. repens (right).

Plumatella fungosa

Plumatella repens