Pectinatellidae

Pectinatellidae is one of seven families of bryozoans belonging to the belong to the class Phylactolaemata. Like most bryozoans, they are colonial organisms, and akin to all Phylactolaemates, they are exclusively freshwater organisms and lack a calcareous exterior, instead forming gelatinous colonies.

To date, there is only one known species of Pectinatellidae: ''Pectinatella magnifica.'' They are found globally across North America, Europe, and Asia.

''Pectinatella magnifica''

''Pectinatella magnifica'' (''P. magnifica'') is the only identified species in the family Pectinatellidae. It was discovered by Joseph Leidy in 1851, near Philadelphia. They are especially unique compared to other bryozoan colonies in that they are able to grow up to 2 meters in diameter, making them some of the largest bryozoan colonies.

Phylogeny

Phylogenetic relationships between the phylactolaemate families is relatively unresolved and remains the subject of scientific debate. Analysis of molecular DNA statoblast morphology are the two main methods for genus and species identification.

Pectinatellidae has recently been placed in the "PCP" clade, with sister taxa Cristatellidae and ''" Plumatella" fruticosa'', the last of which "thus is not a plumatellid." It is assumed that the ancestor to Pectinatellidae and Cristatellidae diverged from ''P. fruticosa'' in the Permian. Later, Pectinatellidae and Cristatellidae diverged from each other in the Middle Triassic. The gelatinous morphology (see below) of the PCP clade is assumed to be a distinct character state, derived from the ancestral "branching type" morphology seen in other phylactolaemate bryozoans.

Morphology

Pectinatellidae form massive gelatinous colonies, attached to solid substrates. A single gelatinous mass of Pectinatellidae is often created by multiple related colonies, derived from only one statoblast. They have two white spots at the end of each lophophore arm, and red pigmentation by mouthparts. Additionally, the lophophore forms a distinct U-shape.

Spinoblasts

Pectinatellidae form buoyant floatblasts, one of three types of free statoblasts found in bryozoans. Pectinatellidae is one of two families (the other being Cristatellidae) that produce only one type of floatoblast called a spinoblast.

In ''P. magnifica,'' the double-hooked spines of the statoblast originate at the periphery of the annulus, unlike in Cristatellidae.  The number of spines ranges from 11-22, and is most variable characteristic in ''P. magnifica''.

Reproduction

Pectinatellidae shares the same reproduction strategies as all phylactolemate bryozoans. Alongside budding, they can reproduce asexually using their statoblasts. They are also able to reproduce sexually and are all hermaphroditic.

Motility

While most bryozoans are sessile, motility has been identified in the gelatinous species, which includes ''P. magnifica''. This motility is essential for colony survival among changing water levels.

The free swimming larvae of ''P. magnifica'' has specialized swimming structures composed of a ciliated outer mantle and an inner mass containing two zooids.

Global Distribution

The species ''P. magnifica'' originated in eastern North America, and is found today in various localities around North America, Europe, and Asia. The live in warm, shallow, and calm freshwater ecosystems, only able to stand temperatures above 12^oC.

They are considered an invasive species in Europe and Asia after their introduction in the 19th century.

Methods of distribution include:

* Distribution of reproductive floatoblasts by birds (on feathers & feet, and in gut.)
* Human activity (fish and aquatic plant trade, shipping, etc.)

Ecological Importance

In Europe and Asia where ''P. magnifica'' has been introduced, the colonies outcompete other organisms and create a variety of issues across industries, including:

* Biofouling of freshwater ecosystems.
* Attach to mussel cages and impact production on mussel farms.
* Clog intake screens, pipes, and fishing nets, creating problems for hydroelectric power plants and water-based industries.
* Have the ability to host the myxozoan parasite ''Tetracapsuloides bryosalmonae,'' which causes proliferative kidney disease (PKD) in salmonid fish.

References

{{Taxonbar, from=Q4188423

Bryozoan families
Phylactolaemata
Monogeneric protostome families