Fossile records of two types of Bryozoa

Stenolaemate Stories
The stenolaemate bryozoans quickly radiated in the earlyPaleozoic and are very characteristic fossils of Paleozoic rocks, sometimes making substantial contributions to the formation of reefs, calcareous shales, and limestones. They included forms with robust skeletons, such as the trepostome Hallopora pictured above; such forms were common in shallow-water habitats that today are dominated by corals. There were also forms with delicate, branching fanlike skeletons such as the fenestrates pictured below (from the Mississippian of Domodedovo, near Moscow, Russia). With the exception of one order of stenolaemates, the Tubuliporata or Cyclostomata, all of these Paleozoic bryozoan lineages were severely impacted in the Permian extinction: cryptostomates disappeared at the end of the Permian (245 million years ago), while a few other lineages lingered until the end of the Triassic, about 210 million years ago. Tubuliporate bryozoans have survived to this day, and in fact underwent a remarkable radiation in the Cretaceous, but are no longer dominant today.

Gymnolaemate Grandeur.

Uncalcified gymnolaemates are known as fossils from the Late Ordovician on, almost exclusively as distinctive borings in carbonate substrates such as shells. Non-boring, non-calcified gymnolaemate bryozoans are extremely rare as fossils and known from the Jurassic and Cretaceous only. Calcareous gymnolaemates did not appear in the oceans until the Cretaceous, during which time they diversified rapidly from a very few species in the early Cretaceous. By the end of the Cretaceous, there were over 100 genera of gymnolaemates. They continued to diversify in the Cenozoic: today there are over 1000 genera, comprising the bulk of bryozoan diversity in today's seas.

Annotaions of Paper

Paper #1:

• May, W.S. et al. 1987. Antineoplastic bryostatins are multipotential stimulators of human Hematopoietic Progenitor Cells. Proceedings of the National Academy of Sciences of the United States of America, Vol. 84, No.23:8483-8487.
• Bryostatins are macrocyclic lactones, extracted from the marine bryozoan Bugula neritina, and have been reported to be potent antineoplastic agents. The bryostatins may also be useful as stimulators of normal human hematopoietic cells since they can (i) directly stimulate bone marrow progenitor cells to form colonies in vitro and (ii) functionally activate neutrophils. Since the administration of antineoplastic agents can be limited severely by their inhibitory effects on normal bone marrow progenitor cells, we tested whether the bryostatins would inhibit hematopoietic progenitors or not.
• Bryostatins 1,3,8,9, and 13 were used for the experiments. May and collegues conducted experiments using the rHGMCSF, fetal calf serum, and purified bryostatinss and normal human bone marrow. Colony forming essays, clone transfer experiment, neutrophil chemiluminescence assay and neutrophil cytotoxity assey were preformed to see the effect of each bryostatin.
• We found that bryostatins can stimulate normal human bone marrow cells to form colonies in vitro.Since polypeptide colony-stimulating factors (CSFs) are the known physiological stimulators of normal hematopoiesis, we compared these results with bryostatin to those for the multipotential recombinant human granulocyte-macrophage colony-stimulating factor (rHGMCSF).
• Bryostatins 1, 3, 8, and 9 were found to mediate a dose dependent stimulation of Granulocyte-macrophage colony forming unit (CFU-GM) with the maximal effective concentration between 1and 100 nM. Bryostatin 13 was found inactive, and bryostatin 1 was the most effective. Analysis of colony morphology revealed that bryostatin 1, like rHGM-CSF, stimulated primarily mixed granulocyte-macrophage and pure granulocyte colonies at 7 and 14 days of culture. The stimulatory effect of bryostatin 1and rHGM-CSF is exerted directly.
• Bryostatin 1stimulated both early, BFU-E, and late, CFU-E,human erythroid progenitors grown in plasma clots. The maximal stimulatory concentration was between 1and 10 pM, with an inhibitory effect noted at concentrations above 1nM. Bryostatin 1, but not bryostatin 13, was found to be a potent activator of neutrophil chemiluminescence.
• May and colleagues concluded that bryostatins will, therefore, be useful as probes to help dissect the mechanism(s) involved in normal hematopoiesis, in particular those regulated by the multipotential GM-CSF.These agents may also prove useful for managing clinical situations related to neoplastic bone marrow failure states.

Paper #2:

• Gappa, J. L. 2000. Species Richness of Marine Bryozoa in the Continental Shelf and Slope off Argentina (South-West Atlantic). Diversity and Distributions, Vol. 6, No. 1:15-27.
• Species riches sampling in continental shelf and slope off Argentina shows that is has been biased towards area off Santa Cruz and Tierra del Fuego. And whether sufficient data has been published to determine bryozoan richness in those areas.
• A systematic bibliography and distributed records of bryozoans’ species from ecological literature were gathered into a database to analyze the bryozoans’ richness.
• The study was restricted to the continental and slope off Argentina area between 35˚ and 56˚S, and between the coast and 50˚W. Total numbers of benthic stations (with and without bryozoans) surveyed by the Shinkai Maru and the William Scoresby trawling cruises were counted
• Bryozoans were taken from 190 benthic stations and 31 coastal localities in the study area. Bryozoans were shown to be more frequent in the southern areas (mainly Santa Cruz and Tierra del Feugo) an intermediate number in Buenos Aires, and a low number of bryozoans in Rio Negro-Chubut. A total of 246 bryozoan species were recorded, 12 of which belong to O. Ctenostomatida, 43 to O. Cyclostomatida, and 191 species to the O. Cheilostomatida.
• A correlation between the number of bryozoans and latitude was positive, different from the Shinkai Maru data. Also the relationship between species number and depth was nonsignificant.
• Gappa concluded that the relationship between species number and depth did not show a simple monotonic trend, instead the richest stations occurred mainly between 80 and 120 depth. But a relationship between the distribution of sediment types in the Argentine continental shelf and the presence and diversity of bryozoans. Also that further study on environmental factors such as the availability of hard substrata that may be important in regulating the bathymetric distribution of bryozoans
• Also concluded that coastal localities comprise only 14% of the records. Wide coastal extensions have no published records of bryozoans. Moreover, data obtained during the two cruises showed that the southern shelf not only has been more thoroughly surveyed, but also shows the highest bryozoan diversity.

Paper #3:

• Okamura, B. 1992. Microhabitat Variation and Patterns of Colony Growth and Feeding in a Marine Bryozoan. Ecology, Vol. 73, No. 4:1502-1513
• Clonal and sessile nature of many animals have a probability of encountering neighboring organisms, but what is the influence of neighbors and flow regime on growth patterns and feeding rates of the bryozoan Electral pilosa? And are the patterns of feeding and growth related? It is predicted that there will be adaptive strategy displayed by E. pilosa.
• Electra pilosa is a cosmopolitan anascan bryozoan forming encrusting colonies on a variety of substrata, including fronds of the brown alga Fucus spp. There are highly variable morphologies observed in e. pilosa and are assumed to reflect environmentally induced. It has been suggest that star-shaped forms may result from rapid growth whereas more circular morphologies may be attained when growth is slow.
• E. pilosa colonies were studied in a series of 18 troughs in which three basic flow rates were effected using gravel-filtered seawater fmo Dalhousie University’s Aqautron system. Troughs consisted of 0.6 x 0.09m length of plastic rain gutter that held water depth of 1.-2cm.
• Neighbors inhibited growth, while flow velocity exerted a negative effect on growth rates of isolated colonies but had no influence on growth rates of colonies with neighboring E.pilosa upstream. No significant effects of neighborhood or flow on zooid dimensions.
• Growth responses displayed by E. pilosa did not display adaptive strategy model, there the prediction was nulled. Evidence that growth patterns resulted from feeding rated suggests a central role for the acquisition of food in the dynamics of benthic assemblages of suspension feeders.

Anti-Cancer agents ?

Bryozoans have been under investigation for being a potential anti-cancer and antineoplastic agents (antitumer antibiotics). Bugula neritina (above image) from the class Gymnolaemata (O. Cheilostomata) in particular has been under investigation.

Bryostatin are being extracted and tested as a potential potent antineoplastic agent. They have been reported to stimulate normal human hematopoietic cells (stem cells that give rise to all blood cell types) by directly stimulating bone marrow progenitor cells to form colonies (in vitro tests), and they functionally activate neutrophils.

Further reading, or interest in an article that tests Bryostatin can be found in Annotated Bibliography section.

Reproduction & Embryology

Bryozoans reproduce by means of sexual and asexually reproduction. Another interesting thing about Bryozoans is that they have both ovaries and testes, in other words they are hermaphroditic. They have the best of both worlds.

Reproductions asexually occurs by budding off new zooids, which is the main way a colony grows in size. Also if a piece of a bryozoan was to break off, the piece can independently continue to grow and survive and form a new colony. This type of reproduction gives rise to colonies that composed entirely of clones of the first animal, called the ancestrula.

Another way of reproduction is by depositing both eggs and sperm directly into the water where they fuse. Yet some byrozoans brood their eggs within zooecium or special chamber called ovicells.


Embryology:

Following fertilization, larvae are produced which show wide variation in body form from species to species. The larvae of non-brooding bryozoans bryozoans feed during the larval stage, while the larvae of brooding bryozoans do not, since these larva tend to settle soon after release. the most common larval type in bryozoans is the cyphonautes larva which is somewhat triangular in shape and has an apical tuft of cilia. Upon settling, larvae attach via adhesive sacs and undergo metamorphosis to the adult form. The first zooid in a colony is called the ancestrula. It is from this individual that the rest of the colony will grow asexually from budding.





The cyphonautes larva. The most common larval form in bryozoa.






Another type of bryozoan larva from Bugula an arborescent type

Ecology

Most of bryozoans (Stenolaemata, Gymnolaemata) are marine, but some are exclusively freshwater. Phylactolaemata are the freshwater bryozoans. Freshwater bryozoan species are small in number, being only about 50 species.

Bryozoans in general are found in all types of hard substrates: rocks, wood, blades of kelp, pipes and ships, and shells. There are some bryozoan colonies which grow on sediments.

They can be found in shallow waters or at depths of 8,200m. And although many bryozoans are sessile there a very colonial and non-colonial bryozoans that can move and creep about.

All bryozoans are suspension feeders. Zooids use the ciliated tentacles to filter phytoplankton and other diatoms.

Below is a video showing a bryozoan feeding.


Credits to GirlScientist from youtube.com

Anatomy

This picture shows the locations of mouth, anus, lophophore, funiculus and many other features typical in a bryozoan.

A lophophore is the ciliated tentacles at the top. They are food gathering structures that can be flower like (the image) or collapsed.

The funiculus is a tendon which joins the end of the gut to the colony wall. It is the site of statoblast production and spermatogenesis.

The inconspicuously located Central Nerve Ganglion has a major nerve tract extending into each arm of the lophophore.

An Exocyst is the chitin made outer layer of the body wall. And the endocyst is the inner layer.

Morphology

Made from calcium carbonate, the Skeleton of bryozoans come in a variety of shapes and patterns, ranging from corkscrew to lacy fans shapes. Their skeletons contain numerous small openings which holds minute animals called zooids. They have a coelomate body with a looped alimentary canal, a mouth, anus, and lophophores.

The mouth opens into a U-shaped gut; the anus is located just outside the lophophore. From this arrangement comes the alternative nam

e for the Bryozoa, the Ectoprocta. The body also contains a coelom and gonads; there is a small central ganglion but they lack specialized excretory or respiratory systems.

Zooids are usually connected to each other by thin strands of tissue. There are four types of zooids typically found in a colony. Each integrat

ing with one another and help the colony with its own particular function:

- Autozooids: Food gathering zooids. Called “feeding zooids”

- Heterozooids: Dependent on autozooid for gaining nutrients. They are also specialized zooids (producing eggs, protection etc.)

- Kenozooids: Provide strength and support

- Vibracula: Clean the bryozoan colony

Colony Contributing to protection, het erozooids have Avicularia whic are small heterozooids having zooecium and operculum formed in a beak like snapping structure. Vibracula on the other hand contains long setae that function in cleaning the colony.

The Phyla and Brief Classifcation

Bryozoans are tiny colonial aquatic animals that generally build stony skeletons of calcium carbonate. There are about 5000 living species known. They superficially resemble corals, and are sometimes called “moss animals”. Known to occur worldwide, they prefer warm tropical waters. Bryozoan phylum consists of three classes: 1) Stenolaemata, 2) Gymnolaemata, 3) Phylactolaemata which can be found in marine habitats and freshwater habitats, respectively. The marine species are distinguished by their soft-anatomy while the freshwater species are distinguished by the lack of zooid polymorphism, and calcification. There hasn’t been a mineralized fossil by this class, but there are some fossil records of tubes in deposits in the Tertiary age. Phylactolaemata, can overcome winter easily by forming overwintering structures (Statoblasts).

Stenolaemata have tubular zooids with calcified walls and their lophophore extends from body by annular muslcles and has five orders.

Gymnolaemata on the other hand have cylindrical or flattened zooids and their lophophore projects by muscles pulling on the frontal wall.

It should also be noted that Bryozoa phylogeny has been very limited, and is still being analyzed.

*~ Classification*~

¢Kingdom: Animilia

¢Superphylum: Lophophorata

¢ Phylum: Bryozoa
+Class: Stenolaemata
O. Cyclostomata
O. Hederellida
O. Trepostomatida
O. Cystoporida
O. Cryptostomida
O. Fenestrida
+Class: Gymnolaemata
O. Ctenostomata
O. Cheilostomata
+Class: Phylactolaemata
O. Plumatellida