Kingdom: Animalia (Animals)

In multicellular body, which is made out of eukaryotic cells, are two basic groups of cells:
• Somatic cells (diploid), which are divided to tissues (connective, muscular, neural, and
epithelial)
• Gametes (haploid), for sexual reproduction (two cells with conjugation).

System of Polycytozoa
Diblastica
Phylum: Sponges - Porifera (hubky)
Phylum: Cnidaria (pŕhlivce)
Phylum: Acnidaria (rebrovky)

Triblastica
Phylum: Mesozoa (morulovce)
Phylum: Acoelomorpha (bezčrevovce)
Phylogeny group: Protostomia (prvoústovce)
Group: Acoelomata (necélomové prvoústovce)
Phylum: Plathelmintes (ploskavce)
Phylum: Nematoda (hlístovce)
Group: Coelomata (célomové prvoústovce)
Phylum: Mollusca (ploskavce)
Phylum: Annelida (obrúčkavce)
Phylum: Arthropoda (článkonožce)
Phylum: Pogonophora (pogonofóry)
Phylogeny group: Deuterostomia
Phylum: Echinodermata (drsnokožce)
Phylum: Chordata (chordáty)

Diblastica
Phylum: Sponges - Porifera (hubky)
The phylum Porifera ("pore-bearing") consists of approximately 5,000 species of sponges. These
asymmetrical animals have sac-like bodies that lack tissues, and are usually interpreted as representing
the cellular level of evolution without nervous system and sense cells and they do not show any
excitability. Size ranges from few cm to some meters and the adults lack the ability to move. Cells from
fragmented sponges can reorganize/regenerate the sponge organism, something not possible with
animals that have tissues. Most zoologists consider sponges as offshoots that represent an evolutionary
dead-end., although others consider some groups of sponges as being related to other animal groups.
Sponges are aquatic, largely marine, animals with a great diversity in size, shape, and color.
Body
Modern sponges greatly resemble some fossil Cambrian sponges. There are no true tissues in
sponges: merely specialized cell layers. Epidermal cells in sponges line the outer surface. Collar cells
line the inner cavity. Beating collar cells produce water currents that flow through pores in sponge wall
into a central cavity and out through an osculum, the upper opening. A 10 cm tall sponge will filter as
much as 100 liters of water a day. Amoeboid cells occupy the "inner" layer, along with hardened
structures known as spicules. There are two germ layers: Ecto and endoderm, and between them is
layer of jellylike substance called mesoglea. Inside of the body is internal cavity. From ectoderm
epithelium is formed (there are thin, leathery cells tightly packed together), there are many microscopic
openings, which go through mesoglea and endoderm like canals and they end in the internal cavity.
Water from outside goes through them. Mesoglea is jellylike substance with sclerocytes. The secretion
of spicules is carried out by sclerocytes. Spicules are from Calcium carbonate, or silicate. Also
archaeocytes are presented in mesoglea, and they ingest and digest food. They are very important
because they they can change into all of the other types of sponge cells. Mesoglea is reinforced
(vystužená) with spongin (organic material). In here archaeocytes can also develop into gametes.
Endoderm is created by choanocytes. These cells have a central flagellum that is surrounded by a
collar of microvilli. Their flagella beat to create the active pumping of water through the sponge, while
the collars of the choanocytes are the primary areas that nutrients are absorbed into the sponge. In the
upper part of the sponge body is opening called osculum.

Digestion
Sponges feed by drawing water into the body through a network of pores (hence the name
porifera, pore-bearer) and passing it out through the large opening (osculum) at one end of the body.
Food, which is caught by choanocytes is going to archaeocytes. So the digestion is not in the body
cavity (like in the most of the animal species), but inside the cells. It is very primitive way of digestion
called intracellular digestion. Waste is removed by water flow.

Reproduction
Sponges reproduce by both asexual and sexual means. Most poriferans that reproduce by sexual
means are hermaphroditic and produce eggs and sperm at different times. Sperm are frequently
"broadcast" into the water column. That is, sperm are created, concentrated and sent out the excurrent
openings, sometimes in masses so dense that the sponges appear to be smoking. These sperm are
subsequently captured by female sponges of the same species. Inside the female, the sperm are
transported to eggs by archaeocytes. Fertilization occurs in the mesoglea and the zygotes develop into
ciliated larvae. Some sponges release their larvae, while others retain them for some time. Once the
larvae are in the water column they settle and develop into juvenile sponges. Sponges that reproduce
asexually produce buds or, more often, gemmules, which are packets of several cells of various types
inside a protective covering. Fresh water sponges often produce gemmules prior to winter. These then
develop into adult sponges beginning the following spring.
The fossil record of sponges has been at times quite good. The oldest sponges date from the
precambrian. One early example of fossil sponges are the archaeocyathids, one of the first reef-building
animals. Archaeocyathids evolved and went extinct before then end of the Cambrian Period. Cladistic
analysis by J. Reitner in 1990 suggests archaeocyathids are properly placed in the Phylum Porifera
instead of having their own phylum. Living sponges fall into three groups: the calcareous glass, and
demosponges, based on the chemical composition of spicules.

Body complexity
There are three basic types of sponges - asconoid, syconoid and leuconoid.

asconoid sponge syconoid sponge leuconoid sponge

Euspongia officinalis (hubka mycia) – sea species, dead bodies were used as a sponges for washing.
Venus Flower Basket (Euplectella aspergillum; venušin kôš)

Spongilla lacustris (hubka jazerná) – freshwater species

Tube sponge, Callyspongia vaginalis (Photo © Corel corporation)

M.H. Note: this text was written with the help of the on-line biology book by Michael J. Farabee