ZOOL2000 Assessment 1: Literature Review on Phylum Porifera

This literature review provides a comprehensive overview of Phylum Porifera, commonly known as sponges. It begins with an introduction to the phylum, highlighting their cellular organization, lack of complex systems, and sessile aquatic nature. The review then delves into the external structure, focusing on pinacocytes, mesophyll, and choanocytes, as well as the skeletal elements such as spicules and spongin. The paper explores the three body types (Ascon, Sycon, and Leucon) and their water flow mechanisms, emphasizing the importance of water currents for food, oxygen, and waste removal. It examines the vital functions of sponges, including filtration, digestion, and nutrient transport, as well as their unique responses to stimuli and internal communication. The review also covers reproduction methods, including both sexual and asexual reproduction, and discusses the ecological significance of sponges in marine environments, their habitat, and their implications. Finally, the review touches upon the immune system and the role of sponges in the ecosystem, including their interactions with other organisms and their contribution to reef societies.

PHYLUM PORIFERA
Name
Institution

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Phylum Porifera
Introduction
The sponges/Porifera are the marine animals comprising loosely organized cells. Porifera
remains distinct in having certain specialized cells capable of transforming into various types,
usually migrating between the main layers of a cell and the mesohyl. Sponges lack nervous,
circulatory or digestive system, rather they depend on upholding a continuous flow of water via
the body to acquire oxygen and food and to eliminate waste. Their body shapes are adapted for
maximization of the water flow efficiency. They are sessile aquatic animals. Even though some
sponge species are found in freshwater, a great number live in saltwater or marine environment.1
This paper presents a comprehensive critical review about Phylum Porifera and its importance.
Review
The sponges’ external surface remains lined within very thin flat cells referred to as
pinacocytes. Such cells remain mildly contractile and thus, the shapes of certain sponges shifts.
In many Porifera, pinacocytes remain specialized into the tube-like contractile porocyte with the
opening serving as the water pathways via the walls of their bodies. As such, they are able to
regulate the circulation of water. 2
Beneath the pinacocytes layer stays a jelly-like layer known as the mesophyll. The
Amoeboid cells or the mesenchyme cells move around mesophyll and stay specialized to
reproduce, secrete, skeletal elements, transport and store food and form contractile rings that
surround the opening within their body walls.
1 Aguilar-Camacho and Grace, Silicatein expression in Haliclona indistincta (Phylum Porifera, Order Haplosclerida) at
different developmental stages, 35.
2 Vargas, Sergio et al., Correction: Diversity in a Cold Hot-Spot, 67.

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The collar or choanocytes cells are beneath the mesophyll lining the interior chamber and
such cells remain flagellated ones with a collar-like ring of the microvilli which encloses the
flagellum. A formation of a net-like mesh is observed in the collar whenever these
microfilaments intersect the microvilli making the flagellum to create a current of water via the
sponge while the collar filters microscopic food particles from water. 3
Sponges get support from the skeleton which might comprise microscopic needle-like
spikes known as spicules or amoeboid cells coming from the spicules. Such spicules are
composed of calcium carbonate or even silica and might take on a range of shapes. The skeleton,
alternatively, might get composed of sponging which is a fibrous protein which formed from
collagen. The skeleton characteristics remain a significant feature in this taxonomy of sponge.
Body Type and Water Flow:
The life of sponge is reliant on the currents of water created by choanocytes. The water
flows supply food and oxygen to the organism and takes away the digestive and metabolic
wastes. As such, the food remains filtered and the flow of water triggers the phylum sponge to
have some type of body. From this flow, three body type of sponge has been discovered by
zoologists. 4
Ascon: This is a sponge which takes the shape of a vase. The outer opening is ostia
which directly leads to the spongocoel or chamber lined by choanocytes. Water is pushed into
this chamber via a movement called flagellar within the choanocytes via ostia. The water leaves
through one big opening at the top called osculum.
3 Vargas et al., Diversity in a cold hot-spot, 56.
4 Moitinho-Silva et al., The sponge microbiome project, 66.

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Sycon: This is also another body form or shape of the sponge in which the organism
seems folded. Water makes entry into this shape via openings known as dermal pores. These are
openings of the body wall’s invaginations known as the in-current canals. The body pores wall
intersect incurrent canals to the radial canal which lead to spongocoel. The choanocytes line
radial canals and the choanocytes flagella beating draws water from ostia, via in current as well
as radial canals into spongocoel, and exit osculum.
Leucon: This a body shape of sponge with an extensive branched system of the canal.
Water gets into sponge via ostia and travels via branched in-current canals. The ex-current
canals lead away from a chamber. The chamber and canals’ proliferation has led to the lack of
spongocoel and usually, many exits or oscula for the water which leaves sponge. 5
Vital Functions and Maintenance
Particles ranging from 0.1 to 50um are consumed by the sponges. The food comprises
bacteria, protest, microscopic algae, and additional suspended organic matter. The pray becomes
gradually drawn into the sponge and subsequently consumed. Sponge assist reduces the coastal
water's turbidity. One leucon sponge with a one-centimeter diameter and ten-centimeter height is
able to filter in more than twenty liters of water daily.
Minute suspended particles of food get filtered by choanocytes with water going via their
collar adjacent to the cells’ base and traveling into the sponge chamber at the hollow end of a
collar. Suspended food is subsequently trapped on collar and travel along the microvilli to the
collar base whereby it is integrated into the vacuole of the food. The digestion of this food is
facilitated by the changes in pH and the activities of the lysosomal enzyme. Partly digested food
is then transferred to amoeboid cells thereby disseminating it to the rest of the cells. 6
5 Tribalat et al., Does the chemical diversity of the order Haplosclerida, 847.

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Sponges are never confined to only feed using filtration approach. Incurrent canals are
lined with pinacocytes which could also phagocytize bigger particles of food to the tune of
50um. The dissolved nutrients in the seawater can get actively transported by these sponges. 7
The sponges are missing nerve cells for coordinating the functions of the body. Many
reactions take place because of the individual reacting to the stimuli like the circulation of water
in certain sponges is lowest when the sun rises and highest when the sun is just about to set. This
is due to light inhibition of the porocytes constrictions and other cells enclosing ostia keep open
the incurrent canals.8 Additional reactions, nonetheless, signify certain communication between
cells. For instance, the circulation rate of water via the sponge is able to plunge abruptly without
any obvious outside trigger. Such a reaction is only possible when choanocytes cease activities
more or less at the same time. This means certain kind of internal communication-though nature
is still not known. The feasible control mechanism is the cells of amoeboid when they transmit
chemical messages as well as the movement of ion over the surfaces of the cells. 9
Because of the existence of an elongated system of canals and the enormous water
volume circulations via these sponges, each of their cells are closely in contact with water and
6 Aguilar-Camacho, Liam and Grace, Evolution of the main skeleton-forming genes in sponges (phylum Porifera) with
special focus on the marine Haplosclerida (class Demospongiae), 249.
7 Miller et al., Analysis of a vinculin homolog in a sponge (phylum Porifera) reveals that vertebrate-like cell adhesions
emerged early in animal evolution, 11679.
8 Simion et al, A large and consistent phylogenomic dataset supports sponges as the sister group to all other animals ,
960.
9 Manconi and Roberto, Phylum Porifera, 77.

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thus the nitrogenous waster elimination, as well as the gaseous exchange, take place via
diffusion.
Certain sponges are hosting photosynthesizing micro-organisms like endosymbionts and
such coalition usually lead to the additional oxygen and food generation than those consumed.
The sponges living in freshwater sites are usually hosting green algae like endosymbionts
enclosed within archaeocytes alongside other cells. They are benefiting from the produced
nutrients by such hosted algae. Several marine species are hosting additional photosynthesizing
organisms. Light is conducted by the spicules composed of silica into a mesohyl whereby the
photosynthesizing endosymbionts is hosted. The sponges hosting these photosynthesizing
organisms remain the most familiar types in water which comparatively supply poor particles of
foods, and with usually leafy shapes maximizing the sunlight amount being collected.10
A small number of sponges remain carnivorous with the ability to capture minute
crustaceans by means of spicule-covered filaments. Little is known regarding how the prey is
captured in many cases. Many known carnivorous ones have fully lost the system of water flow
as well as choanocytes.
Sponges lack complicated immune system shown in several animals. Nonetheless, the
refute grafts arising from additional species yet accept them from some other member of their
individual species. In a small number of marine species, the grey cells serve as the shield for
these sponges. During the invasion, they generate a chemical thereby stopping the movement of
additional cells in the area invaded, hence deterring intruders from utilizing the internal system
of transport of sponges. In case of the persistence by the intruder, these grey cells will gather in
10 Morandini, Márcio and Antonio, Phylum porifera and cnidarian, 312.

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one area and secrete toxins which subsequently kill each of the cells in the attacked site. The
immune system remains activated for about three weeks.
Reproduction
Many sponges remain monoecious yet they do not always self-fertilize since the
individual generate sperms and eggs at varying periods. Some of these choanocytes are losing
their respective collar while their flagella go through meiosis thereby forming flagellated sperms.
Some other choanocytes alongside amoeboid cells in certain sponges likely go through meiosis
hence forming eggs. Eggs and sperms are then released from their oscula.11 The fertilization
takes place in ocean water culminating in the development of planktonic larvae. In certain
sponges, these released eggs are retained inside the parent’s mesophyll. The sperm cell leaves a
sponge via osculum and gets into the next sponge carried by incurrent water. Trapping of this
sperm is done by the choanocytes and then become incorporated into their vacuole. Both
flagellum and collar are lost by the choanocytes; hence becoming amoeboid, and the sperm is
transported to eggs.
In certain sponges, early development takes place within mesophyll. The zygote’s
cleavage leads to a flagellated larval phase formation. This breaks-free and transported via the
water from a parent sponge. Nearly 2 days, the settling of such a larva is experienced within an
appropriate atmosphere and begins its maturity process into an adult.
Asexual reproduction is further possible amongst certain sponges. This encompasses the
creation of resistant capsules, referred to as gemmules with several cells of amoeboid. During
winter, the parent sponge dies, hence releasing the gemmules capable of surviving in extreme
conditions. During spring, favorable conditions are experienced and cells of amoeboid will
stream out of a small hollow, known as micropyle, and subsequently organized into a whole
11 Yang et al., Development of a multilocus-based approach for sponge (phylum Porifera) identification, 34.

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sponge. Certain sponge show noticeable regeneration power in case the right cells are available
in the sponge. Budding is also a possible reproduction form in some few species.
Ecology:
Sponges remain extremely competitive for space for living. Several of them are shedding
their spicules hence creating a thick carpet many meters deep which is able to keep them safe
from organisms that would otherwise feed on them. Sponges are also producing toxins which
deter additional sessile organisms like sea squirts and bryozoans from growing on or even
adjacent to them. Sponges remain significant ecological components of the reef societies.
However, the sponges are never commonly contributing to the reef frameworks’ construction.
Habitat
Sponges remain global in terms of dissemination, from Polar Regions to tropics. Several
of them stay in clear and quiet water because stirred up sediments by currents or wave blocking
their useful pores, hence making it extremely hard for them to breathe and feed. 12 They are
found in their greatest proportion in firm surfaces like rocks. However, some of them have been
discovered on soft sediments where they are individually attaching using base resembling a root.
They are also significantly abundant yet less variety in temperate waters as opposed to tropical
waters, feasible due to the abundance of organisms feeding on them in such tropical waters.
Implication
Silica spicules or calcium carbonate stay extremely rough for many uses. Nonetheless,
such genera as Spongia and Hippospongia possess soft, wholly fibrous skeletons. They
organisms were used by early Europeans for several purposes like helmet paddings, portable
utensils for drinking, and filters for municipal waters. They have also been utilized as tools for
12 Samaai et al., Phylum Porifera In, 63.

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cleaning, paints applicators, discreet contraceptives, and ceramic glazes. A sponge (luffa) that is
commonly sold for utilization in shower or kitchen, is never drawn from the animals. However, it
is derived from a gourd’s fibrous skeleton. Sponges further have potentials for medicine because
of the available chemicals capable of controlling bacteria, fungi, tumors, and viruses.
Conclusion
A detailed critical review of literature about Phylum Porifera is presented in this paper.
The review has covered such areas as body type and water flow, ecology, habitat, vital function
and maintenance, reproduction and uses or implication of phylum porifera. The reviews shows
the various uses of sponges including medicine and cleaning tools.
Bibliography
Aguilar-Camacho, Jose Maria, and Grace P. McCormack. "Silicatein expression in Haliclona
indistincta (Phylum Porifera, Order Haplosclerida) at different developmental
stages." Development genes and evolution 229, no. 1 (2019): 35-41.

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Aguilar-Camacho, Jose Maria, Liam Doonan, and Grace P. McCormack. "Evolution of the main
skeleton-forming genes in sponges (phylum Porifera) with special focus on the marine
Haplosclerida (class Demospongiae)." Molecular phylogenetics and evolution 131
(2019): 245-253.
Manconi, Renata, and Roberto Pronzato. "Phylum Porifera." In Thorp and Covich's Freshwater
Invertebrates, pp. 39-83. Academic Press, 2016.
Miller, Phillip W., Sabine Pokutta, Jennyfer M. Mitchell, Jayanth V. Chodaparambil, D.
Nathaniel Clarke, W. James Nelson, William I. Weis, and Scott A. Nichols. "Analysis of
a vinculin homolog in a sponge (phylum Porifera) reveals that vertebrate-like cell
adhesions emerged early in animal evolution." Journal of Biological Chemistry 293, no.
30 (2018): 11674-11686.
Moitinho-Silva, Lucas, Shaun Nielsen, Amnon Amir, Antonio Gonzalez, Gail L. Ackermann,
Carlo Cerrano, Carmen Astudillo-Garcia et al. "The sponge microbiome
project." GigaScience 6, no. 10 (2017): gix077.
Morandini, André C., Márcio R. Custódio, and Antonio C. Marques. "Phylum porifera and
cnidaria." Marine and Freshwater Toxins (2016): 287-316.
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Tribalat, Marie-Aude, Maria V. Marra, Grace P. McCormack, and Olivier P. Thomas. "Does the
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