1.1 Introduction to Biotoxins
About Toxins, Poison & Venom
•Toxin – any substance that can cause harm.
•Poison – a toxin that causes its effect through ingestion or absorbtion.
•Venom – a toxin that causes its effect through administration via a specialized
delivery system.
The terms venom and poison are often used interchangeably. Although both
venomous and poisonous animals have potentially dangerous toxins in their bodies, the
way that toxin is delivered differs. Venom is injected. Venomous animals have an
active delivery system and may use their toxin for protection or to help them catch food.
Unlike poisonous animals, venomous animals store their toxin in venom glands. They
inject their toxin into their predator or prey using fangs, pinchers, spines, or any other
sharp body part that is hollow, grooved or breaks the skin to introduce venom. Some
venomous animals, such as the spitting cobra, can even squirt at an enemy and are
accurate up to 10 feet!
Poison is eaten or absorbed. Poisonous animals have a passive delivery system and
use their toxin for protection only. They store their toxin in their meat or skin. If
someone or something eats the animal, the predator may get sick or even die. When this
happens, you can be sure the predator won't make that mistake again! An example of a
poisonous animal is a poison dart frog.
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1.1.1 About Toxin & Biotoxin
•Toxin – A poisonous substance, especially a protein, that is produced by living cells
or organisms and is capable of causing disease when introduced into the body
tissues but is often also capable of inducing neutralizing antibodies or antitoxins.
•Biotoxin – Biotoxins are the natural products of microbes, plants & animals
typically used as defensive mechanism, to prevent competition, as antibiotics or in
order to subdue prey. Some biotoxins are happenstance, meaning they exist for
another purpose & serve as a toxin against some species such as steroid based
saponins. Biotoxins, like toxicants, have an array of effects, mechanism & different
outcomes in different species. A cucumber’s toxin, for example, will affect fish but
have no consequence as concerns corals or clams.
1.1.2 Biotoxin from Porifera or Sponges.
The rapid development of the pharmaceutical market has brought about a boom
of information regarding various toxins native to the sponges. Evidence that sponges
contain many toxins is easily noted by empirical observation in that algal overgrowth
observation in that algal overgrowth is rarely seen & predation rates are low. Recall that
the dose is frequently the only factor segregating pharmaceutical use from intoxication.
Sponge toxins tend to fall into a few different broad categories; cytotoxic,
neuroactive or receptor interaction based compounds. The compounds can be steroid
based, peptide/ protein based or novel organic chemicals. Cytotoxic compounds are
those that kill, rupture or cause the derangement of normal cell function leading to cell
termination. Many of the cytotxic compounds have been successfully used to treat
disease such as cancer, malaria or bacterial infection. Neuroactive are those that
interact with system cells directly, such as interruption of synapse signaling (such as
cholinesterase enzyme inhibition or potassium pump dysregulation). Receptor based
interactions (many of the peptides found in sponge extracts are examples) occur when
compound directly bind to various cell receptors causing downstream chain of elements
that are normal in cell’s routine but at non-normal tissue or in excess. These are by no
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means that the only interactions & are only generalizations as to the actual activity of
the various toxins present, but show the diversity of the toxins formed naturally by
sponges. Alongside the variable activity of the toxins, each sponge may produce a host
of different compounds that are in some way toxic.
1.2 Introduction to sponge
1.2.1 Definition & Characteristics
Considered the most primitive of multicultural animals, sponges are really loose
colonies of cells. Most sponges live in saltwater, with only a few freshwater species.
Adult sponges do not move from place to place (they are sessile) but come in a dazzling
variety of shapes and colors. Sponges range from slimy encrusting forms to beautiful
3D structures with lacy skeletons made of silicon. They are found from shallow waters
down to the depths of the ocean. Some grow to a meter or more in height and they are a
prominent and colorful feature of all marine environments. Sponges have been evolving
for many millions of years and have developed an amazing array of chemical toxins to
ward off animals that might eat them and plants that might grow over them. The
pharmacology industry is only now beginning to discover potential uses for the wide
range of chemicals found in sponges.
Characteristics needed to be in Phylum-Porifera.
•A body that is a loose collection of cells without true tissues or organs.
•Cells that can adapt to any function the organism needs (totipotent cells).
Common name : Sponges
Section : Animals without Backbones
Kingdom : Animalia
Phylum : Porifera (pore-bearing)
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•Special cells that that drive water currents through the body called choanocytes
or collar cells. These flagellated cells line the inside of the sponge
•A larval stage that drifts in water currents, changes into a sessile adult stage and
feeds by filtering tiny particles from the water.
A skeleton made of calcium carbonate or silicon dioxide in the form of spicules and
/or collagen fibers, called spongin. Or have no skeleton at all. Other names of these
organisms are Sponges, bath sponges, Venus's flower basket, Calcarea, Demospongiae,
Hexactinellids.
1.2.2 Appearance
Many sponges have an amorphous shape: they look like a slimy, spongy or
prickly layer on the rock. Other types are asymmetrical or radially symmetrical and
have openings in the outer surface called oscula which lead to the canals of the water
system. Shapes of upright sponges can vary from globes to vases and may have many
branches. They come in every color imaginable including lavenders, blues, yellows,
bright reds, orange and white. The beautiful skeleton of Euplectella aspergillum is
known as 'Venus's Flower Basket'. The delicate 3D structure is possible because the 6-
rayed spicules made of silicon fit together in a variety of ways. This group of sponges
called Hexactinellids: The "hex" in their name refers to their 6-rayed spicules. Sponges
used chimneys long before humans existed. They adapt their shape to take advantage of
the different water speeds. Water flow near the bottom is usually slower than that higher
in the water column. The faster water flow over the chimney's exit hole actually sucks
water through the sponge's pores increasing the efficiency of its collar cells whose job it
is to create a water flow through the sponge, allowing the sponge to feed. Sponges are
colonial animals which are made up of many individual cells which specialize to fulfill
the animal's many needs. This means some cells specialize in reproduction, others in
feeding and so on. The acid test as to whether an animal is truly multicellular or made
up of many colonial individuals is to put them through the blender! If you do this with a
sponge the resulting soup will reassemble and recreate itself, given the right conditions.
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If you did this with a mouse you would soon realizes that it is a truly multicellular
animal which will never squeak again!
1.2.3 Habitat
Some of the first reefs made by animals hundreds of millions of years ago were
made of sponges. They were found in many parts of the world until they were gradually
out competed by the corals. Sponges are found in all seas living mainly in shallow
waters but some occur at great depths. Unpolluted shallow water habitats support
especially rich sponge faunas. Where currents are strongest they form flattened or
rounded shapes, but in still waters can grow into tall and often tree-like structures which
greatly increase the surface area. The majority attach themselves to any suitable surface
such as rocks, hard-shelled animals or seaweeds. Some bore into rocks, shells or coral
and are very important in the process of bio-erosion which over time helps to build
reefs. Some crabs (Family Dromiidae or decorator crabs) disguise themselves by
attaching pieces of sponge to their shells. Sponges are dominant animals in many
benthic marine environments. They even occur in large numbers and huge sizes in
Antarctica.
1.2.4 Their Food or Nutrition
Sponges were considered to be plants by the Ancient Greeks and Romans.
Observations of water currents generated by cells pointed to their animal nature and
filter feeding mode of life. Sponges feed by filtering small food particles (some even eat
bacteria) out of water pumped through the system by flagellated collar cells. Huge
volumes of water are processed: a 10 cm. individual of Leucandra pumps 22.5 liters of
water a day!! Water passes directly over cells responsible for food gathering and gas
exchange and at the same time removes wastes and reproductive products. Particulate
matter is taken directly into the collar cells which digest them and food is then passed
into the body by specialized amoeba-like cells.
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1.2.5 Their predators
Because of their impressive chemical toxins sponges have few predators. One
group of animals which has beaten their chemical defenses are the beautiful
nudibranchs. These animals add insult to injury by not only being immune to the toxins,
but by being able to actually reuse them in their own defense! The toxins of sponges are
effective against many bacteria and viruses but they are not completely effective. A
fungal disease attacked a crop of commercial bath sponges in the Bahamas in the 1930's
and almost wiped them out.
1.2.6 Growth & Reproduction
Sponges have no males and females nor specialized reproductive organs.
Individual cells become sex cells and produce either eggs or sperm. Sperm are released
into the water where they pass to a neighbouring sponge, are captured by a collar cell
which then changes shape and function to become an amoeboid cell and transports the
sperm to the oocyte or egg producing cell. Egg and sperm combine to form a zygote
which develops into a motile (flagellated) larva. These usually have a short life in the
plankton before settling and growing into a new sponge. All sponges have great powers
of repair and regeneration. In a laboratory situation new sponges can be grown from
cells taken from an adult organism. Growth rates vary widely between species and can
depend on water temperature and the amount of food present in the water.
1.2.7 They live with
Sponges live attached to any suitable surface including other living organisms.
One species Siphonodictyon coralliphagum infests Montipora corals and exudes a toxic
chemical which kills the coral polyps nearby and so avoids overcrowding by other
sponges. Large sponges have a huge number of organisms living on and in them. Many
sponges on coral reefs have blue green algae living within them which pay rent to their
sponge landlords by producing sugars in much the same way as dinoflagellates do with
corals. Many organisms live on sponges, including various crabs, feather stars, worms
and sea cucumbers. Small sea cucumbers are one of the most common commensal
animals seen on sponges. There may be hundreds of them feeding on the large organic
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debris which accumulates on large barrel sponges. Small prawns sometimes enter
sponges as larvae and develop to adults inside the 'cage' from which they grow too large
to escape. Sponges with a pair of prawns were seen as a symbol of great fidelity in
Japan. This species lives at depths of more than 1200m. off Japan and the Philippines
but may be endangered due to over collecting.
1.2.8 Connection with Human
Some sponges can cause dermatitis partly due to silica spicules and partly to a
toxin. Other sponges have antibacterial properties, but the potential of this group have
not yet been fully explored. Medical science is researching the chemical compounds of
sponges with great interest for their pharmacological properties. In the Mediterranean
and the Bahamas sponges are harvested for the bath sponge industry. Most of these are
in the genus Spongia and have a skeleton made of spongin fibers only with no spicules.
When dried and cleaned they form soft, dense sponges which are used for bathing or
applying makeup. At one time they were planted and grown as a crop but have now
been largely replaced by synthetic sponges. Sponges are often abundant at the entrance
of harbors and river mouths because they thrive on the large amounts of bacteria and
organic debris usually present in those habitats. But large amounts of sediment in the
water can be a problem, as it can clog their pores and smother the sponges. Trawling
can also be a problem for some sponges as they are often dragged up in nets with the
target species and later discarded as by-catch.
1.2.9 About Halichondria panicea
•Form: Very polymorphic, varying from thin sheets, massive forms and cushions to
branching-repent forms (eg. a 3-dimensional clump of anastomosing hollow
branches). Prone to giving off stout branching processes which develop into oscular
chimneys. At certain seasons of the year slender, almost filamentous, branching
processes (the 'albescens' form of Bowerbank) are produced. The photographs
indicate the diversity of form.
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•Color: Green in well-lit sites owing to the presence of algae. Cream-yellow in
shaded sites. "Ash-grey, brown or (rarely) brownish-red when alive."
•Smell: Distinctive, like freshly deposited kelp on the strandline. This smell, once
learned, is of very great help in determining difficult cases. (Halichondria
bowerbanki does not smell like this.)
•Consistency: Compressible, resilient but crumbly - i.e. when handled can readily
break (both cushion and branching forms), until skeleton has become well
consolidated. Branches break if bent through 20 degrees (this is helpful in
separating it from Halichondria bowerbanki.
•Surface: Usually smooth, often with a slightly glassy appearance especially when
air is trapped below the surface in the sub-ectosomal system. Surface spicules are
often united into fibers, which form a light regular net visible with the naked eye,
although a x10 hand lens may be needed. This net is not always present. Even.
•Apertures: Oscules are circular, raised on conules in the cushion form and often
regularly spaced; but are at the branch tips in the branched forms, in addition to
being sited along the branches. In some forms (affected by currents) the oscules can
be flush with the surface, or in lines on ridges. Oscular rims are of regular outline.
•Contraction: Not noticeable.
•Synonyms: This very polymorphic species has given rise to a long list of synonyms
which is now under review. It may be decided to re-establish some of these names,
especially when they refer to distinctive forms, in order to encourage the collection
of more information about the living animal. Names still in use on the continent
include Halichondria membrana (Bwk., 1866:165) and Halichondria topsenti de
Laubenfels 1936 (new name for Halichondria reticulata (Bwk., 1861:159).
•Skeleton: Halichondroid. Main skeleton is a confused incipient reticulation of
megascleres of variable size with little tendency to form ascending fibers and
connecting branches. The ectosomal skeleton is typically a regular reticulation of
tangentially arranged fibers of spicules which are similar to those of the main
skeleton; but it can become confused. The spicules help to reinforce a well defined
ectosomal membrane; the ectosomal fibres are 2 - 5 megascleres thick. A well
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marked system of sub-ectosomal spaces can be present, setting off the ectosomal
skeleton from the confused interior. Very little spongin is present.
•Spicules: Megascleres of slightly curved, slender, oxea only; typically 200-(265)-
320μm long but can vary between 100 and 480μm. These are more slender and
show a wider size range than those of typical Haliclona spp., with which certain
forms of Halichondria might be confused. There are no microscleres.
•Habitat: An opportunistic species, found on the shore down to the circalittoral,
which adapts to a wide range of niches. Usually on rock or any other hard substrate,
e.g. crab carapaces, shells, etc. It sometimes grows profusely on the stipes of
Laminaria hyperborea (in clean water habitats affected by tide and wave induced
water movement); often well developed in tidal rivers and harbours. (the faster the
currents the better developed is the Halichondria panicea).
•Distribution: "Arctic; Atlantic coasts of Europe; Mediterranean; etc."
•Identity: Shore sheet form. If the surface net is obvious, the color is green, and it
looks like the photograph then the identity is probably reliable. Sections must be
examined microscopically, and even then identification is not certain (smell is
helpful). If the surface has a translucent quality (i.e. it is possible to see something
of the underlying tissues through it), the surface spicule net is not obvious, the
texture is pliable and the body skeleton is composed of spicules with a tendency to
form bundles, then suspect Halichondria bowerbanki. Other closely related species
which should be considered when dealing with this Halichondria complex are
Halichondria (Topsentia) difficilis (Lundbeck 1902:28), a deep water form with the
distinctive characteristic of turning a deep purple on collection; Halichondria
agglomerans Cabioch, 1968:226 and Raspaigella (Spongosorites) genitrix Schmidt,
1870:41. As there is so much overlap several workers have tried to pin point one
character which they consider most helpful in separating the two species. Both the
translucence of the surface of Halichondria bowerbanki and the surface net of
Halichondria panicea have been used. However both these features are unreliable.
Several characters need to agree before the identity of a specimen can be reasonably
certain.
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1.3 TAXONOMIC POSITION OF MARINE SPONGE,
Halichondria panicea
Kingdom : Animalia
Phylum : Porifera
Sub-phylum : Cellularia
Class : Demospongia
Sub-class: Ceractinomorpha
Order : Halichondria
Family : Halichondriidae
Genus : Halichondria
Species: panicea
Figure 1: Marine sponge Halichondria panicea
