Coral Reef Lichens Sea sponges

1. 1. Coral Reef
2. Lichens
3. Sea sponges
Ms. Kushbu.R
Kristu Jayanti College

2. The corals and these special cells have a mutualistic
relationship. The coral provides the zooxanthellae with
a protected environment and compounds they need
for photosynthesis. In return, the zooxanthellae produce
oxygen and help the coral to remove wastes.
Zooxanthellae are single-celled algae.
The algae photosynthesize, turning light
and carbon dioxide into food that they
share with the coral.
Video link: https://youtu.be/JENUAv0w8Q4
Coral, any of a variety of invertebrate marine organisms
of the class Anthozoa (phylum Cnidaria) that
are characterized by skeletons—external or internal—of a
stonelike, horny, or leathery consistency.
The term coral is also applied to the skeletons of those
animals, particularly to those of the stonelike corals.

3. Coral reefs are often called the rainforests of the seas. Teeming with
life, reefs harbor a broad range of organisms that rely on a complex
network of ecological interactions and symbiosis (close and often long-
term interaction between two or more different biological species).
The diversity and complexity of coral reefs starts at the microscopic
level. Within the coral tissue, symbiotic algae (dinoflagellates),
commonly called zooxanthellae (their scientific name
is Symbiodinium), are crucial to the coral hosts. Like leaves from a
tree, these microscopic algae harvest light and produce energy in the
form of carbon rich compounds.
Assessments of the photosynthetic efficiency and photosystems
“health” condition, using a special fluorometer is the recent study.

4. These symbiotic algae remove and use the
coral’s waste products (CO2, nitrogen) for
growth and photosynthesis. In return the coral
gains energy rich organic carbon, created by
the algae through photosynthesis. This
symbiotic relationship provides most of the
coral’s energy needs and contributes to the
production of the coral limestone skeleton.
The loss of these symbiotic algae, a process
known as coral bleaching, reveals the coral’s
white limestone skeleton as the tissue looses
all pigmentation. On its own, the coral animal
struggles to meet its’ energy requirements,
and, if prolonged, this is usually lethal for the
coral.

5. • The disruption of this obligate symbiosis can be triggered by
a number of stress factors, including rapid and extreme
temperature changes, high light levels and pollution.
The susceptibility to these factors can vary according to the
coral and type of symbiotic algae, or zooxanthellae, that
they host.
• Corals can harbor one or more types of zooxanthellae. The
type of symbionts also varies with environmental conditions
and geographic region. Widely distributed branching coral
found throughout the Pacific and Indian Oceans.
• So far, the scientific team has found and sampled
several Pocillopora species that are abundant on the fore
reef, but appear to be uncommon and rare on the inner
lagoonal reefs. These samples will be taken to the
laboratory to assess which symbionts they host. This
information about symbiotic algae can help scientists and
managers foresee some of the areas that will be more
susceptible or more resilient to stress factors, such as
increasing temperature.

7.  There are several different mechanisms behind this and
depend on whether the coral reproduces asexually or
sexually.
In the case of an asexually reproducing coral,
zooxanthellae transmission takes place through coral
budding or fragmentation which form a new coral. The
zooxanthellae residing in the donor tissue of clonal coral
automatically relocate, thereby colonizing the new cora.

8. In sexually reproducing coral, zooxanthellae are either acquired
through direct/vertical or indirect/horizontal transfer.
In direct or vertical transfer, the mother coral polyp releases the
eggs with zooxanthellae inside,. But most coral eggs do not have
zooxanthellae in them; the eggs have to obtain the zooxanthellae
through phagocytosis from the coral polyp's gastrovascular cavity.
For the coral larvae that was borne from eggs without
zooxanthellae, they can uptake their parent's zooxanthellae before
their release into the surrounding seawater. But if they do not have
this opportunity, they have to absorb them from the environment.
This is called indirect or horizontal transfer. The concentration of
free-swimming (motile) zooxanthellae over a reef is normally low
but sometimes they show preference to newly settled coral.

9. Chemotaxis is the mode of locomotion of such a zooxanthellae; much
like diffusion of molecules from a region of large concentration to a
region of lower concentration, motile zooxanthellae can show positive
chemotaxis in the direction of corals with zero or lower concentrations
of zooxanthellae (Muller-Parker et al, 2015).
 Additionally, corals can obtain zooxanthellae indirectly through the
ingestion of fecal matter excreted by corallivores (animals that eat
coral) and of animals who have eaten prey with zooxanthellae in their
cells (prey such as jellyfish and sea anemones).
Over the course of their lives, corals are able to obtain multiple
different species of zooxanthellae. During a bleaching event the
zooxanthellae may be expelled from the coral, and if the coral
survives, its tissues can be re-populated by a different species of
zooxanthellae.

10. Lichens are a small group of plants of composite nature,
consisting of two dissimilar organisms, an alga-
phycobiont (phycos — alga; bios — life) and a fungus-
mycobiont (mykes — fungus; bios — life); living in a
symbiotic association.
Generally the fungal partner occupies the major portion
of the thallus and produces its own reproductive
structures. The algal partner manufactures the food
through photosynthesis which probably diffuses out and
is absorbed by the fungal partner.

11.  1. Lichens are a group of plants of composite thalloid nature, formed by the
association of algae and fungi.
 2. The algal partner-produced carbohydrate through photosynthesis is
utilized by both of them and the fungal partner serves the function of
absorption and retention of water.
 3. Based on the morphological structure of thalli, they are of three types
crustose, foliose and fruticose.
 4. Lichen reproduces by all the three means – vegetative, asexual, and
sexual.
(a) Vegetative reproduction: It takes place by fragmentation, decaying of older
parts, by soredia and isidia.
(b) Asexual reproduction: By the formation of oidia.
(c) Sexual reproduction: By the formation of ascospores or basidiospores. Only
fungal component is involved in sexual reproduction.

12. The growth form in which the lichens are leafy or bush-like are
termed macrolichens. The other forms are called microlichens.
 Crustose grow across the substrate.
 Foliose are flat, leaf-like sheets of tissues and not bound closely.
 Fruticose are freely available in standing branching tubes.
 Gelatinous or jelly-like appearance
 Leprose are lichens with powdery appearance.
 Squamulose are closely clustered and lit flattened pebble units.
Likewise, lichens can also be seen in various colours like yellow,
orange, red, brown, etc. These colours are due to the presence of
special pigment called usnic acid. In the absence of this pigment,
they are generally olive gray or green.

13.  The composite plant body of lichen consists of algal and fungal members. : The algal members
belong to Chlorophyceae (Trebouxia, Trentepohlia, Coccomyxa etc.), Xanthophyceae (Heterococcus)
and also Cyanobacteria (Nostoc, Scytonema etc.)
 The fungal members mainly belong to Ascomycotina and a few to Basidiomycotina. Among the
members of Ascomycotina, Discomycetes are very common; producing huge apothecia, others
belong to Pyrenomycetes or Loculoascomycetes.

14.  Ascospores are produced in Ascolichen.
(a) The male sex organ is flask-shaped spermogonium, produces unicellular spermatia.
(b) The female sex organ is carpogonium (ascogonium), differentiates into basal coiled oogonium
and elongated trichogyne.
(c) The fruit body may be apothecia (discshaped) or perithecial (flask-shaped) type.
(d) Asci develop inside the fruit body containing 8 ascospores. After liberating from the fruit body,
the ascospores germinate and, in contact with suitable algae, they form new lichen.
 Basidiospores are produced in Basidiolichen, generally look like bracket fungi and
basidiospores are produced towards the lower side of the fruit body.
 The growth of lichen is very sThe growth of lichen is very slow, they can survive in adverse
conditions with high temperature and dry condition.

18.  1. According to some workers, the fungus lives parasitically, either partially or
wholly, with the algal components. This view gets support for the following
evidences:
(i) Presence of haustoria of fungus in algal cells of some lichen.
(ii) On separation, the alga of lichen is able to live independently, but the fungus
cannot survive.
 2. According to others, they live symbiotically, where both the partners are
equally benefitted. The fungal member absorbs water and mineral from
atmosphere and substratum, make available to the alga and also protects algal
cells from adverse conditions like temperature etc. The algal member synthesises
organic food sufficient for both of them.
 3. According to another view, though the relationship is symbiotic, the fungus
shows predominance over the algal partner, which simply lives as subordinate
partner. It is like a master and slave relationship, termed helotism.

19.  Crustose: These are encrushing lichens where thallus is inconspicuous, flat and
appears as a thin layer or crust on substratum like barks, stones, rocks etc. (Fig.
4.112B). They are either wholly or partially embedded in the substratum, e.g.,
Graphis, Lecanora, Ochrolechia, Strigula, Rhizocarpon, Verrucaria, Lecidia etc.
 Foliose: These are leaf-like lichens, where thallus is flat, horizontally spreading
and with lobes. Some parts of the thallus are attached with the substratum by
means of hyphal outgrowth, the rhizines, developed from the lower surface (Fig.
4.112C), e.g., Parmelia, Physcia, Peltigera, Anaptychia, Hypogymnia, Xanthoria,
Gyrophora, Collema, Chauduria etc.
 Fruticose (Frutex, Shrub): These are shrubby lichens, where thalli are well
developed, cylindrical branched, shrub-like (Fig. 4.112D), either grow erect
(Cladonia) or hang from the substratum (Usnea). They are attached to the
substratum by a basal disc e.g., Cladonla, Usnea, Letharia, Alectonia etc

20. Based on the distribution of algal member inside the thallus, the
lichens are divided into two types. Homoisomerous or Homomerous
and Heteromerous.
Homoisomerous: Here the fungal hyphae and the algal cells are
more or less uniformly distributed throughout the thallus. The algal
members belong to Cyanophyta. This type of orientation is found in
crustose lichens. Both the partners intermingle and form thin outer
protective layer (Fig. 4.11 3A), e.g., Leptogium, Collema etc.
Heteromerous: Here the thallus is differentiated into four distinct
layers upper cortex, algal zone, medulla, and lower cortex. The algal
members are restricted in the algal zone only. This type of
orientation is found in foliose and fruticose lichens (Fig. 4.113B) e.g.,
Physcia, Parmelia etc.

22.  (a) Upper Cortex: It is a thick, outermost protective covering, made up of
compactly arranged interwoven fungal hyphae located at right angle to the
surface of the fruit body. Usually there is no intercellular space between the
hyphae, but if present, these are filled with gelatinous substances.
 (b) Algal Zone: The algal zone occurs just below the upper cortex. The algal cells
are entangled by the loosely interwoven fungal hyphae. The common algal
members may belong to Cyanophyta like Gloeocapsa (unicellular); Nostoc,
Rivularia (filamentous) etc. or to Chlorophyta like Chlorella, Cystococcus,
Pleurococcus etc. This layer is either continuous or may break into patches and
serve the function of photosynthesis.
 (c) Medulla: The medulla is situated just below the algal zone, comprised of
loosely interwoven thickwalled fungal hyphae with large space between them.

23. (d) Lower Cortex: It is the lowermost layer of the thallus.
This layer is composed of compactly arranged hyphae,
which may arrange perpendicular or parallel to the
surface of the thallus. Some of the hyphae in the lower
surface may extend downwards and penetrate the
substratum which help in anchorage, known as rhizines.
The internal structure of Usnea, a fruticose lichen, shows
different types of orientation. Being cylindrical in cross-
section, the layers from outside are cortex, medulla
(composed of algal cell and fungal mycelium) and central
chondroid axis (composed of compactly arranged fungal
mycelia).

24. As shown in this coral reef, sea sponges are an
important part of coral reef ecosystems. As members of
an ecosystem, like all animals, they have an important
role in their environment.
Photosynthesising microorganisms (often
green algae or cyanobacteria)can live on
and in sponges forming a mutualistic
relationship.
Sea Sponges- Filter Feeders

25. Sponges are strictly aquatic organisms as you may expect considering
that their feeding mechanism is based on the filtration of
inflowing water from the environment. Almost all sponge species are
found in the ocean with the exception of about 150 freshwater species.
Sponges can be found throughout the marine world, in both cold polar
waters and warmer tropical regions and at both great depths and in
shallower areas.
Because sponges generally require a solid support for attachment,
they are often found in rocky marine areas or on the ocean floor.
Sponges are critical components of the ecosystems of coral reefs,
where they provide shelter for a variety of organisms including
shrimp, crabs, and algae.
They are also a source of food for many sponge-eating fish species.
Many sponge species form large colonies or aggregates of individual
organisms.

27.  Sponges form symbiotic relationships with a variety of microorganisms,
including bacteria and algae. A symbiotic relationship between organisms
is a close ecological association between two species that may be mutually
beneficial or may benefit one partner at the expense of the other.
 In the case of sponges, the benefit for the microorganisms may be a
sheltered surface area on which to grow, and the benefit for the sponge
may be nutrients provided by the metabolism of the microorganisms.
 Although most sponges are filter-feeders that consume microorganisms or
obtain nutrients by symbiosis, there is one family of sponges that is
actually carnivorous. These sponges capture and consume
small crustaceans using their spicules.
 One such sponge, Chondrocladia lyra, has been called the "harp sponge,"
because its structure resembles a harp or lyre turned on its side.

28. Giant Barrel Sponges
Chondrocladia lyra

31.  AMOEBOCYTES in sponges are motile, amoeba-like cells that transport
nutrients between cells, transform into other cell types, and enable sexual
reproduction. In other words, amoebocytes function to help sponges eat, grow,
and reproduce.
In order to build a structure it requires building materials and a binder to hold
the materials together. Amoebocytes are involved in both.
 Sclerocytes are specialized amoebocytes that secrete biosilica (silica dioxide),
which is a substance that binds calcium. Biolsilica and calcium provide strength
and rigidity to the spicule.
 Archaeocytes secrete galectin, which acts as a cellular glue and holds all the
parts of the spicule together.
 Lophocytes secrete collagen fibrils, which allow the endoskeleton to be flexible
and pliable. Collagen fibrils are not a part of spicules, but they give the mesohyl
its gel-like consistency.

32. Pinacocytes are thin flat cells that line the
outer surface of a sponge. These cells can
contract, which can change the shape of
some sponges. There are specialized
pinacocytes called porocytes. Porocytes
regulate water circulation, this is done by
acting as pathways for water to travel
through the sponge wall.
Mesenchyme cells move freely in
the mesohyl (jelly like layer below
pinacocytes) and are useful in reproduction,
secreting skeletal elements, transporting
and storing food, and forming contractile
rings around openings in the sponge wall.
Choanocytes lay under the mesohyl, they
also line the inner chamber(s) of the
sponge. These cells are flagellated and they
posses a collar-like ring of microvilli that
surrounds a flagellum. The fact that sponges
have choanocytes can explain that
choanoflagellates, a group of protists,
are related.

33.  Choanocytes (not an amoebocyte but a different type of cell) are flagellated cells that capture
and digest food in sponges.
 These cells use their flagella to create a current, bringing food into the pores of the sponge,
capturing them, and packaging them into food vacuoles.
 Once inside a food vacuole, amoebocytes pick up and carry the food to other cells in the sponge.
Choanocytes
Amoebocyte
Given to Sponges as nutrition

34. • Fission
• Fragmentation
• Budding

35. BUDDING
https://youtu.be/Bt7q6eFeHRk

37. For reference notes:
https://www.britannica.com/animal/sponge-
animal/Natural-history