2. Porifera
Sponges are among the most widely used resources for natural marine
substances and are known to be some of the oldest living organisms on
earth. More than 10,000 species exist, covering a wide distribution ranging
from freshwater to intertidal zones and even deep-sea environments. Color
and shape are not defined for those inhabiting shallow waters, and small
animals often live symbiotically within their bodies. Sponges are typically
classified into ordinary, calcareous, and hexactinellid varieties, based on the
components or shape of their spicules (Fig. 10.1).
3. Coelenterata
The bodies of coelenterates—as exemplified by jellyfish, sea anemones,
hydras, corals, and comb jellies—possess a baglike shape with a triple cell
wall and a hollow gastral cavity at the center. Around the entrance to the
gastral cavity (mouth) are tentacles. In addition to digestion, the gastral cavity
functions as a blood vessel supplying nutrients and oxygen. Undigested
matter, waste, eggs, and sperm are discharged through the mouth. Coelenterates are carnivorous animals with mettling thread cells (poisonous
threadlike organs present in coelenterates) among their integument cells.
Within is a needlelike structure called a cnida. Because the organism produces mettle threads when hunting food, they are also known as cnidarians.
Coelenterates possess muscles, nerves, and sensory organs, but no vascular
system, respiratory organs, or excretory organs. In terms of their structural
characteristics, coelenterates have one fixed side. They exist in cylindrical
form like corals; hydra form like sea anemones; or disk form like
free-swimming jellyfish. In addition to embryogenesis, they also propagate
through budding and division. Around 9000 species exist worldwide.
4. Platyhelminthes
Flatworms have bodies that are flattened toward the abdomen and exhibit
left-right symmetry. They possess a head at one end and a tail at the other,
with a mouth located on their abdomen. Flatworms include parasitic cestode, fluke trematode, and rhabdocoel flatworm types.
5. Annelida
Annelid bodies consist of numerous metameres, exhibit zygomorphy, and
possess deuterocoels. Annelids can be classified into six orders: Archiannelida, Polychaeta, Oligochaeta, Hirudinea, Clitellata, and Acanthobdellida.
Among these, Polychaeta and Clitellata are considered representative types.
6. Entoprocta
This phylum consists of a small number of organisms that live in isolation
or in groups by attaching to seaweed or rock surfaces. Their bodies
resemble cups with long handles attached, and they possess several tentacles around a concave portion on their upper surface.
7. Mollusca
Mollusks account for the largest number of invertebrates after arthropods.
They exhibit left-right symmetry, although changes have resulted in many
exhibiting irregular forms. Their bodies consist of three sections (head,
foot, and visceral sac), and most possess a mantle on their body wall. The
following are the most representative types of mollusks.
10.2 Researching Natural Marine Substances
347
Sponges are among the most widely used resources for natural marine
substances and are known to be some of the oldest living organisms on
earth. More than 10,000 species exist, covering a wide distribution ranging
from freshwater to intertidal zones and even deep-sea environments. Color
and shape are not defined for those inhabiting shallow waters, and small
animals often live symbiotically within their bodies. Sponges are typically
classified into ordinary, calcareous, and hexactinellid varieties, based on the
components or shape of their spicules (Fig. 10.1).
3. Coelenterata
The bodies of coelenterates—as exemplified by jellyfish, sea anemones,
hydras, corals, and comb jellies—possess a baglike shape with a triple cell
wall and a hollow gastral cavity at the center. Around the entrance to the
gastral cavity (mouth) are tentacles. In addition to digestion, the gastral cavity
functions as a blood vessel supplying nutrients and oxygen. Undigested
matter, waste, eggs, and sperm are discharged through the mouth. Coelenterates are carnivorous animals with mettling thread cells (poisonous
threadlike organs present in coelenterates) among their integument cells.
Within is a needlelike structure called a cnida. Because the organism produces mettle threads when hunting food, they are also known as cnidarians.
Coelenterates possess muscles, nerves, and sensory organs, but no vascular
system, respiratory organs, or excretory organs. In terms of their structural
characteristics, coelenterates have one fixed side. They exist in cylindrical
form like corals; hydra form like sea anemones; or disk form like
free-swimming jellyfish. In addition to embryogenesis, they also propagate
through budding and division. Around 9000 species exist worldwide.
4. Platyhelminthes
Flatworms have bodies that are flattened toward the abdomen and exhibit
left-right symmetry. They possess a head at one end and a tail at the other,
with a mouth located on their abdomen. Flatworms include parasitic cestode, fluke trematode, and rhabdocoel flatworm types.
5. Annelida
Annelid bodies consist of numerous metameres, exhibit zygomorphy, and
possess deuterocoels. Annelids can be classified into six orders: Archiannelida, Polychaeta, Oligochaeta, Hirudinea, Clitellata, and Acanthobdellida.
Among these, Polychaeta and Clitellata are considered representative types.
6. Entoprocta
This phylum consists of a small number of organisms that live in isolation
or in groups by attaching to seaweed or rock surfaces. Their bodies
resemble cups with long handles attached, and they possess several tentacles around a concave portion on their upper surface.
7. Mollusca
Mollusks account for the largest number of invertebrates after arthropods.
They exhibit left-right symmetry, although changes have resulted in many
exhibiting irregular forms. Their bodies consist of three sections (head,
foot, and visceral sac), and most possess a mantle on their body wall. The
following are the most representative types of mollusks.
10.2 Researching Natural Marine Substances
347