Conus
pertusus (Hwass
in Bruguière, 1972) has
an orange to pink shell with three spiral rows of white blotches, and
a convex spire with
a small and pointed apex. The coloration of pertusus cone is very
variable, and some shells can be mostly white or pale yellow, with
pale brown blotches. This cone it is considered a common specie and
exists throughout the entire Indo-Pacific region excluding the Red
Sea, ranging from the East coast of Africa in the west, Japan and
Korea in the North, Hawaii in the East, and the Australian coast in
the South. It is carnivore, feeding on other mollusks and its size
range from 20 to 69 mm. C.
pertusus
inhabits sandy bottoms and under corals, and can be found at depths
from 5 to 120 meters. C. amabilis
(Lamark, 1810); Rhizoconus
pertusus
(Hwass in Bruguière, 1792) and C.
festivus,
(Dillwyn, 1817) are synonymous of the
C. pertusus.
Seashells to...
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sexta-feira, 9 de maio de 2014
Class Polyplacophora, Monoplacophora, Scaphopoda and Cephalopoda
I
will not expand too much the description of this 4 classes because
the seashells world is huge and I want to focus in gastropods. But it
is good to have a general idea of all the classes of the Philum
Mollusca that are related with seashells.
Class
Polyplacophora
The
members of the class Poliylacophora are primitive mollusks known as
chitons. The chitons have elongated, flattened, bilaterally
symmetrical bodies covered by a shell of eight overlapping transverse
plates or valves that are surrounded by a muscular band called
girdle. Their foot is long and muscular and has a long mantle cavity
on both sides that contains from 6 to 88 pairs of gills. The head of
chitons is reduced lacking eyes and tentacles. Light-sensing cells,
that are exclusive to this class, pass trough tiny canals in the
shell plates. Today exists about 1000 species of chitons and their
size range from 3 mm to 40 cm. All
members of this class live in the ocean, normally on rocks and hard
bottoms in shallow waters of tropical and temperated regions where
they feed on algae and sponges.
Class
Monoplacophora
Also
known as gastroverms are relatively small, ovate, bilaterally
symmetrical mollusks that have a single conical, limpetlike shell
with eight pairs of serial repeated muscle scars. Until 1957 they
were thought to be extinct, but after this it was discovered thirty
living species, almost of all from deep sea habitats. All of the
gastroverms feed on organic matter and on small animals in the
sediment and they inhabit muddy, rocky, or gravelly bottoms.
Class
Scaphopoda
This
class is also known as scaphopods or tusk shells, because the shells
resemble elephant tusks. This class comprises about 600 living
species and all of them inhabit the oceans at shall to abyssal
depths. They have tall, bilaterally symmetrical bodies contained in a
long, curved, tapering tubular shell that is open at both ends. Some
smaller spicemens are broader in the middle than at the ends and the
size of this animals range from 3 mm to 15 cm. Tusk shells can be
polished and smooth or have longitudinal ribs. This animals don't
have eyes or gills and they burrow in soft bottoms using a foot that
emerges from the larger opening (anterior). Tusk shells feed on
microscopic organisms in the sediment, which they capture with thin
tentacles called captacula. This type of shells are rarely
encountered alive.
Class
Cephalopoda
The
earliest cephalopods had external shells, with interconnected
chambers that allowed them to become gas-filled and buoyant. During
their evolution, the vast majority of cephalopods have lost their
external shell. Some have an internal shell that has been reduce,
like is the case of squids and sepias. Others have lost completely
any kind of shell, like octopus. Some cephalopods developed the
ability to swim by undulating their fins, as well as by jet
propulsion.
Of
the approximately 900 species of cephalopods living today , only six,
all belonging to the primitive genus Nautilus have kept the external
shell. These animals only occupy the last chamber of the bilaterally
symmetrical shell, the rest of the shell has chambers filled with gas
that ables the animal to control their buoyancy by regulating the gas
flow into and out of the chambers. Nautilus spices inhabits the deep
waters along coral reefs during the day and rise to shallower waters
at night to feed.
Cephalopods
inhabits all oceans at all depths. Their size can range from 25 mm to
more than 14 meters in length, and include both the Giant Squid and
the even larger Colossal Squid, the largest known invertebrate. All
cephalopods are predatory, with the head and mouth surrounded by
muscular tentacles that capture the prey, which is then eaten by a
parrotlike beak and radular teeth.
quarta-feira, 26 de março de 2014
Bivalves
Bivalvia
is
a class
of
marine and freshwater mollusks
that have a laterally compressed shell composed of to valves (left
and right) joined dorsally by an elastic ligament. This ligament in
conjunction with interlocking "teeth" on each of the
valves, forms the hinge. This arrangement allows the shell to be
opened and closed without the two valves becoming disarticulated.
Bivalves typically display bilateral symmetry both in shell and
anatomy, but there are significant departures from this theme such as
scallops and oysters.
This
class is the second most diverse group of mollusks behind gastropods.
Adult shell sizes vary from one millimeter to over a meter in length,
but the majority of species do not exceed 10 cm.
The
name "bivalve" is derived from the Latin
bis,
meaning "two", and valvae,
meaning "leaves of a door".
Not
all animals with shells with two hinged parts are classified under
Bivalvia; other animals with paired valves include certain gastropods
(small
sea snails
in
the family Juliidae) and some members
of the phylum Brachiopoda (image).
California clam shrimp, Cyzicus californicus |
Bivalves
have long been a part of the diets of coastal human populations.
Oysters were cultured
by the Romans, and mariculture
has
more recently become an important source of bivalves for food.
Besides their use as food, oysters are the most common source of
natural pearls.
The shells of bivalves are used in craftwork and the manufacture of
jewelery and buttons. Bivalves have also been used in the biocontrol
of pollution.
Bivalves appear in the fossil record first in the early Cambrian more than 500 million years ago. The total number of living species is approximately 9,200 that inhabit most aquatics habitats. The marines species range from shallow to the deep waters, from equator to the poles. Bivalves also have colonized brackish-water estuaries and fresh water rivers, streams, and lakes.
The
bivalve shell consists of two valves that are hinged dorsally,
usually with interlocking teeth (the hinge), and always with a horny
ligament that connects the two valves along their dorsal surfaces and
acts to force the valves apart. The interior of the valves contain
scars of the various muscles attached to it, in particular the
(usually two, sometimes one) adductor muscles that, on contraction,
close the valves. The shell can also be internal, reduced or even
absent as in shipworms.
Shipworm |
Near
the hinge of the shell is the umbone
or
beak, a rounded, knobbly protuberance. This represents the oldest
portion of the shell. The hinge area is the dorsal region of the
shell and the lower margin is the ventral region. The anterior or
front of the shell is where the byssus
and
foot are located, and the posterior of the shell is where the siphons
are located. When the umbone is uppermost, the valve with the
anterior end to the left is considered to be the left valve, while
the valve with the anterior end to the right is the right valve.
The valves of bivalves are made of either calcite, as is the case in oysters, or both calcite and aragonite. The ligament and byssus, if calcified, are composed of aragonite. The shell usually consists of three layers: an outer periostracum, and outer an inner shell layers.The outermost layer of the shell is the periostracum, a skin-like layer which is composed of a hard organic substance and is usually olive or brown in colour and easily abraded. The outer layer forms surface details such as scales or spines.
In
all mollusks, the mantle
forms
a thin membrane
covering
the animal's body and extending out from it in flaps or lobes. In
bivalves, the mantle lobes secrete the valves, and the mantle crest
secretes the whole hinge mechanism consisting of ligament,
byssus threads, and teeth.
Most
bivalves have a capacious mantle cavity that accommodates large
gills, but they don't have head, radula or jaws. In addition to
respiration, the gills filter food particles from the water in the
majority of bivalves. Some primitive forms feed directly on the
organic matter in fine sediments, a few specialized groups derive
nutrition from symbiotic algae or bacteria, while others capture and
consume small crustaceans and worms in the deep sea.
The
intestine is irregularly looped and opens dorsally into the exhalant
area. Also opening into this region are the paired kidneys and, when
separate from the kidneys, the gonopores of the paired gonads. The
heart typically lies below the center of the valves and consists of
two auricles and a single ventricle that supplies both anterior and
posterior aorta. The nervous system is made up of three pairs of
ganglia.
The
bivalve foot is modified as a powerful digging tool in many groups,
while in those that live a permanently attached life (e.g., oysters),
it is very reduced.
Most
bivalves burrow in sand or mud, some in wood, clay or coral. Some
attach to hard substrates with threadlike strands of protein
(byssus), others by permanently cementing one of their valves.
The
tiny larva of a bivalve produces a single, uncalcified, caplike
shell,called a pellicle. As the larva growths, it is gradually
enveloped by two mantle lobes, each developing a separate center of
calcification – the dissoconchs, the parts of the shell produced
after the larva metamorphoses, assume the proportions and features of
the adult bivalve.
Bivalves
are divided into the following subclasses:
Protobranchia
Pteriomorpha
Pteriomorpha
Anomalodesmata
RostroconchiaHeterodonta
Chama limbula (Heterodonta) |
Spondylus regius (Pteriomorphia) |
quinta-feira, 13 de março de 2014
Gastropods
The
gastropods are the largest (about 80%) and most diverse class of the
phylum Mollusca. This class comprises
the snails,
which have a singe coiled shell into which the animal can generally
withdraw, and the slugs,
whose
shells have been reduced to an internal fragment or completely lost
in the course of evolution. Gastropods
are not only diverse with respect to the number of species alive
today, they are diverse in terms of their size, shape, color, body
structure and shell morphology.
The
majority of the gastropods are asymmetric and dextraly coiled, and
they occupy all marine habitats from equator to the poles, from shall
to deeper waters. Multiple groups have colonized freshwater habitats,
while others have evolved the ability to breathe air and have
colonized terrestrial habitats, including mountains and deserts. Most
marine gastropods breathe via their gills, however freshwater and
terrestrial species are an exception to this rule and breathe using a
rudimentary lung. Those gastropods that breathe using a lung are
called pulmonates. Gastropods are among the few groups of animals to
have become successful in all three major habitats: the ocean, fresh
waters, and land.
This
mollusks range
in size from 0,33 mm to 1m length, most are mobile, but some cement
them selfs to hard substrates while others are external or internal
parasites. Gastropods may be herbivores,
carnivores, parasites, filter feeders, detritivores or
chemoautotrophs (rare).
Those that feed on plants and algae use their radula to scrape and
shred their food. Gastropods that are predators use a siphon to
suction food into the mantle cavity and filter it over its gills.
Some predatory gastropods feed on shelled prey by boring a hole
through the shell to locate the soft body parts inside.
The
coil of the shell usually twists in a clockwise direction, so that
when viewed with the apex (top) of the shell pointing upward, the
opening of the shell is located on the right. Many gastropods (such
as sea snails, terrestrial snails, and freshwater snails) have a
hardened structure on the surface of their foot called an operculum
that work's as a “trap-door”. The operculum serves as a lid that
protects the gastropod when it retracts its body within its shell.
The operculum seals the shell opening to prevent desiccation or deter
predators. The operculum may be solid and heavy (eg. Turbinidae) or
pliant and horny (eg. Muricidae or Trochidae). Sometimes it is very
small and obsolete and it isn't big enough to seal the aperture,
likes happens in some cones.
Chicoreus
saulii (Muricidae)
|
Conus textile (Conidae) |
During
the larval stage, all gastropods undergo torsion, a very rapid
process that results in the rotation of the visceral mass and mantle
on the foot. The result is that the mantle cavity (including anus)
lies in the anterior body, over the head and mouth, and the gut and
nervous system are twisted. . This twisting means that the head is
between 90 and 180 degrees offset relative to their foot. Torsion
results in asymmetrical growth, with more growth occurring on the
left side of the body. Torsion causes the loss of the right side of
any paired appendages. Thus, although gastropods are still considered
to be bilaterally symmetrical (that's how they start out), by the
time they become adults, gastropods that have undergone torsion have
lost some elements of their "symmetry". The adult gastropod
ends up configured in such a way that its body and internal organs
are twisted and the mantle and mantle cavity are above its head. It
should be noted that torsion involves the twisting of the gastropod's
body, it has nothing to do with the coiling of the shell Some
species reverse torsion ("detorsion"), but evidence of
having passed through a twisted phase can be seen in the anatomy of
these forms. Torsion in gastropods has the unfortunate result that
wastes are expelled from the gut and nephridia near the gills. A
variety of morphological and physiological adaptations have arisen to
separate water used for respiration from water bearing waste
products.
Gastropods
are dioecious (sexually distinct), and some forms are hermaphroditic.
Hermaphroditic forms exchange bundles of sperm to avoid
self-fertilization; copulation may be complex and in some species
ends with each individual sending a sperm-containing dart into the
tissues of the other.
Gastropods
are divided into the following basic groups:
- Patellogastropoda
- Vetigastropoda
- Cocculiniformia
- Neritimorpha
- Caenogastropoda
- Heterobranchia
Turbo
marmoratus ( Vetigastropoda)
|
Mitra
mitra (Caenogastropoda)
|
quinta-feira, 6 de março de 2014
Biological classification
Classificacion
of living things is essential to any study of animals and plants, it
is usually based on anatomical similarities and differences and is
called taxonomy (Taxis means arrangement and nomos means
method). The modern taxonomic system was developed by the Swedish
botanist Carolus (Carl) Linneaeus (1707-1788). To distinguish
different levels of similarity, each classifying group, called taxon
(pl. taxa) is subdivided into other groups. The broadest
category is the domain, followed by kingdom, phylum, class, order,
family, genus and species, the most specific one. The
members of a particular species are similar enough to allow
interbreeding to result in fertile offspring. To complicate a little
bit more we also have intermediate grades such as subclass, suborder,
superfamily, subfamily and subgenera.
In
1990 Carl Woese introduced the taxon domain, he divided all the
living things in three domains that are organised based on the
difference between eukaryotes and prokaryotes. The three domains are
as follows:
Archea
(Archeabacteria) consists of archeabacteria, bacteria which live
in extreme environments. The kingdom Archaea belongs to this domain.
Eubacteria
consists of more typical bacteria found in everyday life. The
kingdom Eubacteria belongs to this domain.
Eukaryote
encompasses most of the world's visible living things. The
kingdoms Protista, Fungi, Plantae, and Animalia fall under this
category.
Under
the three domains we have six kingdoms Plants,
Animals,
Protista, Fungi, Eubacteria and Archae (or Archabacteria). The first
two are commonly understood and will not be expounded here.
Protista,
the third kingdom, was introduced by the German biologist Ernst
Haeckel in 1866 to classify micro-organisms which are neither animals
nor plants. Since protists are quite irregular, this kingdom is the
least understood and the genetic similarities between organisms in
this kingdom are largely unknown. For example, some protists can
exhibit properties of both animals and plants.
Fungi
are organisms which obtain food by absorbing materials in their
bodies. Mushrooms and moulds belong in this kingdom. Originally, they
were part of the plant kingdom but were recategorised when they were
discovered not to photosynthesise.
Eubacteria
are bacteria, made up of small cells, which differ in appearance
from the organisms in the above kingdoms. They lack a nucleus and
cell organelles. They have cell walls made of peptidoglycan.
Archae
(or Archaebacteria) are
bacteria which live in extreme environments, such as salt lakes or
hot, acidic springs. These bacteria are in their own category as
detailed studies have shown that they have unique properties and
features (ex. unusual lipids that are not found in any other
organism)which differ them from other bacteria and which allow them
to live where they live. Their cell walls lack peptidoglycan. Here is
a diagrama of the the taxa in hierarchical order:
Now
we can return to our seashells. Seashells belongs to the phylum
Mollusca
of the animal kingdom that is the larger phylum of invertebrates and
has around 85 000 species. This philum is the second phylum with
larger number of specimens comprising 23% of all the named marine
organisms, but exists mollusks living in fresh water and terrestrial
habitats. This
animals are highly diverse, not only in size and in anatomical structure,
but also in behaviour and in habitat. The phylum
is
typically divided into 9 or 10 classes,
of which two are entirely extinct.
Six of this classes are related to seashells: Gastropoda, Bivalvia,
Cephalopoda, Scaphopoda, Polyplacophora and Monoplacophora that will be
describe in others messages. Cephalopods
mollusks,
such as squid
and
octopus,
are among the most neurologically
advanced of
all invertebrates—and
the giant squid
is
one of the largest known invertebrate species. The gastropods
(snails
and
slugs)
are by far the most numerous mollusKs in terms of classified species,
and account for 80% of the total.
Mollusks
have developed such a varied range of body structures, it is
difficult to find defining characteristics to apply to all. The most
general characteristic of mollusks is that they are unsegmented and
bilaterally symmetrical; the presence of a mantle with a significant
cavity used for breathing and excrecion, and an organized nervous
system.
Here
are 2 examples of seashells biological classification :
Domain: Eukaryota
Animal: Kingdom
Phylum: Mullusca
Class:
Gastropoda
Subclass:
Caenogastropoda
Order:
Neogastropoda
Superfamily:
Conoidea
Family:
Conidae
Genus:
Conus
Species:
pertusus
Domain: Eukaryota
Animal: Kingdom
Phylum: Mollusca
Class:
Bivalvia
Subclass: Heterodonta
Infraclass: Euheterodonta
Order:
Veneroida
Superfamily: Cardioidea
Family: Cardiidae
Subfamily:
Fraginae
Genus: Corculum
Species: roseum
terça-feira, 4 de março de 2014
Xenophora pallidula
Class:
Gastropoda Subclass: Caenogastropoda Order: Littorinimorpha
Superfamily: Xenophoroidea Family: Xenophoridae Genus: Xenophora
Author:
Reeve, 1842
The
seashells that belong to the genus
Xenophora are known as a carrier
shells because they have the habit of
attach empty shells, pieces of coral, stones or grains of sand to
their shells. In most species this only occur during their young
state and the attachments are only on early whorls. In others such X.
pallidula (photos) it continues
throughout the growth giving a beautiful and interesting
seashell. The Xenophora
picks up and clean the selected object, then the animal cements the
object to its shell with secretions from the mantle. Bivalve shells
are placed with the inner side facing upward, while gastropods are
usually attached with the aperture facing up. This process can take
up to an hour and a half to complete, then the animal remains
motionless for up to ten hours to ensure its new attachment is
secure.
It is
not known to what extent an artistic sensibility plays a part in this
behavior. The seashells who live in shallower water (where there is
enough light for them to be seen) probably use their collections for
camouflage. The ones that live in the deeper, dark waters, such as X.
pallidula (photos), are believed to
be motivated more by a desire to not to be sucked into the viscous
muck in which they live. Attaching extensions to their shells spreads
out the shell's surface area and helps prevent the animal from
sinking. The additions may also strengthen the gastropod relatively
thin shell.
Not
all of the items on a Xenophora's
shell are put there by the creature itself. As a solid substrate in a
mucky environment, the shell is an enticing landing spot for tube
worms, oysters, and, most spectacularly, glass sponges. Their new
home even has the advantage of being mobile, transporting a rooted
animal to new feeding grounds.
quinta-feira, 27 de fevereiro de 2014
Clanculus puniceus
Class:
Gastropoda Subclass: Vetigastropoda Superfamily: Trochoidea
Family: Trochidae Subfamily: Trochinae Genus: Clanculus
Family: Trochidae Subfamily: Trochinae Genus: Clanculus
Clanculus
puniceus is a small and attractive
seashell, also known as strawberry top
because reminds a strawberry in color and texture. It is herbivore
mollusk and its size range from 13 to 22 mm. It is a common species
between Tanzania and South Africa, normally found in shallow waters
under rocks. Clanculus puniceus
is among the relatively few gastropod shells that fluoresce or glow
under ultraviolet light, as a result of pigments incorporated in the
shell.
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