Especialidades JA/Moluscos - Avanzado/Respuestas

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Moluscos - Avanzado

Asociación General

Estudio de la naturaleza

Destreza: 3
Año de introducción: 1949

Requisitos

1

Tener la especialidad de Moluscos.

Para consejos e instrucciones, véase Moluscos.

2

Definir el término «moluscos».

3

Conocer los términos de la clasificación de los moluscos, conocer las características distintivas de cada uno y familiarizarse con varias especies de cada clase.

There are ten classes of molluscs; eight of the classes have living representatives, the other two classes are known only from fossils. More than 250,000 species of mollusc are recognized and named. Snails (Gastropoda) account for about 80% of living mollusc diversity.

4

Distinguir entre moluscos unívalvos y bívalvos teniendo en cuenta las siguientes partes:

4a

Concha

4b

Cuerpo del molusco

4c

Reproducción

4d

Movimientos

4e

Asegurando la alimentación

4f

Auto-preservación

5

Identificar a partir de conchas o dibujos y saber el significado de los siguientes términos lógicos de caracoles:

5a

Valva

5b

Ápice

5c

Apertura, orificio

5d

Biso

5e

Pie

5f

Mantel, manto

5g

Opérculo

5h

Nácar

5i

Epidermis

5j

Costillas

5k

Los dientes

5l

Líneas concéntricas

5m

Canal

5n

Espinas

5o

Espira

5p

Labios

6

Explicar el desarrollo de una concha. ¿Cuánto tiempo viven los moluscos?

The marine gastropod Cypraea chinensis, the Chinese Cowry, showing partially extended mantle
The giant clam (Tridacna gigas) is the largest extant bivalve
Fossil shell covered in calcite crystals

In those molluscs which have a shell, the shell grows gradually over the lifetime of the mollusc by the addition of calcium carbonate to the leading edge or opening, and thus the shell gradually becomes longer and wider, in an increasing spiral shape, to better accommodate the growing animal inside. The animal also thickens the shell as it grows, so that the shell stays proportionately strong for its size.

7

Dar algunos datos sobre la vida de un caracol Strombus pugilis (conchas luchadora) y explicar la razón por la que éste molusco es llamado así.

The West Indian Fighting Conch is an aggressive sea snail with a nasty sting which it uses to defend itself against marine predators. These shells are best collected when the tide goes out, as great numbers of them suddenly emerge from the sand and retreat to the surf. If one is flipped over, it can right itself using its sharp operculum.

8

Explicar las actividades del molusco broma.

Adventist Youth Honors Answer Book/Nature/Shipworm

9

¿Cómo se explica la distribución de los moluscos?

molluscs have few requirements in order for them to thrive. They need moisture, but if they find themselves in a dry environment, they are able to seal themselves (and their moisture) inside their shells until external moisture becomes available again. Thus, molluscs can be found in nearly every habitat on Earth - even deserts!

10

Nombrar dos moluscos que no tienen conchas.

Slug
Octopus
Cuttlefish
Squid

11

Encontrar respuestas a las siguientes preguntas interesantes:

11a

¿Cómo están unidos los bívalvos y unívalvos a sus conchas?

The muscles of both types of molluscs attach directly to the shell. These animals (including snails) cannot leave their shells and return any more than a turtle can leave its shell. The shell serves as the animal's skeleton.

11b

¿Cómo es controlado el color del molusco?

The outer edge of a mollusc's mantle contains glands that secrete color pigments during shell formation. These pigments control the colors on the outside of the shell. The iridescence on the inside of the shell is caused by alternating layers of calcite and aragonite refracting different wavelengths of light by different amounts depending on the viewing angle.

The Nautilus, a mollusc with four gills

11c

¿Qué molusco tiene cuatro branquias?

The 'Nautilus has two pairs of gills (that's four!).

11d

¿De qué animal del mar fue hecha la tinta india?

Cuttlefish have ink, like squid and octopuses. This ink was formerly an important dye, called sepia. Today artificial dyes have replaced natural sepia.

11e

¿Qué molusco hace girar un hilo de seda?

Several molluscs spin a byssus which is used to anchor them to a substrate. These include mussels in the family Mytilidae and the zebra mussel (Dreissena polymorpha). However, the mollusc with perhaps the most extensive byssus is the rigid pen shell (Atrina rigida). Like most pen shells, A. rigida lives in soft bottoms, with the majority of the shell buried, point down, leaving only a few inches exposed, held in place by an extensive net of byssal threads.

11f

¿Qué conchas se utilizaban para el dinero de tribus antiguas?

Many people find the very rounded, shiny, porcelain-like shells of cowries pleasing to look at and to handle. Shells of certain species have historically been used as currency in several parts of the world, as well as being used, in the past and present, very extensively in jewelry, and for other decorative and ceremonial purposes.

11g

¿Qué concha se considera sagrado por los tibetanos?

Tibetan Buddhists make use of a particular set of eight auspicious symbols, ashtamangala, in household and public art. The chank shell or conch is one of these eight symbols:

Conch
Knot
Fish
Banner
Lotus
Parasol
Urn
Wheel

11h

¿De qué molusco se obtenía la tinta púrpura en los tiempos antiguos?

Hexaplex trunculus (also known as Murex trunculus or the banded dye-murex) is a medium-sized species of sea snail.

This species of sea snail is important historically because its hypobranchial gland secretes a mucus that the ancient Canaanites/Phoenicians used as a distinctive purple-blue indigo dye. One of the dye's main chemical ingredients is indigotin, and if left in the sun for a few minutes before becoming fast, its color turns to a blue indigo (like blue jeans).

11i

¿Cuál es la fuente de las perlas? ¿Cómo se forman?

Nacre, also known as mother of pearl, is an important part of the shell structure in many gastropod and bivalve molluscs especially the more ancient families such as top shells and pearl oysters. Like the other calcareous layers of the shell, the nacre is created by the epithelial cells (formed by the germ layer ectoderm) of the mantle tissue. mollusc blood is rich in dissolved calcium, and during shell deposition, the calcium is concentrated out from the blood and crystallized as calcium carbonate. Nacre is continually deposited onto the inner surface of the animal's shell (the iridescent nacreous layer or mother of pearl). This is done both as a means to thicken, strengthen and smooth the inner surface of the shell itself and as a defense against parasitic organisms and damaging detritus.

When a mollusc is invaded by a parasite or is irritated by a foreign object that the animal cannot eject, a process known as encystation entombs the offending entity in successive, concentric layers of inner shell material, which in some cases is nacre. This process eventually forms what we call pearls and continues for as long as the mollusc lives. Almost any species of bivalve or gastropod is capable of producing "pearls", even molluscs which have no inner nacreous layer. However, only a few species, such as the famous pearl oysters, can create pearls which are highly prized.

12

Nombrar seis usos comerciales de las conchas (moluscos).

Musical Instruments: Key touches and various decorations on musical instruments such as saxophones, trumpets, violins, banjos, tamburitzas and guitars are sometimes made of mother of pearl. It is used as inlays on many guitar fretboards.
Clothing: Mother of pearl buttons can be found on a variety of clothing such as shirts, skirts and coats.
Decorative Inlays: Nacre is also used as a decorative feature of watch faces, knives, guns and jewelry.
Building Material: Instead of using a marble or tile base, the mother of pearl tesserae can be glued to a fiberglass mesh. The result is a lightweight material that offers a seamless installation, and there is no limit to the sheet size. Mother of pearl sheets may be used on interior floors, exterior and interior walls, countertops, doors and ceilings. Insertion into architectural elements, such as columns or furniture is easily accomplished. Conch shells are occasionally used as a building material, either in place of bricks or as bulk for landfill.
Jewelry: Pearls are highly prized jewelry components.
Souvenirs: In some countries, cleaned Queen Conch (Strombus gigas) shells or polished fragments are sold, mainly to tourists, as souvenirs or in jewelry. Without a permit, however, export is a breach of CITES regulations and may lead to arrest. This is most likely to occur on return to the tourist's home country while clearing customs. In the UK conch shells are the ninth most seized import.
Pets: Snails are often kept in aquariums along with fish.

13

Realizar una de las siguientes actividades:

a. Personalmente encontrar y recolectar 40 especies de conchas que representan a las cinco clasificaciones. Hacer una lista de cada molusco con el lugar y la fecha en que fue encontrado, nombre común, nombre científico y la clase.

b. Hacer una colección de 50 especies de conchas que ha encontrado, recibido o comprado que representen las cinco clasificaciones.

Hacer una lista de cada concha recogida de la siguiente manera: si la encontró personalmente, dar la información solicitada en el punto «a»; si la recibió o compró, dar el nombre de la persona de quien recibió la concha, el hábitat de la concha, la fecha de su adquisición, su nombre común, nombre científico y la clase.

The best approach here is to get a good field guide and then try to identify the shells you have found.

The five classifications of seashells are:

Gastropoda: (snails, conches, etc.)
Cephalapoda: Such as Spirula spirula. Although the whole animal is rarely seen, the internal shell is very light and commonly floats ashore on beaches. The internal shell of this animal is known as the "ram's horn shell".
Bivalvia: (clams, mussels, etc.)
Polyplacophora: (chitons)
Scaphopoda: (tusk shells)

If you opt to purchase your collection, one possibility is to start with a kit containing specimens from all five of these classes. Seashells.com carries a such a kit, reasonably-priced.

References