Tusk shells feed upon
such small organisms as protozoans of the order Forminifera and young bivalves
. Sexes are separate, and the eggs develop into free-swimming trochophore larvae.
Are tusk shells filter feeders?
| Class Species No. | Chitons (Placophora) 750 | Solenogastres 230 | Caudofoveata 120 | Molluscs (Mollusca) 55.400 |
|---|
Which is tusk shell?
The scaphopoda
. The Scaphopoda are a distinctive group of molluscs commonly known as the “tusk shells” because their shells are conical and slightly curved to the dorsal side, making the shells look like tiny tusks (see the photos below).
Where are tusk shell found?
Tusk shells are found in
cool and warm water oceans worldwide
, from seashores to depths down to about 23,000 feet (7,000 meters).
Do tusk shells have gills?
There are no gills
; the entire surface of the mantle cavity absorbs oxygen from the water. Unlike most other molluscs, there is no continuous flow of water with a separate exhalant stream.
How do gastropods make their shells?
The gastropod shell has three major layers secreted by the mantle. The calcareous central layer, tracum, is typically made of
calcium carbonate precipitated into an organic matrix known
as conchiolin. The outermost layer is the periostracum which is resistant to abrasion and provides most shell coloration.
What is a Captacula?
captacula In Scaphopoda,
prehensile tentacles that arise from the base of the proboscis
.
What animal do dentalium shells come from?
Today most dentalium shells in the shell trade are smaller, more brittle, and are harvested from coasts off Asia — i.e. they are shells of
Indo-Pacific species of scaphopods
.
What does a Scaphopoda lack?
Unlike other mollusks, however, scaphopods
lack gills for taking in oxygen
. Instead, they have tiny hairs or cilia that move water around the mantle cavity.
Do scaphopods have Ctenidia?
The shell surrounds a large mantle cavity, and wraps around the viscera to form a tube. The mantle cavity goes along ventral side to a smaller opening at the other end.
No ctenidia are present
, and gas exchange is through the mantle surface.
What is the common name of Dentalium?
Dentalium neohexagonum is a species of tusk shell, a marine scaphopod mollusk in the family Dentaliidae. As the Latin name implies, the cross section of this shell is hexagonal; hence its common name is
six-sided tusk shell
.
Are mollusks soft?
Mollusks are
soft-bodied invertebrates
of the phylum Mollusca, usually wholly or partly enclosed in a calcium carbonate shell secreted by a soft mantle covering the body.
Does Scaphopoda live in freshwater?
In the sea, they range from the deepest parts of the ocean to the intertidal area. They
can live in freshwater as well as
on land.
Which is the most diverse group of mollusks?
Lucinidae (Bivalvia)
–the most diverse group of chemosymbiotic molluscs.
What type of creature is a gastropod?
The Class Gastropoda (in
Phylum Mollusca
) includes the groups pertaining to snails and slugs. The majority of gastropods have a single, usually spirally, coiled shell into which the body can be withdrawn. The shell of these creatures is often what is recovered in a fossil dig.
