Does Aplacophora have shell?

Aplacophora is a relatively small group of molluscs that are characterized by their lack of shells and worm-like appearance. Instead of a shell, their mantle secretes tiny calcareous spicules which give them a beautiful shine.

How many shells do Aplacophora have?

Apart from molluscs with complete shells, such as snails, clams and cuttlefish, there are also the chitons (Polyplacophora). Those do not have a complete shell, but their back is protected by eight shell plates….Shell-less Molluscs (“Aplacophora”)

Class	Species No.
Molluscs (Mollusca)	55.400

Does Aplacophora have foot?

Aplacophorans are characterized by a narrow or completely reduced foot, a unique posterior dorsoterminal sensory organ, and a small mantle cavity restricted to the posterior-most part of the body.

Do Aplacophora have gills?

The animals possess a large flattened foot surrounded by the pallial groove, in which are situated 5 or 6 pairs of gills. Internally, the animals possess 8 pairs of dorsoventral pedal retractor muscles, a feature that is known to have existed in fossil forms.

Do Aplacophora have a nervous system?

This means that the Aplacophora have no viable means of locomotion. Nervous System: In the aplacophorans this consists of a simple cerebral ganglion and a lateral nerve cord. There are no specialized sense organs such as eyespots or electrical or chemical sensors.

Is Aplacophora Monoecious?

Aplacophora may be monoecious or dioecious with single or paired gonads.

How do Aplacophora reproduce?

Solenogasters are hermaphroditic, but caudofoveates have two sexes, and reproduce by external fertilization. During development, the mantle cavity of the larva curls up and closes, creating the worm-like form of the adult.

What do Aplacophora eat?

DIET. Some species prey on sea anemones, corals, hydroids, sea fans, and their relatives, as well as other organisms. Others are scavengers and swallow sand and mud that contain bits of food.

What is the meaning of Aplacophora?

Definition of Aplacophora : an order of Amphineura comprising wormlike mollusks in which the body is without calcareous plates but the mantle bears numerous calcified spicules over its entire surface.

How do Aplacophora eat?

The radula is covered with lots of rows of small teeth. The edges of the teeth are sawlike and made up of even smaller teeth called denticles (DEHN-te-kelz). The radula is used to scrape bits of food off rocks and other hard surfaces.

What is an example of Monoplacophora?

The Phylum Mollusca is composed of seven classes, namely Aplacophora (no shell), Polyplacophora (chitons), Monoplacophora (single external shell), Gastropoda (snails and slugs), Cephalopoda (octopuses and squids), Bivalvia (clams, oysters, mussels, cockles, scallops, and other) and Scaphopoda (tusk shells) comprising …

What is the common name for Monoplacophora?

monoplacophoran, (class Tryblidia), any of a group of primitive marine mollusks characterized by a single, cap-shaped shell and bilateral symmetry.

Where are Monoplacophora found?

Monoplacophorans are found on both soft bottoms and hard substrates on the continental shelf and seamounts, generally in the very deep sea. However, some Paleozoic taxa are associated with relatively shallow water faunas (greater than 100 m), indicating that their relegation to the deep sea is a more recent phenomenon.

What are examples of Monoplacophora?

Monoplacophora

• Mollusc.
• Snail.
• Mollusca.
• Gastropoda.
• Bivalvia.
• Polyplacophora.
• Scaphopoda.
• Teuthida.

Is Monoplacophora a class?

monoplacophoran, (class Tryblidia), any of a group of primitive marine mollusks characterized by a single, cap-shaped shell and bilateral symmetry. The term Tryblidia is preferred over Monoplacophoran and Galeroconcha, because both latter terms are taken to include several fossil groups of uncertain relationships.

Is Monoplacophora extinct?

Monoplacophora were common in the early Paleozoic and were thought to have become extinct during the Devonian Period, approximately 375 Mya.

What makes Monoplacophora unique?

Monoplacophorans are unusual because of the combination of primitive characteristics that they possess. In addition to the single, cap-shaped shell, they have paired multiple organs, reflecting at least partial segmentation (metamerism).