What type of larvae do annelids have?

What type of larvae do annelids have?

trochophore, also called trochosphere, small, translucent, free-swimming larva characteristic of marine annelids and most groups of mollusks. Trochophores are spherical or pear-shaped and are girdled by a ring of cilia (minute hairlike structures), the prototroch, that enables them to swim.

What are 3 types of annelid worms?

Critical appraisal. Most authors accept the annelids as having three major classes: Polychaeta, Oligochaeta, and Hirudinea.

What are the characteristics of annelids for kids?

The animals in the Annelida are segmented worms. They have no legs, and no hard skeleton. Unlike mollusks, annelid bodies are divided into many little segments, like rings joined together. There are many other kinds of worms, but only annelids are segmented this way.

What is the name of the larval stage of Polychaetes?

Larval polychaetes generally develop through three stages: the trochophore, metatrochophore, and nectochaete stages. Trochophores are ciliated larvae (see Fig. 1). A band of cilia, the prototroch, is used for locomotion and sometimes feeding.

What is the larva of Arthropoda?

This larval stage, called a nauplius, is found in barnacles, copepods, penaeid shrimps, and ostracods. It swims by using its jointed appendages that are moved by muscle contraction. These larvae have a nauplier eye, made up of photoreceptor cells that are thought to give rise to the photoreceptors in some adult forms.

Do all mollusks have trochophore larvae?

Molluscs include such familiar creatures as clams, oysters, snails, and octopi. They share a distant common ancestor with the annelid worms, an evolutionary heritage suggested by their larval form, called a trochophore larva, found in all molluscs and in certain marine annelids called polychaete worms.

What are examples of Hirudinea?

The class Hirudinea in the phylum Annelida (segmented worms) comprises the leeches, the most highly specialized of the major annelid groups. Leeches are typically dorsoventrally flattened annelids with suckers at both ends and 34 body segments (designated I-XXXIV) which are externally divided into a number of annuli.

How many Annelid species are there?

9,000 species
A major invertebrate phylum of the animal kingdom, the annelids number more than 9,000 species distributed among three classes: the marine worms (Polychaeta), which are divided into free-moving and sedentary, or tube-dwelling, forms; the earthworms (Oligochaeta); and the leeches (Hirudinea).

How are annelids segmented?

annelid, phylum name Annelida, also called segmented worm, any member of a phylum of invertebrate animals that are characterized by the possession of a body cavity (or coelom), movable bristles (or setae), and a body divided into segments by transverse rings, or annulations, from which they take their name.

How many species of segmented worms are there?

20481 species
Annelida (Segmented Worms) is a phylum of animals. There are 20481 species of Segmented Worms, in 2382 genera and 171 families. This phylum has been around since the ediacaran period.

What are the larval forms of Arthropoda?

Selected types of larvae

Animal Name of larvae
Arthropoda: Xiphosura euproöps larva (“trilobite larva”)
Arthropoda: Pycnogonida protonymphon
Crustaceans General: nauplius, metanauplius, protozoea, antizoea, pseudozoea, zoea, postlarva, cypris, primary larva, mysis Decapoda: zoea Rhizocephala: kentrogon

What is the larval stage of echinoderms?

Echinoderms show a complicated metamorphosis in the course of development. Their larva is strikingly bilaterally symmetrical whereas the adult shows radial symmetry. Larva swims with the help of ciliated bands , which may be complicated by a number of short or long slender projections or arms from the body wall.

What are annelids in biology?

Annelids are a phylum of invertebrate worms. They are the segmented worms, with over 17,0000 known species. Well known species are earthworms and leeches. Annelids can be found in most wet environments.

What is an annelid cross?

Some of the micromeres become arranged in a characteristic pattern known as the annelid cross. A free-swimming immature form called the trochophore larva develops in the polychaete annelids and during the development of certain other invertebrate groups—mollusks, sipunculids, and lophophores.

What kind of nervous system does annelid worms have?

Nervous system. Annelid worms have a nervous system. The brain forms a ring round the pharynx (throat), consisting of a pair of ganglia (local control centers) above and in front of the pharynx, linked by nerve cords either side of the pharynx to another pair of ganglia just below and behind it.

What is Annelida segmentation?

Annelida segmentation is metameric. A well-developed nervous system that includes a nerve ring of fused ganglia is present around the pharynx. The nerve cord is present in a ventral position, that consists of enlarged nodes or ganglia in each of the segments. Sensory organs for detecting light and other stimuli.