Anellide Policheta - Polychaeta

Polychaetes Polychaeta annelid phylum Policheti Anellidi intotheblue.it

Bearded fireworm - Hermodice carunculata

Bearded fireworm, Hermodice carunculata, is a type of marine bristleworm belonging to the Amphinomidae family, native to the tropical Atlantic Ocean and the Mediterranean Sea. Bearded fireworms are usually 15 centimetres in average length, ...

Fanworm - Sabella spallanzanii

Sabella spallanzanii is a species of marine polychaete worms in the family Sabellidae. Common names include the Mediterranean fanworm, ...

Filograna implexa - Salmacina incrustans

Filograna implexa lives throughout the Mediterranean Sea in very small intertwined tubes at a depth that can vary from 10 meters up to over 100 meters and where conditions allow it colonizes the gorgonians, especially the Paramuricea clavata ...

Peacock worm - Sabella pavonina

Sabella pavonina, commonly known as the peacock worm, is a marine polychaete worm belonging to the family Sabellidae. They can be found along the coasts of Western Europe and the Mediterranean. It is found in shallow, tidal waters ...

Red-tuft Protula - Protula tubularia

Red-tuft Protula lives throughout the Mediterranean Sea in small tubes at depths that can vary from 10 meters to over 100 meters.It is a very common annelid throughout the Mediterranean and therefore we can easily find it among the Posidonia ...

Serpulidae - Hydroides Dianthus

Il Serpulide Hydroides Dianthus è un Verme che appartiene al philum degli Anellidi, ed alla classe dei Policheti Sedentari e all’ordine dei Sabellidi ed al genere dei Serpulidi ...

Polychaetes (Polychaeta Grube, 1850) are the phylogenetically oldest class of the annelid phylum, comprising about 13,000 species. They are benthic animals and have a marine habitat.

Lo spirografo (Sabella spallanzanii) – intotheblue.it Polychaetes Polychaeta annelid phylum Policheti Anellidi intotheblue.it

Morphology

They present an indirect development for larvae of the trochophoric type, in which there is the presence of already differentiated and metamerized coelomatic pockets. The trocofora of polychaetes represents the classical form, is characterized by a typical spinning top and by two ciliate bands, prototypical and metatroco, which surround the surface roughly at the level of the equatorial plane. These bands work both for movement and for feeding through plankton filtration.

The development occurs with the elongation at the back and the beginning of the segmentation, so the most recent segments are those near the pigidium. Polychaetes Polychaeta annelid phylum Policheti Anellidi intotheblue.it

spirografo - serpulidae diantus - intotheblue.it — spirografo – serpulidae diantus – intotheblue.it Polychaetes Polychaeta annelid phylum Policheti Anellidi intotheblue.it

The size of most species ranges from 5 to 10 cm, but there are species that measure a few millimeters and others (Dasybranchus caducus) that can exceed the meter in length and the thickness of 2 cm.

The body shows a clear metameric segmentation. Polychaetes Polychaeta annelid phylum Policheti Anellidi intotheblue.it

There are three regions, prosthomia or cephalic region, metastomio or trunk and pigidium or tail. They are devoid of clitello (paracentral swelling rich in muciparous glands present in the earthworms instead).

The prostomium is the pre-oral segment, where the cerebral ganglia and sensory organs are located, including the eyes, the antennas or tentacles, the sensory palps and the nuchal organs; in the sedentary forms both the prostomium and the sensory organs can present themselves in very small dimensions. The peristomial or oral segment, where the mouth opens and where are the organs necessary for the capture of food and the sensory ones related to food. Prostomio and peristomio are not always well diversified, rather frequently they are more or less merged or overlapped. The buccal cavity is frequently evaginable and provided with chitinous papillae and mandibles. Polychaetes Polychaeta annelid phylum Policheti Anellidi intotheblue.it

The metastomio

The remaining metameric segments may be similar (metamer, homonym segmentation) or form clearly distinct regions (metamer, heteronomous segmentation); this is the case with some sedentary polychaetes. the most characteristic structures of the metastomie are the parapods. usually the parapods consist of two parts, a dorsal called notopodio, and a ventral one called neuropodio, both have a cirrus and are provided with bristles, the chitinous formations of a needle very characteristic from which the group name derives, which are connected by muscles to the ventral mesentery, this allows their movement and the consequent movement of the animal. Polychaetes Polychaeta annelid phylum Policheti Anellidi intotheblue.it

The pigidium

Some species have present and very visible parapods that allow them to crawl on the bottom (so-called wandering polychaetes). In many other species (so-called sedentary polychaetes), instead, the parapods are missing: they are often semisextile forms, sunk in the sediment through a tube produced by the secretions of epidermal cells (tubicolates). The composition of the tube is very varied, being able to be mucous, frequently mixed with particles of mud, sand or organic remains, membranous, chitinous or calcareous. Polychaetes Polychaeta annelid phylum Policheti Anellidi intotheblue.it

Some species, like the spirograph, are adorned with a rich and colorful crown of spiral tentacles.