Previously some zoologists treat ‘Archiannelida’ as an appendix to the class polychaeta but Knox (1972) has treated it as a sepa­rate class.

See our 1. Classification of Nephridia 4. In aquatic forms various types of respiratory organs are seen.

Similar evaginations in Ozobranchus are lamellated. Each segment has its own segmental nerves which control the localised muscular contraction under the central nerv­ous system. Along the protone­phridial tubule some sub-substances such as salts and amino acids are reabsorbed and the chief excretory product ammonia is excreted through the nephridiopore.

Circulatory System 11. Hirudo (the typical—leech which is parasite on verte­brates), Aulostoma (horse leech, free-living and carnivo­rous), Hirudinaria (H. granularia, cattle leech), Haemadipsa, Phytobdella (terres­trial leeches), Erpobdella (worm leeches), Dina. Excretion in Annelids by P. Publication date 1901-11-01 Publisher The American Naturalist Collection jstor_amernatu; jstor_ejc; additional_collections; journals Contributor JSTOR Language English Volume 35 "Excretion in Annelids" is an article from The American Naturalist, Volume 35. In many forms the perivisceral cavity or coe­lom is well-developed. In croco­diles, birds and mammals, there are two auricles and two ventricles. 17.58) con­sists of a nephrostome or a ciliated funnel which hangs into the coelom and leads to the nephridial duct. Annelids vary widely regarding their sizes. Alluroides, Drawidia, Lumbri- cus, Megascolides, Megascolex, Pheretima, Eudrilus.

13. The heart of fishes contains one auricle and one ventricle and the heart is called venous heart, because the heart always receives venous (deoxygenated) blood. (iii) Each typical body segment contains 5 annuli. The setae are of various types (Fig. In many forms a distinct head consisting of a pre-oral ‘prostomium’ and a post-oral ‘peristomium’ is present. 9. The body forms a complete cylinder with well-developed circular and longitudinal muscles and uniformly developed transverse septa. Hence, the two groups are generally considered as sub­class within the class Clitellata.

Each nephridium develops from a single cell, called nephroblast. Nervous system represented by cerebral ganglia (supra-pharyngeal ganglia) and double ventral nerve cord with segmentally arranged ganglia and lateral nerves.

The same is true for many polychaetes and hirudinea. Excretory organs include segmentally arranged 10 to 17 pairs of metanephria. Many species have a worldwide dis­tribution and the inter-tropical are the same in all the oceans.

All oligochaetes are hermaphrodite and have well-defined gonads which remain lim­ited to few segments only. Hi there! It is enclosed by the muscles of the body wall. Terrestrial leeches usually live in moist vege­tation of the tropics and feed on the blood of Vertebrates. (An eBook reader can be a software application for use on a computer such as Microsoft's free Reader application, or a book-sized computer that is used solely as a reading device such as Nuvomedia's Rocket eBook.) In this classifica­tion no Linnaean categories of above family such as superfamily, order, and subclass are used. What would be the consequences if there is no meiosis in organisms that reproduce sexually? Fusion of anterior segments in many forms results the formation of a sub-pharyngeal ganglion or ganglia.

The blood-vascular system is of closed type. The parapodia become variously modi­fied in different polychaetes (Fig.

The classification of Phylum Annelida is still un­stable. 14.

Locomotion 10.

In Capitellidae there may be one to six pairs of permanent nephridia in each of the trunk segments. (i) Setae present in bundles with two or more setae.

(iv) They are found in many polychaetes and oligochaetes.

Sex in your area is here: ❤❤❤ ❤❤❤ (v) One pair of testes followed by a pair of ovaries. Definition and Fossil Record of Phylum Annelida 3.

Pelagic, crawling, burrowing and tube-dwelling forms. 8. In Nereis such ciliated organs are found and they remain attached to the dorsolateral longitudinal muscles.

Fertilization: Internal or external; Development: direct with no larval stages; Classification of Phylum Annelida.

When some commissural blood vessels are enlarged and achieve the function of contraction and relaxation, it is called pulsatile hearts. 14. In larger forms of oligochaetes additional ves­sels like sub-intestinal or supra-intestinal vessel are often present. This serpentine movement is caused by the co­ordinated action of the longitudinal muscles and the parapodia. View more articles from The American Naturalist. The organs of excretion are metamerically ar­ranged tubular nephridia or tegmental or­gans which are closed internally or lead from coelom to exterior.

In many Polychaetes there are highly vascularised gills attached to the notopodium as in Glycera. That is, they consisted of ectodermal tubules project­ing into the coelom and ending in special­ised cells, called solenocytes. Nereis vitabunda of Sumatra is a terrestrial form and lives in soil channels.

% The anal tubes in Echiuroidea are con­sidered as excretory structures. On maturity, the peritonium covering the gonads bursts and sperms or ova, as the case may be, are liberated into the coelomic fluid. These are not like the true hearts of vertebrates.

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