cover

Bent Christensen:

Annelida

1980. IV, 81 pages, 29 figures, 7 tables, 16x25cm, 300 g
Language: English

(Animal Cytogenetics, Volume 2)

ISBN 978-3-443-26010-1, paperback, price: 35.00 €

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Keywords

animalcygtogenicAnnelidareproductionTierZytonenetikAnnelidaAnnelidenRingelwürmerVermehrung

Contents

Content Description top ↑

The phylum Annelida comprises the segmented worms and includes the familiar earthworms and leeches, plus a great number of marine and fresh-water species that are less well known.

The most distinguishing characteristic of the phylum is the division of the body into similar segments along the antero-posterior axis. This segmentation is not restricted to the external appearance but is also reflected in the internal structures, including the reproductive organs, which are of special interest in the context of the present monograph. In the ancestral condition no well-defined gonads are present, but during the breeding season ova or spermatozoa arise from the wall of the coelum in each segment except near the anterior end. In the advanced condition the number of gonads is very much limited. Both male and female sexual organs occur in the same individual and they are permanent and often complicated structures in earthworms and leeches.

The phylum is usually divided into three classes: Polychaeta, Oligochaeta and Hirudinea. The class Polychaeta contains the marine annelids and has been generally considered to display the more primitive features of the phylum. The class Oligochaeta, which includes the fresh-water naidids and tubificids and the terrestrial earthworms and enchytraids, may have evolved from some early polychaetes. The class Hirudinea, the leeches, probably arose from some stock of fresh-water oligochaetes.

Contents top ↑

1 The annelids 1
2 Survey of findings 1
2.1 Class Polychaeta 2
2.1.1 Order Errantia 2
2.1.2 Order Sedentaria 4
2.1.3 Order Archiannelia 10
2.2 Class Oligochaeta 11
2.2.1 Potamodrilidae 11
2.2.2 Aelosomatidae 12
2.2.3 Naididae 13
2.2.4 Tubificidae 13
2.2.5 Enchytraeidae 14
2.2.6 Lumbriculidae 16
2.2.7 Haplotaxidae 16
2.2.8 Lumbricidae 16
2.2.9 Branchiobdellidae 16
2.2.10 Megascolicidae 17
2.2.11 Eudrilidae 21
2.3 Class Hirudinea 22
2.3.1 Acanthobdellidae 22
2.3.2 Glossiphonidae 22
2.3.3 Piscicolidae 22
2.3.4 Hirudidae 22
2.3.5 HerpoLdellidae 22
3 Chromosomes and evolution 23
3.1 Evolution of chromosome numbers 23
3.2 Chromosomes and speciation 26
3.3 Karyology and phylogeny 29
4 Meiotic behaviour 30
4.1 Specialized bivalents 30
4.2 Asynaptic meiosis 33
4.3 Anaphasic disjunction 35
5 Parthenogenesis 38
5.1 Meiotic parthenogenesis 38
5.2 Amelotic parthenogenesis 41
5.3 General aspects of parthenogenesis 44
6 Sub-amphimictic reproduction 45
7 Pseudofertilization 49
8 Multiplication through transverse fission 51
9 Polyploidy 52
10 Biogeography and cytogenetics 60
11 Genetical studies on parthenogenetic annelids 61
References 73
Species Index 79