Reproduction and Development in Annelida

<p>This book is a concise informative elucidation of all aspects of reproduction and development in annelids covering from arenicola to tubifex. Annelids flourish between 4900 m depth to 2000 m altitude; some of them occur in unusual habitats like hydrothermal vents and subterranean aquatic system (stigobionts). A few have no gut and acquire adequate nutrients through osmotrophism and/or engaging symbiotic microbes. In the absence of exoskeleton to escape predation the 17000 speciose annelids have explored bewildering modes of reproduction; not surprisingly 42–47% of them are brooders. With 13000 species polychaetes are gonochores but some 207 species of them are hermaphrodites. Clitellates are all hermaphrodites; of them 76 species are parthenogens of which 56 are earthworms.</p><p></p><p>Regenerative potency of annelids ranges from an organ to an entire worm from a single ‘seminal’ segment. The head tail and both together can be regenerated 21 42 and 20 times respectively. However the potency is limited to ~1% of polychaetes and < 2% of oligochaetes. In oligochaetes the chloragogue temporally separates regeneration and reproduction but sedentary polychaetes undertake them together at the reduced reproductive output. Only 79 polychaete and 111 oligochaete species have the potency for clonal reproduction. Within families the potency ranges from 2% in spionids to 54% in naidids. Epitoky a spectacular and unique phenomenon involves the transformation from benthic to meroplanktonic reproductive morphism. It occurs in 106 errant polychaete species. The larger glycerides nereidids and eunicids use muscular energy to climb < 50 m vertical distance. But the small phyllodocids and cteniodrilids may reduce buoyancy to climb 1000–4000 m vertical distance.</p><p></p><p>Heterogamatic sex determination is reported to occur only in six polychaete species although karyotype is known for 83 annelid species. In temperate polychaetes a dozen neuroendocrines arising mostly from the ‘brain’ regulates reproductive cycle. A complete chapter devoted to vermiculture (i) recognizes the fast-growing candidate species (ii) distinguishes 'layers' from 'brooders' (iii) indicates that the harvest of oligochaetes may reduce the input of nitrogenous fertilizer in the ricefield and (iv) explores the scope for increasing wealth from waste.</p>