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Reproduction and Development in Annelida - Series on: Reproduction and Development in Aquatic Invertebrates (Paperback)
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Reproduction and Development in Annelida - Series on: Reproduction and Development in Aquatic Invertebrates (Paperback)
Series: Reproduction and Development in Aquatic Invertebrates
Expected to ship within 12 - 17 working days
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This book is a concise informative elucidation of all aspects of
reproduction and development in annelids covering from arenicola to
tubifex. Annelids flourish between 4,900 m depth to 2,000 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 17,000 speciose annelids have explored
bewildering modes of reproduction; not surprisingly, 42-47% of them
are brooders. With 13,000 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. 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 1,000-4,000 m vertical distance. 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.
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