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Reproduction and Development in Echinodermata and Prochordata

Von:

Pandian, T. J, 1939- [VerfasserIn]

Resource type: Ressourcentyp: Buch (Online)Buch (Online)Sprache: Englisch Reihen: Reproduction and Development in Aquatic InvertebratesVerlag: Boca Raton, FL : CRC Press, 2018Auflage: First editionBeschreibung: 1 Online-RessourceSchlagwörter:

Andere physische Formen: 1351106929 | 9781351106924 | 0815364725 | 9780815364726 | 0815364733. | 9780815364733. | 9781351106900 | 9781351106917 | Erscheint auch als: 9781351106924 Druck-AusgabeDDC-Klassifikation:

SCAG0580
WB042
WB075
WB057
WB071

LOC-Klassifikation:

QL381

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Zusammenfassung: 1.6.5 Ontogenetic Pathways1.7 Larval Developments and Thyroid Hormones; 1.8 Brooding and Viviparity; 1.9 Size and Life Span; 2. Fisheries and Aquaculture; Introduction; 2.1 Capture Fisheries; 2.2 Aquaculture; 2.2.1 Sea Urchins; 2.2.2 Sea Cucumbers; 3. Sexual Reproduction; Introduction; 3.1 Sexuality; 3.2 Gonochorism; 3.2.1 Sex Ratio; 3.2.2 Reproductive Systems; 3.2.3 Gametogenesis; 3.3 Parthenogenesis; 3.4 Hermaphroditism; 3.5 Reproductive Cycle; 4. Asexual Reproduction; Introduction; 4.1 Types and Characteristics; 4.2 Fission and Reproduction; 4.3 Clonal and Sexual ReproductionZusammenfassung: 4.4 Induced Fission4.5 The Trigger; 4.6 Clonal Autotomy; 4.7 Larval Cloning; 4.8 Eggs and Embryos; 4.9 Searching Stem Cells; 5. Regeneration; Introduction; 5.1 Incidence and Prevalence; 5.2 Induction of Autotomy; 5.3 Causes and Consequences; 5.4 Growth and Differentiation; 5.5 Growth Factors and Genes; 6. Sex Determination; Introduction; 6.1 Species and Fidelity; 6.2 Karyotypes and Heteromorphism; 6.3 Ploidy Induction; 6.4 Genome and Sequencing; 7. Sex Differentiation; Introduction; 7.1 Asteroid Model; 7.2 Echinoid Model; 7.3 Induction of Spawning; 7.4 Endocrine DisruptionZusammenfassung: 7.5 Parasitic DisruptionSection Ib Hemichordata; 8. Reproductive Biology; Introduction; 8.1 Life Cycles; 8.2 Gonads and Consequences; 8.3 Regeneration in Enteropneusts; Section II Chordate Deuterostomia; 9. Cephalochordata; Introduction; 9.1 Reproductive Biology; 10. Urochordata; Introduction; 10.1 Pelagic Tunicates; 10.2 Benthic Tunicates; 10.3 Germline Lineage; 11. New Findings and Highlights; Introduction; 11.1 Structure and Distribution; 11.2 Fecundity, Size and Depth; 11.3 Aquaculture: Sea Urchins and Cucumbers; 11.4 Intromittent Organ; 11.5 Gonad and Hormonal EconomyZusammenfassung: "Echinoderms and prochordates occupy a key position in vertebrate evolution. The genomes of sea urchin share 70% homology with humans. Researches on cell cycle in sea urchin and phagocytosis in asteroids have fetched Nobel Prizes. In this context, this book assumes immense importance. Echinoderms are unique, as their symmetry is bilateral in larvae but pentamerous radial in adults. The latter has eliminated the development of an anterior head and bilateral appendages. Further, the obligate need to face the substratum for locomotion and acquisition of food has eliminated their planktonic and nektonic existence. Egg size, a decisive factor in recruitment, increases with decreasing depths up to 2,000-5,000 m in lecithotrophic asteroids and ophiuroids but remains constant in their planktotrophics. Smaller (<18 mm) ophiuroids do not produce a lecithotrophic eggs but larger (> 110 mm) asteroids generate planktotrophic eggs only. Publications on sex ratio of echinoderms indicate the genetic determination of sex at fertilization but those on hybridization, karyotype and ploidy induction do not provide evidence for heterogametism. But the herbivorous echinoids and larvacea with their gonads harboring both germ cells and Nutritive Phagocytes (NPs) have economized the transportation and hormonal costs on gonadal function. Despite the amazing potential just 2 and 3% of echinoderms undergo clonal reproduction and regeneration, respectively. Fission is triggered, when adequate reserve nutrients are accumulated. It is the most prevalent mode of clonal reproduction in holothuroids, asteroids and ophiuroids. However, budding is a more prevalent mode of clonal reproduction in colonial hemichordates and urochordates. In echinoderms, fission and budding eliminate each other. Similarly, autoregulation of early development eliminates clonal reproduction in echinoids and solitary urochordates. In pterobranchs, thaliaceans and ascidians, the repeated and rapid budding leads to colonial formation. Coloniality imposes reductions in species number and body size, generation time and life span, gonad number and fecundity as well as switching from gonochorism to simultaneous hermaphorditism and oviparity to ovoviviparity/viviparity."--Provided by publisherPPN: PPN: 1026327245Package identifier: Produktsigel: ZDB-4-NLEBK

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