Author: T. J. Pandian
Publisher: CRC Press
ISBN: 0429582587
Category : Medical
Languages : en
Pages : 488
Book Description
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 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.
Reproduction and Development in Annelida
Author: T. J. Pandian
Publisher: CRC Press
ISBN: 0429582587
Category : Medical
Languages : en
Pages : 488
Book Description
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 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.
Publisher: CRC Press
ISBN: 0429582587
Category : Medical
Languages : en
Pages : 488
Book Description
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 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.
Reproductive Strategies and Developmental Patterns in Annelids
Author: Adriaan W.C. Dorresteijn
Publisher: Springer Science & Business Media
ISBN: 9401728879
Category : Science
Languages : en
Pages : 314
Book Description
The fascination of the Annelida to scientists lies in the beauty of their structures and the functionality of their body plan, the tremendous adaptive radiation which has made it possible for these animals to colonize almost all marine, limnic and terrestrial biotopes. In doing so they have evolved a great variety of life forms, and their reproduction and development are correspondingly diverse, with many modes and patterns unique in the animal kingdom. In this special volume recent progress in this broad research area is presented by 26 specialists, in general through surveys or treatments of selected examples. Some of them review important annelid taxa such as the Nereididae, Syllidae, Spionidae, Cirratulidae, Clitellata, and Pogonophora; others analyse reproductive and developmental structures and phenomena in annelids, e.g. segmental organs, sex pheromones, oogenesis, mating systems, sperm types, life cycles, larval settlement, cleavage and symmetry of embryos, or discuss controversial approaches to annelid systematics. The book will be of interest to all zoologists who work with annelids as well as to embryologists and other researchers in reproductive biology.
Publisher: Springer Science & Business Media
ISBN: 9401728879
Category : Science
Languages : en
Pages : 314
Book Description
The fascination of the Annelida to scientists lies in the beauty of their structures and the functionality of their body plan, the tremendous adaptive radiation which has made it possible for these animals to colonize almost all marine, limnic and terrestrial biotopes. In doing so they have evolved a great variety of life forms, and their reproduction and development are correspondingly diverse, with many modes and patterns unique in the animal kingdom. In this special volume recent progress in this broad research area is presented by 26 specialists, in general through surveys or treatments of selected examples. Some of them review important annelid taxa such as the Nereididae, Syllidae, Spionidae, Cirratulidae, Clitellata, and Pogonophora; others analyse reproductive and developmental structures and phenomena in annelids, e.g. segmental organs, sex pheromones, oogenesis, mating systems, sperm types, life cycles, larval settlement, cleavage and symmetry of embryos, or discuss controversial approaches to annelid systematics. The book will be of interest to all zoologists who work with annelids as well as to embryologists and other researchers in reproductive biology.
Annelids in Modern Biology
Author: Daniel H. Shain
Publisher: John Wiley & Sons
ISBN: 0470455195
Category : Science
Languages : en
Pages : 384
Book Description
Annelids offer a diversity of experimentally accessible features making them a rich experimental subject across the biological sciences, including evolutionary development, neurosciences and stem cell research. This volume introduces the Annelids and their utility in evolutionary developmental biology, neurobiology, and environmental/ecological studies, including extreme environments. The book demonstrates the variety of fields in which Annelids are already proving to be a useful experimental system. Describing the utility of Annelids as a research model, this book is an invaluable resource for all researchers in the field.
Publisher: John Wiley & Sons
ISBN: 0470455195
Category : Science
Languages : en
Pages : 384
Book Description
Annelids offer a diversity of experimentally accessible features making them a rich experimental subject across the biological sciences, including evolutionary development, neurosciences and stem cell research. This volume introduces the Annelids and their utility in evolutionary developmental biology, neurobiology, and environmental/ecological studies, including extreme environments. The book demonstrates the variety of fields in which Annelids are already proving to be a useful experimental system. Describing the utility of Annelids as a research model, this book is an invaluable resource for all researchers in the field.
Concepts of Biology
Author: Samantha Fowler
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 1409
Book Description
Concepts of Biology is designed for the typical introductory biology course for nonmajors, covering standard scope and sequence requirements. The text includes interesting applications and conveys the major themes of biology, with content that is meaningful and easy to understand. The book is designed to demonstrate biology concepts and to promote scientific literacy.
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 1409
Book Description
Concepts of Biology is designed for the typical introductory biology course for nonmajors, covering standard scope and sequence requirements. The text includes interesting applications and conveys the major themes of biology, with content that is meaningful and easy to understand. The book is designed to demonstrate biology concepts and to promote scientific literacy.
Annelida Basal Groups and Pleistoannelida, Sedentaria I
Author: Günter Purschke
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110291584
Category : Science
Languages : en
Pages : 492
Book Description
This book is the first in a series of 4 volumes in the Handbook of Zoology series about morphology, anatomy, reproduction, development, ecology, phylogeny and systematics of Annelida. This first volume covers members of the so-called basal radiation and the first part of Sedentaria. It is supplemented by chapters on the history of annelid research, their fossil record, and an introduction to the phylogeny of annelids and their position in the tree of life. In the latter chapter the history of their systematic is reviewed giving an almost complete picture of systematic-scientific progress especially in the past years which changed our view on annelid phylogeny dramatically. The most basal annelids, lately united as Palaeoannelida, represent two families of aberrant polychaetes formerly often suggested to be highly derived which now give us a fresh look on how the ancestral annelid may have looked like. These lack certain key characters such as nuchal organs and possess rather simple nervous systems which now likely represent primitive character states. In this basal radiation the first taxon of apparently unsegmented and achaetigerous animals is positioned, the Sipuncula. Most likely another group of platyhelminth-like and unsegmented and even chaeta-lees annelids, Lobatocerebridae falls into this basal radiation. The section of Sedentaria starts with Orbiniida, a taxon characterized by elongated, thread-like worms which do not have anterior appendages like palps and comprises several families representing members of the Meiofauna. These minute worms often inhabiting the interstitial spaces in marine sands are suggested to have evolved by progenesis. The second higher taxon is represented by Cirratuliformia comprising nine families of typical sedentary polychaetes each of which showing a remarkable variation of the annelid body plan. Members of this taxon usually exhibit many annelid characters but certain also lack the most typical prostomial appendages, the palps.
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110291584
Category : Science
Languages : en
Pages : 492
Book Description
This book is the first in a series of 4 volumes in the Handbook of Zoology series about morphology, anatomy, reproduction, development, ecology, phylogeny and systematics of Annelida. This first volume covers members of the so-called basal radiation and the first part of Sedentaria. It is supplemented by chapters on the history of annelid research, their fossil record, and an introduction to the phylogeny of annelids and their position in the tree of life. In the latter chapter the history of their systematic is reviewed giving an almost complete picture of systematic-scientific progress especially in the past years which changed our view on annelid phylogeny dramatically. The most basal annelids, lately united as Palaeoannelida, represent two families of aberrant polychaetes formerly often suggested to be highly derived which now give us a fresh look on how the ancestral annelid may have looked like. These lack certain key characters such as nuchal organs and possess rather simple nervous systems which now likely represent primitive character states. In this basal radiation the first taxon of apparently unsegmented and achaetigerous animals is positioned, the Sipuncula. Most likely another group of platyhelminth-like and unsegmented and even chaeta-lees annelids, Lobatocerebridae falls into this basal radiation. The section of Sedentaria starts with Orbiniida, a taxon characterized by elongated, thread-like worms which do not have anterior appendages like palps and comprises several families representing members of the Meiofauna. These minute worms often inhabiting the interstitial spaces in marine sands are suggested to have evolved by progenesis. The second higher taxon is represented by Cirratuliformia comprising nine families of typical sedentary polychaetes each of which showing a remarkable variation of the annelid body plan. Members of this taxon usually exhibit many annelid characters but certain also lack the most typical prostomial appendages, the palps.
Pleistoannelida, Sedentaria III and Errantia I
Author: Günter Purschke
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110291703
Category : Science
Languages : en
Pages : 492
Book Description
This book is the third volume in a series of 4 volumes in the Handbook of Zoology series treating morphology, anatomy, reproduction, development, ecology, phylogeny, systematics and taxonomy of polychaetous Annelida. It is devoted to the remaining Sedentaria and the first branches of Errantia. These sedentary polychaetes are Terebellida and Arenicolida, all of which are tube-dwelling and deposit feeders. The tubes may be simple burrows stabilized by mucus or the tubes are highly sophisticated often really aesthetic structures build-up of sediment grains glued together by their secretion. Although the former possess anterior appendages used for collecting food particles, these are likely not modified palps rather than a new acquisition. Many of these species are adapted to occur within environments characterized by low oxygen supply and so many members of these taxa possess elaborated branchiae, usually positioned on a number of anterior body segments except for Maldanidae which look like bamboo sticks and thus earned their common name bamboo worms. Members of Arenicolida and Maldanida may occur in high abundance and as such they create biogenically graded sediment beds. The Errantia part starts with Myzostomida, a group of symbiotic animals associated with echinoderms which have been variously placed within the tree of life. As such they show numerous adaptations to this specific mode of life. The next group discussed within Errantia is Protodrilida, a taxon comprising four families of the former archiannelids which belong to the interstitial fauna. Most likely they evolved by miniaturization from larger ancestors. In contrast to typical errants they do not possess well-developed parapodia and antennae. This taxon is followed by Eunicida characterized by possession of a specific jaw apparatus situated ventrally in the foregut and associated with specific musculature. Also being a species rich group showing various feeding modes some of the smallest and the largest members belong to this taxon.
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110291703
Category : Science
Languages : en
Pages : 492
Book Description
This book is the third volume in a series of 4 volumes in the Handbook of Zoology series treating morphology, anatomy, reproduction, development, ecology, phylogeny, systematics and taxonomy of polychaetous Annelida. It is devoted to the remaining Sedentaria and the first branches of Errantia. These sedentary polychaetes are Terebellida and Arenicolida, all of which are tube-dwelling and deposit feeders. The tubes may be simple burrows stabilized by mucus or the tubes are highly sophisticated often really aesthetic structures build-up of sediment grains glued together by their secretion. Although the former possess anterior appendages used for collecting food particles, these are likely not modified palps rather than a new acquisition. Many of these species are adapted to occur within environments characterized by low oxygen supply and so many members of these taxa possess elaborated branchiae, usually positioned on a number of anterior body segments except for Maldanidae which look like bamboo sticks and thus earned their common name bamboo worms. Members of Arenicolida and Maldanida may occur in high abundance and as such they create biogenically graded sediment beds. The Errantia part starts with Myzostomida, a group of symbiotic animals associated with echinoderms which have been variously placed within the tree of life. As such they show numerous adaptations to this specific mode of life. The next group discussed within Errantia is Protodrilida, a taxon comprising four families of the former archiannelids which belong to the interstitial fauna. Most likely they evolved by miniaturization from larger ancestors. In contrast to typical errants they do not possess well-developed parapodia and antennae. This taxon is followed by Eunicida characterized by possession of a specific jaw apparatus situated ventrally in the foregut and associated with specific musculature. Also being a species rich group showing various feeding modes some of the smallest and the largest members belong to this taxon.
Reproductive and Developmental Strategies
Author: Kazuya Kobayashi
Publisher: Springer
ISBN: 4431566090
Category : Science
Languages : en
Pages : 783
Book Description
This book provides new insights into the universality of biological systems in animal reproduction and development by a comparative study of a variety of mechanisms in animals ranging from basal invertebrates to vertebrates, including mammals. Animals accomplish genetic diversity through meiosis and fertilization, and during embryogenesis animals must produce specialized cell types, including germ cells, in accordance with their individual body plan. This series of phenomena is essential to the continuity of life in the animal kingdom, and animals show various reproductive and developmental strategies. This volume, comprising four parts, reviews animal kingdom diversity, including reproductive strategies and germ cell differentiation mechanisms (Part 1), sex determination and differentiation (Part2), the mechanisms of fertilization (Part 3), and body axis formation (Part 4). Readers will find descriptions of the reproduction or development of 180 species, 13 phyla, 35 classes, 74 orders, 117 families, and 151 genera in this book. Of particular interest is the diversity of molecules and mechanisms used to achieve the same biological purpose in different animals. Undergraduates, graduate students, and professional scientists who want a deeper understanding of animal reproductive and developmental mechanisms will find this book to be of great value.
Publisher: Springer
ISBN: 4431566090
Category : Science
Languages : en
Pages : 783
Book Description
This book provides new insights into the universality of biological systems in animal reproduction and development by a comparative study of a variety of mechanisms in animals ranging from basal invertebrates to vertebrates, including mammals. Animals accomplish genetic diversity through meiosis and fertilization, and during embryogenesis animals must produce specialized cell types, including germ cells, in accordance with their individual body plan. This series of phenomena is essential to the continuity of life in the animal kingdom, and animals show various reproductive and developmental strategies. This volume, comprising four parts, reviews animal kingdom diversity, including reproductive strategies and germ cell differentiation mechanisms (Part 1), sex determination and differentiation (Part2), the mechanisms of fertilization (Part 3), and body axis formation (Part 4). Readers will find descriptions of the reproduction or development of 180 species, 13 phyla, 35 classes, 74 orders, 117 families, and 151 genera in this book. Of particular interest is the diversity of molecules and mechanisms used to achieve the same biological purpose in different animals. Undergraduates, graduate students, and professional scientists who want a deeper understanding of animal reproductive and developmental mechanisms will find this book to be of great value.
Reproduction and Development in Platyhelminthes
Author: T. J. Pandian
Publisher: CRC Press
ISBN: 1000054888
Category : Science
Languages : en
Pages : 320
Book Description
This book is a comprehensive elucidation on aspects of reproduction and development in platyhelminthes covering from acoelids to taeniids. With the unique presence of neoblasts, turbellarians serve as a model for studies on cancer and senescence. Of ~ 27,000 species, ~ 77% are parasites; they are harmful to man and his food basket from livestock and fish. The stress hormone, cortisol level is responsible for susceptibility and resistance of the host. In digeneans, the propagatory multiplication potency is retained by all the larval forms and in either direction in sporocyst. The higher clonal diversity, mixing and selection in Second Intermediate Host (SIH) may purge inbreeding depression suffered by the fluke on propagatory multiplication in First Intermediate Host (FIH). Of 12,012 digeneans, 88% may engage 33,014 potential SIH species. They have the choice to select one among the available/awaiting 3.5 host species. The motility of vertebrate host and euryxenic flexibility/scope for selection of SIH species has increased lineage diversification in digeneans. The life cycle of cestodes is divided into aquatic and terrestrial patterns. The former includes (i) oncosphere and (ii) coracidium types and the latter (iii) hexacanth-cysticercoid, (iv) hexacanth-tetrathyridium and (v) hexacanth-cysticercus types. The share for the oncosphere, coracidium and hexacanth types is 17.0, 29.5 and 46.5%, respectively. The staggering fecundity and adoption of the intermediate host in the herbivorous/insectivorous food chain have enriched Taenioidea as the most (2,264) speciose order. Sex specific genes Smed-dmd 1 and macbol have been identified, and neuropeptides and dipeptides are involved in sexualization. Trematodes are unable to parasitize elasmobranchs, as they cannot suck body fluid/blood containing a high level of urea. Relatively higher fecundity supplemented with propagatory multiplication, incorporation of SIH in 88% species, clonal selection in SIH, and euryxenic flexibility and the widest choice for selection of SIH have led to the highest lineage diversification to render digeneans as the most speciose order in Platyhelminthes.
Publisher: CRC Press
ISBN: 1000054888
Category : Science
Languages : en
Pages : 320
Book Description
This book is a comprehensive elucidation on aspects of reproduction and development in platyhelminthes covering from acoelids to taeniids. With the unique presence of neoblasts, turbellarians serve as a model for studies on cancer and senescence. Of ~ 27,000 species, ~ 77% are parasites; they are harmful to man and his food basket from livestock and fish. The stress hormone, cortisol level is responsible for susceptibility and resistance of the host. In digeneans, the propagatory multiplication potency is retained by all the larval forms and in either direction in sporocyst. The higher clonal diversity, mixing and selection in Second Intermediate Host (SIH) may purge inbreeding depression suffered by the fluke on propagatory multiplication in First Intermediate Host (FIH). Of 12,012 digeneans, 88% may engage 33,014 potential SIH species. They have the choice to select one among the available/awaiting 3.5 host species. The motility of vertebrate host and euryxenic flexibility/scope for selection of SIH species has increased lineage diversification in digeneans. The life cycle of cestodes is divided into aquatic and terrestrial patterns. The former includes (i) oncosphere and (ii) coracidium types and the latter (iii) hexacanth-cysticercoid, (iv) hexacanth-tetrathyridium and (v) hexacanth-cysticercus types. The share for the oncosphere, coracidium and hexacanth types is 17.0, 29.5 and 46.5%, respectively. The staggering fecundity and adoption of the intermediate host in the herbivorous/insectivorous food chain have enriched Taenioidea as the most (2,264) speciose order. Sex specific genes Smed-dmd 1 and macbol have been identified, and neuropeptides and dipeptides are involved in sexualization. Trematodes are unable to parasitize elasmobranchs, as they cannot suck body fluid/blood containing a high level of urea. Relatively higher fecundity supplemented with propagatory multiplication, incorporation of SIH in 88% species, clonal selection in SIH, and euryxenic flexibility and the widest choice for selection of SIH have led to the highest lineage diversification to render digeneans as the most speciose order in Platyhelminthes.
The Biology of Reproduction
Author: Giuseppe Fusco
Publisher: Cambridge University Press
ISBN: 1108499856
Category : Medical
Languages : en
Pages : 491
Book Description
A look into the phenomena of sex and reproduction in all organisms, taking an innovative, unified and comprehensive approach.
Publisher: Cambridge University Press
ISBN: 1108499856
Category : Medical
Languages : en
Pages : 491
Book Description
A look into the phenomena of sex and reproduction in all organisms, taking an innovative, unified and comprehensive approach.
Pleistoannelida, Errantia II
Author: Günter Purschke
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110647168
Category : Science
Languages : en
Pages : 500
Book Description
This book is the fourth in a series of 4 volumes in the Handbook of Zoology series about morphology, anatomy, reproduction, development, ecology, phylogeny and systematics of Annelida. It covers the most typical polychaetes, Phyllodocida, together with certain smaller taxa placed incertae sedis. This volume completes the polychaetous Annelida. Phyllodocida are often vagile, possess well-developed parapodia. Due to their broad and flat cirri these parapodia look like leaves in some taxa and leading to the name of the entire group. Many of its members are macrophagous and often predators. Accordingly most species possess elaborate sense structures such as sensory palps, antennae, eyes and nuchal organs. In certain species the eyes comprise thousands of photoreceptor cells and lenses most likely allowing forming true images. Phyllodocida typically possess an axial muscular pharynx called proboscis functioning as a kind of suction pipe allowing them to swallow and ingest their prey or other food. This pharynx may be armed with cuticular jaws and some species even possess venom glands. The probably most popular and important polychaete model organism, Platynereis dumerilii, belongs to this interesting group. Phyllodocida fall into two to three higher clades comprising about 25 families which represent more than one fourth of the polychaete diversity. One of these families, Syllidae, comprises about 700 valid species of mainly small size and may, therefore, represent one of the most complex and somehow difficult polychaete families on Earth.
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110647168
Category : Science
Languages : en
Pages : 500
Book Description
This book is the fourth in a series of 4 volumes in the Handbook of Zoology series about morphology, anatomy, reproduction, development, ecology, phylogeny and systematics of Annelida. It covers the most typical polychaetes, Phyllodocida, together with certain smaller taxa placed incertae sedis. This volume completes the polychaetous Annelida. Phyllodocida are often vagile, possess well-developed parapodia. Due to their broad and flat cirri these parapodia look like leaves in some taxa and leading to the name of the entire group. Many of its members are macrophagous and often predators. Accordingly most species possess elaborate sense structures such as sensory palps, antennae, eyes and nuchal organs. In certain species the eyes comprise thousands of photoreceptor cells and lenses most likely allowing forming true images. Phyllodocida typically possess an axial muscular pharynx called proboscis functioning as a kind of suction pipe allowing them to swallow and ingest their prey or other food. This pharynx may be armed with cuticular jaws and some species even possess venom glands. The probably most popular and important polychaete model organism, Platynereis dumerilii, belongs to this interesting group. Phyllodocida fall into two to three higher clades comprising about 25 families which represent more than one fourth of the polychaete diversity. One of these families, Syllidae, comprises about 700 valid species of mainly small size and may, therefore, represent one of the most complex and somehow difficult polychaete families on Earth.