Journal ArticleDOI
The spermatozoa of the polychaeta (annelida): an ultrastructural review
TLDR
1. Polychaete sperm are divisible into ect‐aquasperm, ent‐aquaperm, and introsperm, which can be divided into ect- and ent-sperm and intro‐sperm respectively.Abstract:
1 Polychaete sperm are divisible into ect-aquasperm, ent-aquasperm, and introsperm 2 Ect-aquasperm are the commonest type of polychaete sperm and are considered plesiomorphic for the Polychaeta Re-evolution of ect-aquasperm (as neo-aquasperm) is, nevertheless, tentatively hypothesized for some Sabellida 3 In terms of ultrastructural studies of sperm in the investigated polychaete families, only ect-aquasperm have been demonstrated for 16 families; only ent-aquasperm for 3 families; ect- and ent-aquasperm for 3; ect- and intro-sperm for 2; ect-, ent- and intro-sperm for 1 family; and only introsperm for 11 families but investigations can only be regarded as preliminary To date no family is known to have ent- and intro-sperm only Sperm ultrastructure has yet to be examined in the orders Magelonida, Psammodrilida, Cossurida, Spintherida, Sternapsida, Flabelligerida and Fauvelopsida 4 Much variation occurs in gross morphology, ultrastructure and configuration of the several components of ect-aquasperm: acrosome, nucleus, mitochondria, and centrioles and associated anchoring apparatus A 9 + 2 axoneme is constant 5 Group-specific sperm structure has been demonstrated for the Nereidae (chiefly ect-aquasperm), and for introsperm of the families Histriobdellidae, Questidae; Capitellidae, Spionidae and Protodrilidae Species-specificity of all classes of spermatozoa is well established 6 The very small size of ect-aquasperm is correlated with production of large numbers of sperm as an adaptation to broadcast spawning Simplicity of structure may relate more to conservation of materials than to hydrodynamics 7 Fertilization by ent-aquasperm requires fewer eggs than in external fertilization and is accompanied by a tendency to lecithotrophy Elongation of the nucleus and development of asymmetry are seen in several of the few known examples of ent-aquasperm Whether modifications are related to transfer or to other features, such as lecithotrophy, is uncertain 8 Evident multiple origins of polychaete introsperm contraindicate their value in establishing relationship between families, in contrast with their utility in groups such as decapod crustacea 9 At the intrafamilial level polychaete introsperm have taxonomic and phylogenetic value, as seen in the Spionidae, Capitellidae, and Histriobdellidae, and are distinctive of each of these and other families 10 At higher taxonomic levels, the ultrastructure of the sperm of the oligochaetoid Questidae distinguishes this family from euclitellates, each class of which has its own distinctive subtype of the euclitellate introsperm 11(ABSTRACT TRUNCATED AT 400 WORDS)read more
Citations
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Journal ArticleDOI
Cladistics and polychaetes
Greg W. Rouse,Kristian Fauchald +1 more
TL;DR: A series of cladistic analyses assesses the status and membership of the taxon Polychaeta and provides a new classification, which does not use Linnaean categories, and comprises two clades, the Scolecida and Palpata.
Journal ArticleDOI
Investigating the Bivalve Tree of Life -- an exemplar-based approach combining molecular and novel morphological characters.
Rüdiger Bieler,Paula M. Mikkelsen,Timothy M. Collins,Emily A. Glover,Vanessa L. González,Daniel L. Graf,Elizabeth M. Harper,John M. Healy,John M. Healy,Gisele Y. Kawauchi,Prashant P. Sharma,Sid Staubach,Ellen E. Strong,John D. Taylor,Ilya Tëmkin,Ilya Tëmkin,John D. Zardus,Stephanie Clark,Alejandra Guzmán,Alejandra Guzmán,Erin McIntyre,Paul Sharp,Gonzalo Giribet +22 more
TL;DR: An analysis of the informativeness of morphological characters showed that sperm ultrastructure characters are among the best morphological features to diagnose bivalve clades, followed by characters of the shell, including its microstructure.
Journal ArticleDOI
Broadcasting fables: Is external fertilization really primitive? Sex, size, and larvae in sabellid polychaetes
Greg W. Rouse,Kirk Fitzhugh +1 more
TL;DR: The cladistic analysis of sabellid genera suggests that gonochorism and brooding of direct‐developing larvae are plesiomorphic in the Sabellidae, with external fertilization and swimming larvae limited to apomorphie clades in the subfamily Sabellinae.
Journal ArticleDOI
The Articulation of Annelids
Greg W. Rouse,Kristian Fauchald +1 more
TL;DR: The Annelida should not be used unless relationships within the Articulata are resolved to show it is a monophyletic taxon, and the Pogonophora should revert to the original family name Lamellisabellidae Uschakov, 1933.
Book ChapterDOI
Reproduction and larval development of the spioniform Polychaeta with application to systematics and phylogeny
TL;DR: A phylogenetic analysis demonstrates that reproductive and larval characters, when used in combination with selected adult characters, provide a more complete database to evaluate systematic and phylogenetic relationships than only adult morphology.
References
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The polychaete worms. Definitions and keys to the orders, families and genera
TL;DR: A review of the classification of the Class Polychaeta (Annelida) with comments on the characters used to identify the different included taxa has led to the recognition of seventeen orders.
Book
The Biology of the Sperm Cell
Baccio Baccetti,Björn Afzelius +1 more
TL;DR: The scientific books will also be the best reason to choose, especially for the students, teachers, doctors, businessman, and other professions who are fond of reading.
Journal ArticleDOI
The interstitial fauna of marine sand
TL;DR: The study of the microfauna living in the interstitial water in marine or freshwater sand, the so‐called interstitial or mesopsammic fauna, has made important contributions to systematic zoology during the past four decades.
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An ultrastructural study of the spermatozoa of the polychaetes Eurythoe complanata (Amphinomidae), Clymenella sp. and Micromaldane sp. (Maldanidae), with definition of sperm types in relation to reproductive biology
Broadcasting fables: Is external fertilization really primitive? Sex, size, and larvae in sabellid polychaetes
Greg W. Rouse,Kirk Fitzhugh +1 more