Figure 5. Phylogenetic tree obtained from one of the three replicate Bayesian inference runs of t... more Figure 5. Phylogenetic tree obtained from one of the three replicate Bayesian inference runs of the combined (18S rDNA, somatic, and spermatozoal) data set. Posterior probabilities ± 0.85 are indicated in front of the nodes.
Figure 4. Parsimony consensus tree of the combined (18S rDNA, somatic, and spermatozoal) data set... more Figure 4. Parsimony consensus tree of the combined (18S rDNA, somatic, and spermatozoal) data set. Bootstrap frequencies ± 50% are indicated above the branches.
Figure 3. Phylogenetic trees obtained from morphological data. A, phylogenetic tree obtained from... more Figure 3. Phylogenetic trees obtained from morphological data. A, phylogenetic tree obtained from one of the three replicate Bayesian inference runs of the somatic data set. Posterior probabilities of ± 0.85 are indicated in front of the nodes. B, phylogenetic tree obtained from one of the three replicate Bayesian inference runs of the spermatozoal data set. Posterior probabilities ± 0.85 are indicated in front of the nodes.
Comparative sperm ultrastructure of Neodasys ciritus and Musellifer delamarei, two species consid... more Comparative sperm ultrastructure of Neodasys ciritus and Musellifer delamarei, two species considered to be basal among Chaetonotida (Gastrotricha)
Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenar... more Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenarius, a species belonging to the subfamily Tubificinae inhabiting the sediments of Lake Baikal. As all tubificines, Isochaetides produces two types of spermatozoa, named eusperm and parasperm. The eusperm are the fertilizing male gametes and consist, in sequence, of an acrosome, a nucleus, a mitochondrial mid-piece, and a tail. The parasperm have the same general architecture, but differ in cytological details: the acrosome is shorter, devoid of a perforatorium, and the acrosome vesicle has a different, simpler, shape. The nucleus is much shorter and rectilinear (the eusperm nucleus is twisted). The mid-piece mitochondria are less numerous but their overall volume is larger. The flagellum has a plasma membrane largely separated from the axoneme, and is devoid of glycogen granules. After mating, the two sperm types gather in the spermathecae to form spermatozeugmata; in these structures the parasperm form an external sheath involving the centrally located eusperm and their tails are connected by conspicuous septate junctions. Parasperm nuclei are produced through a process of fragmentation of the 'spermatocytes', whereas the flagellar basal bodies are produced by a process similar to that giving rise to basal bodies in ciliated epithelia.
Journal of the Marine Biological Association of the United Kingdom, 1979
The Priapulida phylum is a rather homogeneous small group of marine invertebrates, living buried ... more The Priapulida phylum is a rather homogeneous small group of marine invertebrates, living buried in sand and mud of cold waters. These worms present great difficulty in determining their systematic position: in the first instance, Priapulida were considered to be pseudo-coelomates, and classified among the Aschelminthes (Hyman, 1951). How ever, later studies (Shapeero, 1961) have pointed out that the body cavity is actually a coelom, and not a pseudo-coelom. Consequently it seems improper to include Priapulida among Aschelminthes, even if their real position still remains undefined. Today most authors tend to consider priapulids as the last relicts of an originally larger group, forming a separate phylum (van der Land, 1970). We can assume some connexions with other minor Protostoma, but not to an extent sufficient to consider a possible group affinity (Grassé, 1959). The general anatomical organization of a priapulid is now well known (van der Land, 1970), but the only detailed mic...
The origin and evolution of clitellate annelids--earthworms, leeches and their relatives--is poor... more The origin and evolution of clitellate annelids--earthworms, leeches and their relatives--is poorly understood, partly because body fossils of these delicate organisms are exceedingly rare. The distinctive egg cases (cocoons) of Clitellata, however, are relatively common in the fossil record, although their potential for phylogenetic studies has remained largely unexplored. Here, we report the remarkable discovery of fossilized spermatozoa preserved within the secreted wall layers of a 50-Myr-old clitellate cocoon from Antarctica, representing the oldest fossil animal sperm yet known. Sperm characters are highly informative for the classification of extant Annelida. The Antarctic fossil spermatozoa have several features that point to affinities with the peculiar, leech-like 'crayfish worms' (Branchiobdellida). We anticipate that systematic surveys of cocoon fossils coupled with advances in non-destructive analytical methods may open a new window into the evolution of minute,...
SummaryTo determine the degree of systematic affinity between branchiobdellids and lumbriculids, ... more SummaryTo determine the degree of systematic affinity between branchiobdellids and lumbriculids, the ultrastructures of muscle and sperm cells ofBranchiobdella pentodonta andBythonomus lemani were studied.The structure ofBranchiobdella sperms is similar to that of the oligochaete model in terms of nucleus and the middle piece and to that of the hirudinean model in the peculiarity of the flagellum and acrosomal complex. Muscle ofBranchiobdella are very similar to those of the hirudineans.Muscles and sperms ofBythonomus lemani are practically identical to those of the tubificid model and are closely related to the other known oligochaetes.
Mature spermatozoa of Nematogenia panamensis (Annelida: Oligochaeta, Ocnerodrilidae) from Madagas... more Mature spermatozoa of Nematogenia panamensis (Annelida: Oligochaeta, Ocnerodrilidae) from Madagascar were studied by electron microscopy. The spermatozoon is 35 μm long and shows the conventional clitellate sequence of acrosome, nucleus, middle piece and tail. The acrosome is asymmetric, showing an acrosome rod consistently bent to one side and probably exiting laterally for a short distance from the acrosome vesicle, only to re-enter apically. The middle piece consists of six mitochondria with the shape of a cylindrical sector and the tail is a flagellum with a 9+2 axoneme with two central tetragon fibers, surrounded for most of its length by glycogen granules. While the general features of Nematogenia spermatozoon are undoubtedly of megadrile type, some characters, like the shortness of the acrosome and the basal chamber, indicate a plesiomorphic condition within the group. This is in good agreement with the proposed phylogenetic position of Ocnerodrilidae within the Oligochaeta.
The reproductive system and the spermatozoon of Megadasys sterreri from Lanzarote (Canary Islands... more The reproductive system and the spermatozoon of Megadasys sterreri from Lanzarote (Canary Islands, Spain) were studied at structural and ultrastructural levels. The species is a simultaneous hermaphrodite with cross-fertilization and shows paired gonads, the male anterior and the female posterior, and both gametes mature in a caudo-cephalic direction. Sperm ducts converge on the midline and open into a ventral common pore. Two sexual accessory organs are present in the caudal trunk. A pipe-like frontal organ lies between the ovaries and the caudal organ, and is composed of a long, thin region connected to a large zone containing mature and degenerating spermatozoa. The cigar-like caudal organ is elongate, bulky and is made of an anterior glandulo-muscular region and a posterior muscular one. Spermatozoa are long, filiform cells formed by an acrosome, a nucleus-mitochondrial complex, and a flagellum. The long acrosome is composed of an apical twisted region and a basal straight regio...
Figure 5. Phylogenetic tree obtained from one of the three replicate Bayesian inference runs of t... more Figure 5. Phylogenetic tree obtained from one of the three replicate Bayesian inference runs of the combined (18S rDNA, somatic, and spermatozoal) data set. Posterior probabilities ± 0.85 are indicated in front of the nodes.
Figure 4. Parsimony consensus tree of the combined (18S rDNA, somatic, and spermatozoal) data set... more Figure 4. Parsimony consensus tree of the combined (18S rDNA, somatic, and spermatozoal) data set. Bootstrap frequencies ± 50% are indicated above the branches.
Figure 3. Phylogenetic trees obtained from morphological data. A, phylogenetic tree obtained from... more Figure 3. Phylogenetic trees obtained from morphological data. A, phylogenetic tree obtained from one of the three replicate Bayesian inference runs of the somatic data set. Posterior probabilities of ± 0.85 are indicated in front of the nodes. B, phylogenetic tree obtained from one of the three replicate Bayesian inference runs of the spermatozoal data set. Posterior probabilities ± 0.85 are indicated in front of the nodes.
Comparative sperm ultrastructure of Neodasys ciritus and Musellifer delamarei, two species consid... more Comparative sperm ultrastructure of Neodasys ciritus and Musellifer delamarei, two species considered to be basal among Chaetonotida (Gastrotricha)
Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenar... more Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenarius, a species belonging to the subfamily Tubificinae inhabiting the sediments of Lake Baikal. As all tubificines, Isochaetides produces two types of spermatozoa, named eusperm and parasperm. The eusperm are the fertilizing male gametes and consist, in sequence, of an acrosome, a nucleus, a mitochondrial mid-piece, and a tail. The parasperm have the same general architecture, but differ in cytological details: the acrosome is shorter, devoid of a perforatorium, and the acrosome vesicle has a different, simpler, shape. The nucleus is much shorter and rectilinear (the eusperm nucleus is twisted). The mid-piece mitochondria are less numerous but their overall volume is larger. The flagellum has a plasma membrane largely separated from the axoneme, and is devoid of glycogen granules. After mating, the two sperm types gather in the spermathecae to form spermatozeugmata; in these structures the parasperm form an external sheath involving the centrally located eusperm and their tails are connected by conspicuous septate junctions. Parasperm nuclei are produced through a process of fragmentation of the 'spermatocytes', whereas the flagellar basal bodies are produced by a process similar to that giving rise to basal bodies in ciliated epithelia.
Journal of the Marine Biological Association of the United Kingdom, 1979
The Priapulida phylum is a rather homogeneous small group of marine invertebrates, living buried ... more The Priapulida phylum is a rather homogeneous small group of marine invertebrates, living buried in sand and mud of cold waters. These worms present great difficulty in determining their systematic position: in the first instance, Priapulida were considered to be pseudo-coelomates, and classified among the Aschelminthes (Hyman, 1951). How ever, later studies (Shapeero, 1961) have pointed out that the body cavity is actually a coelom, and not a pseudo-coelom. Consequently it seems improper to include Priapulida among Aschelminthes, even if their real position still remains undefined. Today most authors tend to consider priapulids as the last relicts of an originally larger group, forming a separate phylum (van der Land, 1970). We can assume some connexions with other minor Protostoma, but not to an extent sufficient to consider a possible group affinity (Grassé, 1959). The general anatomical organization of a priapulid is now well known (van der Land, 1970), but the only detailed mic...
The origin and evolution of clitellate annelids--earthworms, leeches and their relatives--is poor... more The origin and evolution of clitellate annelids--earthworms, leeches and their relatives--is poorly understood, partly because body fossils of these delicate organisms are exceedingly rare. The distinctive egg cases (cocoons) of Clitellata, however, are relatively common in the fossil record, although their potential for phylogenetic studies has remained largely unexplored. Here, we report the remarkable discovery of fossilized spermatozoa preserved within the secreted wall layers of a 50-Myr-old clitellate cocoon from Antarctica, representing the oldest fossil animal sperm yet known. Sperm characters are highly informative for the classification of extant Annelida. The Antarctic fossil spermatozoa have several features that point to affinities with the peculiar, leech-like 'crayfish worms' (Branchiobdellida). We anticipate that systematic surveys of cocoon fossils coupled with advances in non-destructive analytical methods may open a new window into the evolution of minute,...
SummaryTo determine the degree of systematic affinity between branchiobdellids and lumbriculids, ... more SummaryTo determine the degree of systematic affinity between branchiobdellids and lumbriculids, the ultrastructures of muscle and sperm cells ofBranchiobdella pentodonta andBythonomus lemani were studied.The structure ofBranchiobdella sperms is similar to that of the oligochaete model in terms of nucleus and the middle piece and to that of the hirudinean model in the peculiarity of the flagellum and acrosomal complex. Muscle ofBranchiobdella are very similar to those of the hirudineans.Muscles and sperms ofBythonomus lemani are practically identical to those of the tubificid model and are closely related to the other known oligochaetes.
Mature spermatozoa of Nematogenia panamensis (Annelida: Oligochaeta, Ocnerodrilidae) from Madagas... more Mature spermatozoa of Nematogenia panamensis (Annelida: Oligochaeta, Ocnerodrilidae) from Madagascar were studied by electron microscopy. The spermatozoon is 35 μm long and shows the conventional clitellate sequence of acrosome, nucleus, middle piece and tail. The acrosome is asymmetric, showing an acrosome rod consistently bent to one side and probably exiting laterally for a short distance from the acrosome vesicle, only to re-enter apically. The middle piece consists of six mitochondria with the shape of a cylindrical sector and the tail is a flagellum with a 9+2 axoneme with two central tetragon fibers, surrounded for most of its length by glycogen granules. While the general features of Nematogenia spermatozoon are undoubtedly of megadrile type, some characters, like the shortness of the acrosome and the basal chamber, indicate a plesiomorphic condition within the group. This is in good agreement with the proposed phylogenetic position of Ocnerodrilidae within the Oligochaeta.
The reproductive system and the spermatozoon of Megadasys sterreri from Lanzarote (Canary Islands... more The reproductive system and the spermatozoon of Megadasys sterreri from Lanzarote (Canary Islands, Spain) were studied at structural and ultrastructural levels. The species is a simultaneous hermaphrodite with cross-fertilization and shows paired gonads, the male anterior and the female posterior, and both gametes mature in a caudo-cephalic direction. Sperm ducts converge on the midline and open into a ventral common pore. Two sexual accessory organs are present in the caudal trunk. A pipe-like frontal organ lies between the ovaries and the caudal organ, and is composed of a long, thin region connected to a large zone containing mature and degenerating spermatozoa. The cigar-like caudal organ is elongate, bulky and is made of an anterior glandulo-muscular region and a posterior muscular one. Spermatozoa are long, filiform cells formed by an acrosome, a nucleus-mitochondrial complex, and a flagellum. The long acrosome is composed of an apical twisted region and a basal straight regio...
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