Ultrastructure and formation of the bursa mouthpiece of Philocelis cellata (Plathelminthes, Acoela)

Brüggemann, Jochen

doi:10.1007/bf00008936

Cited by 14 publications

(5 citation statements)

References 13 publications

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“…10 in Achatz and Hooge 2006). Even the sorting apparatus described by Brüggemann (1985) is very likely sperm: a case of a contorted nucleus in a gland cell is unknown, and the microtubules he describes in the cell extensions into the spermatic duct very likely correspond to the axial microtubules of sperm. However, Petrov et al.…”

Section: Resultsmentioning

confidence: 99%

Systematic revision of acoels with 9+0 sperm ultrastructure (Convolutida) and the influence of sexual conflict on morphology

Achatz

Hooge

Wållberg

et al. 2010

Journal of Zoological Systematics and Evolutionary Research

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We have used newly discerned morphological characters as well as molecular-sequence data from 18S and 28S rDNA to revise the families recently designated as the Ô9+0Õ acoels -what we call Convolutida. Characters from the ultrastructure of sperm, with their Ô9+0Õ axonemes, are useful in delineating the Convolutida, but are either species-specific or too conserved within the group to be used to infer relationships within it. Male genital organs, prostatoid organs, and sagittocysts, on the other hand, give a good phylogenetic signal for reconstructing relationships of such genera as Conaperta, Anaperus, and Achoerus; some features of the reproductive organs correlate with habitat and show how the Convolutida probably originated as epiphytic predators and radiated into the mesopsammon, pelagic, and coral-associated realms. In this revision of the Convolutida we provide revised synopses of its families -which we restrict to the Anaperidae, Convolutidae, and Sagittiferidae -and describe a new species, Polychoerus gordoni, from New Zealand. We transfer the genus Adenopea from the Antroposthiidae to the Convolutidae; Conaperta, Neochildia, and Oxyposthia from the Convolutidae to the Anaperidae; Paranaperus and Praeanaperus from the Anaperidae to the Haploposthiidae. Convoluta aegyptica is synonymized with Convoluta boehmigi, Convoluta lacazii with Convoluta sordida, and the genus Picola (Convolutidae) with Deuterogonaria (Haploposthiidae). Amphiscolops blumi, A. carvalhoi, and A. langerhansi, all of which possess a cellular seminal bursa, are transferred to the genus Heterochaerus. Convoluta elegans and Pseudanaperus tinctus are classified as nomina nuda. We use our findings on the ultrastructure of female genital organs and spermatozoa to show that sexual conflict plays a major role in the evolution of diversity of these structures and that the phylogeny of the Acoela would comprise early forms without female genital organs and hyper-or hypodermal transfer of sperm through advanced forms with ever longer and narrower bursal nozzles and sperm with axial microtubules. Moreover, our results show that the acquisition of endosymbiotic algae happened at least twice within the Acoela.

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Section: Resultsmentioning

confidence: 99%

Systematic revision of acoels with 9+0 sperm ultrastructure (Convolutida) and the influence of sexual conflict on morphology

Achatz

Hooge

Wållberg

et al. 2010

Journal of Zoological Systematics and Evolutionary Research

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“…3, 6a, b, c), but some or all of these parts can be missing, leaving the animal with a kind of inconspicuous bursal tissue or no obvious adaptation at all. A seminal bursa is a distinct “pocket” made up of parenchymal cells that serves to store and digest sperm received from a mating partner (Brüggemann 1985a; Petrov et al 2006; Achatz et al 2010; Fig. 6a).…”

Section: Morphologymentioning

confidence: 99%

“…6a). Bursal nozzles are structures, stiffened by F-actin-rich cells, that accompany or are part of the seminal bursa; they appear to select and modify sperm (Brüggemann 1985a; Petrov et al 2006; Achatz et al 2010; Figs. 6a, b, c).…”

Section: Morphologymentioning

confidence: 99%

The Acoela: on their kind and kinships, especially with nemertodermatids and xenoturbellids (Bilateria incertae sedis)

et al. 2012

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Acoels are among the simplest worms and therefore have often been pivotal in discussions of the origin of the Bilateria. Initially thought primitive because of their “planula-like” morphology, including their lumenless digestive system, they were subsequently dismissed by many morphologists as a specialized clade of the Platyhelminthes. However, since molecular phylogenies placed them outside the Platyhelminthes and outside all other phyla at the base of the Bilateria, they became the focus of renewed debate and research. We review what is currently known of acoels, including information regarding their morphology, development, systematics, and phylogenetic relationships, and put some of these topics in a historical perspective to show how the application of new methods contributed to the progress in understanding these animals. Taking all available data into consideration, clear-cut conclusions cannot be made; however, in our view it becomes successively clearer that acoelomorphs are a “basal” but “divergent” branch of the Bilateria.

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“…Variations in morphology of the sorting apparatus are evident in three species examined on the ultrastructural level. Both Philocelis cellata and Polychoerus caudatus have three projections of the eggshaped cells reaching through the duct as canal cells (Henley, 1974;Brü ggemann, 1985), while Wulguru cuspidata has only two extensions, the third never reaching the distal half of the nozzle. Such distinctions might serve as a taxonomic character on the generic (or even family) level.…”

Section: Evolution Of Bursal Appendagesmentioning

confidence: 99%

“…Between the matrix cells are cells lacking fibrous reinforcement-so-called gap cells. As is assumed also in the light microscopic literature (see, for example, Hyman, 1951), Brü ggemann (1985 thought the cells of the nozzle, both the matrix and the gap cells, to be donut-shaped, the hole being the lumen of the spermatic duct. At the tip of the nozzle facing the ovary is a vesicle termed the bursal vestibule, composed of two or more biconcave cells.…”

mentioning

confidence: 90%

Comparative morphology of the bursal nozzles in acoels (Acoela, Acoelomorpha)

Petrov

Hooge

Tyler

2006

Journal of Morphology

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Systematics of the Acoela is particularly difficult because of the paucity of readily discernible morphological features. In other soft-bodied worms, sclerotized structures, such as copulatory stylets, provide important characters that can be seen in whole mounts, but acoels generally lack such features. Among the few sclerotized structures in acoels are bursal nozzles-tubiform outlets on the seminal bursae that are believed to be conduits (spermatic ducts) through which allosperm are transported to the oocytes. Early classifications of the Acoela used features of the female reproductive system, including bursal nozzles, for distinguishing major groups, but the current system essentially ignores them as too plastic to provide higher-level distinctions. We used confocal and electron microscopy to further characterize bursal nozzles in five acoel species, and found all composed of actin-reinforced extensions of stacked, flat mesenchymal cells. In Notocelis gullmarensis, Aphanostoma bruscai, and Daku woorimensis, the nozzle is a stiffened region of the same cells forming the wall of the bursa. By contrast, in Wulguru cuspidata cells forming the nozzle are distinct from those of the bursa. The so-called bursal cap of A. bruscai and D. woorimensis has small sclerotized disjunct units within it, also composed of stacked, flat, actin-reinforced cells. The nozzle of W. cuspidata, prominent like that of other convolutid acoels, is relatively complex, its actin-reinforced cells sandwiched with secretory cells and its base bearing a "sorting apparatus" of egg-shaped cells that send narrow processes inside the spermatic duct. Cases of sperm inside the nozzle corroborate its assumed role in reproduction. Whereas most nozzles sit at the end of the bursa facing the ovary, in species of Pseudmecynostomum and purportedly in a few other acoels, they sit between the female pore and the bursa, constituting what we call a vaginal nozzle. All bursal nozzles of acoels show a common ground pattern indicating common ancestry, but certain features discerned through electron and confocal microscopy show promise of providing synapomorphies for grouping some species.

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Ultrastructure and formation of the bursa mouthpiece of Philocelis cellata (Plathelminthes, Acoela)

Cited by 14 publications

References 13 publications

Systematic revision of acoels with 9+0 sperm ultrastructure (Convolutida) and the influence of sexual conflict on morphology

Systematic revision of acoels with 9+0 sperm ultrastructure (Convolutida) and the influence of sexual conflict on morphology

The Acoela: on their kind and kinships, especially with nemertodermatids and xenoturbellids (Bilateria incertae sedis)

Comparative morphology of the bursal nozzles in acoels (Acoela, Acoelomorpha)

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