Ultrastructure of oocytes and female copulatory organs of Acoela

The ultrastructure of oocytes in four species of Acoela ( Archaphanostoma agile, Otocelis rubropunctata, Symsagittifera japonica, and Amphiscolops sp.) and that of female copulatory organs of S. japonica and Amphiscolops sp. are described for the first time. According to the similarity of the reproductive apparatus structure, the sister relationships between the families Sagittiferidae and Convolutidae are confirmed. The ultrastructure of oocytes and specific features of oogenesis are proposed to be useful in phylogenetics of Acoela

Ultrastructure of oocytes and female copulatory organs of Acoela

© 2014, Pleiades Publishing, Inc. The ultrastructure of oocytes in four Acoela species representing different families (Archaphanostoma agile, Otocelis rubropunctata, Symsagittifera japonica, and Amphiscolops sp.) and of female copulatory organs (bursae) in S. japonica and Amphiscolops sp. is described for the first time. The sister relationship between the families Sagittiferidae and Convolutidae is confirmed by the similarity of their reproductive apparatus structure. It is suggested the ultrastructure of oocytes and specific features of oogenesis can be used in the phylogenetics of Acoela

Main pathways of evolution of spermatozoa of acoelomorpha and free-living plathelminthes

© INVERTEBRATE ZOOLOGY, 2017.On the basis of original and literary data on ultrastructure of spermatozoa and their formation the reconstruction of main pathways of evolution of male gametes of Acoelomorpha and free-living Plathelminthes is proposed. Two species of Acoela — Archaphanostoma agile and Convoluta convoluta — and five species of free-living flatworms from different taxa — Monocelis fusca, M. lineata (Proseriata), Uteriporus vulgaris (Tricladida, Maricola), Provortex karlingi (Rhabdocoela, Dalytyphloplanoida) and Macrorhynchus croceus (Rhabdocoela, Kalyptorhynchia) — have been investigated. Specimens were collected on the littoral zone of various islands of Keretskii Archipelago (White Sea), fixed in the 1% glutaraldehyde and studied with transmission electron microscope JEM 100 CX by the standard methodics. During the evolution of Acoela the axoneme formula of spermatozoa is modified and the position of free microtubules is reorganized. Evolutionary changes of spermatozoa of Plathelminthes are represented firstly by the locomotory apparatus (incorporation of flagellae, change of an axoneme formula and configurations of free microtubules), then by organization of nuclear material. And finally in specialized groups the oligomerization of mitochondria and additional inclusions occurs. In the spermiogenesis of Acoela and the advanced flatworms the specific peculiarities of ancestral forms, representing the examples of recapitulation on the cellular level, are described. The similarities and the differences of the sperm ultrastructure and spermiogenesis in Acoelomorpha and Plathelminthes are discussed in evolutionary-morphological aspec

Observation of intersexuality in land hermit crabs (Anomura: Coenobitidae)

We report here the first observation of intersexuality in a land hermit crab (Coenobitidae). Three species of land hermit crabs from Okinawa were investigated. In the population of the terrestrial hermit crab Coenobita rugosus two per cent of males were found to be intersex. Besides the true male gonopores on the coxae of the 5th pair of pereopods, they had additional openings on the coxae of the 3rd pair of pereopods. Both specimens examined had a normally developed male reproductive system. In the populations of two other species studied, C. brevimanus and C. purpureus, however, no intersex individuals have been found. Examples of intersexuality in decapod crustaceans are discussed and putative explanations of this phenomenon in land hermit crabs are proposed

Ultrastructure of spermatozoa in four species of Acoela flatworms and their significance for systematics

The ultrastructure of sperms in three Acoela species from Japan (Otocelis rubropunctata, Symsagittifera japonica, Amphiscolops sp.) is described for the first time. New data on the sperm ultrastructure of Archaphanostoma agile from the White Sea are presented. Based on the data, the phylogenetic relationships between the families Isodiametridae, Otocelididae, Sagittiferidae and Convolutidae are revised

Ultrastructure of gametes of marine tricladid Uteriporus vulgaris (Tricladida, Maricola)

The data on the ultrastructure of spermatozoa and oocytes and their development in the marine tricladid Uteriporus vulgaris are described for the first time. The conservativeness of the spermatozoal morphology in Tricladida as one of the most advanced turbellarian orders is notified. In addition, some specific ultrastructural features of spermatids and oocytes in U. vulgaris are described

Ultrastructure of aflagellate spermatozoa in rhabdocoel turbellarian provortex karlingi (neorhabdocoela, dalyellioida)

© 2015 r. The ultrastructure of spermatozoa and spermatids in a the rhabdocoel turbellarian Provortex karlingi from the White Sea is described for the first time. Among the unusual morphological features of spermatozoa, the absence of flagellae and the presence of perinuclear condensation of electron-dense granules are notified. The examples of reduction of flagellae in male gametes of various groups of flatworms are discussed. New data support the monophyly of the turbellarian genus Provortex, which is characterized by the number of some unique synapomorphies

Probability of primordial black hole formation and its dependence on the radial profile of initial configurations

In this paper we derive the probability of the radial profiles of spherically symmetric inhomogeneities in order to provide an improved estimation of the number density of primordial black holes (PBHs). We demonstrate that the probability of PBH formation depends sensitively on the radial profile of the initial configuration. We do this by characterising this profile with two parameters chosen heuristically: the amplitude of the inhomogeneity and the second radial derivative, both evaluated at the centre of the configuration. We calculate the joint probability of initial cosmological inhomogeneities as a function of these two parameters and then find a correspondence between these parameters and those used in numerical computations of PBH formation. Finally, we extend our heuristic study to evaluate the probability of PBH formation taking into account for the first time the radial profile of curvature inhomogeneities.Comment: Version 2 with corrections from referees included, changes mostly improve the presentatio

How exactly did the Universe become neutral?

We present a refined treatment of H, He I, and He II recombination in the early Universe. The difference from previous calculations is that we use multi-level atoms and evolve the population of each level with redshift by including all bound-bound and bound-free transitions. In this framework we follow several hundred atomic energy levels for H, He I, and He II combined. The main improvements of this method over previous recombination calculations are: (1) allowing excited atomic level populations to depart from an equilibrium distribution; (2) replacing the total recombination coefficient with recombination to and photoionization from each level directly at each redshift step; and (3) correct treatment of the He I atom, including the triplet and singlet states. We find that the ionization fraction x_e = n_e/n_H is approximately 10% smaller at redshifts <~800 than in previous calculations, due to the non-equilibrium of the excited states of H, which is caused by the strong but cool radiation field at those redshifts. In addition we find that He I recombination is delayed compared with previous calculations, and occurs only just before H recombination. These changes in turn can affect the predicted power spectrum of microwave anisotropies at the few percent level. Other improvements such as including molecular and ionic species of H, including complete heating and cooling terms for the evolution of the matter temperature, including collisional rates, and including feedback of the secondary spectral distortions on the radiation field, produce negligible change to x_e. The lower x_e at low z found in this work affects the abundances of H molecular and ionic species by 10-25%. However this difference is probably not larger than other uncertainties in the reaction rates.Comment: 24 pages, including 18 figures, using emulateapj.sty, to appear in ApJ, the code recfast can be obtained at http://www.astro.ubc.ca/people/scott/recfast.html (in FORTRAN) and http://cfa-www.harvard.edu/~sasselov/rec/ (in C

Ultrastructure of epidermal sensillae in three species of acoela

© INVERTEBRATE ZOOLOGY, 2019. The investigation of the cellular organization of Acoela is of great interest for evolutionary morphologists and neurobiologists, since within this group we can observe the various stages of the formation of the nervous system and sensory organs characteristic of higher Bilateria. However, up to date the ultrastructure of epidermal sensory structures was described only for a relatively small number of acoel species. In the present work, four types of monociliary receptors were found in the epidermis of three species of this taxon (Otocelis rubropunctata, Symsagittifera japonica and Amphiscolops sp.). In the epidermis of O. rubropunctata there are three types of receptors - sensillae with a thin rootlet (with microvilli and without them), sensillae with a thick rootlet and receptors without a rootlet with stereocilia. In S. japonica the sensillae without a rootlet and with two circles of microvilli were found. Finally, in Amphiscolops sp. the sensillae with a thick rootlet and receptors without a rootlet with stereocilia were described. The distribution of certain types of ciliary receptors in various Acoela species is analyzed and their classification is proposed