scholarly journals Intraovarian Gestation in Viviparous Teleosts: Unique Type of Gestation among Vertebrates

2021 ◽  
Author(s):  
Mari-Carmen Uribe ◽  
Gabino De la Rosa-Cruz ◽  
Adriana García-Alarcón ◽  
Juan Carlos Campuzano-Caballero
Keyword(s):  
Reproductive Strategy ◽  
Structural Characteristics ◽  
Evolutionary Process ◽  
Physiological Characteristic ◽  
Intimate Contact ◽  
Unique Type ◽  
Embryonic Tissues ◽  
Mullerian Ducts ◽  
Embryonic Nutrition ◽  
Unique Condition

The intraovarian gestation, occurring in teleosts, makes this type of reproduction a such complex and unique condition among vertebrates. This type of gestation of teleosts is expressed in special morphological and physiological characteristic where occurs the viviparity and it is an essential component in the analysis of the evolutionary process of viviparity in vertebrates. In viviparous teleosts, during embryogenesis, there are not development of Müllerian ducts, which form the oviducts in the rest of vertebrates, as a result, exclusively in teleosts, there are not oviducts and the caudal region of the ovary, the gonoduct, connects the ovary to the exterior. The lack of oviducts defines that the embryos develop into the ovary, as intraovarian gestation. The ovary forms the oocytes which may develop different type of oogenesis, according with the storage of diverse amount of yolk, variation observed corresponding to the species. The viviparous gestation is characterized by the possible intimate contact between maternal and embryonic tissues, process that permits their metabolic interchanges. So, the nutrients obtained by the embryos could be deposited in the oocyte before fertilization, contained in the yolk (lecithotrophy), and may be completed during gestation by additional provisioning from maternal tissues to the embryo (matrotrophy). Then, essential requirements for viviparity in poeciliids and goodeids are characterized by: a) the diversification of oogenesis, with the deposition of different amount of yolk in the oocyte; b) the insemination, by the transfer of sperm to the female gonoduct and their transportation from the gonoduct to the germinal region of the ovary where the follicles develop; c) the intrafollicular fertilization; d) the intraovarian gestation with the development of embryos in intrafollicular gestation (as in poeciliids), or intraluminal gestation (as in goodeids); and, e) the origin of embryonic nutrition may be by lecithotrophy and matrotrophy. The focus of this revision compares the general and specific structural characteristics of the viviparity occurring into the intraovarian gestation in teleosts, defining this reproductive strategy, illustrated in this review with histological material in a poeciliid, of the species Poecilia latipinna (Lesueur, 1821) (Poeciliidae), and in a goodeid, of the species Xenotoca eiseni (Rutter, 1896) (Goodeidae).

Evolutionary theodicies – an attempt to overcome some impasses

2018 ◽  
Vol 60 (3) ◽  
pp. 428-434
Author(s):  
Asle Eikrem ◽  
Atle Ottesen Søvik
Keyword(s):  
Evolutionary Process ◽  
Unique Type ◽  
Do So

Summary Mats Wahlberg argues that evolutionary theodicies fail to show how an evolutionary process was necessary in order to reach the goal(s) God is said to have had when creating our world. The authors of this article argue that Wahlberg‘s critique fails if one takes into consideration the distinction between type- and token-values. The question that guides Wahlberg‘s discussion is whether or not unique type-values require an evolution in order to be instantiated or not. He does not, however, discuss whether unique token-values require evolution. This article will address this question, and argue that the theodicies he claims to fail does not do so for the reasons put forward by Wahlberg if interpreted as focusing on token-unique values. The authors will also argue that theodicies other than those evaluated by Wahlberg succeed in identifying type-unique values that can only be brought about through evolution.

Mechanics and paleo geomorphy of the platform margin of Dengying formation in the Jiulongshan field, Sichuan Basin, China

2020 ◽  
Author(s):  
Lining Wang
Keyword(s):  
Sichuan Basin ◽  
Middle Triassic ◽  
Structural Characteristics ◽  
Evolutionary Process ◽  
Lower Triassic ◽  
Late Triassic ◽  
Structural Restoration ◽  
Seismic Reflection Data ◽  
Dengying Formation ◽  
Platform Margin

<p><span lang="EN-US"><span>The northwestern Sichuan region experienced the evolutionary process of a marine Craton basin in the Sinian-Middle Triassic and a continental basin in the Mesozoic-Cenozoic. Several regional tectonic activities cause the complicated stratigraphic distribution and structural deformations in deep layers. During key tectonic periods, the characteristic sedimentary and deformation structures were formed, including the platform margin of Dengying formation, the western palaeohigh at the end of Silurian, and the passive continental margin of late Paleozoic-middle Triassic. The Meso-Cenozoic intra-continental compressional tectonic processes since the late Triassic controlled the formation of complex thrusting structures surrounding and inside the basin. The northern Longmenshan fold-thrust belt has footwall in-situ thrust structures, controlled by two sets of detachments in the Lower Triassic and the Lower Cambrian, presenting a multi-level deformation structure with shallow folds, the middle thin-skin thrusts and the deeper basement-involved folds. From the perspective of structural geology, the Dengying formation of the Upper Sinian is mainly distributed in the eastern and northern areas of the northwest Sichuan basin where the Jiulongshan fold is the favorable exploration belts. Using the three-dimensional seismic reflection data, we recognize the structural characteristics of the platform margin of Dengying formation. Meanwhile, we apply new methods of two-dimensional and structural restoration based on mechanical constrains to gain insights into the development of the Jiulongshan anticline which forms the trap for the Jiulongshan field. The result of structural restoration indicates that, the formation of the Jiulongshan anticline is controlled by two-stage contractional thrusts. In the early days, there was no significant relief in Jiulongshan area, and the southwestern top of the Sinian Dengying formation was the paleo-high. The anticline was gradually formed in the Late Jurassic-the Early Cretaceous, presenting an approximately E-W strike structure. This structure was transformed by the N-E contractional stress to become an anticline in NE-SW direction.</span></span></p> <p> </p>

scholarly journals Changes in Reproductive Traits in Physalis philadelphica; An Unexpected Shift Toward Self-Incompatibility in a Domesticated Annual Fruit Crop

2021 ◽  
Vol 12 ◽  
Author(s):  
Lislie Solís-Montero ◽  
Lorena Aceves-Chong ◽  
Mayumi Vega-Polanco ◽  
Ofelia Vargas-Ponce
Keyword(s):  
Artificial Selection ◽  
Reproductive Strategy ◽  
Evolutionary Process ◽  
Pollen Grains ◽  
Fruit Production ◽  
Wild Plants ◽  
Cultivated Plants ◽  
Self Incompatibility ◽  
Reproductive Parameters ◽  
Crossing Experiment

Domestication is an evolutionary process with an impact on plant reproduction. Many domesticated plants are self-compatible (i.e., they lack mechanisms to reject their own pollen), but few domesticated plants are fully or partially self-incompatible. We used the husk tomato, Physalis philadelphica, as a study model to investigate changes in the reproductive strategy of an annual partially self-incompatible plant during the process of domestication. Wild and cultivated populations of this species coexist in close proximity. These different populations present a high level of morphological and genetic variation associated with different degrees of domestication. We hypothesized that artificial selection favors self-compatibility in cultivated plants through changes in their reproductive strategy and some reproductive parameters associated with domestication. To test this hypothesis, we characterized the floral morphology and some reproductive parameters of weedy plants (wild plants), landraces (semi-domesticated plant), and commercial plants (domesticated plants). We conducted an artificial crossing experiment, germinated the seeds, and recorded seedling growth. Commercial plants had the largest flowers and the highest number of ovules. Yet, they did not differ in other reproductive parameters (e.g., herkogamy, size of pollen grains, stigmatic area, and pollen:ovule ratio) from landraces and weedy plants. Physalis philadelphica produced fruits by autonomous autogamy in the artificial crossing experiment. These fruits were the smallest and lightest fruits at all degrees of domestication; however, fruit set of autonomous autogamy was higher in weedy plants. In addition, fruit production was higher when weedy plants donated pollen to commercial plants. Although seeds produced by autonomous autogamy of weedy plants had a low germination percentage, their cotyledons and the embryonic foliage leaves appeared earlier than in landraces and commercial plants. In conclusion, the domestication syndrome in this plant was manifested as increments in flower size and ovule production. Contrary to expectations, there was higher fruit production by autonomous autogamy in weedy plants than in cultivated plants. It seems that artificial selection in P. philadelphica favors self-incompatibility in cultivated plants. Nonetheless, spontaneous self-pollination seems to be advantageous in weedy populations because they produced viable seeds from which cotyledons and the embryonic foliage leaves emerged earlier than in cultivated plants.

scholarly journals Peering through the Windows of the Brain

1987 ◽  
Vol 7 (6) ◽  
pp. 663-672 ◽  
Author(s):  
Paul M. Gross ◽  
Adolf Weindl ◽  
Karl M. Knigge
Keyword(s):  
Cerebrospinal Fluid ◽  
Brain Function ◽  
Structural Characteristics ◽  
Mammalian Brain ◽  
Intimate Contact ◽  
The Brain

These seven specialized circumventricular structures of the mammalian brain represent windows with individualized structural characteristics permitting intimate contact between blood and cerebrospinal fluid, neurones and specialized ependyma-glia. These “Seven Windows of the Brain”, like the seven lucky deities of Japan, may each have a specific patron of body -brain function which they serve.1

XVIII.—Studies on Reproduction in Wild-Type and Female-Sterile Mutants of Drosophila melanogaster (Meig)

1949 ◽  
Vol 63 (3) ◽  
pp. 249-270 ◽  
Author(s):  
R. A. Beatty ◽  
C. H. Waddington
Keyword(s):  
Drosophila Melanogaster ◽  
Structural Characteristics ◽  
Physiological Characteristic ◽  
Wild Type ◽  
Germinal Cells

Drosophila mutants are usually defined by structural characteristics exhibited by the adult fly. In certain cases (homozygous lethal mutants and female-sterile mutants) the mutant may or may not be defined structurally, but does exhibit the physiological characteristic of death at some stage.The females of homozygous lethals are sterile, for the F1; represented by the germinal cells, dies with the mother. The term female-sterile, however, is applied to the well-known cases in which the mother but not her F1 achieve imaginal life.

Triassic sponges (Sphinctozoa) from Hells Canyon, Oregon

1988 ◽  
Vol 62 (03) ◽  
pp. 419-423 ◽  
Author(s):  
Baba Senowbari-Daryan ◽  
George D. Stanley
Keyword(s):  
Endemic Species ◽  
Upper Triassic ◽  
Island Arc ◽  
Tropical Island ◽  
The Family ◽  
Wallowa Terrane ◽  
Unique Condition ◽  
Hells Canyon

Two Upper Triassic sphinctozoan sponges of the family Sebargasiidae were recovered from silicified residues collected in Hells Canyon, Oregon. These sponges areAmblysiphonellacf.A. steinmanni(Haas), known from the Tethys region, andColospongia whalenin. sp., an endemic species. The latter sponge was placed in the superfamily Porata by Seilacher (1962). The presence of well-preserved cribrate plates in this sponge, in addition to pores of the chamber walls, is a unique condition never before reported in any porate sphinctozoans. Aporate counterparts known primarily from the Triassic Alps have similar cribrate plates but lack the pores in the chamber walls. The sponges from Hells Canyon are associated with abundant bivalves and corals of marked Tethyan affinities and come from a displaced terrane known as the Wallowa Terrane. It was a tropical island arc, suspected to have paleogeographic relationships with Wrangellia; however, these sponges have not yet been found in any other Cordilleran terrane.

Suppression of γ’ Precipitation in a Laser-Melted Nickel-Base Alloy

1977 ◽  
Vol 35 ◽  
pp. 270-271
Author(s):  
J. M. Walsh ◽  
J. C. Whittles ◽  
B. H. Kear ◽  
E. M. Breinan
Keyword(s):  
Cooling Rate ◽  
Base Alloy ◽  
Material Surface ◽  
Intimate Contact ◽  
Absorbed Power ◽  
Perfect Contact ◽  
Nickel Base ◽  
Rapidly Solidified ◽  
Limiting Case ◽  
The Heat Transfer Coefficient

Conventionally cast γ’ precipitation hardened nickel-base superalloys possess well-defined dendritic structures and normally exhibit pronounced segregation. Splat quenched, or rapidly solidified alloys, on the other hand, show little or no evidence for phase decomposition and markedly reduced segregation. In what follows, it is shown that comparable results have been obtained in superalloys processed by the LASERGLAZE™ method.In laser glazing, a sharply focused laser beam is traversed across the material surface at a rate that induces surface localized melting, while avoiding significant surface vaporization. Under these conditions, computations of the average cooling rate can be made with confidence, since intimate contact between the melt and the self-substrate ensures that the heat transfer coefficient is reproducibly constant (h=∞ for perfect contact) in contrast to the variable h characteristic of splat quenching. Results of such computations for pure nickel are presented in Fig. 1, which shows that there is a maximum cooling rate for a given absorbed power density, corresponding to the limiting case in which melt depth approaches zero.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system

1978 ◽  
Vol 36 (1) ◽  
pp. 456-457
Author(s):  
V. Annamalai ◽  
L.E. Murr
Keyword(s):  
Structural Characteristics ◽  
Secondary Electron Emission ◽  
Copper Deposit ◽  
Reaction Rates ◽  
Sem Analysis ◽  
Experimental Conditions ◽  
Major Drawback ◽  
Emission Mode ◽  
Scrap Iron ◽  
Image Position

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.

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