Growth and moulting in nematodes: moulting and development of the hatched larva of Rotylenchulus reniformis

Parasitology ◽  
1984 ◽  
Vol 89 (1) ◽  
pp. 107-120 ◽  
Author(s):  
A. F. Bird
Keyword(s):  
Developmental Changes ◽  
Adult Males ◽  
Rotylenchulus Reniformis ◽  
Head Region ◽  
Immature Female ◽  
The Third ◽  
Final Moult ◽  
Developmental Sequences ◽  
Transmission Electron ◽  
Moist Environment

SummaryThe morphology of the post-hatch moulting and developmental sequence of an amphimictic population of Rotylenchulus reniformis has been examined in living and fixed material. Under suitable conditions of temperature and in a moist environment the 2nd-stage larva (L2) undergoes a series of 3 moults and developmental changes which result in the formation of males and immature females. After hatching and prior to the start of the first of these moults (the second moult), there is a pre-moult period, usually of 3–5 days duration. The morphology of the entire moulting and developmental sequences, from L2 to just after the final moult, has been followed in single living specimens of a parasitic nematode using differential interference contrast optics, and sections cut through different stages have been observed under the transmission electron microscope. These moulting sequences (at 24 °C) take place at similar times in developing males and females. The second moult takes place on the second day after commencement of moulting, the third on the third or fourth days and the fourth and final moult on the sixth or seventh days, followed by further development over several days to give rise to the adult male and the immature female. The ultrastructure associated with some of the more obvious of these developmental changes is described and includes the morphology of the head region and cuticles of L2, L4, adult males and immature females, the oesophageal glands of the immature female and the copulatory spicules and spermatozoa of the male.

Microstructure Imaging, Precipitation Formation and Mechanical Properties: Al–Li and Al–Mg–Zn Alloys

2019 ◽  
Author(s):  
Wilfried Wunderlich ◽  
Janos Lendvai ◽  
Hans-Joachim Gudladt
Keyword(s):  
Hydrogen Embrittlement ◽  
Driving Force ◽  
Hydrogen Diffusion ◽  
Nano Particles ◽  
Peak Hardness ◽  
Free Zone ◽  
The Third ◽  
Transmission Electron ◽  
Moisture Conditions ◽  
Precipitation Formation

This article describes concepts of three features of microstructure–properties relationship, first the imaging and formation of nano-particles, then their contribution to hardness, and finally hydrogen embrittlement during fatigue. First, we briefly review the imaging modes in transmission electron microscopy (TEM) for nano-sized precipitates. The next issue is the hardening in Aluminum alloys, which is caused by GP-zones or precipitates, formed at the second step of the annealing process. After homogenization, the peak-hardness can be generally achieved by a few hours of annealing between 120°C and 200°C. Hardness measurements and equal-channel axial pressing (ECAP) showed that even at room temperature the driving force for formation of the particles is so strong that already within one hour of annealing after homogenization a remarkable hardening occurs. The third issue, hydrogen embrittlement, is caused by oxidation of pure Al surfaces produced at the crack tip during fatigue under ambient or wet moisture conditions. The cracks propagate preferentially along the precipitation free zone adjacent to grain boundaries, where hydrogen diffusion is fastest.

Hypostase development in Ornithogalum caudatum (Liliaceae) and notes on other types of modifications in the chalaza of angiosperm ovules

1980 ◽  
Vol 58 (19) ◽  
pp. 2059-2066 ◽  
Author(s):  
Varien R. Tilton
Keyword(s):  
Embryo Sac ◽  
Mitotic Division ◽  
Integral Function ◽  
Developmental Changes ◽  
Storage Tissue ◽  
Storage Product ◽  
The Third ◽  
Carbohydrate Storage ◽  
Mature Ovule ◽  
Ornithogalum Caudatum

Seven types of chalazal modifications have been reported to occur as normal developmental changes in angiosperm ovules. Among them is the hypostase, a group of usually lignified cells. In Ornithogalum, hypostase differentiation becomes evident during the meiotic–mitotic interphase. Differentiation proceeds toward the micropylar end of the ovule at first but later becomes bidirectional. Differentiation is usually completed after the third mitotic division of the megagametophyte has occurred. One to three hypostase cells per ovule have what appears to be a nonstarch carbohydrate storage product. The greatest proportion of starch reserves in the mature ovule occurs in the chalazal end of the nucellus and, although the hypostase does not seem to be an important storage tissue, it probably has an integral function in the translocation of nutrients into the megagametophyte and, after fertilization, into the embryo sac.

Ultrastructure of Human Enamel Specimens Prepared by Ion Micromilling

1973 ◽  
Vol 52 (4) ◽  
pp. 703-710 ◽  
Author(s):  
W.J. Hamilton ◽  
G. Judd ◽  
G.S. Ansell
Keyword(s):  
Electron Microscope ◽  
Crystallite Size ◽  
Transmission Electron Microscope ◽  
Preferred Orientation ◽  
Head Region ◽  
Transmission Electron ◽  
Human Enamel

Ion-thinning techniques for the preparation of transmission electron microscope samples of mature enamel were used to examine ultrastructural details that included crystallite size and orientation in relation to the enamel rod geometry. The three-quarter arcade of the sheath is visible as the perimeter of the keyhole. Diffraction studies indicate a preferred orientation in the c axis of the crystallites in the head and tail of the keyhole and in other directions in the head region.

Aluminum and Ni–silicide lateral reactions

1990 ◽  
Vol 5 (2) ◽  
pp. 334-340 ◽  
Author(s):  
Joyce C. Liu ◽  
J. W. Mayer
Keyword(s):  
Electron Microscope ◽  
Lateral Diffusion ◽  
Second Step ◽  
Lateral Growth ◽  
Diffusion Couples ◽  
The Third ◽  
Third Phase ◽  
Transmission Electron ◽  
Sequential Formation

The Al–Ni2Si reactions were studied in lateral diffusion couples containing Al islands on Ni–Si multiple layers. The samples were first in situ annealed in a transmission electron microscope at a temperature of 370°C for 5 min to form the Ni2Si phase in the multiple-layer area. Then they were in situ annealed at temperatures ranging from 498–545 °C. During the second-step anneal, a sequential formation of Al3Ni, Al3Ni2, and Ni3Si2 was observed. After the nucleation of the third phase (Ni3Si2), the three phases grew simultaneously with time. The lateral growth of Al3Ni and Al3Ni2 is a result of the Al diffusion and the Al–Ni silicide reactions; the lateral growth of Ni3Si2 is caused by the diffusion of Si atoms dissociated from the silicides.

Aspects of ecology of the threatened ringed sawback turtle, Graptemys oculifera

1991 ◽  
Vol 12 (2) ◽  
pp. 161-168 ◽  
Author(s):  
Christopher P. Kofron
Keyword(s):  
Sexual Maturity ◽  
River System ◽  
Pearl River ◽  
Museum Specimens ◽  
Adult Males ◽  
Important Food ◽  
The Third ◽  
The Pearl River ◽  
The U.S ◽  
Growth And Reproduction

AbstractThe ringed sawback turtle, Graptemys oculifem, is endemic to the Pearl River system of Louisiana and Mississippi in southern USA. In 1986 the species was placed on the U.S. Federal List of Endangered and Threatened Species with status designation of 'threatened'. Existing museum specimens were examined to determine geographic distribution, food, growth and reproduction. Caddisflies, dipteran flies, mayflies, beetles and plant material were the most important food. Many stomachs contained small pieces of wood, suggesting that fallen tree trunks were a "grazing" substrate. Males ranged from 3.2-8.6 cm plastron length, and attained sexual maturity during the third or fourth year at lengths of about 6.0-7.0 cm. Adult males experienced recrudescence of testes, with maximum testis lengths during August and September indicating the probable time of spermatogenesis. Females ranged from 3.3-18.9 cm plastron length, and appeared to attain sexual maturity during the seventh or eighth year at lengths greater than 10.0 cm. The data suggested that ovulation occurs from May through July, nesting during June and ,July, and hatching at least during August. Clutch size appeared to be just two or three eggs.

A new species of Hohenbergia (Bromeliaceae) endemic to the Dolphin Head Mountains in western Jamaica

Phytotaxa ◽  
2016 ◽  
Vol 247 (2) ◽  
pp. 133 ◽  
Author(s):  
JULIÁN AGUIRRE-SANTORO ◽  
KERON C. ST. E. CAMPBELL ◽  
GEORGE R. PROCTOR
Keyword(s):  
New Species ◽  
Geographical Distribution ◽  
Conservation Status ◽  
Coastal Areas ◽  
Habitat Conservation ◽  
Head Region ◽  
The Third ◽  
The Caribbean ◽  
Geographic Distributions ◽  
A New Species

Recent botanical expeditions to the Dolphin Head Mountains in western Jamaica allowed the collection of different specimens of a new species, Hohenbergia rohan-estyi, an enigmatic plant that resembles the also Jamaican-endemic H. negrilensis. In this study, we describe H. rohan-estyi and include notes on its geographical distribution, habitat, conservation status and taxonomy. The length of the stipes and number of flowers per spike permit the differentiation of H. rohan-estyi from H. negrilensis. In addition, the geographic distributions of these two species do not overlap, as H. rohan-estyi inhabits mountainous forests of the Dolphin Head region while H. negrilensis occurs in coastal areas of western Jamaica. Finally, H. rohan-estyi is the third species of Hohenbergia reported as endemic to the Dolphin Head Mountains, indicating the importance of this area in the evolution and conservation of the genus in Jamaica and the Caribbean.

scholarly journals Octopamine Signaling Via Oamb is Essential for A Well-Orchestrated Climbing Performance of Adult Drosophila Melanogaster

2021 ◽  
Author(s):  
Samar Ezzat El-Kholy ◽  
Basma Afifi ◽  
Iman El-Husseiny ◽  
Amal Seif
Keyword(s):  
Nervous System ◽  
Ultrastructural Changes ◽  
System Control ◽  
Muscular Tissue ◽  
Adult Males ◽  
Leg Muscles ◽  
Transmission Electron ◽  
Severe Impairment ◽  
Climbing Ability ◽  
Almost All

Abstract The biogenic amine octopamine (OA) orchestrates many behavioural processes in insects. OA mediates its function by binding to OA receptors belonging to the G protein-coupled receptors superfamily. Despite the potential relevance of OA for controlling locomotion, our knowledge about the role of each octopaminergic receptor still limited. In this study, RNA interference (RNAi) was used to knockdown each OA receptor type in almost all Drosophila melanogaster tissues using a tubP-GAL4 driver to investigate the loss of which receptor affects the climbing ability of adult flies. The results demonstrated that oamb-deficient flies had impaired climbing ability more than those deficient in other receptors receptive for OA. Targeted RNAi-mediated kockdown of oamb in the nervous system or muscular system decreased the climbing ability, indicating that within Drosophila legs, OA through oamb orchestrated the nervous system control and muscular tissue responses. Oamb-deficient adult males showed morphometric changes in the length and width of leg parts. Transmission electron microscopy revealed that the leg muscles oamb-deficient flies have severe ultrastructural changes compared to those of control flies. The severe impairment in the climbing performance of oamb-deficient flies correlates well with the completely distorted leg muscle ultrastructure in these flies. Taken together, we could conclude that OA via oamb plays an important role in the locomotor activity of Drosophila.

scholarly journals The non-brain anterior nerve center and tentacle crown structure of Owenia borealis (Annelida, Oweniidae): the evolution of the nervous system and tentacles in Bilateria

2021 ◽  
Author(s):  
Nadezhda Rimskaya-Korsakova ◽  
Vyacheslav Dyachuk ◽  
Elena Temereva
Keyword(s):  
Electron Microscopy ◽  
System Development ◽  
Sister Group ◽  
Ultrastructural Level ◽  
Myoepithelial Cells ◽  
Coelomic Cavity ◽  
Head Region ◽  
Blood Capillaries ◽  
Crown Structure ◽  
Transmission Electron

Abstract The Oweniidae are marine annelids with many unusual features of organ system, development, morphology, and ultrastructure. Together with magelionds, oweniids have been placed within the Palaeoannelida, a sister group to all remaining annelids. The study of this group may increase our understanding of the early evolution of annelids (including their radiation and diversification) and of the morphology of the last common bilaterian ancestor. In the current research, scanning electron microscopy revealed that the tentacle apparatus consists of 10 branched arms. The tentacles are covered by monociliary cells that form a ciliar groove that extends along the oral side of the arm base. Light, confocal, and transmission electron microscopy revealed that head region contains two circular intraepidermal nerves (outer and inner) that give rise to the neurites of each tentacle, i.e., intertentacular neurites are absent. Each tentacle contains a coelomic cavity with a network of blood capillaries. Monociliar myoepithelial cells of the tentacle coelomic cavity form both the longitudinal and the circular muscles. The structure of this myoepithelium is intermediate between simple and pseudo-stratified myepithelium. Overall, tentacles lack prominent zonality, i.e., co-localization of ciliary zones, neurite bundles, and muscles. This organization, which indicates a non-specialized tentacle crown in O. borealis and other oweniids with tentacles, is probably ancestral for annelids and for all Bilateria. The outer circular nerve of O. borealis is a dorsal medullary commissure that apparently functions as an anterior nerve center and is organized at the ultrastructural level as a stratified neuroepithelium. Given the hypothesis that the anterior nerve center of the last bilateral ancestor might be a diffuse neural plexus network, these results suggest that the ultra anatomy of that plexus brain might be a stratified neuroepithelium. Alternatively, the results could reflect the simplification of structure of the anterior nerve center in some bilaterian lineages.

Two new species of Cnemidophorus (Squamata: Teiidae) of the C. ocellifer group, from Bahia, Brazil

Zootaxa ◽  
2011 ◽  
Vol 3022 (1) ◽  
pp. 1 ◽  
Author(s):  
FEDERICO ARIAS ◽  
CELSO MORATO DE CARVALHO ◽  
MIGUEL TREFAUT RODRIGUES ◽  
HUSSAM ZAHER
Keyword(s):  
New Species ◽  
Color Pattern ◽  
Northwestern Part ◽  
Temporal Region ◽  
Dorsal Part ◽  
Adult Males ◽  
The Third ◽  
Bluish Green ◽  
Two New Species ◽  
The Right

Two new species of Cnemidophorus are described from the right bank of the São Francisco river, in the northwestern part of state of Bahia, Brazil. Both species are assigned to the Cnemidophorus ocellifer group and are distinguished from all other congeners on the basis of lepidosis and color pattern. One of them, Cnemidophorus cyanurus, shares with the species of the subgroup of C. littoralis (C. abaetensis, C. littoralis and C. venetacaudus), a bluish green tail, spurs on the heels of males, 6–7 supraciliaries, a high number of femoral pores (27–45), a row of enlarged scales in the dorsal part of the humerus, and 8 to 10 rows of ventral scales. The second species, Cnemidophorus nigrigula, shares with the C. ocellifer subgroup (composed of C. ocellifer, C. mumbuca, C. jalapensis and C. confusionibus) a low number of femoral pores (14– 21), enlarged scales in the temporal region posterior to the third subocular, 5 supraciliaries, 6 to 8 rows of ventral scales, and a brown tail color. It is also characterized by males being conspicuously larger than females and by females retaining the juvenile color pattern, which is lost in adult males. The latter characteristic has not been reported in any species of the C. ocellifer group before now. The two new species occur sympatrically at Santo Inácio.

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