SUMMARY / RELATED TOPICS

Ecdysis

Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals forms a inelastic exoskeleton, it is shed during growth and a new, larger covering is formed; the remnants of the old, empty exoskeleton are called exuviae. After moulting, an arthropod is described as a callow. Within one or two hours, the cuticle hardens and darkens following a tanning process analogous to the production of leather. During this short phase the animal expands, since growth is otherwise constrained by the rigidity of the exoskeleton. Growth of the limbs and other parts covered by hard exoskeleton is achieved by transfer of body fluids from soft parts before the new skin hardens. A spider with a small abdomen may be undernourished but more has undergone ecdysis; some arthropods large insects with tracheal respiration, expand their new exoskeleton by swallowing or otherwise taking in air. The maturation of the structure and colouration of the new exoskeleton might take days or weeks in a long-lived insect.

Ecdysis allows damaged tissue and missing limbs to be regenerated or re-formed. Complete regeneration may require a series of moults, the stump becoming a little larger with each moult until it is a normal, or near normal, size; the term ecdysis comes from Ancient Greek: ἐκδύω, "to take off, strip off". In preparation for ecdysis, the arthropod becomes inactive for a period of time, undergoing apolysis or separation of the old exoskeleton from the underlying epidermal cells. For most organisms, the resting period is a stage of preparation during which the secretion of fluid from the moulting glands of the epidermal layer and the loosening of the underpart of the cuticle occur. Once the old cuticle has separated from the epidermis, a digesting fluid is secreted into the space between them. However, this fluid remains inactive. By crawling movements, the organism pushes forward in the old integumentary shell, which splits down the back allowing the animal to emerge; this initial crack is caused by a combination of movement and increase in blood pressure within the body, forcing an expansion across its exoskeleton, leading to an eventual crack that allows for certain organisms such as spiders to extricate themselves.

While the old cuticle is being digested, the new layer is secreted. All cuticular structures are shed at ecdysis, including the inner parts of the exoskeleton, which includes terminal linings of the alimentary tract and of the tracheae if they are present; each stage of development between moults for insects in the taxon endopterygota is called an instar, or stadium, each stage between moults of insects in the Exopterygota is called a nymph: there may be up to 15 nymphal stages. Endopterygota tend to have only five instars. Endopterygotes have more alternatives to moulting, such as expansion of the cuticle and collapse of air sacs to allow growth of internal organs; the process of moulting in insects begins with the separation of the cuticle from the underlying epidermal cells and ends with the shedding of the old cuticle. In many species it is initiated by an increase in the hormone ecdysone; this hormone causes: apolysis – the separation of the cuticle from the epidermis secretion of new cuticle materials beneath the old degradation of the old cuticleAfter apolysis the insect is known as a pharate.

Moulting fluid is secreted into the exuvial space between the old cuticle and the epidermis, this contains inactive enzymes which are activated only after the new epicuticle is secreted. This prevents the new procuticle from getting digested; the lower regions of the old cuticle, the endocuticle and mesocuticle, are digested by the enzymes and subsequently absorbed. The exocuticle and epicuticle are hence shed at ecdysis. Spiders change their skin for the first time while still inside the egg sac, the spiderling that emerges broadly resembles the adult; the number of moults varies, both between species and sexes, but will be between five times and nine times before the spider reaches maturity. Not since males are smaller than females, the males of many species mature faster and do not undergo ecdysis as many times as the females before maturing. Members of the Mygalomorphae are long-lived, sometimes 20 years or more. Spiders stop feeding at some time before moulting for several days; the physiological processes of releasing the old exoskeleton from the tissues beneath cause various colour changes, such as darkening.

If the old exoskeleton is not too thick it may be possible to see new structures, such as setae, from outside. However, contact between the nerves and the old exoskeleton is maintained until a late stage in the process; the new, teneral exoskeleton has to accommodate a larger frame than the previous instar, while the spider has had to fit into the previous exoskeleton until it has been shed. This means the spider does not fill out the new exoskeleton so it appears somewhat wrinkled. Most species of spiders hang from silk during the entire process, either dangling from a drop line, or fastening their claws into webbed fibres attached to a suitable base; the discarded, dried exoskeleton remains hanging where it was abandoned once the spider has left. To open the old exoskeleton, the spider contracts its abdomen to supply enough fluid to pump into the prosoma with sufficient pressure to crack it open along

Outline of energy development

The following outline is provided as an overview of and topical guide to energy development: Energy development – the effort to provide sufficient primary energy sources and secondary energy forms for supply, impact on air pollution and water pollution, mitigation of climate change with renewable energy. Energy development Fossil fuels: coal and natural gas Wind power: wind turbines and wind farms Biofuel: biomass Solar power: photovoltaics and space-based Marine energy: wave power, tidal power and osmotic power Hydrogen Geothermal power Hydroelectricity Nuclear energy History of energy development History of fossil fuel History of vegetable oil used as fuel History of biodiesel History of electromagnetism and electricity generation History of nuclear power History of fusion energy research History of wind power History of geothermal power History of energy storage 1973 oil crisis Climate change Electric power transmission Net metering OPEC Peak oil Photovoltaics Pipeline transport Sustainable development Synthetic fuel United States Department of Energy United States Atomic Energy Commission List of emerging energy technologies RECaBS REcalculator Interactive Renewable Energy Calculator - compare renewable energy to conventional energy sources

Emil Riis Jakobsen

Emil Riis Jakobsen is a Danish footballer who plays for Danish club Randers FC as a forward. Jakobsen joined the youth academy of Randers at the age of 14, he went on to become the top-scorer of the under-17 team by scoring 24 goals in the youth league. After two trials, he joined the youth team of English club Derby County in July 2015. After joining the club, he was assigned to the under-18 team, he further progressed on to play for the under-23 team and scored 11 goals as his side gained the Premier League 2 Division 1 status. In December 2017, Jakobsen trialled with Dutch club VVV-Venlo. On 11 January 2018, he joined the club on a loan deal till the end of the season. Jakobsen has been capped by Denmark under-17 team; as of match played on 17 March 2018 Emil Riis Jakobsen at Soccerway Emil Riis Jakobsen at DBU