China
Africa
Explore chapters and articles related to this topic
The Protozoa
Published in Donald L. Price, Procedure Manual for the Diagnosis of Intestinal Parasites, 2017
Oocysts of I. belli are light-bulb shaped, being nearly oval but narrowing bluntly at one end (see Plates 6, 40). Occasionally, they are oval. A small plug-like spot, the micropyle, lies in the center of the narrower end. After the combination of the two gametes, the zygote forms an outer cyst covering to become an oocyst. Within the oocyst wall, the zygote divides to form two sporoblasts. Each sporoblast secretes a cyst wall to become a sporocyst. Within the sporocysts, four sporozoites develop along with a residual body (see also Plate 70).
Aedes Mosquitoes: The Universal Vector
Published in Jagriti Narang, Manika Khanuja, Small Bite, Big Threat, 2020
Annette Angel, Bennet Angel, Neelam Yadav, Jagriti Narang, Surender Singh Yadav, Vinod Joshi
The gonotrophic cycle of mosquitoes, as defined by Beklemishev (1940), is the search for a host, ingestion of a blood meal, digestion of the meal, maturation of ovaries, and laying of mature eggs after searching an oviposition site (Beklemishev, 1940). A fully matured female mosquito prepares itself for the next stage by finding a host, preferably a vertebrate host. It feeds on the blood until its gut is filled, and sometimes it can consume blood even more than its body size (Fig. 1.21). This can be seen sometimes when blood starts oozing out of its body. After blood sucking, the female then rests on some comfortable surface for some time (Birley and Rajagopalan, 1981). Blood is necessary for the development of oocytes. For egg laying, the female prefers containers or small niches filled with water and lays eggs on the surface (ovipositioning), a bit above the water line, ensuring delivery of the first larval instars born in the water. The egg released by the female is a fertilized one, formed when the oocyte meets the sperm while traveling down the common oviduct before releasing out from the vagina (Briegel, 1990). The sperm enters the oocyte through the micropyle. The female then looks for some site for ovipositioning and starts laying eggs. A single mosquito can lay hundreds of eggs in batches. Usually it undergoes three gonotrophic cycles, but in each cycle, it can consume more than one blood meal from a host as per its body needs (Beklemishev, 1940). After releasing the eggs, a permanent structural change can be seen in the female’s abdomen, which can be observed if one wants to keep a record of the female’s reproductive history and, thereafter, her age (Birley and Rajagopalan, 1981).
Sperm Chemotaxis
Published in Claude Gagnon, Controls of Sperm Motility, 2020
Fertilization in insects follows a multistep protocol starting with sperm transfer into the female copulatory pouch, then sperm migration towards storage organs (often a spermatheca) where they might remain for as long as several years.126-128 Sperm released from storage organs is frequently synchronized with the arrival of one egg close to the aperture of the storage organ, and fertilization is obtained with a striking economy of sperm deployment, from one to ten spermatozoa in various species.129,130 This success rate is achieved through the structure of the female reproductive system, which releases the egg in correct orientation (micropyle close to the spermatheca aperture) with respect to delivery of a few spermatozoa. Such conditions of fertilization leave little active role to the spermatozoa, and the possibility of a chemotactic attraction of the sperm towards the eggs has been rejected in various cases.131 However, in several species, it has been suggested that secretions of the spermathecal gland may have the possibility to attract the spermatozoa towards their storage compartment.132,133 Evidence in favor of sperm chemotaxis towards the spermatheca was obtained in coleóptera.134 In an in vitro assay, using pieces of solid agar soaked into a solution of spermathecal gland extract, a strong positive chemotactic response of the spermatozoa was demonstrated in the boll weevil.135 The sperm response was not observed if the spermathecal gland extract had been previously heated at 60 °C for 1 h. Although the report does not describe sperm behavior during the attraction towards the agar piece, it does suggest strongly the existence of a chemotactic response. At the level of the egg itself, observations of oriented sperm trajectories in the micropyle area of the blow fly Musca vomitoria seem to reflect the existence of a fibrous matrix through which bundles radiate outwards from the micropyle.136 This structure would guide the sperm towards the opening of the micropyle.131,137 Obviously, fertilization in insects is a poorly explored field and as a consequence, sperm chemotaxis is still an open subject.
Ethnobotanical, phytochemical and therapeutic effects of Myrtus communis L. berries seeds on gastrointestinal tract diseases: a review
Published in Archives of Physiology and Biochemistry, 2018
Mohamed-Amine Jabri, Lamjed Marzouki, Hichem Sebai
The seeds are numerous with irregularities of shapes and sizes. They are reniform, shiny, ivory coloured, and resinous (Campbell 1968). It has an elaiosome in the centre and a thick coat. The elaiosome develops rapidly from the outer tegument cells near the funicular and micropylar zone, through cell divisions and enlargement. At the end of development, some internal integument cells contribute to its formation so that myrtle elaiosome can be classified among those originating from both epidermal and inner tissues (Ciccarelli et al.2005).
Assessment of gamma radiation through agro-morphological characters in camellia sinensis L. (O.) kuntze
Published in International Journal of Radiation Biology, 2023
Shobhit K. Singh, Devajit Borthakur, Abhijit Tamuly, J. G. Manjaya, Pradeep K. Patel, Boby Gogoi, Santanu Sabhapondit, Nabajyoti J. Neog, A. K. Barooah
Tea (Camellia sinensis L.) is a long duration, cross-pollinated, entomophilic, perennial cash crop, and most popular refreshing beverage. Tea green leaf is the raw material for all the varieties of tea and two leaves and a bud is a viable parts of the tea plant which are utilized for the making of good quality tea. It is a labor-intensive industry because the best leaf is best plucked by fingers. Since the beginning of the commercial cultivation of tea in Assam in 1937 tea was exclusively grown from seeds up to 1950. Thereafter, seeds were produced by a large number of tea estates by raising Assam, China, and Combo genotypes on a commercial scale. Botanically, it belongs to the family Theaceae and attracts a high volume of foreign cash to the country. Singh et al. (2015) reported that about 204 tea planting materials are available for commercial planting to date. Singh (1980) advocated that for producing high-quality tea with a high production rate it would be necessary to improve the existing tea varieties with the help of the non-conventional technique of breeding. Barman (2011) explained that tea seed is circular marble-like and surrounded by a dark brown or black hard shell. The seed population is a mixture of genetically diverse genotypes, they can adapt to a wide range of environmental conditions without much variation in their overall performance. Barua (2008) described that there is two way of planting: one, with the help of seed from seedbarie; and the other, by growing leaf cuttings from the mother bush. After collection of seeds from the seed barie, seeds are brought to a central shed and passed through a rotatory type sifter to eliminate the very small seeds. The mesh size used for the elimination of small seeds should not determine arbitrarily; it should correspond to the model seed size of the barie. After eliminating the very small seeds, the remaining seeds are transferred to a tank or a trough filled with water and allows soaking for 2-3 hours. The sinker seeds are taken out of the water and spread on a concrete floor, plastic sheet until the adhering water evaporates. The store seeds are again put through the sinker-floater test. Floaters are discarded and the sinkers are examined for the germination test. If the seed is stored well with a good level of moisture, the germination percentage of the tea seeds is 85 − 90 percent. The nursery technique for seed propagation of the tea plant is well defined by Barua (2008). Accordingly, two major things are important, the first is soil pH (pH 5.0) and the Second is good soil texture free from parasitic eelworms is satisfactory for nursery practices. Tea seeds are planted in rows as soon after harvest as possible to a depth of about 1.5 cm with the eye (micropyle) pointing downward or parallel to the ground surface. When sowing the seeds cover the seedbed with a thin layer of mulch and the seeds may get germinate within a month of planting. Pre-germinated seeds can also be used but the nature of the experiment is more suitable to get maximum advantage of radiated materials.