What are the evolutionary constraints on larval growth in a trophically transmitted parasite?

For organisms with a complex life cycle, a large larval size is generally beneficial, but it may come at the expense of prolonged development. Individuals that grow fast may avoid this tradeoff and switch habitats at both a larger size and younger age. A fast growth rate itself can be costly, however, as it requires greater resource intake. For parasites, fast larval growth is assumed to increase the likelihood of host death before transmission to the next host occurs. Using the tapeworm Schistocephalus solidus in its copepod first intermediate host, I investigated potential constraints in the parasite’s larval life history. Fast-growing parasites developed infectivity earlier, indicating there is no functional tradeoff between size and developmental time. There was significant growth variation among full-sib worm families, but fast-growing sibships were not characterized by lower host survival or more predation-risky host behavior. Parental investment also had little effect on larval growth rates. The commonly assumed constraints on larval growth and development were not observed in this system, so it remains unclear what prevents worms from exploiting their intermediate hosts more aggressively

Potential Role of Zeolite on Improvement of Aquaculture Sector”

Aquaculture, which is very important in many regions of the world, attracts attention as the fastest growing sector in the livestock sector in our country. The share of our country's aquaculture production in the production of total aquatic products is increasing day by day. According to TURKSTAT data, the total production of aquatic products in 2003 was 587,715 tons whereas the amount of aquaculture was 79,943 tons with 13.6 %. These amounts reached 672,241 tons in 2015 and 240.334 tons with a rate of 35.75 %. While the amount of crops obtained by cultivation increased every year, the increase rates decreased after 2007. One of the most important reasons for this is the issue of feed and feed raw materials and quality problems. Studies have been carried out to solve these problems and importance has been attached to additives that reduce cost and feed conversion ratio (FCR) to contribute to feed quality. In these materials, zeolites came to the forefront. Zeolites were first described as a mineral group in 1756 and crystal structures were resolved in the 1930s. After that, synthetic materials were started to be produced because it was thought that they were in small quantities in nature. There are about 150 zeolites, 40 of which are natural and the rest are synthetic. Due to the gap between 20 and 50 % in the structure, the molecules can be taken into the structures and they are named as molecular sieves. Because of these properties, various types of zeolites nowadays have been used in many fields such as paper, detergent, construction and health sectors and mining and metallurgy in addition to prevention of road icing, vegetation and animal production, storage of fruits and vegetables and transplantation, pollution control and aquaculture clinoptilolite and mordenite type have no side effects. Zeolites are used for purposes such as controlling the pollution in pools in the aquaculture sector, increasing the growth parameters of the fish by incubation, fish transport and removal of nitrogen compounds from aquarium water, increasing ambient oxygen in aquarium and fish transport, and as feed additive. In previous studies carried out in our country, rainbow trout rootstocks using clinoptilolite type zeolite in our country have not been able to accumulate in the tissues and have been found to be effective in development in tilapia and rainbow trout weighing 20 g have been found to be very effective both in terms of growth and growth parameters and body composition although they do not affect the growth rates used in rainbow trout rootstocks. According to the present situation, Japan is the first country in the world to produce zeolite. In Turkey, billions of tons of zeolite have been detected and clinoptilolite type zeolite is found mostly in the beds of Ankara-Polatlı-Mülk-Oğlakçı Region and Bigadiç, Şaphane, Gediz, Emet and Gördes Districts. We believe that the use of zeolites produced in our country as a local and natural product as feed additive substance in the aquaculture industry in the aquaculture sector will contribute to the production of lower cost fish as well as contribute to the development of 2 different sectors (aquaculture and mining) in interaction with each other

Growth and ontogeny of the tapeworm <it>Schistocephalus solidus</it> in its copepod first host affects performance in its stickleback second intermediate host

<p>Abstract</p> <p>Background</p> <p>For parasites with complex life cycles, size at transmission can impact performance in the next host, thereby coupling parasite phenotypes in the two consecutive hosts. However, a handful of studies with parasites, and numerous studies with free-living, complex-life-cycle animals, have found that larval size correlates poorly with fitness under particular conditions, implying that other traits, such as physiological or ontogenetic variation, may predict fitness more reliably. Using the tapeworm <it>Schistocephalus solidus</it>, we evaluated how parasite size, age, and ontogeny in the copepod first host interact to determine performance in the stickleback second host.</p> <p>Methods</p> <p>We raised infected copepods under two feeding treatments (to manipulate parasite growth), and then exposed fish to worms of two different ages (to manipulate parasite ontogeny). We assessed how growth and ontogeny in copepods affected three measures of fitness in fish: infection probability, growth rate, and energy storage.</p> <p>Results</p> <p>Our main, novel finding is that the increase in fitness (infection probability and growth in fish) with larval size and age observed in previous studies on <it>S. solidus</it> seems to be largely mediated by ontogenetic variation. Worms that developed rapidly (had a cercomer after 9 days in copepods) were able to infect fish at an earlier age, and they grew to larger sizes with larger energy reserves in fish. Infection probability in fish increased with larval size chiefly in young worms, when size and ontogeny are positively correlated, but not in older worms that had essentially completed their larval development in copepods.</p> <p>Conclusions</p> <p>Transmission to sticklebacks as a small, not-yet-fully developed larva has clear costs for <it>S. solidus</it>, but it remains unclear what prevents the evolution of faster growth and development in this species.</p