Clonorchis sinensis, the Chinese liver fluke, is trophically transmitted Trophically-transmitted parasites are transmitted by being eaten by a host. They include trematodes (all except schistosomes), cestodes, acanthocephalans, pentastomids, many round worms, and many protozoa such as Toxoplasma. They have complex life-cycles involving hosts of two or more species. In their juvenile stages they infect and often encyst in the intermediate host.
|
|
When the intermediate-host animal is eaten by a predator, the definitive host, the parasite survives the digestion process and matures into an adult; some live as intestinal parasites. Many trophically-transmitted parasites modify the behaviour of their intermediate hosts, increasing their chances of being eaten by a predator. As with directly-transmitted parasites, the distribution of trophically transmitted parasites among host individuals is aggregated. Coinfection by multiple parasites is common.
|
|
Euhaplorchis californiensis is a trophically transmitted parasite (TTP) that lives in the salt-water marshes of Southern California. It lives in three hosts: shorebirds, horn snails, and killifish. As with many TTPs, E. californiensis modifies the behavior of the host to increase the likelihood of transmission to its next host.
|
|
Robert A. Heinlein's behaviour- altering The Puppet Masters on the cover of the September 1951 issue of Galaxy Science Fiction Several types of parasite, corresponding more or less accurately to some of those known in biology, are found in literature. These include haematophagic parasites (fictional vampires), parasitoids, behaviour- altering parasites, brood parasites, parasitic castrators, and trophically transmitted parasites, as detailed below.
|
|
An ecological community is a group of trophically similar, sympatric species that actually or potentially compete in a local area for the same or similar resources. Interactions between these species form the first steps in analyzing more complex dynamics of ecosystems. These interactions shape the distribution and dynamics of species. Of these interactions, predation is one of the most widespread population activities.
|
|
Rossman, S., Ostrom, P.H., Stolen, M., Barros, N.B., Gandhi, H., Stricker, C.A. and Wells, R.S., 2015. Individual specialization in the foraging habits of female bottlenose dolphins living in a trophically diverse and habitat rich estuary. Oecologia, 178(2), pp.415-425. Benefits of group living on defence from predators is very evident in nature, however in locations of high resource competition poses an effect on the mortality of certain individuals.
|
|
These other theropods, however, were recovered in sediments that were Oxfordian in age. This rich paleofauna also included pterosaurs like Sericipterus, ornithischians like Jiangjunosaurus and Yinlong and the sauropods Bellusaurus, Klamelisaurus, Tienshanosaurus and Mamenchisaurus. Aorun was probably a predator of small lizards and mammals. Aorun is the seventh thropod, and oldest coelurosaur known from the Shishugou Formation, which is considered one of the most phylogenetically and trophically diverse middle to late Jurassic theropod faunas.
|
|
For complex life cycles to emerge in parasites, the addition of intermediate host species must be beneficial, e.g., result in a higher fitness. It is probable that most parasites with complex life cycles evolved from simple life cycles. The transfer from simple to complex life cycles has been analyzed theoretically, and it has been shown that trophically transmitted parasites can be favored by the addition of an intermediate prey host if the population density of the intermediate host is higher than that of the definitive host.
|
|
Parasite aggregation with respect to hosts is, according to Robert Poulin "a defining feature of metazoan parasite populations." The main reason for this is probably either that some hosts are more exposed to parasites, or that they are more susceptible to them. Aggregation is seen in directly transmitted parasites (those not using a vector) from many groups: ectoparasites like lice and mites, marine parasites like copepods and cyamid amphipods, and many kinds of nematode, fungi, protozoa, bacteria, and viruses. It is widespread, too, in trophically transmitted parasites of animals.
|
|
The unified neutral theory of biodiversity and biogeography (here "Unified Theory" or "UNTB") is a theory and the title of a monograph by ecologist Stephen Hubbell. The hypothesis aims to explain the diversity and relative abundance of species in ecological communities. Like other neutral theories of ecology, Hubbell assumes that the differences between members of an ecological community of trophically similar species are "neutral", or irrelevant to their success. This implies that niche differences do not influence abundance and the abundance of each species follows a random walk.
|
|
Unified neutral theory is a hypothesis proposed by Stephen Hubbell in 2001. The hypothesis aims to explain the diversity and relative abundance of species in ecological communities, although like other neutral theories in ecology, Hubbell's hypothesis assumes that the differences between members of an ecological community of trophically similar species are "neutral," or irrelevant to their success. Neutrality means that at a given trophic level in a food web, species are equivalent in birth rates, death rates, dispersal rates and speciation rates, when measured on a per-capita basis. This implies that biodiversity arises at random, as each species follows a random walk.
|
|
Kellet's whelk has been observed feeding together at the same time with the Giant sea star Pisaster giganteus on common food items and thus these two species are trophically interrelated. Pisaster giganteus also preys on Kelletia kelletii more often than any other motile gastropod, and yet the whelks do not appear to be eaten in proportion to their abundance or accessibility in studied localitions. The sea star appears to be a major predator of the whelk, even though Kelletia kelletii makes up less than 10% of the diet of the sea star. The whelk does not display an avoidance response in the presence of Pisaster giganteus.
|
|
General characteristics of a large marine ecosystem (Gulf of Alaska) Large marine ecosystems (LMEs) are regions of the world's oceans, encompassing coastal areas from river basins and estuaries to the seaward boundaries of continental shelves and the outer margins of the major ocean current systems. They are relatively large regions on the order of 200,000 km² or greater, characterized by distinct bathymetry, hydrography, productivity, and trophically dependent populations. Productivity in LME protected areas is generally higher than in the open ocean. The system of LMEs has been developed by the US National Oceanic and Atmospheric Administration (NOAA) to identify areas of the oceans for conservation purposes.
|
|
An ecological community is a group of trophically similar, sympatric species that actually or potentially compete in a local area for the same or similar resources. Under the Unified Theory, complex ecological interactions are permitted among individuals of an ecological community (such as competition and cooperation), provided that all individuals obey the same rules. Asymmetric phenomena such as parasitism and predation are ruled out by the terms of reference; but cooperative strategies such as swarming, and negative interaction such as competing for limited food or light are allowed (so long as all individuals behave in the same way). The Unified Theory also makes predictions that have profound implications for the management of biodiversity, especially the management of rare species.
|
|
This parasitic method is known as the "cuckoo" strategy and is an alternative to the predatory strategy employed by most other members of the genus such as Phengaris arion. Though less common, the cuckoo strategy has been found to have several advantages over the predatory strategy. For one, it is more trophically efficient than preying directly on other ant grubs, and as a result, significantly more cuckoo-type larvae can be supported per nest than predatory larvae. Another advantage of cuckoo feeding is that individuals, having pursued a higher degree of social integration, have a higher chance of surviving when a nest is overcrowded or facing food shortage because ants preferentially feed the larvae; compared to the type of scramble competition that can devastate predatory larvae, this contest competition results in much lower mortality.
|
|
The Bryozoa (moss animals) colonies, both encrusted and erected, such as the molluscs Arca noae (Noah's Ark shells), Mimachlamys varia (a genus of scallops) and queen scallops (Aequipecten opercularis), are very dense and are often epibiont (live on the surface of another organisms). Among the many molluscs there are the sea snails Diodora graeca (Greek keyhole limpet) Diodora italica (Italian keyhole limpet) and Bolma rugosa. There are numerous species of nudibranchs (soft- bodied, marine gastropod molluscs), which are often tied trophically to a sole species of sponges or hydrozoa (very small, predatory animals), as well as the big bivalvia such as fan mussels (Pinna nobilis) and pen shells (Atrina pectinata), which are still common in the inner or proximal areas of the mobile substrates. There are many species of Tunicates among which there are the big and colourful colonies of Aplidium conicum, the camouflaged Microcosmus vulgaris, Ascidia mentula, Polycitor adriaticus and the small ascidiacea (sea squirts filter feeders) of the Didemnum genus.
|
|
Although not strictly necessary for a neutral theory, many stochastic models of biodiversity assume a fixed, finite community size (total number of individual organisms). There are unavoidable physical constraints on the total number of individuals that can be packed into a given space (although space per se isn't necessarily a resource, it is often a useful surrogate variable for a limiting resource that is distributed over the landscape; examples would include sunlight or hosts, in the case of parasites). If a wide range of species are considered (say, giant sequoia trees and duckweed, two species that have very different saturation densities), then the assumption of constant community size might not be very good, because density would be higher if the smaller species were monodominant. However, because the Unified Theory refers only to communities of trophically similar, competing species, it is unlikely that population density will vary too widely from one place to another.
|
|