Schistocephalus solidus
Schistocephalus solidus | |
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Schistocephalus solidus with its host, the three-spined stickleback | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Platyhelminthes |
Class: | Cestoda |
Order: | Diphyllobothriidea |
Family: | Diphyllobothriidae |
Genus: | Schistocephalus |
Species: | S. solidus
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Binomial name | |
Schistocephalus solidus (Müller, 1776) Steenstrup, 1857
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Synonyms[1] | |
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Schistocephalus solidus is a
Life cycle
It parasitizes fish and fish-eating water birds. The fish-eating water bird is the
Ecology
Prevalence — the proportion of host population infected — in naturally infected populations of the first intermediate hosts is likely low.[5] Conversely, in populations where Schistocephalus solidus infects the second intermediate host (three-spined stickleback) it can reach high prevalence, up to 93% in both European and North American populations [6][7]
The growth of S. solidus in the second intermediate host is largely dependent upon the environmental temperatures. At an increase of temperature from 15 °C to 20 °C the growth of S. solidus can grow four times as fast. At the same time, the growth rate of the stickleback is significantly reduced.[8]
Reproduction
Reproduction of S. solidus in the definitive bird host in which it resides for a maximum of two weeks.
In Schistocephalus solidus inbreeding is indeed disadvantageous, as mating between siblings generally produce a 3.5 times reduction in hatching success of the eggs produced from these matings compared to mating with unrelated individuals.[2][10] Outcrossing also increases the chances of infecting the second intermediate host.[11] However, there is also a preference to pair with larger mates, and to avoid very small mates.[12] The later means that self-fertilisation can also occur when potential partners are available. Under some circumstances, there could exist a significant advantage for incestuous mating, despite inbreeding depression.[13] In species where there is low parental investment and sexual encounters are rare and sequential, incestuous breeding is indirectly beneficial. If the prospective mates are related there is an increase mutual interest in finding a resolution with respect to playing the unpreferred sexual role. With less time allotted to conflicting over sexual roles and dominating one another, procreation is more cost-effective. Under these conditions, the greater effectiveness of inbreeding prevails over the detriment of incestuous mating and evolutionarily select for a preference for related mates.[13]
Infectivity
Corracidia are more infective to male copepods than to female copepods.[14] This has been suggested to be due to the negative impacts sex hormones such as testosterone can have on the immune system.
Viruses
Schistocephalus solidus itself a parasite, can also get infected by parasites (known as hyperparasites), including viruses.[15] These viruses are likely to affect the evolution of the virulence and broader interactions of S. solidus with its hosts.[15][16]
Host manipulation
The Schistocephalus solidus parasite is capable of host manipulation in both intermediate hosts, the copepod and the three-spined stickleback.
First intermediate host
In the copepod host, it is able to suppress activity while uninfective to the stickleback host.[17] This reduces the likelihood of the copepod host being consumed and consequently unsuccessful transmission of the parasite.[18] Once the parasite becomes infective, after approximately two weeks, activity increases[17] and, as a consequence, the risk of consumption by three-spined sticklebacks increases.[19] However, when multiple, non-simultaneous infections by S. solidus occur, host manipulation is orchestrated by the first infecting parasite. This increases the risk of premature consumption of the subsequent infections by the fish host.[20] Consistent differences in manipulation are seen between parasite genotypes [21] and populations.[22] Differences in host genotypes are maintained after infections, but less pronounced.[21]
Second intermediate host
In the fish host, host manipulation induces more risk taking behaviour like positive
Model species
Schistocephalus solidus is effectively used a
in vitro breeding
The option to breed S. solidus in the laboratory
References
- ^ "Schistocephalus solidus". Global Biodiversity Information Facility.
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