Nematode Parasites of Vertebrates: Their Development and Transmission

A list of myxozoan genera is presented in the current taxonomical scheme. These genera are defined; their type species and most important pathogens along with their hosts are listed. Simultaneously, definitions of actinospore stages representing sexual stages of the myxosporean life cycle are given; altogether, 17 actinospore collective groups with 180 types have been described. Life cycles of the two classes of the phylum Myxozoa, Malacosporea and Myxosporea, are briefly outlined with specification of the appropriate terms. Up to now, 4 malacosporean and 2,180 myxosporean species assigned to a total of 62 genera, have been established. The surviving classification of myxosporeans, based on spore morphology, is discussed in the context of the still fragmentary data resulting from SSU rDNA sequence analyses. The main task for the future is a rigorous, detailed morphological description combined with molecular techniques in establishment of new species and in revision of the existing ones. Establishment of a classification acceptable from morphological, biological and phylogenetical viewpoints is necessary.

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Myxozoan genera: definition and notes on taxonomy, life-cycle terminology and pathogenic species.

A critical link missing from our understanding of the nursery role of specific marine habitats is the evidence of connectivity between juvenile and adult habitats. This paper reviews and evaluates evidence of, and spatial scales for, movements from juvenile to adult habitats and it sum- marises the methods used to study movements. Examples include many fish families but few inverte- brate taxa, and most are species of economic importance for USA and Australia. The types of juvenile habitat range from the entire estuary or shallow open coastal waters to specific habitats within estu- aries or coastal waters; in some cases juvenile habitats include habitats not traditionally regarded as nursery areas (e.g. the surf zone). The duration of time spent in juvenile habitats averages 13 mo (range 8 d to 5 yr). The majority of organisms move distances of kilometres to hundreds of kilometres from juvenile to adult habitats, although the scale of movements ranged from metres to thousands of kilometres. Changes in abundance among separate habitats and the progression of size classes among separate habitats are the main methods used to infer movement and habitat connectivity. Spa- tial partitioning of stages of maturity, natural parasites, and a variety of artificial tagging methods have also been used. The latter will become more useful with continued developments in the minia- turisation of artificial tags. More recent studies have used natural tags (e.g. trace elements and stable isotopes) and these methods show great promise for determining movements from juvenile to adult habitats. Few studies provide good evidence for movement from specific juvenile habitats to adult habitats. Future studies need to focus on this movement to supplement data on density, growth and survival of organisms in putative nursery habitats. Such information will allow management and con- servation efforts to focus on those habitats that make the greatest contribution to adult populations.

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Evidence of connectivity between juvenile and adult habitats for mobile marine fauna : an important component of nurseries

https://www.esf.edu/efb/mitchell/Marcogliese2005-Parasites_of_the_superorganism.pdf

Parasites of the superorganism: Are they indicators of ecosystem health?

The application of molecular systematics to the anisakid nematodes of the genera Anisakis, Pseudoterranova and Contracaecum, parasites of aquatic organisms, over the last two decades, has advanced the understanding of their systematics, taxonomy, ecology and phylogeny substantially Here the results of this effort on this group of species from the early genetic works to the current status of their revised taxonomy, ecology and evolutionary aspects are reviewed for each of three parasitic groups It has been shown that many anisakid morphospecies of Anisakis, Contracaecum and Pseudoterranova include a certain number of sibling species Molecular genetic markers provided a rapid, precise means to screen and identify several species that serve as definitive and intermediate and or/paratenic hosts of the so far genetically characterized species Patterns of differential distribution of anisakid nematodes in various definitive and intermediate hosts are presented Differences in the life history of related species can be due both to differential host-parasite co-adaptation and co-evolution, and/or to interspecific competition, that can reduce the range of potential hosts in sympatric conditions Phylogenetic hypotheses attempted for anisakid nematodes and the possible evolutionary scenarios that have been proposed inferred from molecular data, also with respect to the phylogeny of their hosts are presented for the parasite-host associations Anisakis-cetaceans and Contracaecum-pinnipeds, showing that codivergence and host-switching events could have accompanied the evolution of these groups of parasites Finally, examples in which anisakid nematodes recognized genetically at the species level in definitive and intermediate/paratenic hosts from various geographical areas of the Boreal and Austral regions and their infection levels have been used as biological indicators of fish stocks and food-web integrity in areas at high versus low levels of habitat disturbance (pollution, overfishing, by-catch) are presented

Advances and trends in the molecular systematics of anisakid nematodes, with implications for their evolutionary ecology and host-parasite co-evolutionary processes.

Parasites as biological tags for stock discrimination of marine fish: a guide to procedures and methods

Parasites as Pollution Indicators in Marine Ecosystems: a Proposed Early Warning System

This chapter provides a guide for parasitologists and fishery biologists to the use of parasites as biological tags for stock identification of marine fish. Parasite tags have certain advantages over other methods of stock identification, but they also have their limitations, so we strongly recommend an interdisciplinary approach in which the results from different methods are compared and used to complement one another. Some biological features to consider in the selection of a good tag parasite are described here, but these should be regarded as guidelines rather than strict criteria. Two different approaches to the use of parasites as biological tags are described, one in which a large number of fish are examined for a small number of parasite taxa and the other in which entire parasite assemblages are analyzed using multivariate statistical methods. Example case studies are given, which are representative of the two approaches. The statistical methods applied to parasite infection data tag studies are described and discussed, with references to studies in which they have been used. Recommendations are given for the collection of hosts and parasites to ensure that parasites are collected in the best possible condition, and methods for the preparation of parasites for examination are described. Parasite groups requiring special attention in their collection and preparation are highlighted, and publications giving identification keys to different taxonomic groups of parasites are provided. There is also a section dealing with the interpretation of results in terms of stock identification.

Parasites as Biological Tags

Phylogenetic analysis of Gyrodactylus salaris Malmberg, 1957 based on the small subunit (18S) ribosomal RNA gene.

This paper is the first to address the suitability and potential of the cytochrome oxidase-1 (CO1) region of the parasitic marine nematode Anisakis simplex sensu stricto as a genetic marker. A. simplex s.s. is an ubiquitous parasite of many marine organisms and has been used as a ‘biological tag’ for population studies of pelagic fish stocks. The CO1 marker informs not only about nematode population structure but also about its hosts. The large CO1 sub-unit (∼800 bp) was analysed from third stage larvae of A. simplex s.s. from Atlantic herring, Clupea harengus L. caught off the north-west coast of Scotland. In total 161 A. simplex s.s.
CO1 sequences were analysed from 37 herring that represented three spawning periods over 2 years. Overall very high haplotype and low nucleotide diversities were observed (h = 0.997 and π = 0.008, respectively). These results are in keeping with studies investigating parasitic nematodes of ungulates and are symptomatic of the high rate of substitutions accumulated by mtDNA and effective dispersal strategies of the parasite. The Tamura-Nei I + Г (Г = 1.2243) model of nucleotide substitution best suited the present data which were dominated by a high thymine bias and associated transitions. Large within population differences were highlighted by hierarchal AMOVAs with little variation related to spawning events or years which may indicate localised temporal stability. Temporal homogeneity in the CO1 gene coupled with the ubiquitous and widespread nature of the parasite indicates both the potential and limitations for its incorporation in stock-separation studies of its hosts.

Levels of intra-host and temporal sequence variation in a large CO1 sub-units from Anisakis simplex sensu stricto (Rudolphi 1809) (Nematoda: Anisakisdae): implications for fisheries management

Ken MacKenzie

Papers

Parasites as biological tags for stock discrimination of marine fish: a guide to procedures and methods

Parasites as Pollution Indicators in Marine Ecosystems: a Proposed Early Warning System

Parasites as Biological Tags

Phylogenetic analysis of Gyrodactylus salaris Malmberg, 1957 based on the small subunit (18S) ribosomal RNA gene.

Levels of intra-host and temporal sequence variation in a large CO1 sub-units from Anisakis simplex sensu stricto (Rudolphi 1809) (Nematoda: Anisakisdae): implications for fisheries management