Parasites As Biological Tags In Population Studies Of Marine Organisms

Parasites have been used to identify and trace the migrations of different intraspecific populations of commercially important marine fish since 1939, Literature research shows how the numbers of publications involving this method of tagging has increased in every successive decade since then, reflecting increasing interest. More recently the same approach has been applied to population studies of marine invertebrates, such as squid and prawns and of marine mammals. The efficiency of the method improves as research adds to our knowledge of the biology of marine parasites, particularly their life cycles. This paper describes the general principles of using parasites as biological tags and highlights the advantages and disadvantages of the method. It offers guidelines to the selection of the most appropriate tags for the main tubes of population study ; stock discrimination, recruitment studies and seasonal migrations. It also gives a guide to the interpretation of results following analyses of the parasitological data. These results are often open to more than one interpretation; the correct one is arrived at by a process of elimination. Tow main approaches to the use of parasites as tags are recognised. In one, a small number of parasite species are selected according to established criteria and a large number of host individuals are examined specifically for these species. In the other, entire parasite assemblages are analysed using sophisticated statistical methods. Examples are given of each approach and of the use of parasite tags for each type of fish population study, together with examples of the use of parasites as tags in population studies of marine invertebrates and cetaceans

Parasites As Indicators Of Environmental Change And Pollution In Marine Ecosystems

Good biological indicators to monitor the effects of pollutants on marine organisms must be exceptionally sensitive to environmental change so that a significant reduction in their numbers can be used as a warning of deteriorating conditions before the majority of less sensitive organisms are seriously affected. There are good reasons for focusing on parasites in the search for such indicators. Firstly, there are more parasitic than free-living species and parasitic organisms show enormous biological diversity, reflecting adaptations to the parasitic way of life in different types of host and in diverse sites and environments. Secondly, in metazoan parasites with complex life cycles, the different developmental stages have widely differing biological requirements, so that each stage must be assessed separately, thereby greatly extending the number of potential indicators. Thirdly, many parasites have delicate short-lived free-living transmission stages which are highly sensitive to environmental change. They can therefore be adversely affected by even minor changes in the environment. A reduction in their transmission rate, and consequently in their levels of infection, will serve as an early warning that changes are occurring. Conversely, many ectoparasites are highly resistant to environmental change and will respond to such change by increased levels of infection. As a general rule, infections with endoparasitic helminths with complex indirect life cycles tend to decrease, while infections with ectoparasites with direct single-host life cycles tend to increase, with increasing levels of pollution. However, there are enormous variations in the responses of different parasite taxa to different pollutants

Prospectus, February 12, 2014

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Expanding the Flow Model in Adventure Activities: A Reversal Theory Perspective

This study integrated flow theory and reversal theory perspectives to investigate a potential range of flow states amongst adventure participants in a sequence of two studies. Study one was conducted with expert (n = 6) adventure participants via retrospective interviews, while study two collected prospective data from novice whitewater riversurfers (n = 10) via waterproof-surveys and head-mounted video cameras. These methods were used to evaluate previous conjectures that distinct \u27serious\u27 (telic) and \u27playful\u27 (paratelic) flow states may occur in adventure activities and to identify key characteristics which may underpin distinct flow states. Results highlighted qualitative differences amongst flow states, as well as suggesting that flow research in adventurous pursuits could benefit from the integration of reversal theory constructs

Prospectus, March 19, 2014

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Morphological features of the testis of freshwater blood flukes of the genus Sanguinicola Plehn, 1905, with consideration of the testicular patterns in the Aporocotylidae

This is the first detailed study assessing the morphological features of the testis and testicular sperm of members of the freshwater blood flukes Sanguinicola sp. from Leuciscus idus (Cyprinidae) and for S. volgensis from Pelecus cultratus (Cyprinidae), and the marine blood fluke Aporocotyle simplex from Hippoglossoides platessoides (Pleuronectidae). The present study reports a unique feature in the distribution of germinal cellular components in freshwater Sanguinicola sp., showing the presence of the individual spermatocytes or their clusters in the testicular lobes, and the gathering of spermatid rosettes and spermatozoa within middle testicular lumen, which extends along the entire length of the testis. In contrast, each testis of marine A. simplex contains the usual mixed distribution of germ cells at various stages of development. The first TEM data on spermatozoon character of studied species has shown, unusual for digenean sperm structure, the absence of cortical microtubules in sperm principal region. Moreover, a variation in axoneme patterns is revealed in the studied aporocotylids, belonging to the different aporocotylid lineages a 9 + 0 axonemal type observed for freshwater teleost-infective species, Sanguinicola sp. and S. volgensis, and a 9 + ‘1’ axonemal type revealed in spermatozoa of marine teleost-infective species A. simplex. The results discussed with the published data on the digenean sperm structure and the testicular patterns in the Aporocotylidae likely represent additional characteristics supporting the divergent evolutionary lineages of freshwater and marine aporocotylids. We anticipate future morphological studies of the sperm structure in aporocotylids of three lineages for an understanding of their phylogenetic relationships

Prospectus, April 23, 2014

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Prospectus, March 5, 2014

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