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Trematodes of the genus Alaria develop into an arrested stage, known as mesocercariae, within their amphibian second intermediate host. The mesocercariae are frequently transmitted to a non-obligate paratenic host before reaching a definitive host where further development and reproduction can occur. Snakes are common paratenic hosts for Alaria spp. with the mesocercariae often aggregating in the host's tail. In the current study, we used morphological examination and molecular analyses based on partial sequences of nuclear large ribosomal subunit gene and mitochondrial cytochrome C oxidase subunit 1 gene to identify larvae in the tails of red-sided garter snakes (Thamnophis sirtalis parietalis) as mesocercariae of Alaria marcianae, Alaria mustelae, and Alaria sp. as well as metacercariae of Diplostomidae sp. of unknown generic affiliation. We assessed infection prevalence, absolute and relative intensity, and associated pathological changes in these snakes. Infection prevalence was 100 % for both male and female snakes. Infection intensity ranged from 11 to more than 2000 mesocercariae per snake tail but did not differ between the sexes. Gross pathological changes included tail swelling while histopathological changes included mild inflammation and the presence of mucus-filled pseudocysts surrounding mesocercariae, as well as the compression and degeneration of muscle fibers. Our results indicate that mesocercariae can lead to extensive muscle damage and loss in both sexes which likely increases the fragility of the tail making it more prone to breakage. As tail loss in garter snakes can affect both survival and reproduction, infection by Alaria mesocercariae clearly has serious fitness implications for these snakes.

Effective parasite management can be achieved through strategically timed treatments that break the life cycle. We examined the effects of temperature (2 °C increments from 22 to 34 °C) and salinity (0, 11, 22, 35, 40‰) on the life cycle (embryonation period, hatching success, oncomiracidia (larvae) longevity, infection success, and time to sexual maturity) of Neobenedenia sp. (Monogenea: Capsalidae), a harmful ectoparasite of farmed marine fishes. Experiments were conducted in controlled conditions in the laboratory. The life cycle was faster in warm, high saline conditions compared to cooler conditions (10-13 days between 26-32 °C, 40‰; 15-16 days between 22-24 °C at 40‰). Warm seawater and high saline conditions (24-32 °C, 35-40‰) improved egg hatching success, reduced time to sexual maturity, and resulted in parasites reaching sexual maturity at a larger size (at 30-32 °C) compared to cooler conditions (22 °C). In contrast, cool, hypersaline conditions (22 °C, 40‰) increased oncomiracidia longevity and infection success. Linear and quantile regression models were used to construct an interactive, online parasite management interface to enable strategic treatment of parasites in aquaculture corresponding to observed temperature and salinity variation on farms in the tropics. It was recommended that farmers treat their stock more frequently during summer (27-31 °C) when parasites can complete their life cycle more quickly. Nevertheless, farmers should be aware of the potential for increased Neobenedenia sp. infections during winter months (21-26 °C) due to increased infection success.

Seasonal population dynamics of the monogenean, Diplozoon kashmirensis Kaw, on the gills of two cyprinid fish species, Schizothorax niger Heckel and Carassius carassius (Linnaeus), was investigated in three limnologically distinct trophic habitats located along the flood plain of River Jhelum in Kashmir from June 2006 to May 2008. The parasite infrapopulations exhibited a marked seasonal regime in infestation pattern as the infection indices increased to a much higher plateau during summer season at all the lakes, while the lows were recorded in winter. The heterogeneity in infection pattern indicates that water temperature is an important determinant of the seasonality of infrapopulations at all the localities. Furthermore, the results of our work clearly indicate that the parasite infrapopulations increased proportionally with eutrophication level and, as such, the highly eutrophic habitat, Anchar Lake, was significantly more favourable for parasite infrapopulations than the less eutrophic ones. However, the lakes presented no significant interlake differences in water temperature. Therefore, we could argue that interlake differences in the infestation pattern of parasite can be safely attributed to respective water quality in the lakes rather than water temperature. We propose that infrapopulations of the diplozoid studied herein do respond to differences in water quality of lakes and, thus, could qualify as simple and reliable indicator species in short-term comparative assays by lake managers.

A filtration-aided acid cleaning method was used to collect biosilica structures from a diatom culture medium, natural seawater, or water bloom. Cell extraction, acid cleaning, and acid removal were all performed on a polytetrafluoroethylene (PTFE) filter cloth, significantly improving the treatment capacity and efficiency of the traditional acid wash method. Five typical diatoms were cultivated in the laboratory for acid cleaning. Different growth speeds were introduced, and different process parameters for acid cleaning were utilized. After the acid cleaning, biosilica structures were collected from the frustules of diatoms using different methods. Girdle bands and valves of Coscinodiscus sp. were separated by floating of the valves. Central spines of Ditylum brightwellii and valves of Skeletonema costatum were separately collected by settling or filtration. Rod-like frustules, such as those of Bacillaris paradoxa, are not suitable for large quantities of acid wash. The silica structures were observed and tested using an AFM-calibrated glass needle to determine their elasticity. Elasticity tests showed that ringent girdle bands are more flexible than complete ones (Coscinodiscus sp.) and that both long-chain clusters of Nitzschia palea and central spines of D. brightwellii have certain elasticities. The required pressure for deforming or breaking the biosilica structures of diatoms was also determined.

Sparicotyle chrysophrii infections were highlighted during a parasitological monitoring carried out on cultured Gilthead sea bream Sparus aurata Linnaeus 1758 from aquaculture sites in Corsica. Factors and biological mechanisms regulating parasites populations, particularly controlling the infestation and survival of monogeneans have been studied. Variations in infection support the hypotheses that the main factor determining the infection of S. chrysophrii was temperature and that the parasite life cycle could be influenced by fish size and fish age. One hundred forty-nine of 280 S. aurata studied were infected. Seasonal differences in prevalence of infection were observed in all farms studied. A similar pattern was observed for parasite abundance with maximal infection levels occurring when water temperature were lower. A statistically significant dependence between infection and host size was also observed. The study of the surface topography of S. chrysophrii with scanning electron microscopy highlighted morphological adaptations not previously described. Parasites have developed diverse mechanisms of survival within the host that facilitate the establishment of infection. We mainly studied sensory structures and the anchoring systems of the parasite, i.e., filaments of eggs and haptor, enabling it to ensure the dispersal and survival of the species.

The anterior adhesive system of the oncomiracidium and adult of Merizocotyle icopae (Monogenea: Monocotylidae) were compared. The oncomiracidium has one ventrally placed aperture on either side of the head near the anterior extremity. In the adult, there are three ventrally placed apertures on either side of the head region. Both systems have three types of electron-dense secretory bodies opening into each aperture. A rod-shaped secretion (S1) and a small electron dense ovoid secretion (S2) are common to larvae and adults. The third secretion type differs: in adults, it is a large, spherical (S3) type but in larvae, it is an ovoid (S4) body. S4 bodies do occur in adults, but appear to be secreted as a general body secretion. An additional anteromedian secretion (S5) is also present in the oncomiracidium, but is not secreted into the anterior apertures. Homology and function of secretions are discussed.