Medium-term dynamics of element concentrations in a sparid fish and its isopod parasite after the Prestige oil-spill: Shifting baselines?

The use of fish parasitic isopods as element accumulation indicators in marine pollution monitoring

Marine ecosystems are continuously under threat due to pollutants, which endanger marine biodiversity. The present study determines the potential use of the parasitic isopod, Cinusa tetrodontis Schjödte et Meinert, 1884, together with its fish host, Amblyrhynchotes honckenii (Bloch) for marine bioaccumulation monitoring. The concentrations of As, Cd, Cu, Mn, Ni, Pb, Se, and Zn were determined in muscle and liver tissues of infested and uninfested fish, and male and female parasites on the South African temperate south coast. The concentrations of Cu and Ni in C. tetrodontis differed significantly between two sampling sites, a near-pristine (Breede River Estuary, Witsand) and a more polluted site (harbour area in Mossel Bay). Mossel Bay isopods had higher concentrations of Ni, while Witsand isopods had higher concentrations of Cu. In contrast to fish hosts, parasitic isopods accumulated significantly higher levels of all elements except Cd. Most significant relationships between elements accumulated by C. tetrodontis and an increase of elements in fish tissues were seen in liver, rather than muscle tissue samples. Specimens of C. tetrodontis can be defined as good bioindicators for elements such as As, Cu, Mn, Ni, Pb, Se, and Zn, as they possess high bioaccumulation capabilities. This study addresses one of several future directions needed within environmental parasitology and highlights the importance of studying and utilising this host-ectoparasite model system.

Parasite communities in a marine fish indicate ecological recovery from the impacts of the Prestige oil-spill 12-13 years after the disaster

The Prestige oil-spill (2002) is one of the major marine accidents resulting in contamination of virtually all types of marine habitat along c.900 km of coastline in the North-East Atlantic. Environmental pollution affects parasite populations and communities, both directly and through effects on intermediate and definitive hosts. However, the effects of oil-spills on shelf benthic communities are poorly known. This study addressed the hypothesis of recovery of parasite communities in a marine sparid teleost, the bogue Boops boops (L.) (Teleostei: Sparidae), as indicators of environmental pollution and its effects on benthic/pelagic invertebrate communities in an impacted area off the Galician coast, Spain, 12-13 years after the Prestige oil-spill. Novel data for the metazoan parasite communities collected during 2014-2015 were analysed in association with two unique datasets, one comprising baseline data collected in 2001, one year before the Prestige oil-spill, and one comprising data collected 3-4 years post-spill (2005-2006). Using the taxonomically consistent data on parasites in a series of fish seasonal samples, we found significant differences between the two seasonal post-spill datasets taken at a 9-year time interval (3-4 years and 12-13 years post-spill) in most community metrics and infection parameters of the common species. This was in sharp contrast with the few differences between the long-term post-spill dataset of 2014-2015 and the pre-spill dataset of 2001. Multivariate community similarity analyses confirmed that these differences reflected in the substantial differentiation of parasite community composition and structure of the post-spill communities and the significant homogenisation of communities sampled 12-13 years post-spill and baseline communities. Overall, the novel analyses demonstrated a long-term directional trend in parasite community succession towards ecological recovery irrespective of the natural seasonal variability. These findings suggest longer-term oil-spill impacts on shelf benthic/pelagic invertebrate communities lasting over 10 years.

Metal accumulation in ecto- and endoparasites from the anadromous fish, the Pontic shad (Alosa immaculata)

Among the parasitic taxa studied for their metal accumulation properties, especially Acanthocephala and Cestoda proved to be promising sentinels for metal pollution. However, studies on metal accumulation are still sparse for other parasite groups, mainly due to their small body size. In the present study, we collected the relatively large-sized monogenean Mazocraes alosae Hermann, 1782 from the gills of Pontic Shad (Alosa immaculata Bennet 1835) from its spawning region – the Danube River. The host tissues gills, muscle, intestine and liver, the monogeneans as well as the nematode Hysterothylacium aduncum (Rudolphi, 1802), in the cases of coinfected fish, were analysed for the elements As, Cd, Co, Cu, Fe, Mn, Pb, Se and Zn. All elements (except of As) were found in higher concentrations in monogeneans and nematodes compared to host muscle tissue. High bioconcentration factors were obtained for toxic elements such as Cd and Pb with concentrations being approximately 12 and 251 times higher in monogeneans and 773 and 33 in nematodes, respectively, as compared to host muscle tissue. In comparison to other host organs, however, some elements were found in similar or even lower concentrations in the parasites. Thus, monogeneans do not exhibit the high accumulation potential reported for other parasitic taxa. Physiological adaptations of the migratory host fish between freshwater and marine habitats with differences in uptake pathways and biological availability of elements can be discussed as a possible explanation for this divergent accumulation pattern.

Review of the global distribution and hosts of the economically important fish parasitic isopod genus Ceratothoa (Isopoda: Cymothoidae), including the description of Ceratothoa springbok n. sp. from South Africa

Fish parasites from the isopod family Cymothoidae have, in recent years, received increased global attention due to both their ecological and economic importance. This is particularly true for the buccal inhabiting genus Ceratothoa Dana, 1852, whose members have been implicated in negatively impacting the health of both farmed and wild-caught fishes. As research on this group increases, so does our understanding of their host specificity and distribution. The aims of this paper were thus to review the current distribution and host records of Ceratothoa and describe a new species, Ceratothoa springbok n. sp. from South Africa. Including the new species described here, there are currently 25 accepted Ceratothoa spp. known from eight of the 12 marine biogeographical realms of the world. The majority of Cymothoidae species are known to occur in the tropical realms, whereas our analyses show that the greatest diversity of Ceratothoa spp. can be found in temperate realms. These results indicate the possibility that Ceratothoa is more diverse in temperate regions. This review also highlights the low diversity of Ceratothoa from the oceans around both North and South America. Current records indicate that species of Ceratothoa parasitise 108 fish species in 76 genera and 41 families. Eleven Ceratothoa spp. demonstrate host specificity up to host genus or family level. Amongst the hosts, members of the Sparidae are parasitised by 13 species of Ceratothoa, making it the host family with the highest diversity of parasites from this genus. The new species, C. springbok n. sp., also parasitises a sparid and was found in the buccal cavity of the carpenter seabream, Argyrozona argyrozona. This new species, the largest of all recorded Ceratothoa (up to 65 mm) and amongst the largest of all Cymothoidae, is characterised by its truncate and ventrally folded frontal margin, pereonite 1 with medial indentations, the wide anterolateral margins of pereonite 1 with an inwardly produced point, and a well-developed carina on the basis of pereopod 7. A key to the southern African Ceratothoa is provided.