Are different parasite guilds of Pagrus pagrus equally suitable sources of information on host zoogeography?

A new species of Colobomatus Hesse, 1873 (Copepoda: Philichthyidae) parasitic in the interorbital canals of the Caitipa mojarra Diapterus rhombeus (Cuvier, 1829) (Actinopterygii: Gerreidae) from Sepetiba Bay, southeastern Brazil

A new species of parasitic copepod, Colobomatus deborae n. sp., belonging to the cyclopoid family Philichthyidae Vogt, 1877, is proposed based on adult female specimens collected from the interorbital canals of the Caitipa mojarra Diapterus rhombeus (Cuvier) (Gerreidae) from Sepetiba Bay, off the State of Rio de Janeiro, southeastern Brazil. The new species closely resembles six species of Colobomatus Hesse, 1873, but differs from these close congeners based on the combination of the following characters: lateral cephalic processes forked basally with sharp tips, midventral cephalic process representing about one third of the length of the laterals, thoracic processes forked and caudal rami with a pair of unequal processes. Together with the new species described in the present study, the philichthyid fauna of Brazil rises to 10 species reported from 14 Brazilian marine fish species. This is also the third report of Colobomatus in a gerreid fish, but the first species found parasitizing the genus Diapterus.

A century of parasitology in fisheries and aquaculture

Fish parasitological research associated with fisheries and aquaculture has expanded remarkably over the past century. The application of parasites as biological tags has been one of the fields in which fish parasitology has generated new insight into fish migration and stock assessments worldwide. It is a well-established discipline whose methodological issues are regularly reviewed and updated. Therefore, no concepts or case-studies will be repeated here; instead, we summarize some of the main recent findings and achievements of this methodology. These include the extension of its use in hosts other than bony fishes; the improvements in the selection of parasite tags; the recognition of the host traits affecting the use of parasite tags; and the increasingly recognized need for integrative, multidisciplinary studies combining parasites with classical methods and modern techniques, such as otolith microchemistry and genetics. Archaeological evidence points to the existence of parasitic problems associated with aquaculture activities more than a thousand years ago. However, the main surge of research within aquaculture parasitology occurred with the impressive development of aquaculture over the past century. Protozoan and metazoan parasites, causing disease in domesticated fish in confined environments, have attracted the interest of parasitologists and, due to their economic importance, funding was made available for basic and applied research. This has resulted in a profusion of basic knowledge about parasite biology, physiology, parasite-host interactions, life cycles and biochemistry. Due to the need for effective control methods, various solutions targeting host-parasite interactions (immune responses and host finding), genetics and pharmacological aspects have been in focus.

Euryhaliotrema dolichodrilus n. sp. and Euryhaliotrema mimulus n. sp. (Monogenoidea: Dactylogyridae) infecting the gill lamellae of porgies, Calamus spp. (Perciformes: Sparidae) from the Gulf of Mexico off Florida, U.S.A

Two new species of Euryhaliotrema Kritsky & Boeger, 2002 (Monogenoidea: Dactylogyridae) were described from the gill lamellae of porgies, Calamus spp. (Perciformes, Sparidae), collected from the Gulf of Mexico off Florida: Euryhaliotrema dolichodrilus n. sp. from littlehead porgy Calamus proridens Jordan & Gilbert (type host), knobbed porgy Calamus nodosus Randall and Caldwell, grass porgy Calamus arctifrons Good & Bean, sheepshead porgy Calamus penna (Valenciennes), and jolthead porgy Calamus bajonado (Bloch & Schneider); and Euryhaliotrema mimulus n. sp. from jolthead porgy. The two new species along with Euryhaliotrema amydrum Kritsky & Bakenhaster, 2011, Euryhaliotrema carbuncularium Kritsky & Bakenhaster, 2011, Euryhaliotrema carbunculus (Hargis, 1955) Kritsky & Boeger, 2002, Euryhaliotrema luisae Cruces, Chero & Luque, 2018, Euryhaliotrema magnopharyngis Cruces, Chero & Luque, 2018, and Euryhaliotrema spirulum Kritsky & Bakenhaster, 2011 appeared to form a subgroup of species that developed secondarily within Euryhaliotrema.

Diversity, consistency, and seasonality in parasite assemblages of two sympatric marine fish Pagrus pagrus (Linnaeus, 1758) and Pagellus bogaraveo (Brünnich, 1768) (Perciformes: Sparidae) off the coast of Algeria in the western Mediterranean Sea

Various host characteristics (i. e., feeding habits, geographic distribution) and habitat characteristics (i.e., seasonality) influence the structure of parasite assemblages. To compare the parasite assemblages of hosts representatives of two genera of the same fish family, simultaneously occupying a geographic region, and to examine if seasonal variations influence parasite occurrence and abundance, we examined the parasite assemblages of two sympatric marine fish, Pagrus pagrus (n = 308) and Pagellus bogaraveo (n = 315) off the coast of Algeria in the western Mediterranean. Specimens were collected during summer and autumn over three consecutive years (2014-2016). Parasite assemblages were high in species richness and abundance. We compiled an inventory of 40 parasite taxa, including ectoparasitic monogeneans and crustaceans, and endoparasitic trematodes, cestodes, acanthocephalans, and nematodes. Endoparasite taxa primarily consisted of adult gastro-intestinal parasites and long lived larval helminths. Information on the parasite community structure and seasonal variations in parasite populations of these two hosts from the Mediterranean is here provided. Observed patterns of composition, diversity, dominance, and similarity indicate an overall consistency in assemblage structure. Although each host species harbored distinct parasite communities, they shared a high proportion of parasite species suggesting similar use of a common local pool of parasites. However, most shared species did not contribute to structuring the assemblages. Seasonal patterns in parasite abundance were observed for both hosts, with peak prevalence, abundance, and diversity in autumn. Results suggest that, regardless of a common pool of parasites being available to sympatric species, several ecological filters over time, led to distinct, independent variations in the parasite assemblages in each species.

Two new species of Colobomatus Hesse, 1873 (Crustacea: Philichthyidae) parasitic in the interorbital canals of Holocentrus spp. (Holocentriformes: Holocentridae) in the South Atlantic Ocean

Two new species of parasitic copepods of the genus Colobomatus Hesse, 1873 (Cyclopoida) are proposed based on specimens collected from the squirrelfishes (Holocentridae) off the coast of Rio de Janeiro, Brazil. Colobomatus luquei n. sp. from the interorbital canals of Holocentrus adscensionis (Osbeck) can be distinguished from its closest congeners by the following combination of characters in the adult female: first to fourth thoracic somites fused, two pairs of thoracic processes, fifth pedigerous somite without processes, and process in the third abdominal somite not transpassing the margins of the caudal rami; and in the adult male: antenna with two elements in the second endopodal segment, leg 1 with three spines and three setae in the second endopodal segment, and leg 2 with three spines and three setae in the second exopodal segment. Colobomatus freirei n. sp. from the interorbital canals of Holocentrus rufus (Walbaum) can be distinguished from its closest congeners through the possession of an anterior pair of thoracic processes four times longer than the posterior pair. The two new species described herein are the first representatives of the family Philichthyidae found to parasitize fish of the order Holocentriformes.

Discrimination of red porgy Pagrus pagrus (Sparidae) potential stocks in the south-western Atlantic by otolith shape analysis

Otolith shape analysis is a powerful method for fish stock identification. We compared the otolith shape of Pagrus pagrus (Linnaeus 1758) along with its distribution in four south-western Atlantic regions where it is commercially fished: Rio de Janeiro, Rio Grande do Sul in southern Brazil, the Argentine-Uruguayan Common Fishing Zone (UA) and the Argentinian Exclusive Fishing Zone (AR). Otolith shapes were compared by Elliptical Fourier and Wavelet coefficients among specimens in a size range with similar otoliths, morphometric parameters and ages. Four potential stocks were identified: one in the AR, a second along the UA which included specimens from southern Brazil with well-marked opaque bands in its otoliths (MRS), the third in southern Brazil with faint or absent opaque bands in its otoliths (FRS) and the fourth along Rio de Janeiro. The difference in the otolith shape among regions followed differences reported using other stock identification techniques. The similarity between otoliths from UA and MRS (ANOVA-like, P > 0.01) can be explained by seasonal short-range migrations. Otoliths shape differences between MRS and FRS (ANOVA-like, P < 0.01) suggest that P. pagrus does not form a homogeneous group in southern Brazil.

Distribution patterns of two species of Corynosoma (Acanthocephala: Polymorphidae) in fishes from Southwestern Atlantic

Corynosoma australe and C. cetaceum are the most frequently reported acanthocephalans in fish from the Argentine Sea, particularly in central and northern areas. Their definitive hosts are otariids and odontocete cetaceans, respectively. The low specificity of these larvae, in combination with high infective capability and long survival periods in fish, make them potentially good biological markers for stocks and other biological features of their fish hosts. In order to determine the distribution patterns of these species and their determining factors, a large dataset composed by newly collected fish samples, published and unpublished data from previous studies by the authors in the region were analysed in relation to host and environmental variables. The complete dataset comprised a total of 5084 fish, belonging to 29 species distributed in 21 families and 9 orders. Host size and trophic habits arose as the main determinants of abundance for both species of Corynosoma, showing higher abundances on larger fish and on higher trophic levels, as it is usual for trophically transmitted parasites. Biogeographic province and depth (indirectly representing the temperature of water) were the main drivers of the spatial distribution, displaying a latitudinal pattern associated to the temperature clines created by the interaction of Malvinas and Brazil currents, determining a decrease in abundance southwards and towards the deeper areas. No patterns were found regarding the distribution of definitive hosts. The knowledge of these distribution patterns of Corynosoma spp. in fish at regional scale, as well as of their causes, provides useful information to design management and conservation policies thus contributing to maintain the full and sustainable productivity of fisheries.