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Two species of Acanthobothrium (Onchoproteocephalidea: Onchobothriidae) are described from the spiral intestine of Narcineentemedor Jordan & Starks, 1895, in Bahía de Acapulco, Acapulco, Guerrero, Mexico. Based on the four criteria used for the identification of species of Acanthobothrium , A.soniae sp. nov. is a Category 2 species (less than 15 mm in total length with less than 50 proglottids, less than 80 testes, and with the ovary asymmetrical in shape). Acanthobothriumvidali sp. nov. is a Category 6 species (more than 15 mm in total length with more than 50 proglottids, fewer than 80 testes, and the ovary is asymmetrical). The new species differ from similar species from the Pacific Ocean by total length, the number of proglottids, diameter of the accessory sucker, the length of the cirrus sac, the number of testes per proglottid and the measurements of hooks. With the recognition of A.soniae sp. nov. and A.vidali sp. nov. , 42 species of Acanthobothrium have been reported from the Pacific coast of the Americas. This is the first report of species of Acanthobothrium from a member of Narcine from Mexico and it brings the number of species reported from elasmobranchs from the Pacific Coast of Mexico to 13.

The Mediterranean Sea is recognized as a marine biodiversity hotspot. This enclosed basin is facing several anthropogenic-driven threats, such as seawater warming, pollution, overfishing, bycatch, intense maritime transport and invasion by alien species. The present review focuses on the diversity and ecology of specific marine trophically transmitted helminth endoparasites (TTHs) of the Mediterranean ecosystems, aiming to elucidate their potential effectiveness as ‘sentinels’ of anthropogenic disturbances in the marine environment. The chosen TTHs comprise cestodes and nematodes sharing complex life cycles, involving organisms from coastal and marine mid/upper-trophic levels as definitive hosts. Anthropogenic disturbances directly impacting the free-living stages of the parasites and their host population demographies can significantly alter the distribution, infection levels and intraspecific genetic variability of these TTHs. Estimating these parameters in TTHs can provide valuable information to assess the stability of marine trophic food webs. Changes in the distribution of particular TTHs species can also serve as indicators of sea temperature variations in the Mediterranean Sea, as well as the bioaccumulation of pollutants. The contribution of the chosen TTHs to monitor anthropogenic-driven changes in the Mediterranean Sea, using their measurable attributes at both spatial and temporal scales, is proposed.

In a parasitological survey of fishes from Moreton Bay (southeastern Queensland, Australia), 169 teleost fishes, representing 54 species from 28 families, were examined for larval cestodes. Of these 54 species, 36 were found to be infected by metacestodes. Metacestodes were characterised by morphological and molecular data (the D1-D3 region of the 28S rDNA gene); these data were analysed in parallel to inform larval type allocation. Metacestodes collected represented eight morphological types, seven previously reported (Types I, II, IV, V, VI, VII, and X) and one novel type (Type XVI). Phylogenetic analyses were conducted to genetically match larval types to adult cestodes. Six of the eight larval types found were matched to adult forms: Type I metacestodes matched species of Phoreiobothrium Linton, 1889 (Onchobothriidae); Type II metacestodes matched species of Acanthobothrium van Beneden, 1849 (Onchobothriidae); Type IV metacestodes matched species of Scyphophyllidium Woodland, 1927 and Alexandercestus Ruhnke & Workman, 2013 (Phyllobothriidae); Type VI metacestodes matched species of Anthobothrium van Beneden, 1850 (Tetraphyllidea incertae sedis); Type X metacestodes matched species of Ambitalveolus Caira & Jensen, 2022 (Tetraphyllidea incertae sedis); and Type XVI metacestodes matched species of Platybothrium Linton, 1890 (Onchobothriidae). Based on phylogenetic topology, Type V metacestodes are inferred to match Pedibothrium Linton, 1909 (Balanobothriidae) and Type VII metacestodes are inferred to match Spongiobothrium Linton, 1889 (Rhinebothriidae). These findings support and extend the unified morphological type system proposed previously, but suggest that morphological types will ultimately be informative to identify metacestodes to a group of related genera rather than any distinct genus.

Tapeworms of the genus Anindobothrium Marques, Brooks & Lasso, 2001 are found in both marine and Neotropical freshwater stingrays of the family Potamotrygonidae. The patterns of host association within the genus support the most recent hypothesis about the history of diversification of potamotrygonids, which suggests that the ancestor of freshwater lineages of the Potamotrygonidae colonized South American river systems through marine incursion events. Despite the relevance of the genus Anindobothrium to understand the history of colonization and diversification of potamotrygonids, no additional efforts were done to better investigate the phylogenetic relationship of this taxon with other lineages of cestodes since its erection. This study is a result of recent collecting efforts to sample members of the genus in marine and freshwater potamotrygonids that enabled the most extensive documentation of the fauna of Anindobothrium parasitizing species of Styracura de Carvalho, Loboda & da Silva, Potamotrygon schroederi Fernández-Yépez, P. orbignyi (Castelnau) and P. yepezi Castex & Castello from six different countries, representing the eastern Pacific Ocean, Caribbean Sea, and river basins in South America (Rio Negro, Orinoco, and Maracaibo). The newly collected material provided additional specimens for morphological studies and molecular samples for subsequent phylogenetic analyses that allowed us to address the phylogenetic position of Anindobothrium and provide molecular and morphological evidence to recognize two additional species for the genus. The taxonomic actions that followed our analyses included the proposition of a new family, Anindobothriidae fam. n., to accommodate the genus Anindobothrium in the order Rhinebothriidea Healy, Caira, Jensen, Webster & Littlewood, 2009 and the description of two new species-one from the eastern Pacific Ocean, A. carrioni sp. n., and the other from the Caribbean Sea, A. inexpectatum sp. n. In addition, we also present a redescription of the type species of the genus, A. anacolum (Brooks, 1977) Marques, Brooks & Lasso, 2001, and of A. lisae Marques, Brooks & Lasso, 2001. Finally, we discuss the paleogeographical events mostly linked with the diversification of the genus and the protocols adopted to uncover cryptic diversity in Anindobothrium.

This review brings together decades of work on elasmobranch tapeworms. The field has advanced significantly over the past 20 yr, with an emphasis on the discovery and description of novel taxa, and the establishment of phylogenetic frameworks for individual orders and their interrelationships. Tapeworms parasitizing elasmobranchs represent 9 orders and include 977 species and 201 genera—over 250 species and 50 genera are new within the last 2 decades. The 9 orders are treated individually, highlighting recent assessments of phylogenetic relationships informed by molecular sequence data. All but the “Tetraphyllidea” are monophyletic. Although much remains to be learned about their interrelationships, existing phylogenetic hypotheses suggest that elasmobranch tapeworms have played a key role in the evolution of the cestodes of essentially all other vertebrate groups. The apical organ is a defining feature (i.e., a synapomorphy) of a clade consisting of acetabulate taxa and Litobothriidea. Novel hook amino acid composition data support the independent origin of hooks in the various groups of hooked tapeworms. Cestode records exist for representatives of most of the major groups of elasmobranchs, however skates (Rajiformes) and catsharks (“Scyliorhinidae”) are particularly neglected in terms of species sampled. The majority of tapeworm species are extremely host-specific exhibiting species-specific (i.e., oioxenous) associations with their hosts. Rapid advancements in elasmobranch taxonomy, with over 300 of the 1,200 species appearing new in the past 20 yr, signal the need for careful attention to be paid to host identifications; such identifications are best documented using a combination of specimen, photographic, and molecular data. Above the species level, many cestode taxa are restricted to host orders, families, or even genera. Documentation of these affiliations allows robust predictions to be made regarding the cestode faunas of unexplored elasmobranchs. Trypanorhynchs are the notable exceptions. Life cycles remain poorly known. Recent applications of molecular methods to larval identifications have reinvigorated this area of research. Tapeworms are more diverse in elasmobranchs of tropical and subtropical waters, but they occur globally not only at the poles and in deep waters, but also in freshwaters of South America and Southeast Asia. The cestode faunas of batoids are much more speciose and complex than those of sharks. The faunas of deeper water sharks are particularly depauperate. The tapeworms of elasmobranchs and their hosts are now among the most well documented host-parasite systems in existence. This system has not yet reached its potential as a resource for investigations of basic ecological and evolutionary principles.

Invasive species can disrupt disease dynamics in new areas. Upon introduction, an invasive species in its new range may be colonised by novel parasites that normally infect native fauna. If the infected invasive host then helps to spread and boost the parasites to native hosts, this is known as spillback. Chinook salmon ( Oncorhynchus tshawytscha ) were released into rivers in southern Chile around 1924 and became invasive from 39°S to 53°S. Its anadromous migration and predatory behaviour involve multiple interactions with various native species. We examined the digestive tracts from 114 adult Chinook salmon returning from the sea to the estuary in the Toltén River, Chile to characterise their enteroparasite diversity, classify parasite developmental stages and assess Chinook’s potential as a definitive host for local, native parasites. We enumerated 12,277 larvae of parasitic individuals belonging to the genera Anisakis and Hysterothylacium (Nematoda), Nybelinia (Cestoda) and orders Pseudophyllidea, Tetraphyllidea and Trypanorhyncha (Cestoda). Amongst these, we also found adults — one immature female, four gravid females and eight males of the nematode Hysterothylacium sp., six adults of the trematodes Lecithaster sp. and one Lampritrema sp. Finding advanced and adult stages suggests chinook are a competent non-native host for Hysterothylacium , Lecithaster and Lampritrema , as well as a non-native host for larval stages of Nybelinia sp., Pseudophyllidea and Tetraphyllidea. Our study demonstrates the integration of native parasites into an invasive host along the coast of Chile. Namely, Chinook salmon are now acting as a novel host that is positioned as a new node in trophic interactions and host-parasite networks. Additionally, our study provides valuable baseline data for further research on the impact of these parasites on native species and ecosystem dynamics, including the extent to which spillback is occurring.

Two species of (Onchoproteocephalidea: Onchobothriidae) are described from the spiral intestine of Jordan & Starks, 1895, in Bahía de Acapulco, Acapulco, Guerrero, Mexico. Based on the four criteria used for the identification of species of , is a Category 2 species (less than 15 mm in total length with less than 50 proglottids, less than 80 testes, and with the ovary asymmetrical in shape). is a Category 6 species (more than 15 mm in total length with more than 50 proglottids, fewer than 80 testes, and the ovary is asymmetrical). The new species differ from similar species from the Pacific Ocean by total length, the number of proglottids, diameter of the accessory sucker, the length of the cirrus sac, the number of testes per proglottid and the measurements of hooks. With the recognition of and , 42 species of have been reported from the Pacific coast of the Americas. This is the first report of species of from a member of from Mexico and it brings the number of species reported from elasmobranchs from the Pacific Coast of Mexico to 13.

A total of 21 helminth species were recovered from 52 specimens of red snapper, Lutjanus campechanus, captured in the reef Santiaguillo, Parque Nacional Sistema Arrecifal Veracruzano, State of Veracruz, in the Southern Gulf of Mexico. These helminths included 9 trematodes (7 adults and 2 metacercariae), 4 nematodes (3 adults and 1 larva), 4 acanthocephalans (1 adult and 3 juvenile), 2 cestodes (both larvae), and 2 monogeneans. Sixteen of the 21 species are new host records; 7 are common species with a prevalence >40% and mean intensity >4.1. The monogenean Euryhaliotrema tubocirrus was the most-prevalent parasite with a prevalence of 78.8%, followed by the intestinal plerocercoids of Tetraphyllidea with a prevalence of 59.6%. The richness (S = 21), and diversity (Shannon index H = 2.17) in the component community, as well as in the infracommunity level (S = 5.1 ± 2.2, H = 0.92 ± 0.4), was similar to those found in other marine fish of temperate and tropical latitudes. The present study suggests that the composition of the parasite community is associated with the host feeding habits because 18/21 of the recorded species are trophically transmitted.

The lack of information on marine tapeworm life cycles can be addressed with knowledge derived from trophic interactions in marine environments. These trophically transmitted parasites exploit transmission routes involving predator–prey interactions. Porbeagle sharksLamna nasusare apex predators feeding on a wide range of organisms, including teleosts and cephalopods. Although the biology of this shark species is relatively well studied, there is a surprising lack of information about the trophic interactions involving this species that lead to the acquisition of tapeworms. Recently, the use of molecular tools, combined with phylogenetics, has proven useful in identifying trophic links involved in the transmission of marine tapeworms. In the present study, we used sequence data from the D2 domain of the large subunit ribosomal DNA to link adult tapeworms of the speciesClistobothriumcf.montaukensisandDinobothriumsp. parasitising porbeagle sharks to larvae recovered from the squidDoryteuthis gahi. To the best of our knowledge, it is the first to provide empirical evidence for a trophic link between porbeagle sharks andD. gahias a definitive route for the successful transmission of these tapeworms. Furthermore, our data suggest an ontogenetic shift in diet away from squid. Parasite abundance data inD. gahiindicate that the abundance of porbeagle sharks can be significant in some years.

Un total de 326 helmintos parásitos fueron recuperados de 94 especímenes de Halichoeres bivittatus (Pisces: Labridae) en dos sitios de la zona arrecifal en los límites del Parque Nacional Sistema Arrecifal Veracruzano, Veracruz, México, el suroeste del Golfo de México: Punta Gorda (n = 51) y Mata de Uva (n = 43). Los peces fueron capturados entre mayo y septiembre de 2001. Cada muestra se analizó a nivel de comunidad componente e infracomunidad. Tres especies de helmintos se localizaron en intestino: Nicolla halichoeri (Digenea) considerándose nuevo registro de localidad, Procamallanus (Spirocamallanus) garnotus (Nematoda) es nuevo registro de hospedero, y las larvas de Tetraphyllidea gen. sp. (Cestoda) fueron los parásitos con mayor prevalencia e intensidad promedio para cada sitio. La riqueza de especies para ambos sitios fue de S = 3 y el índice de diversidad de Shannon-Wiener (Punta Gorda, H´'= 0,42; Mata de Uva, H´'= 0,49) fueron inferiores a los registrados para las comunidades hospedero-parásito de lábridos y de hospederos de la localidad. No hubo correlación entre el número total de especies o el número total de helmintos con respecto a la longitud total o el peso del hospedero. El análisis de las curvas de especies acumuladas para la comunidad componente sugirió, que el inventario de especies de helmintos estaba casi completo para ambos sitios. La abundancia de larvas del céstodo ubica a H. bivittatus como hospedero intermediario del parásito.