Based on previous molecular phylogenetic analyses, Bothriocestus n. gen. is erected to accommodate bothriocephalid tapeworms that have an elongate scolex, a well-developed apical disc, and a narrow neck region, parasitize freshwater fishes in the Holarctic, and were previously placed in the polyphyletic genus Bothriocephalus Rudolphi, 1808 (Cestoda: Bothriocephalidea). Bothriocestus claviceps (Goeze, 1782) n. comb., a parasite of eels (Anguilla spp.) in the Holarctic region, is designated as the type species. Another species of the new genus, Bothriocestus cuspidatus (Cooper, 1917) (syn. Bothriocephalus cuspidatusCooper, 1917) is redescribed from type and voucher specimens, and new material from the type host, the walleye, Sander vitreus (Mitchill, 1818) (Perciformes: Percidae), in Manitoba and Ontario (where the type locality is located) (Canada) and in New York state and Wisconsin. Bothriocestus cuspidatus of S. vitreus is characterized primarily by the possession of a narrow, long strobila (total length up to 18 cm) composed of distinctly craspedote, trapezoidal proglottids, with primary, secondary, and tertiary proglottids differing in size, and by an arrow-shaped (=cuspidatus) scolex that is distinctly broader than the first proglottids, widest near the base in lateral view and gradually becoming broader toward the anterior end in dorsoventral view. A "dwarf" form of B. cuspidatus (total length of 9-27 mm) from Johnny darter, Etheostoma nigrum Rafinesque, 1820, and tessellated darter, Etheostoma olmstedi Storer, 1842 (both Percidae: Etheostominae), is also characterized morphologically in the present paper.

• Keywords
• Canada, Fish, Intraspecific variability, Morphology, Percidae, Tapeworms, Taxonomy, USA,
• MeSH
• Cestoda * MeSH
• Cestode Infections * veterinary   parasitology   MeSH
• Phylogeny MeSH
• Fish Diseases * parasitology   MeSH
• Perches * parasitology   MeSH
• Perciformes * parasitology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Geographicals
• Ontario MeSH
• North America MeSH

The tapeworms of fishes (Chondrichthyes and Actinopterygii) account one-third (1670 from around 5000) of the total tapeworm (Platyhelminthes: Cestoda) species diversity. In total 1186 species from 9 orders occur as adults in elasmobranchs (sharks, rays and chimaeras), and 484 species from 8 orders mature in ray-finned fishes (referred to here as teleosts). Teleost tapeworms are dominated by freshwater species (78%), but only 3% of elasmobranch tapeworms are known from freshwater rays of South America and Asia (Borneo). In the last 2 decades, vast progress has been made in understanding species diversity, host associations and interrelationships among fish tapeworms. In total, 172 new species have been described since 2017 (149 from elasmobranchs and 23 from teleosts; invalidly described taxa are not included, especially those from the Oriental region). Molecular data, however, largely limited to a few molecular markers (mainly 28S rDNA, but also 18S and cox1), are available for about 40% of fish tapeworm species. They allowed us to significantly improve our understanding of their interrelationships, including proposals of a new, more natural classification at the higher-taxonomy level (orders and families) as well as at the lower-taxonomy level (genera). In this review, we summarize the main advances and provide perspectives for future research.

• Keywords
• DNA sequencing, Distribution, elasmobranchs, host associations, pathogens, phylogenetic relationships, ray-finned fish, species diversity, taxonomy,
• MeSH
• Cestoda * genetics   MeSH
• Cestode Infections * epidemiology   veterinary   MeSH
• Diphyllobothrium * MeSH
• Elasmobranchii * MeSH
• Phylogeny MeSH
• Fish Diseases * epidemiology   MeSH
• Fishes MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

Transmission electron microscopy (TEM) was used to study the ultrastructure of the uterus and egg morphology in the enigmatic bothriocephalidean tapeworm Tetracampos ciliotheca. The uterine wall, underlain by well-developed muscle bundles, consists of a syncytial epithelium which is characterized by the abundance of free ribosomes, mitochondria and cisternae of granular endoplasmic reticulum (GER). On the apical surface of the uterine epithelium, there is an abundant network of cytoplasmic microlamellae projecting into the uterine lumen. The lumen is filled with freely lying eggs which are located close to the uterine wall but do not contact with the microlamellae of the uterine epithelium. The developed eggs possess an oncosphere surrounded by four envelopes: (1) a thin egg shell; (2) an outer envelope; (3) a syncytial, ciliated inner envelope; and (4) the oncospheral membrane. The mature hexacanth is armed with three pairs of oncospheral hooks, as well as somatic and hook muscles and five types of cells (1) binucleated subtegumental cell, (2) somatic cells, (3) penetration gland cells, (4) nerve cells and (5) germinative cells. Considering the relative scarcity of descriptive and comparative studies on the ultrastructure of the uterus and egg morphology in the order Bothriocephalidea, we concluded that Tet. ciliotheca displays a unique type of egg development. Based on these results, we discuss plausible ideas relating to the function of these structures for consideration in future studies.

• Keywords
• Bothriocephalidea, Egg, Evolution, Oncosphere, TEM,
• MeSH
• Cestoda physiology   ultrastructure   MeSH
• Cestode Infections parasitology   veterinary   MeSH
• Larva ultrastructure   MeSH
• Fish Diseases parasitology   MeSH
• Ovum ultrastructure   MeSH
• Catfishes parasitology   MeSH
• Microscopy, Electron, Transmission MeSH
• Uterus ultrastructure   MeSH
• Animals MeSH
• Check Tag
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

The Asian fish tapeworm, Schyzocotyle acheilognathi (Yamaguti, 1934) (Cestoda: Bothriocephalidea), is an invasive parasite of freshwater fishes that have been reported from more than 200 freshwater fish worldwide. It was originally described from a small cyprinid, Acheilognathus rombeus, in Japan but then has spread, usually with carp, minnows or guppies, to all continents including isolated islands such as Hawaii, Puerto Rico, Cuba or Sri Lanka. In the present account, we report the first case of the infection of a native cichlid fish, Ptychochromis cf. inornatus (Perciformes: Cichlidae), endemic to Madagascar, with S. acheilognathi. The way of introduction of this parasite to the island, which is one of the world's biodiversity hotspots, is briefly discussed.

• Keywords
• Cestoda, Cichlidae, Invasive parasite, Madagascar, new geographical record,
• Publication type
• Journal Article MeSH

As part of a complex revision of proteocephalid cestodes parasitic in freshwater bony fishes of the Neotropical Region, the genus Chambriella Rego, Chubb & Pavanelli, 1999 is redefined based on detailed examination of type-specimens and newly collected material of both nominal species of the genus. This examination revealed that the type-species C. agostinhoi (Pavanelli & Santos, 1992) from Zungaro jahu (Ihering) (type-host) and Z. zungaro (Humboldt) is indistinguishable from Lenhataenia megacephala (Woodland, 1934) from Sorubimichthys planiceps (Spix & Agassiz) (all hosts Siluriformes: Pimelodidae), the type- and only species of the genus. New molecular data (partial sequences of the large subunit nuclear ribosomal RNA gene) support the conspecificity of these taxa. As a result, Lenhataenia de Chambrier & Scholz, 2008 becomes a junior synonym of Chambriella and its type-species, C. agostinhoi, a junior synonym of C. megacephala (Woodland, 1934) n. comb. The second species of Chambriella, C. paranaensis (Pavanelli & Rego, 1989) from Hemisorubim platyrhynchos (Valenciennes), is transferred to a new genus, Riggenbachiella n. g., as R. paranaense (Pavanelli & Rego, 1989) n. comb. Riggenbachiella amazonense n. sp. (syn. Chambriella sp. of de Chambrier & Scholz, 2008) from S. planiceps (type-host), Phractocephalus hemioliopterus (Bloch & Schneider) and Z. zungaro is described and designated as the type-species of the new genus. Riggenbachiella n. g. is placed in the subfamily Monticelliinae Mola, 1929, because of the cortical position of the testes, ovary, vitelline follicles and uterus, and is mainly characterised by the possession of a sigmoid cirrus-sac with voluminous, chambered internal seminal vesicle, and bi-loculate suckers.

• MeSH
• Cestoda anatomy & histology   classification   genetics   MeSH
• DNA, Helminth genetics   MeSH
• Species Specificity MeSH
• Rivers MeSH
• Intestines parasitology   MeSH
• Catfishes parasitology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Brazil MeSH
• Names of Substances
• DNA, Helminth MeSH

An exhaustive literature search supplemented by a critical examination of records made it possible to present an annotated checklist of tapeworms (Cestoda) that, as adults or larvae (metacestodes), parasitize freshwater, brackish water and marine fishes, i.e. cartilaginous and bony fishes, in South America. The current knowledge of their species diversity, host associations and geographical distribution is reviewed. Taxonomic problems are discussed based on a critical evaluation of the literature and information on DNA sequences of individual taxa is provided to facilitate future taxonomic and phylogenetic studies. As expected, the current knowledge is quite uneven regarding the number of taxa and host-associations reported from the principal river basins and marine ecoregions. These differences may not only reflect the actual cestode richness but may also be due to the research effort that has been devoted to unravelling the diversity of these endoparasitic helminths in individual countries. A total of 297 valid species, 61 taxa identified to the generic level, in addition to unidentified cestodes, were recorded from 401 species of fish hosts. Among the recognized cestode orders, 13 have been recorded in South America, with the Onchoproteocephalidea displaying the highest species richness, representing c. 50% of all species diversity. The majority of records include teleost fish hosts (79%) that harbour larval and adult stages of cestodes, whereas stingrays (Myliobatiformes) exhibit the highest proportion of records (39%) among the elasmobranch hosts. Fish cestodes are ubiquitous in South America, being mostly recorded from the Warm Temperate Southeastern Pacific (WTSP; 31%) for marine hosts and the Amazon River basin (45%) for freshwater ones. The following problems were detected during the compilation of literary data: (i) unreliability of many records; (ii) poor taxonomic resolution, i.e. identification made only to the genus or even family level; (iii) doubtful host identification; and (iv) the absence of voucher specimens that would enable us to verify identification. It is thus strongly recommended to always deposit representative specimens in any type of studies, including faunal surveys and ecological studies. An analysis of the proportion of three basic types of studies, i.e. surveys, taxonomic and ecological papers, has shown a considerable increase of ecological studies over the last decade.

• Keywords
• Biodiversity, marine ecoregions, river basins, species richness, tapeworms,
• Publication type
• Journal Article MeSH