Tomáš Scholz

The species diversity of reptile parasites in the New World, including South America, remains poorly understood, and this also applies to tapeworms (Cestoda: Onchoproteocephalidea). Only 17 species of the non-monophyletic genus Ophiotaenia La ...

Caryophyllidean tapeworms (Cestoda) are widespread parasites of suckers (Catostomidae) in North America, but their phylogenetic relationships remain poorly understood. This study presents molecular data on species of the recently established genus Pseudoglaridacris Oros, Uhrovič et Scholz, 2018. The type species, P. laruei (Lamont 1921), a very common parasite of the white sucker Catostomus commersonii (Catostomidae) in North America, is characterised both molecularly and morphologically based on recently collected, properly fixed specimens from the type host (C. commersonii) and four species of redhorse (Moxostoma spp.), including new host and geographical records from Canada and the United States. Pseudoglaridacris laruei differs from other species in the genus by its size, being the largest species (body length up to 12.7 mm), a high number of testes (62–119) and very few (0–6) postovarian vitelline follicles. Mackiewiczus etowanum from Hypentelium etowanum and Mackiewiczus rarus from Moxostoma poecilurum in Alabama are nomina nuda. The taxonomic status of P. confusa (Hunter 1929), which occurs in ictiobines, and of P. oligorchis (Haderlie 1953), which is most probably a junior synonym of P. laruei with a reduced number of testes, is also discussed, based on molecular data indicating the presence of a putative new species from ictiobines that has not yet been described.

Tapeworms of the order Caryophyllidea (Cestoda) are widespread parasites of cypriniform and siluriform fishes. Most species occur in suckers (Catostomidae) in the Nearctic, including 4 species of the enigmatic genus Archigetes Leuckart, 1878. Species of this genus can mature in oligochaetes, i.e., may have a monoxenous (direct) life cycle. In this article, Archigetes notemigoni n. sp. is described from the golden shiner Notemigonus crysoleucas (Mitchill, 1814) (Leuciscidae) in Wisconsin. The new species differs from other Archigetes species in having a small (≤2 mm long), spindle-shaped body with the maximum width at the middle, tapering toward the scolex and posterior end, and a small scolex wider than the neck, with a pair of narrow, deep median loculi on the dorsal and ventral sides and 2 pairs of lateral, very shallow loculi. Phylogenetic analyses suggest that A. notemigoni is closely related to Archigetes sieboldi Leuckart, 1878 and Archigetes vadosus Uhrovič, Oros, Kudlai, Kuchta, & Scholz, 2022. In addition, Hypocaryophyllaeus gilae Fischthal, 1953 from the Utah chub Gila atraria (Girard, 1856) in Wyoming and Biacetabulum oregoni Williams, 1978 from the largescale sucker Catostomus macrocheilus Girard, 1856 in Oregon are placed as new combinations in Archigetes because their morphology, such as the shape of the small body (usually <5 mm in total length), bulboloculate scolex, distribution of vitelline follicles, and shape of the ovary, corresponds to that of Archigetes species. In total, the Nearctic fauna of Archigetes now comprises 7 species: 4 from minnows (Leuciscidae) and 3 from suckers (Catostomidae). In addition, there are 2 undescribed Archigetes morphotypes from Notropis spp. (Leuciscidae) in northern Mexico.

Dicyemids (phylum Dicyemida), primarily found in the renal organs of coleoid cephalopods, are a unique group of morphologically simple parasites with global distribution. Here, we investigated the diversity and prevalence of dicyemid communities in a wide range of cephalopod hosts across four geographic zones (the North East Atlantic, Mediterranean Sea, China Sea in the Western North Pacific, and Australia in the South Pacific) using Illumina sequencing of the 18S rDNA amplicons. Across 227 host samples, we identified 482 amplicon sequence variants, which clustered into 95 genetic types. The results indicated a higher number of distinct genetic types within Dicyemida than those currently identified through morphology-based taxonomy. Our finding of 46 dicyemid types in the common cuttlefish ( Sepia officinalis ) contrasts sharply with the previous records of a maximum of four species in this host. Furthermore, only a few host species exhibited a single dicyemid type, while most harbored multiple types; several types were distributed worldwide. Additionally, we identified eight new cephalopod hosts in the Pacific. Analyses of community (α) diversity suggested the unique character of certain geographical areas, such as the Bass Strait (Australia). β-diversity analyses confirmed that geographic location and host species were significant determinants of the dicyemid community composition. These results suggest that current species classifications may underestimate the true diversity of dicyemids. They emphasize the intricate interplay between geography, host specificity, and dicyemid community diversity.

Tapeworms (Cestoda) are a diverse group of parasitic flatworms that are highly specialized in a parasitic lifestyle. The freshwater fish tapeworms of North America have been relatively well studied since 1855, although their diversity is limited compared to other regions. Most knowledge was gained in the 20th century, with research declining in recent decades, although some groups have recently been revised based on morphological and molecular data. This review updates the current understanding of species diversity, phylogenetic relationships and host–parasite interactions based on a critical re-evaluation of the earlier records. The new data can also inform fisheries management, invasive species control and public health surveillance. Currently, 130 valid adult species are known in six orders, most of which are native to the Nearctic, with the USA having the greatest diversity (121 species). The vast majority of North American fish tapeworms exhibit narrow host specificity, with almost three quarters specializing in a single host species or host genus. Larval stages (metacestodes) from four orders also occur in fish, but are difficult to identify morphologically. Future work should focus primarily on little-studied fish groups and regions with probably undescribed diversity (e.g., the southern USA), combined with integrative taxonomic approaches.

Scanning electron microscopy was used to study the scolex morphology of 3 morphotypes of metacestodes of the order Phyllobothriidea (Cestoda) from the spiral intestine of the North Sea rabbitfish Chimaera monstrosa and the intestine and gall bladder of the pink salmon Oncorhynchus gorbuscha. Transmission electron microscopy allowed a detailed examination of the ultrastructure of the tegument, unicellular gland cells, muscle cells, and calcareous corpuscles of metacestodes of different sizes from chimaeras. Based on our morphological data, we propose that the studied intestinal metacestodes from chimaeras and pink salmon belong to the type XV metacestodes of Jensen and Bullard, possibly related to members of the genus Clistobothrium Dailey and Vogelbein, 1990.

The caryophyllidean tapeworms (Cestoda) of the genus Isoglaridacris Mackiewicz, 1965 are revised on the basis of the study of type specimens and newly collected material from suckers (Cypriniformes: Catostomidae) in North America. Molecular data reveal the presence of 14 lineages, each representing a separate species. An overview of all nominal species is provided, with updated information on their hosts, distribution and phylogenetic relationships. Isoglaridacris multivitellaria Amin, 1976 is excluded from Isoglaridacris, but its generic affiliation remains unclear, and it is considered incertae sedis. Homeomorpha mackiewiczi Dutton et Barger, 2014 from Minytrema melanops is transferred to Isoglaridacris as I. mackiewiczi (Dutton et Barger, 2014) new combination. Based on molecular and morphological data, four new species are described: Isoglaricris mattisi n. sp. from Moxostoma collapsum in South Carolina, USA, I. mcallisteri n. sp. from Erimyzon claviformis in Arkansas and Oklahoma, USA, I. mexicanus n. sp. from Moxostoma cf. austrinum in Chihuahua, Mexico, and I. floriani n. sp. from M. macrolepidotum in South Carolina. A key to the identification of all 16 valid species is provided. Isoglaridacris species exhibit strict host specificity, with most species parasitising only a single host species (strict specialists), while a few species occur in more than one species within the same host genus (congeneric specialists). The distribution range of Isoglaridacris species includes southern Canada, the United States and northwestern (nearctic) Mexico.

The caryophyllidean tapeworm Khawia armeniaca has long been regarded as an exceptionally widespread species within its genus, notable for its significant morphological variability. However, with the accumulation of molecular data from different fish hosts, K. armeniaca was suspected to represent a species complex. To clarify the true identity of these parasites, a comprehensive morphological and molecular study (using 18S, 28S and ITS2 ribosomal regions) of K. armeniaca tapeworms from barbels (Barbinae) across the Iberian Peninsula and the Middle East has been conducted. The results revealed two genetically distinct lineages within the K. armeniaca complex. The first lineage, found in Arabibarbus grypus, Barbus lacerta, Capoeta birunii, Carassobarbus luteus, Luciobarbus barbulus, L. esocinus and L. kersin in Iraq and Iran, is genetically congruent with K. armeniaca (Cholodkovsky, 1915), originally described from the Sevan khramulya (Capoeta sevangi) in Armenia. The second lineage, identified in Luciobarbus bocagei (type host), L. comizo and L. guiraonis from Portugal and Spain, is described as Khawia iberica n. sp. In addition to clear molecular divergence, K. iberica can be distinguished from K. armeniaca by notable morphological differences, including variations in the shape, structure and size of the ovary, the anterior extension of the vitelline follicles, the testes and several morphometric parameters.