Patterns of specificity and diversity in species of Paraorygmatobothrium Ruhnke, 1994 (Cestoda: Phyllobothriidae) in Moreton Bay, Queensland, Australia, with the description of four new species

Morphological and molecular identification of metacestodes infecting teleost fishes of Moreton Bay, Australia

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.

Molecular phylogenetic analysis of the problematic genus Cardicola (Digenea: Aporocotylidae) indicates massive polyphyly, dramatic morphological radiation and host-switching

Novel multi-locus sequence data were used to assess the molecular phylogenetic relationships of fish blood flukes showing similarity to the genus Cardicola Short, 1953 (Trematoda: Aporocotylidae). Analyses of three ribosomal (ITS2, 28S & 18S) subregions and one mitochondrial (cox1) DNA subregion shows that the hitherto-monophyletic clade formed by species of Cardicola Short, 1953 also includes species of three other genera - Braya Nolan & Cribb, 2006, Elaphrobates Bullard & Overstreet, 2003 and Rhaphidotrema Yong & Cribb, 2011 - as well as a new, morphologically distinct species discovered from the heart of the yellowfin tripodfish, Tripodichthys angustifrons (Tetraodontiformes: Triacanthidae). In the context of conflicting morphological, molecular and ecological data, we argue that the recognition of seven genera produces a more satisfactory taxonomy for these parasites than considering them all as species of Cardicola. We thus recognise Cardicola (as an explicitly polyphyletic taxon) together with Braya, Elaphrobates, Rhaphidotrema and three new genera. We propose Allocardicola n. gen. for A. johnpagei n. sp. from T. angustifrons, Chanicola n. gen. for three species of Cardicola that infect the chanid Chanos chanos, and Spirocaecum n. gen. for six species of Cardicola that infect siganid fishes. We interpret the pattern of diversification seen in the clade of these seven genera as one of multiple host-switching events followed by diversification among closely-related hosts and differing levels of morphological divergence.

Emerging global novelty in phyllobothriidean tapeworms (Cestoda: Phyllobothriidea) from sharks and skates (Elasmobranchii)

New genera are erected for three clades of tapeworms originally discovered using molecular sequence data. The morphological features of each are characterized after examination of specimens with light and scanning electron microscopy. Rockacestus gen. nov. parasitizes skates. Ruhnkebothrium gen. nov. parasitizes hammerhead sharks. Yamaguticestus gen. nov. parasitizes small squaliform sharks and catsharks. The novelty of these genera is supported by a taxonomically comprehensive molecular phylogenetic analysis of the D1–D3 region of the 28S rDNA gene, which, with the addition of newly generated sequence data, is the first to include representation of 15 of the 18 genera of phyllobothriideans plus the three new genera. Five new species are described from elasmobranchs in the western Atlantic Ocean, the Gulf of California, Chile, the Falkland Islands and South Africa to help circumscribe the new genera. Two of the genera provide appropriate generic homes for ten species of phyllobothriideans from catsharks and skates with uncertain generic affinities and thus resolve longstanding taxonomic issues. Given that these genera parasitize some of the most poorly sampled groups of elasmobranchs (i.e. hammerhead sharks, squaliform sharks, catsharks and skates), based on the strict degree of host specificity observed, we predict that further work on other members of these groups will yield as many as 200 additional species in these three genera of tapeworms globally. This brings the total number of genera in the Phyllobothriidea to 21.

Insights from new cestodes of the crocodile shark, Pseudocarcharias kamoharai (Lamniformes: Pseudocarchariidae), prompt expansion of Scyphyophyllidum and formal synonymization of seven phyllobothriidean genera - at last!

Three new cestode species are described from the crocodile shark (Pseudocarcharias kamoharai) in Ecuador. All three were examined with light and scanning electron microscopy. The unique combination of morphological features in one of the new species prompted formal investigation of the non-monophyly of Paraorygmatobothrium relative to the morphologically similar genera Doliobothrium, Guidus, Marsupiobothrium, Nandocestus, Orectolobicestus, Ruhnkecestus and Scyphophyllidium. Sequence data generated for part of the 28S rDNA gene were subjected to maximum likelihood (ML) analysis. The resulting tree led to the synonymization of six of these seven genera with Scyphophyllidium, and transfer of their species to the latter genus. With the new species, the number of described members of Scyphophyllidium is now 45. The diagnosis of Scyphophyllidium is revised to accommodate these species. In addition, to expedite future descriptions, eight categories of Scyphophyllidium species are circumscribed, based largely on bothridial features. Scyphophyllidium timvickiorum n. sp. is a category 1 species. Beyond being the smallest category 1 species, it bears, rather than lacks, apical suckers and lacks, rather than bears, strobilar scutes. The two other new species are members of Clistobothrium. Clistobothrium amyae n. sp. differs from its congeners in bothridial shape, elongate cephalic peduncle and tiny size. Clistobothrium gabywalterorum n. sp. differs from the two of its congeners that also possess foliose bothridia in overall size and testis number. Despite their substantial morphological differences, the ML tree indicates they are sister taxa. Both are unique among their congeners in possessing cephalic peduncle spinitriches. The diagnosis of Clistobothrium is revised accordingly.

A new species of Alexandercestus Ruhnke and Workman, 2013 (Cestoda: Phyllobothriidea) from the sicklefin lemon shark, Negaprion acutidens (Elasmobranchii: Carcharhinidae), in the Gulf of Oman

A new species, Alexandercestus masoumehae n. sp., is described from the sicklefin lemon shark, Negaprion acutidens (Rüppell), from the Iranian coast of the Gulf of Oman. The new species is the third in this genus, all parasitizing species of Negaprion Whitley. Based on morphological characters and scanning electron microscopy the new species is different from its congeners of in a combination of characters including total length, terminal proglottid length, cirrus sac length, and genital pore position. Compared to Alexandercestus gibsoni Ruhnke & Workman, 2013 and A. manteri Ruhnke & Workman, 2013 the specimens of the new species are smaller (7.08-8.5 mm), with a smaller terminal proglottid length to width ratio (1:0.7-1.3 vs. 1.4-3.2:1 and 1.2-3.1:1, respectively), and have a more anterior genital pore (70-73% of proglottid length vs. 42-66% and 41-65%, respectively). In addition, A. masoumehae possesses less foliose bothridia compared with A. gibsoni, and more densely packed vitelline follicles in comparison with A. manteri. The SEM examination of the scolex in the new species reveals a specific pattern of microtriches adding new details in our understanding of the surface morphology of members of Alexandercestus. Finally, the new species increases the total number of described tapeworm species from N. acutidens to five and the described tapeworms in the Persian Gulf and Gulf of Oman region to 65.