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

Syst Parasitol (2024) 101:57 https://doi.org/10.1007/s11230-024-10183-y Morphological and molecular identification of metacestodes infecting teleost fishes of Moreton Bay, Australia Scott C. Cutmore · Michael B. Bennett · Thomas H. Cribb Received: 27 June 2024 / Accepted: 8 August 2024 © The Author(s) 2024 Abstract 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 This article is registered in the Official Register of Zoological Nomenclature (ZooBank) as urn:lsid:zoobank. org:pub:9827FA42-3E1E-448C-8642-C8C39D59EFB1. S. C. Cutmore (*) · T. H. Cribb Queensland Museum, Biodiversity and Geosciences Program, South Brisbane, QLD 4101, Australia e-mail: S. C. Cutmore · T. H. Cribb School of The Environment, The University of Queensland, St Lucia, QLD 4072, Australia M. B. Bennett School of Biomedical Sciences, The University of Queensland, St Lucia, QLD 4072, Australia 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. Introduction Since the original descriptions of Scolex pleuronectis Müller, 1788 and Scolex polymorphus Rudolphi, 1819, there has been disorder in the identification of “tetraphyllidean” metacestodes. The lack of development in scolex morphology at this stage, and the usually complete absence of strobila development, has rendered metacestodes notoriously challenging to Vol.: (0123456789) 57 Page 2 of 26 identify. While identification has occasionally been attempted using morphological techniques (e.g., Cake, 1976; Carvajal et al., 1982; Chambers et al., 2000; Hamilton & Byram, 1974), more often than not, identification to species or genus was not attempted at all and specimens have simply been reported as metacestode morphotypes. Chambers et al. (2000) provided the only comprehensive Australian report of metacestodes infecting teleosts, describing 11 metacestode types, from teleosts off Heron Island on the Great Barrier Reef. These authors assigned putative generic identities to the metacestode types using morphological features and, in some cases, on the basis of some in vitro development (Chambers et al., 2000). Over the last two decades, however, there have been substantial advances in our understanding of metacestode identities, with molecular data enabling the definitive association of metacestode types to their adult forms (e.g., Agustí et al., 2005; Aznar et al., 2007; Brickle et al., 2001; Gordeev & Sokolov, 2016; Holland & Wilson, 2009; Jensen & Bullard, 2010; Randhawa, 2011; Tedesco et al., 2020). In the most comprehensive review of marine metacestodes to date, Jensen & Bullard (2010) drew on both morphological and molecular data to present a classification of “tetraphyllidean” and rhinebothriidean metacestodes. These authors proposed a classification scheme of 15 larval types (Types I–XV), eight of which were characterised by partial 28S rDNA sequence data. Seven of these eight types were genetically matched to known genera: Larval Type I was linked to Phoreiobothrium Linton, 1889 and Triloculatum Caira & Jensen, 2009; Type II to Acanthobothrium van Beneden, 1849; Type III to Duplicibothrium Williams & Campbell, 1978; Type IV to Paraorygmatobothrium Ruhnke, 1994 (now Scyphophyllidium Woodland, 1927); Type VI to Anthobothrium van Beneden, 1850; Type VII to Rhinebothrium Linton, 1890 and Spongiobothrium Linton, 1889; and Type VIII to Rhodobothrium Linton, 1889. Despite the major advances represented by the work of Jensen & Bullard (2010), there is clearly more that remains to be clarified in the identification and biology of these metacestodes. In this study we integrate morphological and molecular data to expand on the work of Jensen & Bullard (2010). This study focuses on piscivorous elasmobranchs of the orders Carcharhiniformes Vol:. (1234567890) Syst Parasitol (2024) 101:57 and Orectolobiformes as definitive hosts and the infraclass Teleostei as intermediate hosts, all within a single locality, Moreton Bay, in southeastern Queensland, Australia. The cestode fauna of Moreton Bay, although incompletely described, is rich and provides an ideal location for a study of this type as several genera absent from the analysis of Jensen & Bullard (2010) have been reported, and genetically characterised, from the region (Cutmore et al., 2010; Cutmore et al., 2017; Cutmore et al., 2018; Cutmore et al., 2011). Methods Sample collection Teleost fishes belonging to 29 families (Table 1) were collected from eastern Moreton Bay (27°26’S, 153°24’E) and western Moreton Bay (27°22’S, 153°13’E) by baited lines, seine nets, cast nets or sourced from the commercial fishery. Systematics of host fishes follows that of FishBase (Froese & Pauly, 2023). Intestines were removed, opened longitudinally and examined under a dissecting microscope. Metacestodes found were washed and subsequently killed in near-boiling vertebrate saline (0.85% NaCl solution) and fixed 10% formalin for morphological examination and in 100% ethanol for molecular analysis. Larval cestodes were analysed as paragenophore pairs (hologenophores sensu Pleijel et al., 2008), where two morphologically identical specimens were processed for parallel morphological (one specimen) and molecular (one specimen) analyses. Carcharhiniform and orectolobiform sharks (Table 2) were collected from eastern Moreton B (...truncated)