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Taxonomy and phylogeny of the buccal-attaching Cymothoidae (Crustacea: Isopoda) of Australia

posted on 2023-05-27, 11:10 authored by Martin, MB
The family Cymothoidae consists of crustacean parasites of marine, brackish and freshwater fishes, with 383 species in 43 genera. Different genera attach to different site on its host (externally, inside the flesh, branchial and buccal cavity) and display high host and site specificity. In the Australian context, one flesh-burrowing species is known, and the external and gill-attaching species have been thoroughly reviewed. The buccal-attaching genera remain unrevised, thus this research focuses on the revision of four genera: Ceratothoa Dana, 1852, Glossobius Schioedte & Meinert, 1883, Cymothoa Fabricius, 1793 and Smenispa (Bleeker, 1857). Ceratothoa is represented in Australia by nine species, including two new species (Ceratothoa barracuda sp. nov. and Ceratothoa globulus sp. nov) and two new records (Ceratothoa carinata (Bianconi, 1869) and Ceratothoa oxyrrhynchaena Koelbel, 1878). Three widely recorded species: Ceratothoa imbricata (Fabricius, 1775), Ceratothoa banksii (Leach, 1818) and Ceratothoa trigonocephala (Leach, 1818) were impossible to separate or synonymize with any degree of confidence. Ceratothoa imbricata is here redescribed, with Ceratothoa trillesi (Avdeev, 1979) and Ceratothoa huttoni Filhol, 1885 placed into junior synonymy; the preferred hosts are species of the genus Trachurus (Carangidae). Ceratothoa banksii (Leach, 1818) is here validated and brought out of synonymy with Ceratothoa imbricata. Ceratothoa trigonocephala (of unknown host identity and type locality) is excluded from the Australian fauna, including Ceratothoa lineata Miers, 1876a, which is here transferred to the genus Mothocya Costa, 1851, with Mothocya ihi Bruce, 1986 placed into junior synonymy. This research regards Ceratothoa contracta (Miers, 1880), Ceratothoa novaezelandiae Filhol, 1885 and Ceratothoa gaudichaudii (Milne Edwards, 1840) as species inquirenda. Glossobius is represented by seven species worldwide, with Glossobius anctus Bruce & Bowman, 1989 being the only known species in Australia. This research contributes to the redescription of Glossobius impressus (Say, 1818), new to Australian and southern African waters. Glossobius arimae Nunomura, 2001 is incorrectly placed in the genus and transferred to Ceratothoa; whereas Glossobius ogasawarensis Nunomura, 1994 is here placed in synonymy with Glossobius auritus Bovallius, 1885, reducing the number of accepted species in the genus to five. The identity of Glossobius crassa (Dana, 1853) is impossible to resolve, and is here removed from synonymy with G. auritus and placed into nomen dubium. Cymothoa hermani Hadfield, Bruce & Smit, 2011, previously known from Tanzania, is new to Australian waters. Cymothoa carangi Avdeev, 1979; Cymothoa epimerica Avdeev, 1979; Cymothoa parupenei Avdeev, 1979; Cymothoa propria Avdeev, 1979; Cymothoa rotunda Avdeev, 1979; Cymothoa pulchrum Lanchester, 1902; Cymothoa curta Schioedte & Meinert, 1884 and Cymothoa plebeia Schioedte & Meinert, 1884 are here redescribed, the latter two excluded from the Australian fauna. Cymothoa limbata Schioedte & Meinert, 1884 is placed into junior synonymy with Cymothoa eremita (Br‚àö¬¿nnich, 1783). Cymothoa eremita and Cymothoa indica Schioedte & Meinert, 1884 are both known to have high morphological variability and display low host specificity, occurring on 12 and 10 host families respectively. Smenispa irregularis (Bleeker, 1857) is one of the smaller and least known of the cymothoid genera, with only two species listed in The World Register for Marine Species. There have been few records of Smenispa since its original description and its host preferences and geographical distribution remain little known. This research discusses the nomenclatural change from Enispa Schioedte and Meinert, 1884 to Smenispa ‚àöv±zdikem, 2009, and a full description provided for female and male of the species. This study also aims to investigate the phylogeny of both morphological (outgroup comparison) and molecular (using mitochondrial genes 16S rRNA and cytochrome oxidase 1) relationships within the Cymothoidae by expanding morphological and limited genetic data sets. Both morphological and molecular analyses showed that 1) the family is monophyletic, 2) neither analyses support the view of a linear evolutionary pathway based on site attachment (from the externalattaching cymothoids to a derived buccal and gill-attaching cymothoids) 3) neither analyses revealed that the host-specificity is higher in the more derived genera. The morphological cladistics resulted in two fairly distinct clades: 1) the predominantly buccal and gill attaching cymothoid clade and 2) the South American freshwater cymothoid clade. The Anilocrinae is basally unresolved, which also includes nonexternal attaching genera such as Livoneca, Norileca and Smenispa. The molecular cladistics for 16S rRNA formed congruent generic clades (Anilocra and Ceratothoa) whereas COl cladistics formed weakly supported generic clades for Nerocila and Cymothoa. It is likely that cymothoid taxonomic classifications reflect convergence due to similar life styles (morphological adaptations). This project has contributed to the knowledge of the buccal-attaching cymothoids by increasing species numbers and providing full accounts of the species synonymy, species and generic diagnosis, distribution, known hosts and species keys. This thesis also highlights the complexities of the Cymothoidae phylogenetics and that the preliminary results suggest complex history (e.g. parasitic diversification strategies, pathogenicity, life history) within the family.


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Copyright 2015 the Author Chapters 3-6 removed for copyright reasons.

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