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

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Martin, MB (2016) Taxonomy and phylogeny of the buccal-attaching Cymothoidae (Crustacea: Isopoda) of Australia. PhD thesis, University of Tasmania.

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Abstract

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 (Brünnich, 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 Özdikem, 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.

Item Type: Thesis (PhD)
Keywords: Ceratothoa, Cymothoa, Glossobius, Smenispa, molecular phylogeny, morphological cladistics
Copyright Information:

Copyright 2015 the Author

Additional Information:

Chapters 3-6 removed for copyright reasons.

Date Deposited: 07 Nov 2016 21:18
Last Modified: 16 Nov 2016 00:13
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