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Morphotaxonomy and genetic affinities of five novel, potentially fish-killing, Australian gymnodinioid dinoflagellates

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De Salas, Miguel Felix (2004) Morphotaxonomy and genetic affinities of five novel, potentially fish-killing, Australian gymnodinioid dinoflagellates. PhD thesis, University of Tasmania.

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Abstract

Water samples from several southern Australian locations (Tasmania,
Victoria, New South Wales, South Australia and Western Australia) have
revealed a range of previously undescribed gymnodinioid dinoflagellates.
Five new species are described in this study, from field samples and
laboratory cultures, with the use of light microscopy, scanning and
transmission electron microscopy, pigment analysis and sequencing of the
large subunit ribosomal gene (LSU rDNA).
Karenia umbella de Salas, Bolch & Hallegraeff sp. nov., has a straight apical
groove typical of the genus. This species is morphologically similar to K.
longicanalis but has an asymmetrically shaped hypocone, irregularly shaped
chloroplasts, and is ornamented by 8 radial furrows on the epicone surface.
Karenia asterichroma de Salas, Bolch & Hallegraeff sp. nov. is a dorsoventrally
flattened unarmoured dinoflagellate resembling K. brevis. Unlike
other known Karenia species, the chloroplasts of K asterichroma radiate
from a central pyrenoid, and its nucleus is located in the centre of the epicone.
While the ichthyotoxicity of K asterichroma is yet to be confirmed, it was
associated, together with K. umbella and further undescribed Karenia species,
with the recent mass mortality in May 2003 of over 100,000 salmonoids in an
aquaculture facility in southern Tasmania.
A new, potentially ichthyotoxic genus, Takayama de Salas, Bolch, Botes et
Hallegraeff gen. nov. is described with two new species: T. tasmanica de
Salas, Bolch et Hallegraeff, sp. nov., and T helix, de Salas, Bolch, Botes et
Hallegraeff, sp. nov., isolated from Tasmanian (Australia) and South African
coastal waters. The new Takayama species have sigmoid apical grooves and
close affinities to the other fucoxanthin-containing genera Karenia and
Karlodinium.
A new mixotrophic species in the toxigenic genus Karlodinium, K. australe
de Salas, Bolch & Hallegraeff sp. nov., is morphologically similar to
Gyrodinium corsicum and Karenia digitata but has an anteriorly located
nucleus and a different amphiesmal pattern. K. australe lacks the hexagonal
arrays of plug-like structures below the amphiesma that define the genus, and its chloroplasts contain pyramidal rather than lenticular pyrenoids. Thus the
definition of Karlodinium needs to be emended, as it is too narrow, and
currently excludes K australe.
Pigment analyses of these species, all from previously well studied fishkilling
groups, have determined that they contain fucoxanthin and its
derivatives as the main accessory pigments. The pigment gyroxanthin-diester,
was present in all Karenia species tested, but its presence was variable in
Karlodinium and Takayama. Furthermore, phylogenetic analysis of these and
other gymnodinioid species show that all the fucoxanthin-containing, fishkilling
species in the genera Karenia, Karlodinium and Takayama form a
well-defined, monophyletic clade within the Gymnodiniales.
The description and detailed characterisation of these five new species will
help design more effective monitoring tools, such as molecular probes, for the
early detection of these potentially fish killing dinoflagellates.

Item Type: Thesis (PhD)
Keywords: Dinoflagellates, Gymnodiniales
Copyright Holders: The Author
Copyright Information:

Copyright 2004 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2004. Includes bibliographical references

Date Deposited: 09 Dec 2014 00:09
Last Modified: 19 Jul 2016 23:53
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