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Dinoflagellate Cysts and Chattonella resting stages from recent sediments of the South Coast of Iran

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Attaran-Fariman, G (2007) Dinoflagellate Cysts and Chattonella resting stages from recent sediments of the South Coast of Iran. PhD thesis, University of Tasmania.

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Abstract

Many harmful microalgae, including dinoflagellates and raphidophytes, produce
long-lived, resistant, resting stages called resting cysts. Mapping the presence and
abundance of these stages in coastal sediments combined with germination studies
can provide valuable information on the distribution of potentially harmful species in
an area. The resting cyst flora of equatorial and tropical regions of the world is
poorly known, particularly in coastal waters. This thesis examines the dinoflagellate
resting cyst flora in coastal marine sediments collected along the southern coast of
Iran. The aim of the study was twofold. Firstly, to determine whether potentially
harmful dinoflagellates or raphidophytes are present in the area. Secondly, to
document the species diversity of dinoflagellate resting cysts in a little studied
tropical region.
Nine sediment samples were collected at three locations (i.e. the Bahoo-kalat estuary,
Pasabandar coast and Chabahar Bay) along the southeast coast of Iran.
Dinoflagellate cyst species abundance and diversity was examined by light and
scanning electron microscopy, and the resting cyst identity and affinity confirmed by
cyst germination, where possible. Established cultures were further characterised by
PCR amplification and DNA sequencing of the large subunit ribosomal RNA gene
(LSU-rDNA) and internal transcribed spacer (rDNA-ITS) regions.
Over forty ( 40) distinct cysts morphotypes were identified in the samples examined.
The most common groups identified were: Scrippsiella species (79%),
Protoperidinium species (10%) and, at three sites (Pasabandar) an unusual angular,
trapeziform resting cyst was common (7% ). Potentially harmful species were also
found in some sites; for example, the paralytic shellfish poisoning (PSP) causative
species, Alexandrium tamarense, yessotoxin producing species Lingulodinium
polyedrum.
Cyst incubation and germination studies established over 30 dinoflagellate cultures
that were further characterised by detailed morphological (LM and SEM) and
molecular approaches. The unusual trapeziform resting cysts were successfully
germinated and identified as a previously undescribed dinoflagellate. Morphological
studies of the resting cysts showed a microreticulate paratabulation, with the pattern
reflecting amphiesmal patterning of the motile cell, including the cingulum and
sulcus. Using cultures established from cyst germination the phylogenetic affinities
ofthe species was examined by comparison of partial LSU-rDNA sequences with a
range of other Gymnodinioids. The resulting analyses indicated a clear relationship
to the other three known microreticulate cyst-forming Gymnodinoid species,
Gymnodinium catenatum, G. nolleri and G. microreticulatum. Identical resting cysts
were also successfully produced in nutrient depleted laboratory cultures, and the
pattern of successful crosses indicated a homothallic mating system for this species.
This dinoflagellate is described as a new species G. trapeziforme Attaran-Fariman &
Bolch sp. nov.
The majority of the remaining cultures established from single cyst incubations were
found to be allied with the Calciodinelloidean genera Scrippsiella, Calciognellum,
Calciodinellum. Of these cultures, four distinct morphotypes were identified and
subjected to DNA sequencing ofthe rDNA-ITS regions. Three morphotypes were
allied with Scrippsiella trochoidea var. aciculifera, Scrippsiella sp., and Scrippsiella
trochoidea respectively. The fourth morphotype, possessing a small second anterior
intercalary plate, was allied with but distinct from the similarly tabulated Scrippsiella
precaria and S. ramonii. Morphological examination shows that its overall size and
shape is similar to S. precaria, but with a more equatorially placed cingulum, an
antapically placed nucleus and a larger, rounded 2nd anterior intercalary plate similar
to S. ramonii. This species is described here as Scrippsiella irregularis AttaranFariman
& Bolch sp. nov.
Mixed sediment incubations from site 6 (Pasabandar coast) also commonly released
a raphidophyte belonging to the genus Chattonella Biecheler. Uni-algal cultures
established from incubations were examined and determined to be allied with
Chattonella subsalsa Biecheler. Analysis ofthe LSU-rDNA and rDNA-ITS regions
sequences compared to other known Chattonella species showed that this species is
related to C. subsalsa, but is genetically distinct, and may represent a new species.

Item Type: Thesis (PhD)
Copyright Information:

Copyright 2007 the Author

Date Deposited: 07 Apr 2008 15:10
Last Modified: 11 Mar 2016 05:53
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