International Journal of Marine Science, 2016, Vol.6, No.18, 1-14
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Pascual et al., 1996; Knudsen et al., 2004), relationships of host with other organisms (Marcogliese, 2005),
describe niche changes (Marcogliese, 2005), determine the presence of predators or seasonal migrants
(George-Nascimento, 1987; Jirku et al., 2002), and determine changes from pollution and climatic stressors
(Overstreet, 1981, 1993; Overstreet, et al., 1984, Khan and Thulin, 1991, Mackenzie et al., 1995; Marcogleise,
2004; Jirku and Modry, 2006; Duszynski et al., 2007). This overview is meant to provide a deeper appreciation for
the role of parasites in marine organism`s health assessments.
The general lack of information on ascidian parasites applies equally to the protozoa and helminthes. Although
behavior, ecology and physiology are well known, relatively few studies have documented the incidence of
parasites and their influence on their hosts (Hoberg 1996, Upton, 2000). Many ascidians, including
Styela plicata
,
Styela partita
and
Ascidia mentula
breed during summer in Mediterranean Sea (Saad, 2008, 2010). Ascidians
serve as ideal habitats for ectoparasites (own observation; Cox, 1994). Many parasitic species have become highly
specialized in synchronizing their life cycles with their hosts‟ breeding phenology (Marcogliese, 2004). However,
most species of ascidians spend the greater part of the year in dispersed estuaries like Arabian Gulf where
transmission and survival of parasites represents a major challenge. Nevertheless, foraging behavior and diet
facilitate the transmission of a variety of endoparasites through marine invertebrate and vertebrate species.
Ciancio et al., (1999) studied the vegetative and sporulation stages of
Hapiosporidium ascidiarum
from the
ascidian
Ciona intestinaiis
. Scippa et al., (2000) observed an Apicomplexan microparasite from the Pericardic
Body of
Ciona intestinalis.
Although those parasites, too, are better transmitted during the breeding season
because of the abundance of marine littoral intermediate hosts (Hoberg, 1996). The colonial ascidian
Botryllus
schlosseri
is a stable microhabitat potentially favourable for feeding, shelter, brooding and reproduction of many
marine microorganisms. Saad and Barakat (2010) identified the microfauna including parasites living on and in
this colonial ascidian using light and electron microscopies.
Ascidians may obtain microorganisms or/and parasites from their food through water filtration, or directly
swallow an unsporulated parasitic stage in the sea water. Parasites may have complex life-cycles involving up to 3
or more different host species (including ascidians), or direct life-cycles involving a single host species. Ascidians
are probably infected when they ingest infected crustaceans.
I found accidently in a previous study a coccidian sporocyst completely embedded in the intestinal mucosa of
Styela plicata
(Saad, 2008). Later on I tried to find and collect all stages of the life cycle of this coccidian parasite.
This study based totally on natural infection in the marine ecosystem and continued four years.
M
aterials and Methods
Adult specimens of
Styela plicata
(Lesuaer, 1823) and
Ciona intestinalis
(Linnaeus, 1767) were collected from the
shallow waters of the Arabian Gulf, Saudi Arabia during 2011 – 2014. Breeding and non breeding seasons were
considered according to Saad, 2008, 2010; Saad,
et al.,
2011). Identification of these ascidians was carried out
according to Millar (1988).
Microscopic observation
Adult specimens were dissected alive in seawater and isolated parts from the gastrointestinal tract were fixed in
10% formalin and washed in distilled water for 24 hours. Ascending series of ethyl alcohol used for dehydration,
followed by another dehydration series of tertiary butyl alcohol, then tertiary butanol and paraffin oil (1:1) and
finally in pure paraffin oil. All preparations were washed in tissue mate (paraplast) with melting point 54-58°C and
blocked in fresh paraplast. Sections of 5-8µm were obtained. A number of triple stains were tried to enable the
differentiation of the tissues (Toluidine Blue Pearse, 1968; Mercury bromphenol blue Pantin, 1948). Ortholux
Leintz Wetzler Stereoscopic microscope with different magnification capacities and Lampe house 250 with
external light source of Schott KL 1500 was used. The Camera used was full-automatic microscope camera for
research and laboratory purposes.
