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Presence of viral pathogens amongst wild Penaeus monodon in Thailand
(2017-05-01)
Hamano, Kaoru
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Maeno, Yukio
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Klomkling, Sirimas
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Aue-Umneoy, Dusit
;
Tsutsui, Isao
An epizootiological study of 230 wild Penaues monodon collected from a set net in the seashore of Klong Khone, Samut Songkhram, Thailand was conducted from December 2012 to November 2013. Each month approximately 20 wild P. monodon were tested for the following five pathogenic shrimp viruses: yellow head virus (YHV), white spot syndrome virus, infectious hypodermal and hematopoietic necrosis virus, taura syndrome virus, and infectious myonecrosis virus (IMNV). Among all P. monodon individuals, 45.7% were positive for YHV, which causes yellow head disease that is commonly encountered in Thai shrimp cultivation. Overall, pathogenic viruses were detected in 80.9% of all the shrimp; however, IMNV, which has yet to be identified in Thailand, was not detected in any shrimp. This finding suggests that there is a link between the prevalence of pathogenic viruses in wild shrimp and the outbreaks of viral diseases in farmed shrimp.
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Co-culture with Chaetomorpha sp. enhanced growth performance and reduced feed conversion ratio of the giant tiger prawn, Penaeus monodon
(2015-09-08)
Tsutsui, Isao
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Songphatkaew, Jaruwan
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Meeanan, Chonlada
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Aue-Umneoy, Dusit
;
Sukchai, Halethichanok
The increase in global demand for fishery products has led to a fivefold increase in aquaculture production since 1990. Commercial feed is the highest production cost in intensive aquaculture, and residual commercial feed leads to eutrophication; hence it is important to find a low-cost alternative that has less environmental impact. We investigate the use of the filamentous green algae, Chaetomorpha sp., as a raw feed for giant tiger prawns. The giant tiger prawn, Penaeus monodon was grown in monoculture, and in co-culture with Chaetomorpha sp. to investigate the potential benefits of co-culturing. Five 20-day-old giant tiger prawn juveniles were released in 70-L monoculture and co-culture tanks, and the specific growth rate (SGR) and feed conversion ratio (FCR) were measured after 10 weeks. The final mean body weight of co-cultured prawns was approximately 50 % heavier than that of monocultured prawns. The SGR in co-culture tanks was 4.79 ± 0.08 % day−1, which was higher than that in monoculture tanks (4.14 ± 0.27 % day−1). The FCR was 38.9 % lower in co-culture than in monoculture tanks. The protein content of Chaetomorpha sp. obtained from proximate analysis was almost the same or a little lower than other filamentous green seaweeds; however, the Chaetomorpha sp. has higher fiber and gross energy. These results show that Chaetomorpha sp. has potential for reducing feed costs in prawn intensive aquaculture through co-culturing.
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Ecological and morphological profile of floating spherical Cladophora socialis aggregations in Central Thailand
(2015-04-21)
Tsutsui, Isao
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Miyoshi, Tatsuo
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Sukchai, Halethichanok
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Pinphoo, Piyarat
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Aueumneoy, Dusit
The unique beauty of spherical aggregation forming algae has attracted much attention from both the scientific and lay communities. Several aegagropilous seaweeds have been identified to date, including the plants of genus Cladophora and Chaetomorpha. However, this phenomenon remains poorly understood. In July 2013, a mass occurrence of spherical Cladophora aggregations was observed in a salt field reservoir in Central Thailand. The aims of the present study were to describe the habitat of the spherical aggregations and confirm the species. We performed a field survey, internal and external morphological observations, pyrenoid ultrastructure observations, and molecular sequence analysis. Floating spherical Cladophora aggregations (1-8 cm in diameter) were observed in an area ∼560 m2, on the downwind side of the reservoir where there was water movement. Individual filaments in the aggregations were entangled in each other; consequently, branches growing in different directions were observed within a clump. We suggest that water movement and morphological characteristics promote the formation of spherical aggregations in this species. The molecular sequencing results revealed that the study species was highly homologous to both C. socialis and C. coelothrix. However, the diameter of the apical cells in the study species was less than that of C. coelothrix. The pyrenoid ultrastructure was more consistent with that of C. socialis. We conclude that the study species is C. socialis. This first record of spherical aggregations in this species advances our understanding of these formations. However, further detailed physical measurements are required to fully elucidate the mechanism behind these spherical formations.
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High tolerance of Chaetomorpha sp. to salinity and water temperature enables survival and growth in stagnant waters of central Thailand
(2015-03-01)
Tsutsui, Isao
;
Miyoshi, Tatsuo
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Aue-umneoy, Dusit
;
Songphatkaew, Jaruwan
;
Meeanan, Chonlada
The effects of salinity and water temperature on growth and survival of Chaetomorpha sp., one of the green tidal filamentous algae, were investigated. Field surveys revealed that this alga was abundant throughout the year in stagnant coastal waters of central Thailand. Chaetomorpha sp. was found in salinities of 3.4–90.0 and water temperatures of 20.1–40.9 °C. Chaetomorpha sp. biomass fluctuated between 9.2 and 162 kg dry weight in a saline swamp, without significant differences among seasons. The highest mean specific growth rate of approximately, 60 % day−1 was observed in laboratory experimental trials at salinities of 20–30 at 30 °C. Salinity and water temperature significantly affected growth of this alga independently and interactively. Based on these results, Chaetomorpha sp. can easily grow, survive and monopolize in stagnant waters where the salinity and temperature greatly fluctuate because of their euryhaline and eurythermal nature as well as their high growth rate.

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