Use of a filamentous green alga (Chaetomorpha sp.) and microsnail (Stenothyra sp.) as feed at an early stage of intensive aquaculture promotes growth performance, artificial feed efficiency, and profitability of giant tiger prawn (Penaeus monodon).

With the worldwide demand for tropical penaeid prawn increasing in recent decades, more research on shrimp culture methods is needed to enhance efficiency and profitability for shrimp farmers. The objective of this study was to develop a technique to boost the productivity, feed efficiency, and profitability of the giant tiger prawn (Penaeus monodon). To accomplish this, a novel culture setup was established in which two benthic organisms, a filamentous green alga (Chaetomorpha sp.) and a microsnail (Stenothyra sp.), were propagated together with P. monodon post-larvae during an early culture stage and then offered to shrimp as supplementary live feeds in intensive aquaculture ponds. For the experiment, shrimp post-larvae (density: approximately 33 individuals m-2) were cultured in outdoor concrete ponds (9 × 9 × 1.2 m) under either control (fed only artificial feed, n = 3) or experimental (fed artificial feed and benthic organisms, n = 3) conditions until they reached marketable size (15 weeks). Apparent green algae consumption was 6.81 kg (8.4% green alga to total feed consumption), whereas microsnail consumption was 1.96 kg (2.4% microsnail to total feed consumption). Compared with the control group of giant tiger prawn, the experimental group showed significantly higher productivity (total number of shrimp produced: 118%; total shrimp production: 133%), feed efficiency (feed conversion ratio of artificial shrimp feed: 89%), and profitability (shrimp sales: 139%; balance between shrimp sales and costs: 146%), while labor and financial costs were kept minimal. These results can be explained by the enhanced growth of shrimp at the early stages of culture. The techniques developed in this study will help to advance the efficiency of intensive aquaculture operations for giant tiger prawn and also improve profitability for shrimp farmers

Ecological and morphological profile of floating spherical Cladophora socialis aggregations in central Thailand.

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

Monthly maximum velocity (m s⁻¹) and wind direction in Central Thailand.

<p>Graphs were drawn from raw data provided by the Thai Meteorological Department [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124997#pone.0124997.ref038" target="_blank">38</a>].</p

Mass floating spherical aggregations of <i>Cladophora socialis</i> in a salt field reservoir in Central Thailand.

<p>Mass floating spherical aggregations of <i>Cladophora socialis</i> in a salt field reservoir in Central Thailand.</p

Homology of <i>Cladophora socialis</i> 28S rDNA sequence to related species.

<p>Homology of <i>Cladophora socialis</i> 28S rDNA sequence to related species.</p

Floating spherical aggregations of <i>Cladophora socialis</i> in a salt field reservoir, a natural habitat.

<p>(a) A lower hemisphere of spherical aggregations of a solid, dark green color: (b) On-land view of floating spherical aggregations: (c) Underwater view of Indeterminate turf forms.</p

Morphological characteristics of <i>Cladophora socialis</i>.

<p>(a) A fresh individual thallus: (b) Filaments attaching to one another by rhizoids formed apically (filled-arrow) and intercalary (open-arrow): (c) Apical cell in natural individual: (d) Apical cell cultured in static water showing longer length: (e) Main axis cells: (f) Branching system: (g) Filaments showing different growing directions because of a bent obtuse angle: (h) Newly formed lateral (filled-arrow) without cross-wall at its base: (i) Multi-nuclei in a cell stained by the Wittmann method: (j) Parietal chloroplasts along the cell wall: (k) Transmission electron microscopic image of bilenticular type pyrenoid: (l) Transmission electron microscopic image of zonal type pyrenoid.</p

Map showing field survey location in Central Thailand.

<p>Map showing field survey location in Central Thailand.</p

Transverse schematic diagram showing the location of several <i>Cladophora socialis</i> forms at the study site.

<p>Transverse schematic diagram showing the location of several <i>Cladophora socialis</i> forms at the study site.</p

Maximum likelihood phylogenetic trees for <i>Cladophora socialis</i> and relatives.

<p>(a) A tree based on nearly complete 18S rDNA sequences: (b) A tree based on partial 28S rDNA sequences. Other data on Cladophorales were downloaded from GenBank for comparison. Numbers close to the nodes are ML/MP bootstrap values.</p