DIATOMS AS FEED FOR AQUACULTURE

By John J. Perez C.

Greek diatomos, ‘cut in half ’

Pennate diatom

Pseudo-nitzschiaCentric diatomThalassiosira

siliceous hoops (girdle bands)

chlorophyll a, fluorescing red when illuminated with blue Light

Pores are species specific

Diatoms support the most productive fisheries

Crucial role of diatoms in the global carbon cycle

Thalassiosira pseudonana (34Mb)

Phaeodactylum tricornutum (27 Mb)

Fragilariopsis cylindrus (80 Mb)

Fragilariopsis cylindrus (Grunow in Cleve & Möller) W. Krieger in Helmcke & Krieger 1954

Pseudo-nitzschia multiseries (300 Mb)

Unique combination of genes and metabolic pathways distinguish diatoms

Enormous amounts of diversity encapsulated

within diatoms

Thalassiosira nordenskioeldii

Young auxospore of Pseudo-nitzschia multiseries

Two of the novel type of spores of Chaetoceros furcillatus

Thalassiosira taelata

http://www.aquatic.uoguelph.ca/Human/Research/ijkl/kaczmarskai.htm

Life in the ocean wavesCyanobacteria

Heterotrophic bacteriaArchaea

viruses

Eukaryotic phytoplankton

Protists

Benthic diatoms are the main food source for abalone post-larvae

monospecific cultures of benthic diatoms have successfully been employed as feed for the culture of abalone post-larvae

in Taiwan, abalone post-larvae grown in hatcheries are usually fed with natural populations of benthic diatoms, following the traditional method of using biofilms of

mixed benthic diatoms as the settlement substrata for abalone post-larvae in hatcheries

a photosynthetically active biofilm of diatoms, e.g. Gyrosigma spp

Biofilm of mixed centric diatoms

postlarvae of various abalone species have a better growth rate when fed with cultured diatoms than those fed with natural unknown species

of diatoms

Post Larval 'spat': After 2-3 weeks swimming around in the water column, the pelagic veliger larva loses its velium and metamorphoses into the post-larval stage (spat). It loses its positive phototaxis (movement towards the sunlight), moves down from the water surface, and settles on hard surfaces in intertidal and subtidal areas. Settlement is triggered by a chemical that is produced by Coralline algae and adult abalone. Abalone feed on Coralline algae and the presence of adults indicates a good habitat to live! The post-larva sheds its swimming hairs (cilia) and begins to develop the adult shell form. This is the first feeding stage where they start to feed on diatoms.

Carbajal-Miranda et al. (2005)

Navicula incerta

Amphiprora paludosa

Haliotis rufescens

Daume et al. (2000)

Navicula sp., N. jeffr

Cylindrotheca closterium

Cocconeis sp

Haliotis rubra Amphora sp.

Gordon et al. (2006)

Amphora luciae 

Navicula cf. lenzii 

Haliotis discus

Achnanthes longipes

Nitzschia spCocconeis p. Navicula britannica

Nitzschia ovalis

Kawamura et al. (1998)

Haliotis iris

Gallardo and Buen (2003)

Mixed diatoms vs. monospecific cultures of

Navicula

Haliotis asinina

little information concerning

diatoms as feed for Haliotis diversicolor

Kawamura et al., 1998

differences in the species of diatoms they have been fed

lipid, protein and extracellular polymeric substances (EPSs)

Poor and unpredictable performance of abalone postlarvae

Hypothetical cellular pathways and processes in iron-limited pennate diatom cells. All roman green or red type depicts gene transcripts found to be up- or down-regulated, respectively. Italicized and underlined green type indicates metabolites found to be enriched relative to total protein in iron-limited cells. DF, diffusion factor; EPS, extracellular polymeric substances; FR, ferric reductase; HMA, heavy metal-associated; PCD, programmed cell death; ROS, reactive oxygen species.

AIMS• to improve the growth and the survival of

abalone post-larval stages in a specific growth system using specific diatoms species

• a better understanding of their basic dietary requirements

farmers attempting to produce mollusks and crustaceans from the larval stage

• high cost of producing live food (microalgae)• up to 30% of the total cost of production

(Valenzuela-Espinoza et al., 1999).

Alternative

• use immobilized microalgae

• can be cheaper than algae produced by traditional methods

• ready for use (Chen, 2003).

Specific aims

• Survey the diversity of diatoms species found in H. diversicolor hatcheries.

• Isolate and develop a monoculture that could be immobilized and encapsulated in alginate beads for long-term storage as algal stock.

monospecific algal stocks used as feed for cultivating the post-larvae of H. diversicolor

• Lipids• Proteins• EPS – soluble EPS– bound EPS– internal carbohydrate– residual carbohydrate

Collection and preparatory cultures of benthic diatoms

Diatoms from small abalone hatchery ponds

scraped from abalone post-larvae settlement substrates (plastic plates)

collected in l L collection bottles

placed in a cool icebox

transported to the Algal Laboratory of the National Taiwan Ocean University, Keelung, Taiwan

Yean-Chang Chen, Ph.D.Associate Professor,

Department of Aquaculture,

National Taiwan Ocean University,

Keelung, TaiwanEmail:

ycchen@mail.ntou.edu.twb0232@ind.ntou.edu.tw

Tel: 886 2 24622192 ext. 5221Fax: 886 2 24633150====

Martek 120-liter photobioreactor

Deep aerated tank used for the culture of Nannochloropsis for aquaculture

Eicosapentaenoic acid (EPA, 5,8,11,14,17-cis-eicosapentaenoic acid)

• an n-3 C20-polyunsaturated fatty acid that is metabolically active.

20:5(n-3)

a carboxylic acid with a 20-carbon chain and five cis double bondsthe first double bond is located at the third carbon from the omega end.

with a double bond (C=C) starting after the third carbon atom from the end of the carbon chain.

EPA is an omega-3 fatty acid

EPA and its derivatives have proved beneficial in prevention and treatment of certain medical conditions

• coronary heart disease• blood platelet

aggregation• abnormal cholesterol

levels• several carcinomas

EPA is effective also in arresting and minimizing tumor growth

EPA is currently sourced from fish oil• No other sources are

commercially available. – fluctuates in price and quality. – contamination of fish oil with

pesticides and heavy metals.– an alternative economic and

consistent source of EPA is needed.

– Microalgae are one potential source.

Annual EPA demand

125 tones in Japan

demand is expected to increase dwindling supplies of

fish oil

Current market price of EPA ethyl ester (95% pure) about $650/kg