Traditionally , the nutrients present in Artemia cysts (protein,
fat, minerals, etc.) are provided to young shrimp larvae by the use of recently
hatched living Artemia nauplii. This involves a time consuming operation: decapsulation;
disinfection; hatching; separation and rinsing. Hatching typically takes 24
hours, requires the use of chemicals and is not totally efficient, since the
hatching percentage is variable. But recent research has shown that this is
not necessary the only way Artemia cysts can be fed. It is well known that
Artemia cysts contain an embryo whose development has been arrested at gastrula
stage (Clegg et al., 1996). This embryo is composed of a small number of cells
and is surrounded by a huge number of very tiny packed granules of nutrient
reserves called yolk platelets (Clegg, 2005). Yolk platelets are very regular,
well defined bodies measuring 3 £gm in width x 5 £gm in length and present
a disk like structure at both ends (Figure 1). These yolk platelets are extremely
stable in water and contain virtually all the nutrients needed by the Artemia
embryo to continue its development (Figure 2). When properly extracted and
processed into the right particle size, these yolk platelets show nutritional
properties similar or better than the live Artemia nauplii, when fed to shrimp
larvae under commercial hatcheries conditions. The conditions of pH and temperature
are key to preserving the integrity of the yolk platelets.
Yolk platelets are the most perfect micro-capsules that nature
has produced - or man has invented. It is extremely stable in the slightly
acid pH (<6.5) found in diets and spontaneously dissolves at alkaline pH prevailing
in the shrimp larval gut (8.5) (Utterback and Hand, 1987). Yolk platelets are
therefore the ideal nutrient supply to the young shrimp larvae since its digestion
does not rely uniquely on shrimp larval enzymes, but is endogenous to the yolk
platelet. Several experiments carried out in hatcheries have shown that Litopenaeus
vannamei shrimp larvae fed with yolk platelets particles, replacing fully the
use of live Artemia nauplii, grow better and survive better than the shrimp
larvae fed with live Artemia nauplii. The water quality of culture tanks and
the bacteria load of the water remained similar in both treatments.
Table 2 presents the detailled results of the experiment carried in Mexico in August 2009. Results
indicate that Vitellus has produced shrimp post larvae of equal size and quality (CV, Stress test
survival and pigmentation) as compared to live Artemia nauplii. The variability of the results in all
tanks was well in line with the average of the hatchery.
Later in the next production season (Dec 2009-Mar2010) a total of 3.5 billion shrimp were raised in Mexico with Vitellus as total replacement of live Artemia nauplii, confirming the validity of the first experiment.
These pictures show the digestive track of PL3 sampled to evaluate their feeding behavior. Feed can be found in animals from both treatments. The coloration found in the shrimp digestive track fed with Vitellus is more intense probably because the shrimp has ingested more feed.
For more information, please contact Bernard Devresse.
James S. Clegg (2005): Desiccation Tolerance in Encysted Embryos of the Animal Extremophile, Artemia.
INTEGR. COMP. BIOL., 45:715–724 (2005)
Paul J. Utterback and Steven C. Hand (1987): Yolk platelet degradation in preemergence Artemia
embryos: response to protons in vivo and in vitro. Am J Physiol 1987, 252:R774-R781.
James S. Clegg, Laurie E. Drinkwater and Patrick Sorgeloos (1996): The metabolic status of Siapause
Embryos of Artemia fransciscana (SFB). Physiological Zoology 69(1): 49-66.
This article is reproduced with permission from the Aquafeed.com
magazine: Autumn 2010 issue of AQUAFEED - Advances in Processing & Formulation
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