X
تبلیغات
آرتمیا-شیلات و محیط زیست - A comparative study of two methods‎ for Artemia urmiana cyst processing‎
مطالب زیست محیطی و جانوران آبزی

Artemia 2009

December 13-14, 2009, Urmia-Iran                                                                            | 213

    

A comparative study of two methods, fluidized bed drying and layer drying, for Artemia urmiana cyst processing

 

Autor: Esmaeili, L.    E-Mail  :  latifsmaili@gmail.com

 

Introduction

  

Although Artemia has been known for centuries, its use as a food for the larviculture

of aquatic species began in the 1930's. With the expansion of aquaculture industries

in  1970's,  providing  adequate  amount  of  Artemia  cyst  and  biomass  has  become  a

bottleneck  for  the  larviculture  of  crustaceans,  and  freshwater  and  marine  fishes

(Lavens and Sorgeloos, 1996). Nowadays, processing and preservation of hatchable

Artemia cysts and  their  long-term storage  is essential  for a sustainable supplying of

Artemia nauplii  for  aquaculture  applications. Proper processing of Artemia  cysts  is

very  important  to  achieve maximal  hatching  quality. The  quality  of Artemia  cysts

can be preserved by reduction of their water content to under 4%, and avoiding direct

1996). 

Urmia Lake  is one of  the  largest permanent hypersaline  lakes  in  the world and  the

habitat of  a unique bisexual Artemia  species, namely A. urmiana  (Azari Takami,

1993;  Eimanifar  and  Mohebbi,  2007).  In  Iran,  the  economic

harvesting of A. urmiana from the Urmia Lake began in 1996s. 

In  this  study  the  effects  of  the  application  of  two methods  of  fluidized  bed  drying

(FBD) and layer drying (LD) for processing of A. urmiana cysts are investigated. 

 

Materials and Methods 

       

A method proposed by Lavens et al. (1996) was applied  to prepare the cysts for the

experiment; a batch of A. urmiana cysts with  similar characteristics was harvested,

screened  and washed. The  cysts were  then dehydrated  in  saturated brine,  and  their

diapause was deactivated by cold  storage at  20 C  for 2 months. After  this period,

the cysts were placed  in room  temperature for 2 days and  the diapause deactivation

was  confirmed  by means  of  hatching  a portion of  the  cysts  by  a  standard method.

The cysts were divided into 2 groups:  one group was dried by FBD method with 20

treatments  comprising  4  processing  time  (0.5,  1,  1.5  and  2  h)  and  5  drying

temperatures (28, 30, 32, 34 and 36  C). The second group of the cysts was dried by

LD method with 30  treatments consist of 6 processing  times  (1, 2, 3, 4, 5 and 6 h)

and  5  drying  temperatures  (28,  30,  32,  34  and  36 C). Each  treatment was  done  in

triplicate by using ca. 200g cysts per  replicate. The cysts of all  the  treatments were

packed  under  vacuum  and  stored  at  4 C.  About  45  subsamples  of  each  treatment

were  examined  monthly  for  qualitative  assessments,  i.e.  estimation  of  hatching

 

 

| 214

    

percentage  and  efficiency  and  residual  water  content,  for  a  period  of  up  to  15

months. All data were analyzed by one-way ANOVA. Duncan and t tests were used

to compare the results of each two treatments at a significance level of 95% (p<0.5).  

 

Results and Discussion

  

The  hatching  percentage  (mean  ±  SE)  of  the  cysts  processed  by LD  (N=450)  and

FBD  (N=320) methods were 88.87±4.1 and 83.16±7.4%,  respectively. The average

hatching  efficiency of  the cysts processed by LD and FBD  (N=320) methods were

106040.09±17303.3 and 101186.25±19149.5, respectively. The average final water-

content  of  the  cysts  processed  by  LD  and  FBD  methods  were  15.03±8.5  and

10.67±4.4%,  respectively. There was  significant difference between water  contents

of the cysts of the two examined methods (p<0.05). 

The  lowest cyst water-content  (15%) was  in  the  treatment of using FBD method at

28  C  for 0.5 hour, and  this was significantly different  from  the other  treatments  in

this  drying  method.  For  the  cysts  processed  by  LD  method,  the  minimum  water

content  (10-15%) was observed  in  the cysts dried at 34 C  for 4 hours, and  this was

significantly  different with  the  other  treatments  in  this method  (p<0.05). Hatching

percentage and efficiency were significantly different between the cysts dried by the

two studied methods. 

Drying of Artemia cysts  is one of  the most critical  steps of  their processing, which

can affect hatching quality of the cysts. The methods for different stages of Artemia-

cyst processing, including washing, dehydration, drying and packing were explained

by  Voronov  (1974)  and  Sorgeloos  et  al.  (1986).  In  many  strains  of  Artemia,

dehydration  has  been  found  to  be  an  effective  practice  for  the  inactivation  of

researchers  revealed  that  in addition  to dehydration,  the used  temperature and  final

water  content  of  the  processed  cysts  are  the  most  important  factors  which  have

significant  effects  on  the  maintenance  of  the  cyst  hatchability  in  a  high  rate.

Furthermore,  it  has  been  suggested  that  long Artemia-cyst  drying  times,  specially,

long storage period may cause considerable decrease  in  its hatching percentage and

Miller and McLennan (1988) reported high mortality in the hydrated cysts after they

were  kept  at  the  temperatures  higher  than  48  C.  Sorgeloos  et  al.  (1986)

recommended 35 40  C as a suitable temperature range for drying of Artemia cysts.

Other studies proposed that the water content of the cysts should be reduced to below

10%  for  long Lavens and Sorgeloos, 1987).  In  the study of Sorgeloos et al.  (1986) using FBD  to process  A.  franciscana  cysts  at  42 C  for  2.25  hours  resulted  in  the  highest  cyst quality  preservation  in  long  time  storage. So,  this  technique was  suggested  for  the drying of Artemia cysts  from  the Great Salt Lake. However,  the use of FBD  for A. urmiana  cysts  led  to  different  results,  as  hatching  percentage  and  efficiency were higher in the cysts processed by LD method.            

    

 

 

 

 

The best  inner  temperature and processing  time  for A. urmiana cyst dried by FBD

method were 28  C and 0.5 hour, respectively. In comparision, using 32 hours were  determined  as  the most  suitable  condition  for  processing  of  the  same cysts  by  LD  method.  Nevertheless,  these  results  may  be  attributed  to  the  15% residual water content of the cysts and/or the different characteristics of A. urmiana cyst  from  those  of  the  other  species  and  strains,  especially  in  terms  of  corion thickness.  In  spite  of  more  than  10%  water  content  of  the  cysts,  we  observed  a considerable  hatching  percentage  and  efficiency  and  long  survival  time  of  the  A. urmiana cysts. However, the temperatures higher that 34  C and the drying time of 5-6 hours caused significant decreases in the cysts hatching percentage and efficiency. 

 

 

Artemia 2009

 

December 13-14, 2009, Urmia-Iran          

+ نوشته شده در  یکشنبه سی ام آبان 1389ساعت 14:46  توسط اسماعیلی |