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Changes in Body Shape of the Great Beluga (Huso huso) During the Early Development
Reza Asgari1, Soheil Eagderi *1, Gholamreza Rafiee 1, Hadi Poorbagher1, Naser Agh2
1 Department of Fisheries, Faculty of Natural Resources, the University of Tehran, P.O. Box: 31585-4314, Karaj, Iran * Corresponding author: firstname.lastname@example.org
The early development of fish larvae is accompanied with very complex shape changes. Different growth rates of various parts of the body or allometric growth is a common phenomenon during this period (Osse and van den Boogaart, 1995). Recognition of morphogenesis process and growth pattern of fishes may lead to better understanding of biological priorities during the early developmental stages and gives insights into biological, behavioral and ecological characteristics (Gisbert, 1999).
Many studied have been carried out on change of the body shape during the early ontogeny of various fishes using traditional morphometric approaches but recently, geometric morphometric techniques have been applied (Bookstein, 1991; Rohlf, 1998; Zelditch et al., 2004). Geometric morphometric methods are useful tools in developmental biology to extract shapes data and analyze using multivariate statistical tests, explaining how morphological structures are generated (Zelditch et al., 2004). Hence, this study is conducted to study the changes of the body shape in beluga sturgeon (Huso huso) using landmark-based a geometric morphometric method covering a period from hatching up to 50 DPH (days post hatch) that is synchronized with the transition of larvae from internal to external feeding.
Material and methods
Specimens were obtained from the Dadman International Sturgeon Research Institute (Guilan, Iran). Newly hatched larvae were stored in 500 L fiberglass tanks with a water depth of 20 cm and reared up to 50
DPH. Ten specimens were sampled every day from each tank, anaesthetized with MS 222, preserved in 10% buffered formalin and stored in 70% ethanol after 24 hours. Before fixation, the total length (TL) was measured (in mm) as an independent data using the software ImageJ (version 1.240) and PAST (version 2.10) (Zelditch, 2004). The left sides of specimens were photographed using a stereomicroscope equipped with a Cannon camera with a 5 MP resolution. Nine landmarks were digitized to follow and describe the body shape changes using the software tpsDig2: (1) anterior tip of the snout; (2) center point of the eye; (3) pseudo-landmark on the dorsal edge of head in the front of center of the eye; (4) posterior most point of the gill slit; (5) ventral point of the gill slit; (6) anus; (7) posterior end of vertebrate; (8) pseudo-landmark on the dorsal edge of body in the front of the anus; (9) pseudo-landmark on the ventral edge of head in the front of center of the eye.
The consensus configurations were computed for each age sample (Rohlf, 2005). The data were analyzed using generalised procrustes analysis (GPA), in order to remove all non-shape related information and relative warp analysis using PAST soft (version 2.10). The relative warp scores (RW1 and RW2) were used as descriptors for the variation in shape (Bookstein, 2005). The shape changes during growth were visualized as generating wireframe graph using the software MorphoJ. Growth trajectory was computed by plotting RW1 against TL. Allometric growth was calculated as a power function of total length using non-transformed data: Y = axb, where Y was the independent variable, x the dependent variable, a the intercept and b the growth coefficient. Isometric growth, positive and negative allometric growth are indicated by b = 1, b > 1 and b < 1, respectively (Zelditch et al., 2004). The Inflexion points of growth curves were determined according to Fuiman (1983) and Van Snik et al. (1997).
The first two relative warps explained 91.06% of the body shape
changes during ontogeny (RW1 63.86% and RW2 27.20%). RW1
reflects (1) elongation of the head (including the snout and post-orbital region) and (2) elongation of caudal area i.e. allometric growth pattern of the trunk region, whereas RW2 indicated an increase in depth of the head and trunk (Fig. 1). There was a weak correlation between RW1 scores and TL (r2 = 0.433) (Fig. 2). However, the regression model showed that RW1 scores were strongly correlated to TL during early ontogeny upto 18 DPH (r2 = 0.963) but no correlation onwards (r2 = 0.007; Fig. 2).
The inflection point of body shape corresponds to a TL of 23.3 mm, which was coincided with the age of 18 DPH. Ontogenetic shape changes encompassed two phases: (1) pre-inflection shape changes, which included the elongation of the head and tail regions (positive allometric growth) and (2) post-inflection shape changes, with a nearly isometric growth pattern. In summary, main changes of the shape occurred during the absorption of yolk sac when a period started that the body shape became a miniature form of the adults.
Figure 1. Scatterplot of relative warp analysis, depicting RW1 and RW2. the youngest specimens labeled from 1, the older ones have higher numbers.
Figure 2. RW1 versus TL. The dotted line represents the inflexion point of growth. Discussion
The present study indicated that most important changes in shape of H. huso larvae occur during early development up to 18 DPH and involve the elongation of head and caudal area along with the increase of the body depth. During this period, the trunk had a negative allometric growth. As the first study of allometric growth in sturgeons using geometric morphometric approach, our study is in agreement with other researches that used traditional methods (Gisbert, 1999; Russo et al., 2007; Fuiman, 1983; Osse, 1990; Osse and Boogart, 1995; Van snik et al., 1997) confirming that there is a correlation between changes of body shape and growth pattern, which is according to their functional importance. Since predation and starvation are the main causes of mortality in fish larvae, development of feeding and swimming organs appears to be two important priorities during the early ontogeny (Osse et
Changes in body shape pattern of the beluga larvae at the length of 23 mm (18 DPH), reflects full swimming ability that is necessary for external feeding. It has been suggested that ability to escape from
predation and prey is synchronous with fully development of fins (Hale, 1999, Gibb et al, 2006). Formation of fins in beluga is occurred at 15 DPH being coincided with stiffening of fin rays. Also the cephalic lateral line canals are completed at 18 DPH. The neoromasts of these canals play a vital role in reception of environmental stimuli during feeding and swimming (Omori et al., 1996). The present study show the importance of body shape changes during the early development of beluga larvae, which are associated with development of feeding apparatus, swimming, respiration and sense organs. Based on the pattern of body shape changes, beluga larva can be considered fully developed or fry after 18 DPH.
Bookstein, F.L. 1991. Morphometric tools for landmark data. Geometry and biology. Cambridge: Cambridge University Press.
Fuiman, L.A. 1983. Growth gradients in fish larvae. Journal of Fish Biology, 23: 117-123.
Gibb, A.C., Swanson, B.O., Wesp, H., Landels, C., Liu, C. 2006. Development of the escape response in teleost fishes: do ontogenetic changes enable improved performance? Physiological and Biochemicalal Zoology 79:7-19.
Gisbert, E. 1999. Early development and allometric growth patterns in Siberian sturgeon and their ecological significance. Journal of Fish Biology 54: 852-862.
Hale, M.E. 1999. Locomotor mechanics during early life history: effects of size and ontogeny on faststart performance of salmonid fishes. Journal of Experimental Biology 202:1465-1479.
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Osse, J.W.M., van den Boogaart, J.G.M., van Snik, G.M.J. van der Sluys, L. 1997. Priorities during early growth of fish larvae. Aquaculture 155: 249-258.
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Russo, T., Costa, C. Cataudella, S. 2007. Correspondence between shape and feeding habit changes throughout ontogeny of gilthead sea bream Sparus aurata L.,
Van Snik, G.M.J., Van Den Boogaart, J.G.M., Osse, J.W.M. 1997. Larval growth patterns in Cyprinus carpio and Clarias gariepinus with attention to the finfold. Journal of Fish Biology 50: 1339-1352.
Zelditch, M.L., Swiderski, D.L., Sheets, H.D., Fink, W.L. 2004. Geometric
Morphometrics for biologists: A primer. Elsevier (USA).
Ontogeny of Feeding Apparatus Skeletal System in Beluga (Huso huso)
Reza Asgari *1, Soheil Eagderi 1, Gholamreza Rafeei 1, Hadi poorbagher 1, Naser Agh 2
1 Department of Fisheries, Faculty of Natural Resources, University of Tehran, P.O. Box 4314, Karaj, Iran
2 Artemia and Aquatic Animals Research Institute, Urmia University * Corresponding author: Reza Asgari: email@example.com
Understanding of animal morphogenesis is one of fields in which researchers are working to reveal its different aspects i.e. to know how an animal forms (Kunz, 2004). Findings of this type of researches on fishes are crucial in aquaculture. In this regard, the ontogeny of feeding apparatus skeletal system during early development of fishes can provide the valuable information about their feeding strategies at different developmental stages (Boucaud-Camou and Roper, 1995). Furthermore, this information can help to determine food requirements and providing a feeding protocol for aquacultural propose (Fernandez-Diaz and Yufera., 1997).
Sturgeon fishes are one of the most valuable commercial fishes in the Caspian Sea that their natural stock has been declined due to human activities (Kirshner, 1998). Hence, its artificial propagation program in hatcheries is developing for both aquacultural and restocking proposes (Bronzi et al., 1999). Among sturgeon fishes, production of beluga larvae (Huso huso) has drawn a great attention due to its high economic value and suitability for aquacultural propose.
Because of high value of beluga for aquacultural propose and since no information is available about ontogeny of its muscklo-skeletal system, this study was conducted to investigate the ontogenic process of its food acquisition skeleton for during early development. The member of family Acipenseridae share a variety of characteristics such as the cartilaginous endoskeleton and jaw suspension, but they bear different head shapes and feeding mechanisms that enable some species to have very different feeding modes (Miller, 2005). Hence, the results of this study can help to
understanding better its feeding mode and then to improve feeding protocol in beluga farming.
Material and Method
The samples were obtained from the artificial propagation of four (3 male and 1 female), nine years old farmed beluga sturgeon from at the Dadman International Sturgeon Research Institute (Guilan, Iran). Newly hatched beluga larvae were stored in 500L fiberglass tanks with water depth of 20 cm. Larvae were stocked in tanks with a density of 1800 tank-1. The water was supplied from a mixture of ground and river water with a discharge of 400 and 250 mL-1 min-1, respectively. The water temperature (°C), DO (mg L-1) and pH of were 15.9, 7.7 and 7.8 during experiment, respectively. Due to asynchrony in external feeding of pre-larvae and to avoid starving and cannibalism, feeding was started from 8 DPH using artemia nauplii (500 nauplii larvae-1) which continued till 12 DPH. The larvae were then fed using a mixture of artemia nauplii and daphnia till 25 DPH. Afterwards the larvae were fed using a mixture of commercial food pellet (Biomar) and mashed chironomid larvae in a rate of 30 % bw d-1 (4-6 times per day).
Ten specimens were sampled from 0DPH till 15DPH, every other day from 17DPH till 25 DPH and 32, 37, 42 and 50DPH and then anaesthetized with MS 222, preserved in 10% buffered formalin and stored in 70% ethanol after 24 hours.
The alcian blue-alizarin red double staining methodology is used to study the skeletal development in fish. In this study, also, specimens were prepared via clearing and staining using a modified protocol of Gavaiaet et al (2000) (Asgari et al., 2012). For mycological study, serial sections of head region were prepared according to Pousti (1999). The preparatory process included 1-h submersion in three series of alcohol (80%, 96%, 100%) and two series of Xylene (Xylene I and II) and finally, embedding in paraffin. They were stained with hematoxylin-eosine staining.
Length and weight of newly hatched larvae were 18.2 mm and 11.2 mg, respectively. At this day, the mouth was closed and jaws uncompleted. The mouth opened at 2 DPH and one day latter the dentary (D) and dermopalatine (DPL) (maxillary) cartilages along with barbels were completed on the ventral surface of the head. Formation of hyomandibula (H) and supraorbital sensory canal (sop) and palatopterygoid (ppt) of the palatal complex were started at 4DPH. At 6 DPH, teeth appeared on jaw elements including D, DPL and ppt cartilages and three days later (9DPH), these bony elements were calcified. The formation of H and Ihy bones were completed at 18 DPH (Fig. 1). The palatal complex extends the oral surface of upper jaw posteriorly in 18 DPH. Classification of the gill apparatus was occurred at 23 DPH. The cartilaginous chondrocranium as a single unit was extensive with short rostrum in newly hatched larva. Ossifications of the dermal bones of the skull roof observed at 42 DPH specimens.
Larval sturgeon quickly develops the morphological features associated with their primary feeding apparatus. Their uncompleted elements of the feeding apparatus can not provide a suction feeding ability and then it seems they begin external feed with biting of small prey items. The presence of teeth on D, Dpl and ppt can confirm this.
Sturgeons are unique fishes in their unusual sensory systems, jaw structures, and feeding modes (Miller, 2005). The common features sturgeon fishes include a ventrally flattened rostrum with ventrally protruding jaws. Based on head shapes and the position of jaws, acipenserid species appear to use the powerful suction feeding mechanism that enables them to feed on aquatic animals, within the upper sediment layer or to prey on small fishes (Miller, 1987; Bemis et al., 1997; Carroll and Wainwright, 2003). The jaws were induced to be protruded by pulling both of the hyomandibula via interhyal (Ihy) and anterior ceatohyal (cha)
(Miller, 2005). The jaws of sturgeon are not fixed to the cranium and can therefore be protruded quite far outside of the head. Hence, the completion of the hyomandibula viaand interhyal at 18 DPH can be considered as beginning of suction feeding mechanism in beluga.
Figure 1: cleared and stained specimen upto 1 DPH.
Figure2: section of bucal cavity at 12 DPH, H&E.
In sturgeon fishes, jaw protrusion is caused by forward movement of the hyomandibula bone that results from contraction of the large protractor hyomandibularis muscle that is attached to anterior margin of hyomandibula (Carrol and Wainwright, 2003). The jaws are closed by retraction of the adductor mandibulae muscle that connects the top of palate to the lower jaw and functions to pull the D up to the Dpl (Carrol and Wainwright, 2003). The jaws are retracted by contraction of the retractor hyomandibularis muscle attaching to the posterior margin of the hyomandibula, which would result in the jaws being pulled back into the head (Carrol and Wainwright, 2003). The formation of these muscles observed at 12 DPH bucal cavity of larva.
Bemis, W.E., Findeis, E.K., and Grande, L. 1997. An overview of Acipenseriformes. Environmental Biology of Fishes, 48: 25-71.
Boucaud-Camou E. and Roper C.F.E., 1995. Digestive enzymes in paralarval Cephalopods. Bull. Mar. Sci. 57: 313-327.
Bronzi, P., Rosenthal, H., Arlati, G. Williot, P. 1999. A brief overview on the status and prospects of sturgeon farming in western and Central Europe. Journal of Applied
Ichthyology, 15: 224-227.
Carrol, A.M., Wainwright, P.C. 2003. Functional morphology of prey capture in the sturgeon, Scaphirhynchus albus. Journal of Morphology, 256: 270-284.
Gavaia P.J., Sarasquete C., Cancela M.L., 2000. Detection of mineralized structures in early stages of development of marine Teleostei using a modified alcian blue-alizarin red double staining technique for bone and cartilage. Journal of Biotechnic and Histochemistry, 75: 79-84.
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Kunz, Y.W., 2004. Developmental biology of teleost fishes. Netherlands: Springer.
Springer.Miller, M.J. 1987. Feeding in the White Sturgeon, Acipenser transmontanus: Ontogeny, Functional Morphology, and Behaviour. M.S. Thesis, University of Washington. 75 pp.
Miller, M.J. 2005. The ecology and functional morphology of feeding of North American sturgeon and paddlefish. In: Sturgeons and Paddlefish of North America. LeBreton, G.T.O., Beamish, F.W.H., McKinley, R.S. (eds.). Kluwer academic publishers, New York.
Pousti, I., 1999. Comparative histology and histotechnique. Tehran University Publication, Tehran. (In Farsi).
Hatching characteristics of Phallocryptus spinosaMilne Edwards, 1840 (Branchiopods: Anostraca) populations
BehrozAtashbar*, NaserAgh, Lynda Beladjal and Johan Mertens
*Department of Biology, Faculty of Science, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium, behroz.atashbarkangarloei@UGent.be
Anostraca, which typically inhabit temporary pools,survive adverse periods by producing "dormant eggs"(cysts). A certain fraction of them resumes metabolismwhen favorable environmental conditions are restored,while others remain paused for one or moreseasonal cycles passed. This observed delay in cysthatching is supposed to be an adaptation to overcomepredictable and unpredictable seasonal changes thatcould be fatal for the adult life-phase. In this sense, theexistence of a marked inter- and intraspecific variationobserved in the hatching pattern of fairy shrimps (Brendonck 1996; Simovich& Hathaway1997), provided evidencethat a different cyst reactiveness related to thedegree of environmental unpredictability exists (Belk& Cole 1975).The cysts then await a drying period, after which they will hatch upon rehydration, given the appropriate levels of temperature, light, and oxygen within the pool (Brendonck, 1996).Little is known regarding the hatching process or about the environmental conditions present in temporary ponds that may stimulate hatching. From studies on a number of notostracanspecies, desiccation of the eggs for varying periods of time has been found to promote subsequent hatching (Takahashi, 1977 a, b). Temperature and salinity of the water appear to be important in achieving optimal egg hatch (Scott &Grigrick, 1979), as is photoperiod (Takahashi, 1975).It is recommended for future research on dormancy, either in the field or laboratory, to include ample information on the habitat of target species. Laboratory experiments should be able to increase repeatability of results and reliability of interpretations (Brendonck, 1996). In this study, we
examined the effect of salinity and temperature on the hatching characteristics of diapau sing eggs of thePhallocryptus spinosaoccurring in Azerbaijan area, northwest of Iran.
Material and methods
Diapausing eggs of the Phallocryptus spinosawere collected from the sediments of 3ponds located at north western region of Iran (East and West Azerbaijan). These habitats are considered as temporary and their salinity vary from 0 g-1to more than 60 g-1 and representing a wide ecogeographic range where Anostraca species occur.Hatching fractions were compared in a multifactorial design at seven temperatures (12, 15, 18, 21, 24,27 and 30°C) and three salinity conditions (0, 10, and20g/l) under a 24 h light photoperiod. For each of the conditions, 3 replicates of 30 dormant eggswere incubated in multi well (10 ml) plastic trays. The number of hatchlings was recorded and removed daily during 10 days. Dormant eggs that remained unhatched at the end of the experiment were tested for their viability by testing for the presence of a yolky embryo. A correction was made for the number of empty dormant eggs in each well.
Hatching examinations were conducted on each habitat individually and finally all data on each measured variable were combined. Results were analyzed using multivariate (using the software package SPSS version 15.5) (dependent variables: day of first hatching, hatching percentage at the first day of hatching and cumulative hatching percentage on day 10).
The hatching characteristics of Phallocryptus spinosais illustrated in Figure 1-3.Hatching started fastest at the temperature/salinity combination 30°C, 0g/l(1.1±0.1 day after inundation, n = 9) and significantly slowest hatching was occurred at 12°C,20 g-1combination (7.61± 0.3day after inundation, n = 9) (Figure 1).
5 4 ^ 2
15 18 21 24
temprature conditions (°C)
Figure 1.The interaction between salinity and temperature on first day hating.
The initial hatching fraction was significantly highestat 30°C, 0 g-1 (60.0+7.57%, n = 9), while was lowest at 30°C and 20 g-1 (1.40+0.39%, n = 9) (P < 0.05) (Figure 2).
18 21 24
temprature conditions (°C)
Figure 2.The interaction between salinity and temperature on first day hating percentage.
Cumulative hatching success was highest at the combination of 27°C and 0 g-1 (86.1+4.6%, n = 9) and significantly lower (p<0.01) at 30°C and 20 g-1 (1.39+0.0%, n = 9)( Figure 3).
BO (ppt) rJlO (ppt) Q20 (ppt)
12 15 18 21 24 27 30
temprature conditions (°C)
Figure 3.The interaction between salinity and temperature on cumulative hatching percentage.
A number of researchers have studied the hatching characteristics of anostracan dormant egg at different conditions (Brendonck, 1996) but there are no literatures data available on Iran's fairy shrimps.Results of this study like the previous studies provide important life history data on the species that have important implications for natural populations of fairy shrimp. The fauna of hot arid and semi-arid zones are uniquely adapted to cope with changing often extreme temperature, oxygen level, pH, salinity and turbidity (Lahr, 1997).
Our experimental design was based on testing the critical factors such as high salinity and water temperature that usually has major impact on incomplete filling of the habitats. According to the results obtained, cysts of P. spinosa showed conditional hatching under different salinity-temperature treatments, with low cumulative hatching at the highest values tested for temperature and salinity. The increase in salinity had a negative effect on the hatching of fairy shrimps, hatching was more successful in less salinities.In present study the optimal temperature and
salinity for hatching P. spinosa eggs with intact shells was 27°C at salinity 0 g/l (up to 86 %). Cysts of this species hatch within the temperatures range of 12°C to 30°C after one to six days of inundation at the salinity 0 g/l.In many species, hatching extend over several days or even weeks even under favorable conditions. The highest peak, however, is generally on first or second day of hatching (Brendonck, 1996).
Brendonck L., Centeno M.D. &Persoone G. (1996).The influence of processing and temperature conditions on hatching of resting eggs of Streptocephalus proboscideus. Hydrobiologia, 320, 99-105.
Lahr J. (1997) Ecotoxicology of organisms adapted to life in temporary freshwater ponds in arid and semi-arid regions. Archives of Environmental Contamination and Toxicology 32:50-57.
Scott, S. R. and A. A. Grigarick. (1979). Laboratory studies offactors affecting egg hatch of Triops longicaudatus (LeConte) (Notostraca: Triopsidae). Hydrobiologia, 63: 145-152.
Simovich M.A. & Hathaway S.A. (1997) Diversified bet-hedging as a reproductive strategy of some ephemeral pool anostracans (Branchiopoda). Journal of Crustacean Biology, 17, 38-44.
Takahashi, F. (1977 a). Pioneer life of the tadpole shrimps, Triops spp. (Notostraca: Triopsidae). Applied Entomology and Zoology, 12: 104-117.
Takahashi, F. (1977 b). Triops spp. (Notostraca: Triopsidae) for thebiological control agents of weeds in rice paddies in Japan. Entomophaga, 22: 351-357.
Takahashi, F., (1975).Effect of light on the hatching of eggs inTriops granarius. (Notostraca: Triopsidae). Environmental ControlinBiology13: 29-33.
Geographical distribution of Anostraca (Crustacea: Branchiopoda) in west Azerbaijan, Iran
Behroz Atashbar*, Naser Agh, Lynda Beladjal and Luc Brendonck
*Department of Biology, Faculty of Science, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium, behroz.atashbarkangarloei@UGent.be
Temporary aquatic habitats have a global distribution being most abundant in semi-arid and arid regions (Brendonck et al., 2008). Due to the threats to the existence of these special habitats, there is a need to understand the factors and processes structuring animal communities in these habitats. Temporary pools have a widespread distribution in all types of habitats but they are also an integral part of the landscape of dryland regions (Brendonck &Williams, 2000). These water bodies can be very important habitats for occurrence of endangered animals in the absence of predators. Fairy shrimp inhabit alkaline pools, ephemeral drainages, rocky outcrop pools, ditches, stream oxbows, stock ponds, vernal pools, vernal swales, and other seasonal wetlands (Eriksen and Belk 1999). Potential factors affecting their distribution include water chemistry, hydrology and depth of unfrozen water in the winter and presence of algae in the spring. Certain environmental conditions required by the encysted embryos for maturation and hatching, including soil moisture conditions, precipitation patterns, and freezing (Colburn
Artemia urmiana was reported from Urmia Lake as a new species by Gunther (1899), and lately 17 sites were described for parthenogenetic Artemia throughout Iran (Abatzopoulos et al. 2006). Except Artemia, the knowledge about the occurrence and geographical distribution of other anostracans is limited. Nevertheless scientific interest has been increasing in the community structure of fairy shrimps in Iran and neighboring countries. Previous studies on large branchiopods in Iran reported seven species including Artemia urmiana Gunther (1899), parthenogenetic
Anemia (Agh and Noori 1997), Streptocephalus auritus Waga 1842 and Branchipus schaefferi Fischer, 1834 (Mura and Azari Takami 2000) and Chirocephalus skorikowi Daday 1913; Branchinecta orientalis Sars 1901 and Phallocryptus spinosa Milne Edwards, 1840 (Brehm 1954).The objective of this study was determine the presence, geographical distribution and biotopes of anostracan (fairy shrimps) in West Azerbaijan.
Material and methods
Study area, sample collection and laboratory studies
Anostraca specimens were collected from 25 temporary pools (12 sites) scattered over the area (Tables 1) using a 250-^m mesh net. The animals were immediately transferred to Formalin (4%) for later identification. Specimens collected from each sample were identified to the taxon using a Zeiss SV 11 stereomicroscope based on morphologic characteristics (Daday 1910).The physical - chemical parameters; pH, dissolved oxygen, temperature, salinity, conductivity, suspended materials, nutrients chlorophyll a, surface area and average depth were measured according to standard methods (Table 2).
Table 1. Location and altitude of the study sites (N= number of pools). The average of surface area and depth of pools are summarized._
39° 39' 20"
44° 50' 29"
39° 33' 18"
44° 44' 10"
Sari Su (1)
39° 24' 34"
44° 26' 22"
39° 26' 33"
44° 57' 26"
39° 24' 21"
44° 58' 55"
37° 44' 26"
45° 15' 54"
37° 34' 49"
45° 15' 28"
37° 32' 38"
45° 15' 05"
45° 08' 37"
36° 56' 16"
45° 37' 15"
Haji Khosh (2)
36° 54' 23"
45° 48' 41"
36° 59' 20"
45° 32' 52"
Table 2. Average values of measured physical and chemical variables in the pools.