Abstract: Background and Objective: Scorpions are considered as one of the most important natural hazards and introduced as a dangerous arthropods. Reproduction is the key factor for survival of any species, then interest has increased in knowing the litter size of a female scorpion species. The aim of present study was to determine the litter size and abundance of newborns in the most important of scorpions in laboratory condition. Materials and Methods: In this descriptive study, scorpions which represented six medically important species were collected from their natural habitats in two provinces of Khuzestan and Isfahan of Iran. All females gave birth in laboratory condition. The number of juveniles for each species were counted immediately after newborns were detected. Data analyses were conducted using SPSS for window version 16.0. Results: The litter size for Hemiscorpius lepturus was 15-31, Odonthobutus doriae 10-25, Mesobuthus eupeus 14-29, Androctonus crassicauda 15-45, Orthochirus scrobiculosus 12-21 and Olivierus caucasicus 19-23 . All parturitions were occurred from late August to mid-October in the laboratory. The findings of the present study indicated that in the laboratory conditions, the litter size for A. crassicauda was the most whereas this value for O. scrobiculosus was less than the other species. Conclusion: It can be concluded that perhaps there is a positive correlation between the maternal female size and the litter size.
INTRODUCTION
Scorpions are arthropods of medical importance, classified in the Class Arachnida. They have known as animal with poisonous and painful sting. They exist up to 52 latitudes of northern hemisphere and 50 latitudes of southern hemisphere. They are more present in the tropical and subtropical areas. More than 2000 species of scorpion have been identified1-3. A limited number of species, about 50-79 are actually responsible for serious or lethal incidents. Most deadly species belong to the family Buthidae; though, species belonging to two other families, Scorpionidae and Hemiscorpiidae, also threaten humans3,4.
Scorpion sting is the main health concern in some African, Middle Eastern, Eastern and Central American countries5-14. More than 1.23 million scorpion stings are occur in the world annually, of which resulting to over 0.27% deaths15,16. Scorpions are common arthropods in urban and rural areas of Iran. The Iranian species have been classified in three families of Buthidae, Scorpionidae and Hemscorpiidae, comprising of 64 species from 19 genera17. A few known species of these responsible for severe envenoming and considered medically important18.
Hemiscorpius lepturus, Androctonus crassicauda and Mesobuthus eupeus are the scorpions of medical importance in Iran. Whereas Buthotus schach, Odonthobutus doriae, Buthotus saulcyi, Apistobuthus pterygosercus and Olivierus caucasicus are less important species in this country and their stings have happened sporadically19-23. About 40000-50000 cases of scorpion sting and a number of deaths has been reported annually in Iran24,25.
Scorpions are viviparous2. Two different reproductive strategies are found in female scorpions: the female breeds only a single time during its life (Semelparity) and the other one when the female breeds more than a single time during its lifetime (Iteroparity)26.
In spite of the fact that scorpions are a major public health problem, It knowless about scorpions than other arachnids. Without knowledge of the reproductive biology of scorpions, the other aspects of their life cannot be fully achieved. Litter size is one of the important point of scorpion life which is poorly known. Studies have been shown that the larger females usually produce more broods and have a greater reproductive investment. However this subject do not happen for all species even for populations of a species26,27.
Because of the studies on litter size of scorpion in Iran are rare, the present study was conducted to identify and determine the litter size of these arthropods in laboratory condition.
MATERIALS AND METHODS
In this descriptive study, six important scorpion species were collected from their natural habitats in provinces of Khuzestan and Isfahan. This study was conducted in May, July, August and September during 2014-2016 at the entomology lab of Kashan University of Medical Sciences.
Each sample was collected by three collector in 3 h. The collected scorpions were put in glass containers labeled essential information and delivered to the entomology laboratory of Kashan University of Medical Sciences for an accurate identification of the species using diagnostic keys28,29. Males were separated and excluded of the study. Totally 54 females of different species of scorpions were kept in glass containers separately in the laboratory conditions (27-31°C) and fed them with the German cockroach, to study their litter size. The gravid scorpions were identified by observing their big bellies. All females gave birth in laboratory condition. The number of living and dead juveniles for each species were counted immediately after parturition. Data analyses were conducted using SPSS for window version 16.0.
RESULTS
The result of present study for 54 females representing six species of scorpion summarized in Table 1. According to presented data the mean litter size of each species was as follow: H. lepturus (Fig. 1 and 2), 24.54±2.04 (Mean±SD) in 13 delivery, O. doriae, 19.33±1.98 in 12 delivery, M. eupeus (Fig. 3), 20.25±1.75 in 12 delivery, A. crassicauda (Fig. 4), 28.87±2.7 in 8 delivery, O. scrobiculosus (Fig. 5 and 6), 16.83±4.13 in 6 delivery and O. caucasicus, 20.67±1.75 in 3 delivery (Table 1). According to this data, the litter size of A. crassicauda was the most whereas this value for O. scrobiculosus was the least.
The first molt, in offsprings for all studied species was observed in the first 10 days after birth while juveniles were carrying by their mother. Hemiscorpius lepturus species showed cannibalistic behavior in the laboratory condition. Fifty percent of samples of H. lepturus females fed their own juveniles. This phenomenon was not observed among other scorpion species.
| Table 1: | Litter size of six scorpions of medical importance in Iran |
| Fig. 1: | Gravid female of Hemiscorpius lepturus |
| Fig. 2: | Hemiscorpius lepturus carrying first instar juveniles |
| Fig. 3: | Mesobuthus eupeus carrying first instar juveniles |
| Fig. 4: | Gravid female of Androctonus crassicauda |
| Fig. 5: | Gravid female of Orthochirus scrobiculosus |
| Fig. 6: | Orthochirus scrobiculosus carrying first instar juveniles |
DISCUSSION
The results of the present study indicated that the litter size for different species of scorpions was varied in the laboratory condition. The findings revealed that the litter size for six important scorpion species in the laboratory condition varies from 10-45. While other researcher reported that this value was vary30-32 from 6-91. It reported the litter size for different species of scorpions from 6-90 and 20-60 respectively28,33. Studies have been shown that the litter size for different species of scorpion is variable27. The number of larvae born by A. crassicauda species was the most whereas this number for O. scrobiculosus species was less than the other species. It can be concluded that there is a direct correlation between the female body size of scorpions and increase the litter size.
The significant positive correlation between litter size and female size has been reported in some studies30,34. while Outeda-Jorge et al.27 reported that the non-significant correlation between these two variables for Tityus serelatus species. However it was observed that bigger females tended to born larger litter but it do not always happen. It may be associated with environmental condition and physiological structure of female scorpion. Litter size can be decrease in any female scorpion species in the end of their age, because of decrease of their follicles35,36.
In this study all deliveries were occurred from late August to mid-October. It shown that majority of births occurred during warm seasons in south America, (September-April). Most of scorpions give birth during December-March (Summer)27. Opportunistic and Synantropic scorpions, are able to deliver their brood throughout the year, thus can increase their population and threaten the human health32,37.
Among the species studied in the present study, only H. lepturus showed cannibalistic behavior and fed on their own larvae. Cannibalism can be observed among scorpions. This behavior may be resulting of the laboratory conditions26,38. It can be varied among specific species due to their physical and physiological structures and various environmental condition. It was reported that about 16% of the adults total diet was provided by newborn mortality. Most newborn mortality happen within the first 90 days of their life39. It was observed that a few Tityus bahiensis juveniles cannibalized by the female during delivery40. Likewise results of a study revealed that 80% of female Rhopalurus rochai Borelli, 1910 showed cannibalistic behavior during delivery41.
For each species, the reproductive rate and the number of newborns should be studied under laboratory conditions. Also, as scorpion nesting behavior is an essential issue in scorpionology, the nesting behaviors of scorpions should be examined. Meanwhile, it is suggested to identify the habitats of scorpions in each region in order to optimize prevention.
CONCLUSION
In small species, the number of newborns per birth was lower in compared with big species. The birth of scorpion newborns in laboratory conditions may not be the same as normal conditions .Therefore, at the same time, the number of newborns in both natural and laboratory conditions should be investigated. Level of knowledge of important aspects of scorpion reproduction is still elementary. For better understanding the scorpion reproduction, doing more experiments for any species are recommended.
SIGNIFICANCE STATEMENT
This study discovered the numbers of newborn of some medical important of scorpions that can be beneficial for future studies. This study will help the researchers to uncover the critical areas of biology of scorpions that many researchers were not able to explore. Thus a new theory on breeding of scorpions may be arrived at.
ACKNOWLEDGMENTS
We highly appreciate the assistance and collaboration of the honorable Social Determinants of Health (SDH) Research Center and Department of Environment Health, Kashan University of Medical Sciences, the laboratory staffs and other stakeholders and also Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. The study was approved by the Social Determinants of Health Research Center of Kashan University of Medical Sciences. The ethical principles of this research were investigated and discussed in the research committee of the above mentioned department and after making needed modifications, it was approved. The study has been done in accordance with the provisions of the Hillsinki Declaration.