Hemprich’s long-eared bat (<Emphasis Type="Italic">Otonycteris hemprichii</Emphasis>) as a predator of scorpions: whispering echolocation,passive gleaning and prey selection

Over 70% of the droppings of the gleaning bat Otonycteris hemprichii can contain scorpion fragments. Yet, some scorpions found in its desert habitat possess venom of the highest known toxicity, rendering them a very dangerous prey. In this study, we describe how O. hemprichii catches and handles scorpions, quantify its flight and echolocation behaviour in the field, investigate what sensory modality it uses to detect scorpions, and test whether it selects scorpions according to their size or toxicity. We confirmed that O. hemprichi is a whispering bat (approx. 80 dB peSPL) with short, multi-harmonic calls. In a flight room we also confirmed that O. hemprichii detects scorpions by their walking noises. Amplitudes of such noises were measured and they reach the flying bat at or below the level of echoes of the loess substrate. Bats dropped straight onto moving scorpions and were stung frequently even straight in their face. Stings did not change the bats’ behaviour and caused no signs of poisoning. Scorpions were eaten including poison gland and stinger. Bats showed no preference neither for any of the scorpion species nor their size suggesting they are generalist predators with regard to scorpions.     

Evidence of Mate Trailing in the Giant Hairy Desert Scorpion, Hadrurus arizonensis (Scorpionida, Iuridae)

During the mating season, male desert scorpions are often found wandering through dune environments, presumably in search of female conspecifics. For a male desert scorpion, finding a receptive female is a potentially difficult and hazardous task, suggesting that wandering by the male may actually be a form of guided mate searching. In this study we examined whether male giant hairy desert scorpions (Hadrurus arizonensis) were capable of trailing female conspecifics using a Y-maze choice test. In three separate experiments, a significant proportion of male scorpions preferred the arm of the maze that a reproductive female scorpion had walked down. Male scorpions did not prefer maze arms that male conspecifics had walked down, indicating that this response was sex specific. When the substrate was repeatedly exposed to a reproductive female, males took significantly longer to complete the Y-maze test, exhibited an increase in pausing behavior, and displayed precourtship behaviors and a novel lunging behavior resembling sex-specific mate seizing behavior. The results from this study suggest that male H. arizonensis can orient and respond to substrate-borne signals from female conspecifics that are likely chemical in origin.     

Patterns of hemolymph osmoregulation in three desert arthropods

Summary Hemolymph osmoregulation was examined in three species of desert arthropods: a tenebrionid beetle,Eleodes hispilabris, a vejovid scorpion,Paruroctonus aquilonalis, and a spirostreptid millipede,Orthoporus ornatus. During desiccation, beetles regulated hemolymph osmolality and scorpions tolerated increasing osmolality. Millipedes displayed both osmotic regulation and tolerance patterns depending on sex and on duration of desiccation. Rehydration after desiccation depressed blood osmolality of male scorpions and beetles below levels found for freshly collected specimens. This was not the case in millipedes. Seasonal osmolality changes were studied and recorded among field-collected scorpions and beetles. Patterns of regulation and tolerance of hemolymph osmolality appear to vary among different kinds of desert arthropods.     

How does the scorpionEuscorpius flavicaudis (Deg.) manage to survive in Britain?

Field observations at Sheerness suggest thatE. flavicaudis is night-active: it fluoresces strongly in ultra-violet light. Aktograph experiments demonstrated a marked circadian rhythm of noctural locomotory activity whose free-running period in constant light is 24.7 h. In darkness, the free-running period is variable. The rate of transpiration is not unduly low compared with that of other scorpions, as might have been expected wereE. flavicaudis day-active. It is argued that the survival of this species in southern England does not involve any special physiological adjustments since most if not all species of scorpions are able to withstand freezing temperatures.     

Sprint Speeds of Juvenile Scorpions: Among Family Differences and Parent Offspring Correlations

Sprinting from predators is an important part of the defensive repertoire of some scorpions. This study examined sprint speed in juvenile scorpions and its relation to sprint speed of the mothers. Sprint speeds of juvenile scorpions, Centruroides vittatus, were determined by repeated trials on a small racetrack. Speeds were repeatable across trials within individuals and differed among individuals. There were marked among family differences in juvenile sprint speeds. Juvenile sprint speeds were correlated with maternal sprint speeds. Although the effect of common maternal environment may inflate the measures of heritability to an unknown extent, these results suggest that sprint may respond to natural selection and there is an underlying genetic basis to observed performance differences among scorpions.     

Reproductive investiment in the scorpion Centruroides vittatus

Among invertebrates, scorpions possess a relatively unique set of reproductive traits. The interrelationships of these traits may have important implications for life history theory, yet there have been few studies of these traits in scorpions. Our data indicate that larger female Centruroides vittatus produce more offspring and have a higher total litter mass than smaller females. There was, however, no significant relationship between offspring size and female or litter size. Mean offspring mass increased with increases in total litter mass and within litter variation in offspring size (coefficients of variation) decreased with increasing total litter mass. These results suggest that large female scorpions with a larger investment in reproduction produced more offspring that were more uniform in size, but not significantly larger, than small females with less investment. The fractional clutch principle and physiological and functional constraints on size and number of offspring are suggested as possible explanations for the relationships we found among offspring size, variation in offspring size and total investment in offspring in C. vittatus.     

Relationship between environmental variables and surface activity of scorpions in the Arid Chaco ecoregion of Argentina

Many environmental factors may influence the activity of scorpions in arid ecosystems. In this study, we examined the effects of such factors on scorpion activity at a mature and a secondary forest site in the Chancaní Reserve (Arid Chaco ecoregion in Córdoba, Argentina). Scorpions were collected using pitfall traps, and their nocturnal activity was observed by means of UV light during 14 nights. Temperature, air humidity, atmospheric pressure, and wind velocity were measured, and the percentage of visible moon was estimated. A total of 440 scorpions, representing seven species belonging to two families (Bothriuridae and Buthidae), were observed in the study area. Brachistosternus ferrugineus was the species most commonly observed using both methods. Mature and secondary forest shared slightly more than 50% of species. Surface activity of scorpions observed with the two methods differed significantly between the two areas. Surface activity of all scorpions and of B. ferrugineus were negatively related to the phase of the moon and positively related to air temperature. Physical factors thus have important effects on scorpion activity.     

Evidence for Eurogondwana: the roles of dispersal,extinction and vicariance in the evolution and biogeography of Indo‐Pacific Hormuridae (Scorpiones: Scorpionoidea)

Scorpions previously assigned to the genus Liocheles Sundevall, 1883, of the family Hormuridae Laurie, 1896, are widely distributed in the tropical forests of the Indo‐Pacific region. Revisionary systematics of these poorly known scorpions has revealed a tremendous diversity of species. As part of an ongoing investigation, the first analysis of Indo‐Pacific hormurid scorpion phylogeny based on morphological data scored for all currently recognized species of Hormiops Fage, 1933 , Hormurus Thorell, 1876, and Liocheles, is presented. The taxonomy of these scorpions is reassessed and their biogeography reinterpreted in the light of the phylogeny. Phylogenetic, morphological, and distributional data support the revalidation of Hormiops and Hormurus, previously synonymized with Liocheles. The phylogeny indicates that the Australasian hormurids are more closely related to the Afrotropical and Neotropical hormurids than to the Indian hormurids, as previously proposed, refuting the “out‐of‐India” origin of Asian hormurids. A recent paleogeographical hypothesis, the “Eurogondwana model”, is supported instead. According to this hypothesis, hormurid scorpions colonized Laurasia from Africa via the Apulia microplate (Europa terrane) in the Cretaceous, subsequently colonized the Australo‐Papuan archipelago in the early‐mid Cenozoic, and then went extinct in the Northern Hemisphere during the second half of the Cenozoic. These results suggest that, contrary to the traditional paradigm, dispersal and extinction may affect spatial and temporal biotic distributions as much as vicariance, even in animals with limited vagility, such as scorpions.     

The Life History of Chactas reticulatus Kraepelin, 1912 (Scorpiones, Chactidae), with a Comparative Analysis of the Reproductive Traits of Three Scorpion Lineages in Relation to Habitat

An account is given of the life history, growth, population densities, habitat, reproductive systems, courtship and mating, litter size and sex ratio, iteroparity, molting and development of the scorpion Chactas reticulatus Kraepelin. These same traits are compared in three distinct scorpion lineages, buthid, chactid and ischnurid in relation to habitat characteristics. Correlations are drawn between reproductive and adaptative strategies, and it is suggested that if non-buthid scorpions may present some homogeneity as equilibrium species, buthid scorpions are not necessarily opportunistic species. Many groups can be characterized within the buthids, and these different lineages show variable ecological requirements.     

Ecological modeling and distribution analysis of digger scorpions: Odontobuthus doriae,Odonthubutus bidentatus (Scorpiones: Buthidae) and Scorpio maurus (Scorpiones: Scorpionidae) in Iran using the maximum entropy method

Prediction models are essential for the potential geographic distribution of scorpions, prevention of scorpion stings and diverse applications in conservation biology. There is limited information about habitat suitability and the factors affecting the distribution of Iranian digger scorpions. This study was undertaken to model the distribution of three types of digger scorpion in Iran, Odontobuthus doriae Thorell, Odonthubutus bidentatus Lourenco (Scorpiones: Buthidae) and Scorpio maurus Pocockin (Scorpiones: Scorpionidae), and investigate the factors affecting its distribution using the maximum entropy method. A total of 20 environmental and climate variables were used for modeling and evaluation of the ecological niche. The similarities and differences between the ecological overlap of the digger scorpions were evaluated using comparative environmental niche model (ENM Tools software). The results showed that the main factors for habitat suitability of O. doriae were soil type, mean temperature of the wettest quarter and slope. The variables for S. maurus were soil type, precipitation of the coldest quarter and slope. Annual temperature range, mean temperature of the driest quarter and land use had the greatest influence on the distribution of O. bidentatus. The ecological niches for O. doriae and O. bidentatus overlapped. The niche of these species differed from the niche of S. maurus. This approach could be helpful for the prediction of the potential distribution of three digger scorpion species and this model can be an effective for the promotion of health.

     

The influence of the quantity of food on fecundity in the desert grassland scorpion (Paruroctonus utahensis) (Scorpionida,Vaejovidae): An experimental test

Summary Females of the desert grassland scorpion Paruroctonus utahensis were maintained in field enclosures and fed differing amounts of food. The number of young scorpions per female varied from 0 to 32. The mean weight of second-instar young varied significantly among broods. The number of young, the size of the young, and total brood weight were not related to adult female size. There were no significant relationships between any of the brood characteristics and the amount of food eaten by the mother during the 11 month gestation. This suggests that foraging success is not an important proximate factor influencing fecundity in Paruroctonus utahensis.     

Mechanoreceptive function of pectines in the Brazilian yellow scorpion Tityus serrulatus: perception of substrate-borne vibrations and prey detection

Environment perception by scorpions is an issue of great interest, and there is controversy about the use of pectines in this function. This paper investigates the mechanoreceptive function of pectines of the yellow scorpion Tityus serrulatus. The study was conducted in laboratory conditions from July 2003 to July 2004. Ninety females were maintained in six terraria (N = 15). Three of them were named “control” group (intact pectines) and the others “treatment” group (pectines covered with paraffin). Three experimental tests (an ethogram, a test of prey detection and a test of perception of substrate-borne vibrations) were performed to compare skills of animals with and without blocked pectines. The ethogram showed that treated individuals significantly reduced their exploratory activities, spent more time resting, and aggregated more than the control ones. Prey detection tests showed that the blocking of pectines made the yellow scorpions inefficient to detect and capture prey. Vibration tests showed that animals with blocked pectines also did not respond to the vibrations produced in the substrate, whereas the opposite occurred with the control group. These results suggest a mechanoreceptive function for T. serrulatus pectines, and show that the detection of ground vibrations by these structures is important for prey perception and orientation in the Brazilian yellow scorpion.     

Friend or foe: behavioral responses to conspecifics in the northern scorpion, <Emphasis Type="Italic">Paruroctonus boreus</Emphasis> (Scorpionida: Vaejovidae)

We investigated the behavioral response of male Paruroctonus boreus to male and female pheromones of conspecifics. Adult male scorpions actively search for females during the mating season, but lack visual cues to direct their movement. Chemical cues (pheromones) are thought to be responsible for directing movement. In a series of laboratory experiments, in Y-mazes, males were exposed to areas that had contained males and females from the same population and areas that had contained conspecifics from different populations. Males spent significantly more time in areas that had contained females from the same population but did not show a preference for areas exposed to females from different populations. Males also significantly avoided areas exposed to males from the same population. Our results suggest that P. boreus has a sex-specific response to pheromones and that this response may be population-specific.     

The ecology of the scorpion Euscorpius flavicaudis in England

A large colony of Euscorpius flavicaudis was studied at Sheerness Docks, Isle of Sheppey, Kent. It was probably established in the late nineteenth century. The scorpions inhabit cracks in the dockyard perimeter wall where the mortar pointing has crumbled away. They are nocturnal, "sit-and-wait", generalist predators. They are extremely sedentary: females leave their cracks fewer than 10 times per year; males are more active as they become vagrant prior to the mating season, which occurs in summer. Marked adults were resighted at intervals of over a year and the distance scorpions moved between resightings was not proportional to the interval. The number of scorpions seen per night was influenced by temperature, amount of rainfall and phase of the moon. In winter, the scorpions retreated far into the wall and, by doing so, reduced the risk of suffering mortality due to cold. During this time, they were seldom active. In general, this species does not behave in any way that can be correlated with living in a temperate rather than a desert area. This illustrates the extreme adaptability of scorpions.     

Cost of venom regeneration in Parabuthus transvaalicus (Arachnida: Buthidae)

Scorpion venom has many components, but is mainly made up of water, salts, small molecules, peptides, and proteins. One can reasonably assume that the production and storage of this complex secretion is an expensive metabolic investment. However, to date, no study has addressed the costs associated with the regeneration of venom by scorpions. Using a closed-system respirometer, we examined the difference in oxygen consumption between milked and unmilked scorpions to determine the metabolic costs associated with the first 72 h of subsequent venom synthesis. During this time period, milked scorpions had a significantly higher (39%) metabolic rate than unmilked scorpions. The regenerated venom from a second milking had significantly lower (74%) protein concentration, suggesting that venom regeneration was incomplete after 72 h. The protein content in the regenerated venom was not correlated with oxygen consumption. The significant increase in oxygen consumption after milking supports existing hypotheses about the metabolic cost associated with venom regeneration and provides further insight on why scorpions appear to be judicious in their stinger use.     

Impact of climate changes from Middle Miocene onwards on evolutionary diversification in Eurasia: Insights from the mesobuthid scorpions

The aridification from Middle Miocene onwards has transformed the Asian interior into an arid environment, and the Pleistocene glacial–interglacial oscillations exerted further ecological impact. Therefore, both aridification and glaciation would have considerably influenced the evolution of many mid‐latitude species in temperate Asia. Here, we tested this perspective by a phylogeographic study of the mesobuthid scorpions across temperate Asia using one mitochondrial and three nuclear genes. Concordant mitochondrial and nuclear gene trees were obtained, which are consistent with species tree inferred using a Bayesian approach. The age of the most recent common ancestor (MRCA) of all the studied scorpions was estimated to be 12.49 Ma (late Middle Miocene); Mesobuthus eupeus diverged from the clade composing Mesobuthus caucasicus and Mesobuthus martensii in early Late Miocene (10.21 Ma); M. martensii diverged from M. caucasicus at 5.53 Ma in Late Miocene. The estimated MRCA ages of M. martensii and the Chinese lineage of M. eupeus were 2.37 and 0.68 Ma, respectively. Central Asia was identified as the ancestral area for the lineage leading to M. martensii and M. caucasicus and the Chinese lineage of M. eupeus. The ancestral habitat of the genus Mesobuthus is likely to have been characterized by an arid environment; a shift towards more humid habitat occurred in the MRCA of M. martensii and a lineage of M. caucasicus, finally leading to the adaptation of M. martensii to humid environment. Our data strongly support the idea that the stepwise intensified aridifications from Mid‐Miocene onwards drove the diversification of mesobuthid scorpions, and suggest that M. martensii and M. eupeus observed today in China originated from an ancestral lineage distributed in Central Asia. Both the colonization and the ensuing evolution of these species in East Asia appear to have been further moulded by Quaternary glaciations.     

Abdominal plates,spiracles and sternites in the ventral mesosoma of embryos of the desert scorpion Paruroctonus mesaensis (Scorpiones,Vaejovidae)

Summary

The scanning electron microscope was used to study changes in the ventral mesosoma of the vaejovid scorpion, Paruroctonus mesaensis. Observations are compared with those from scorpion fossils. The oldest fossils are from the Silurian period; migration from water to land occurred in the Carboniferous and Permian periods. All recent scorpions are terrestrial with four pairs of booklungs and spiracles in mesosomal sternites. Ancient eurypterids and scorpions had flap-like abdominal plates attached to the ventral surface of five mesosomal segments. The abdominal plates were apparently an aquatic adaptation, and authors have described possible gill tissue in the chamber above. In scorpion embryos, rectangular (holostem) plate-like structures precede the formation of sternites in the ventral mesosoma. Transverse folds were seen in the space above the abdominal plates. The lack of elaborate gill-like structures here supports an earlier hypothesis that aquatic scorpions had other mesosomal respiratory sites (e.g., pectines), resulting in less reliance on respiratory tissues above the abdominal plates. Spiracles initially appear as round or ovoid patterns in the epidermis at the latero-posterior margins of the ventral plates. The booklung spiracles are positioned farther anterior in sternites, but the developmental sequence for this transition is still unclear and may occur later than the stages of this study. The abdominal plates lengthen and enlarge laterally and/or epidermis is added at the lateral edges so that broad, overlapping sternites eventually cover the ventral surface of the mesosoma.     

Intraspecific differentiation of social behavior and shelter selection in Mesobuthus gibbosus (Brullé, 1832) (Scorpiones: Buthidae)

We compared seasonal shelter selection and social behavior of Mesobuthus gibbosus from autumn to mid-summer in two similar phryganic ecosystems, in continental Greece (near Volos city) and in insular Greece (eastern Crete), and in the laboratory under simulated abiotic conditions. Our results showed that shelter selection is a critical indicator of the seasonal social behavior of the species. The abrupt climatic changes in spring caused a differentiation in shelter selection between the cold period (November–February) and the warm period (March–June) at both sites. Sociality was exhibited only during winter in the field and was more extensive under cold conditions in the laboratory. Co-occurrence of scorpions proved to be age-specific, facilitated by population density and by harsh abiotic conditions during winter, and negatively influenced by intraspecific competition, which was higher in continental Greece. The response of scorpions to changes of abiotic factors reveals synchronization of seasonal shelter selection with climatic changes.     

Intra- and interspecific cohabitation of scorpions in the field and the effect of density, food, and shelter on their interactions

Scorpion cohabitation was studied qualitatively and quantitatively for several years in the field and in controlled experimental conditions in the laboratory. In the field, several cases were recorded of scorpions sharing the same shelter, either intra- or interspecifically. Intraspecific cohabitation was more prevalent than interspecific cohabitation. Among the five scorpion species studied here, Compsobuthus werneri judaicus shows the highest degree of sociality and aggregates both intra- and interspecifically. Leiurus quinquestriatus was never observed to cohabit interspecifically. Both Buthotus judaicus and C. werneri judaicus shared shelters with other scorpions more frequently during the wet season, whereas Nebo hierichonticus and Scorpio maurus fuscus cohabitated more often during the dry season. Under controlled laboratory conditions, density and availability of either food or shelter appear to be significant in facilitating cohabitation, even in the more aggressive species. Received: April 28, 1999 / Accepted: July 30, 1999