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| Striped Bark Scorpion - Centruroides vittatus | |
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| Tweet Topic Started: May 29 2014, 01:23 PM (3,841 Views) | |
| Taipan | May 29 2014, 01:23 PM Post #1 |
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Striped Bark Scorpion - Centruroides vittatus![]() Scientific classification Kingdom: Animalia Phylum: Arthropoda Subphylum: Chelicerata Class: Arachnida Order: Scorpiones Family: Buthidae Genus: Centruroides Species: Centruroides vittatus The striped bark scorpion (Centruroides vittatus) is an extremely common scorpion found throughout the midsection of the United States and northern Mexico. It is perhaps the most frequently encountered scorpion in the U.S. Appearance A medium-sized scorpion that is rarely longer than 70 mm (up to around 2 3/4 inches), The striped bark scorpion is a uniform pale-yellow scorpion that can be identified by two dark, longitudinal stripes on its carapace, with a dark triangular above the ocular tubercle. There are minor variations on this theme, however; specimens that are lighter-colored and lack the characteristic stripes have been described as separate species in the past. Their color suits their environment well, providing them with a natural camouflage from predators as well as prey. Males have a pectinal tooth count of 21-30, while females count 20-27. Distribution and Habitat The natural geographic distribution of C. vittatus is formed by several adjoining South-Central US states and northern Mexico. Beginning in the northern Mexico Border States, Chihuahua, Coahuila, Nuevo Leon, and Taumalipas, C. vittatus’ range extends upward longitudinally through Texas, Oklahoma, and Kansas, to reach as far north as Thayer Co., Nebraska. The area also extends laterally from the Sangre de Cristo Mountains and Rio Grande in New Mexico and Southern Colorado to the Missouri and Mississippi Rivers in Missouri and Louisiana. In all, the range includes the following states: Arkansas, Colorado, Illinois, Kansas, Louisiana, Missouri, Nebraska, New Mexico, Oklahoma, Texas. Reports have also found C. vittatus in locations inconsistent with the natural geographic distribution aforementioned. Populations seem to be found only in particular cities outside its natural distribution, so it is thought likely that human activity has introduced C. vittatus to these areas. They include locations east of the Missouri and Mississippi rivers in Illinois (Cook and McHenry Counties), Iowa (County unknown, Missouri Valley), Kentucky (Marshall and Calloway Counties), Louisiana (East Baton Rouge Parish and Orleans Parish), Mississippi (Lamar, Pike and Rankin Counties), Missouri (Clark County), North Carolina (Dare, Nash, and Wake Counties), and Tennessee (Rutherford and Shelby Counties). Additional sightings have occurred in Arizona (Maricopa County), California (Contra Costa County), and Colorado (Boulder County). A wide geographic distribution allows C. vittatus to occupy desert, deciduous and coniferous forest, and temperate grassland [biomes], where they can be found in crevices under rock and surface debris, vegetation, old rural structures like sheds and barns, and houses during the day. At night, this species emerges from its daytime home and can be found on the open ground or in vegetation like microphyllous desertic brushwood or other classification. ![]() Behavior While the genus Centruroides implies this species is a semi-arboreal one, the striped bark scorpion spends a substantial amount of its time on the ground and can be found in under rock and surface debris, within vegetation, and in weathered rural structures like old sheds and barns during the day. The terrestrial preferences of this species carry into the night hours, when the scorpion will emerge from its temporal shelter at or after sunset to search forage for potential prey. Juveniles, however, spend a substantial amount of time in vegetation likely to avoid predation to which they are more vulnerable. C. vittatus has a very dynamic diet which includes insects, smaller arachnids and juveniles of the same species. It is preyed on by birds, reptiles, some mammals and larger arachnids. Unlike most species of scorpion, C. vittatus is social, presenting it with more opportunities to mate and compete for mates. Consequently, the process of reproduction is one that is both intricate and extensive. Males begin by engaging behavior to establish dominance to mate. They engage in a showdown that highlights tail-waving and shifting until one male backs down. Once one male has established it is the one to mate, male engages the female in the first “step” of courtship called the “promenade a deax” (PAD). During this step, the smaller male maneuvers the female to a spot where he can deposit spermatophore, a small capsule containing the male’s sperm, for reception. This step will determine whether the female will assume the male’s spermatophore, as the male must hold the female long enough to coax her over the spermatophore. Larger males tend to have more success at maneuvering the female than smaller ones. If the male has successfully maneuvered, the male and female will move onto join together and rub chelicera in the “kiss” stage where the female will uptake the spermatophore. The female will then allow approximately eight months for gestation whereupon she will have live offspring which will spend the time for at least one molt on the protection of her back. ![]() Human significance Thousands of people are stung each year by Centruroides vittatus while barefoot or accidentally making contact with the scorpion in houses and other man-made structures. While a sting from C. vittatus is very rarely deadly, it is painful and causes localized swelling. Neurotoxins in the venom can also cause paresthesia and muscle spasms, while more severe cases have resulted in a more intense hypersensitive reaction characterized by symptoms like angioedema, abdominal cramping, chest tightness, flushing, lightheadedness, a large localized reaction, nausea and vomiting, syncope, shortness of breath, urticarial, wheezing and in severe cases, anaphylactic shock. Several studies have revealed that C. vittatus venom is composed of multiple proteins which serve as allergens to the human body. SDS-PAGE and IgE Immunoblots reveal that nine of these proteins elicit an IgE mediated immune response, which is known to be consistent with a hypersensitive reaction. In addition, Api-Zym and Radial Diffusion Assays show that C. vittatus venom contains the enzymes alkaline phosphatase, esterase, esterase lipase, acid phosphatase and phospholipase A. On 30 June 2011, a man on an Alaska Airlines flight was reportedly stung by a striped bark scorpion. The flight had originated from Austin, Texas, which is where authorities believe the scorpion originated. The man reportedly did not experience any serious medical conditions. While a Centruroides vittatus sting is not typically deadly, and signs like swelling can be treated using an ice pack, several other species from the genus Centruroides can have a deadly sting and medical attention should be sought immediately. |
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| Taipan | May 29 2014, 01:52 PM Post #2 |
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The Fiercer Sex: Why Female Scorpions Sting More Quickly By Tia Ghose, Staff Writer | May 28, 2014 05:00pm ET ![]() The bark scorpion,Centruroides vittatus, lives from Arkansas to New Mexico. Female scorpions may sting more quickly to compensate for their slower running speed, new research shows. And that sluggish running, and extra female fierceness, may be a result of the extra weight they carry from pregnancy, the researchers said. "The females are heavier, and they can't sprint as fast," said study co-author Bradley Carlson, an ecologist at The Pennsylvania State University. "Heavier ones have to compensate for that by stinging more." The fiercer sex Past studies had suggested that female scorpions tended to be extra aggressive, wielding their venom-packed stingers more quickly in comparison to males. Carlson and his colleagues suspected this aggression was a result of differences in their tails, with males' longer, skinnier ones perhaps being more difficult to wield. (A scorpion "tail" is, in fact, just an extension of the abdomen, with a stinger at the end.) So the researchers ventured into the New Mexican desert to trap bark scorpions. This particular scorpion species, Centruroides vittatus, can be found from Arkansas to New Mexico and grows to about 3 inches (7.6 centimeters) long. Unlike the deadlier bark scorpions found farther west, C. vittatus has a sting that's not much worse than a bad bee sting, Carlson said. Because the nocturnal creatures contain a chemical that glows under ultraviolet light, the researchers set out in the dead of night, shining blacklight flashlights on the desert landscape. "If the light hits one, you'll suddenly see this bright-green glowing shape in the grass or the rocks," Carlson told Live Science. They eventually scooped up 30 females and 31 males by the tail using long tweezers, dropping them into a plastic bag. The researchers weighed the scorpions, then placed a 1-inch-long (2.5 cm) cardboard target on their backs and tracked how often they stung. In another trial, they measured how fast the insects sprinted across a track. Speedy and meeker No matter the sex, heavier animals were more aggressive. But on average the females were heavier, likely because they are pregnant eight months of the year and have to lug around a belly full of baby scorpions in addition to their own body weight. The females stung the target about four times per second, compared to about three times per second for the males. The males were the speedier sprinters, running about 30 percent faster than the females. The females seemed averse to sprinting, Carlson said. "Females would sometimes just run a little ways and then give up," Carlson added. So the females may simply be too heavy to scurry away quickly, and would rather wield their stingers to defend themselves, Carlson suspects. As a follow-up, the team wants to figure out exactly why male scorpions have longer, skinnier tails than females. The findings were detailed today (May 28) in the journal PLOS ONE. http://www.livescience.com/45938-female-scorpions-bite-more.html Meek Males and Fighting Females: Sexually-Dimorphic Antipredator Behavior and Locomotor Performance Is Explained by Morphology in Bark Scorpions (Centruroides vittatus) Bradley E. Carlson, Shannen McGinley, Matthew P. Rowe Published: May 28, 2014DOI: 10.1371/journal.pone.0097648 Abstract Sexual dimorphism can result from sexual or ecological selective pressures, but the importance of alternative reproductive roles and trait compensation in generating phenotypic differences between the sexes is poorly understood. We evaluated morphological and behavioral sexual dimorphism in striped bark scorpions (Centruroides vittatus). We propose that reproductive roles have driven sexually dimorphic body mass in this species which produces sex differences in locomotor performance. Poor locomotor performance in the females (due to the burden of being gravid) favors compensatory aggression as part of an alternative defensive strategy, while male morphology is coadapted to support a sprinting-based defensive strategy. We tested the effects of sex and morphology on stinging and sprinting performance and characterized overall differences between the sexes in aggressiveness towards simulated threats. Greater body mass was associated with higher sting rates and slower sprinting within sexes, which explained the greater aggression of females (the heavier sex) and, along with longer legs in males, the improved sprint performance in males. These findings suggest females are aggressive to compensate for locomotor costs of reproduction while males possess longer legs to enhance sprinting for predator evasion and mate finding. Sexual dimorphism in the metasoma (“tail”) was unrelated to stinging and sprinting performance and may best be explained by sexual selection. ![]() FIGURE 1: Morphology of representative male and female scorpions (Centruroides vittatus). Whole body, metasoma-alone, and leg-alone (right 4th leg) images are presented on different scales, though relative sex differences are preserved. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0097648 |
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