By Michiel Cozijn
T.obscurus adult couple, left: ♀, right: ♂ M.A.C.Cozijn © 2009
What’s in a name? Tityus obscurus has no generally accepted common name.
Etymology: The name ‘obscurus’ in apposition to the generic name (Tityus) means dark or the dark one.
Junior synonyms: T.amazonicus Giltay 1928, T.cambridgei Pocock 1897, T.paraensis Kraepelin 1896, T.werneri Mello-Leitão 1931, T.sampaiocrulsi Mello-Leitão 1931 (Lourenço, 2008). T.piceus Caporiacco 1947 is a junior synonym of T.cambridgei Pocock 1897 (Kovařik, 1999).
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Distribution Brazilië (Amapá, Pará), Frans Guyana, Suriname (Tafelberg, Brownsberg, Suriname and Marowijne riversystems). Ecuador, Guyana, Venezuela and Panama (1).
Area of reports of T.obscurus (after Lourenço et al, 2000). © Google maps 2009
Natural habitat T.obscurus is a common element of the tropical forests of the Amazon basin. In Surinam, it occurs in mesic highland forests. The lower vegetation of these forests consists of palm trees (i.e. Astrocaryum spp.), and there are also trees of 35-45 meters, like Ceiba pentandra (kapok tree) and Manilkara bidentatus (balata/ rubbertree) that form the canopy. The forest floor is covered with ferns and fernmoss. T.obscurus can be found in the canopy, but also on the forest floor under fallen logs and other debris, aswell as in the rootsystems of large trees. They are also found in rural areas near human settlements, in example in the villages of Moengo and Albina, along the “east-west connection” in Suriname.
Venom The LD50 (mg/ kg) value of the venom is 12.14 and this value seems rather high when compared to T.serrulatus Lutz & Mello 1922 (0.43 Zlotkin et al, 1978) or T.bahiensis Perty 1833 (1.38, Hassan 1984). Lethal incidents have been reported in this species. The symptoms that where caused in three patients by T.obscurus envenomation are localized pain, discoloration of the stingsite, profuse sweating and cyanosis, hypersensitivity, salivation and vomiting. One of the patients experienced numbness of the legs, muscle contractions, convulsions, collaps and he eventually became semi-comatose. This patient recovered after treatment, but he felt ill for five days (Floch et al, 1950). In 1997 a seven year old child died in Cayenne, French Guyana after being stung by T.obscurus. The child was admitted to a hospital seven hours after the stingincident. Six hours later the child was transferred to the intensive care unit. This child suffered from breathing problems, which led to unconsiousness, resulting in heart failure. Attempts to resuscitate the child failed and 16,5 hours after being stung, the patient passed away (Hommel et al, 2000). Because of it’s medical importance, this species should only be kept by very experienced keepers.
T.obscurus adult ♀ (4 days after molting) M.A.C.Cozijn © 2009
Morphological information The genus Tityus C.L.Koch, 1836 comprises more than 180 valid species and subspecies. It is a complex and dynamic genus and the taxonomic position of some of it’s species is unclear. Earlier described species (2) are frequently synonimized and new species are still being described regularly. A revision of the genus is much needed to solve taxonomic unclarities and to gain more insight into this genus. Given the number of species, this would be a labourintensive and timeconsuming project. T.obscurus belongs to the subgenus Atreus. This subgenus contains mostly large (65-100 mm+) scorpions, that have a dark, blackish coloration when adult. Juveniles have a yellowish, variegated pigmentation. The basal middle lamellae of the females is dilated in most species (Lourenço,2006). The total size of T.obscurus is between 80-100 mm. Their overall coloration is darkbrown to blackish, with only some pale area’s on the sternites. Pectinal toothcount is 18-22 for both sexes. They have 17 rows of granules on the moveable finger. The subaculear tooth is strong and spinoid. The species shows strong sexual dimorphism, the adult males having longer and more slender pedipalps and metasomal segments. Even someone who knows nothing about scorpions should be able to see the differences between males and females. Juveniles can be sexed by checking the exuvia’s for dilated basal middle lammelae, indicating the females (3).
Keeping in captivity Most of the following information is based on my own experience and should be regarded as an example. In my opinion the minimum size for keeping a pair of adults is around 30x20x20 cm (12x 8x 8 inch). Juveniles can be kept in all kind of deli cups. I keep my juveniles separate to avoid the risk of cannibalism (especially just molted specimens are vulnerable for hungry siblings). I keep adults in pairs, but I separate the male before the female gives birth. I try to maintain a temperature of 26-30 Celsius ( 78.8-86 F) in the daytime and around 18-20 C (64,4-68 F) at night. The relative humidity should be around 75-80%, this can be done by keeping ca. one third of the substrate dry (or an occasional misting) and two thirds moist (not wet to prevent mold or mites). I mist the enclosure well once a week or occaisonally twice if necessary (depending on temperatures and evaporationrate). When the scorpions are getting close to a molt, make sure the relative humidity is sufficient, to prevent molting problems. Most of the time these scorpions molt on a vertical structure facing downwards to the substrate.
T.obscurus ♀ with instar 1 M.A.C.Cozijn © 2009
Plain humus is ideal as a substrate. This species does not dig burrows and pieces of cork bark will be accepted as a retreat. Sometimes, a small scrape is made under the bark. They hide during the day, but at night they can be observed sitting on top of the cork bark with open pedipalp fingers, or walking around on the substrate. It does not actively hunt it’s prey, but it rather uses the sit-and-wait tactic. These scorpions typically walk very slowly, they almost creep across the substrate, this makes them seem docile, but they can flee or react very fast when startled. I have never seen any Tityusspecies drink from a source of standing water, like a bottle cap. They drink the drops of water from the sides of the enclosure after misting. It is best to mist their enclosures in the afternoon or early evening, to prevent the drops of water to evaporate before the scorpions can drink them. Provide adequate ventilation to create airflow. This is very important because of the high relative humidity that Tityus species generally need. Insect remains (and exuvia) need to be removed regularly, because they decompose quickly in humid environments, which attracts mold and also unwanted organisms like mites (Acari sp.).
T.obscurus ♀ with instar 2 M.A.C.Cozijn © 2009
Adults should be fed one or two appropriate sized prey items once a week. I feed my scorpions housecrickets (Acheta domestica) twice a week untill they are passed the third instar. Prey is killed by a quick sting or stings, this depends on the size of the prey and on the size of the scorpion. Juveniles can subdue surprisingly large prey for their size, sometimes up to 150% of their own bodysize. Newborn scorpions will readily feed on small crickets. This species has been bred several times in captivity and T.obscurus is known for producing iteroparous litters. The young molt for the first time after 4 to 5 days. Average litter size is between 15-40 (Lourenço et al 2000, Kovařik 2005). The adult male and female shown in picture 1 of this factsheet mated on the 8th of february 2009, and on the 15th of july (gestation 157 days) 33 juveniles where born. The young molted to instar 2 on the 19th of July. They started to explore their surroundings from the 23rd of July and they all left their mother on 26th of July. Because of it’s medical importance, this species should only be kept by very experienced keepers.
Notes Notes (1) Reports from Ecuador, Guyana, Venezuela and Panama (Fet & Lowe, 2000: 254) are not confirmed by reliable specimens. The presence in Guyana could yet be confirmed and reports from the other countries mentioned here most certainly correspond to misidentifications of Tityus asthenesPocock 1893 (Lourenço, 2008).
(2) For example see junior synonyms, pg.1
(3) I use this method to sex my specimens, but sometimes it is difficult to see the differences (especially in earlier instars) between the basal middle lammelae of the available specimens.
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