Comparative anatomy of the mesosomal organs of scorpions (Chelicerata, Scorpiones), with implications for the phylogeny of the order

Abstract

We present a review and reassessment of anatomical variation in the ovariuterus (and associated follicles), digestive gland, and lateral lymphoid organs of scorpions, and discuss the contribution of these character systems to the understanding of scorpion phylogeny. New data, obtained using light microscopy, are presented from an examination of 55 scorpion species, representing most scorpion families, and are collated with observations from the literature. Six distinct types of ovariuterine anatomy are identified: five in the family Buthidae and one in the remaining (nonbuthid) families. The buthid genera Lychas C.L. Koch, 1845 and Rhopalurus Thorell, 1876 are exceptional in possessing multiple types of ovariuterine anatomy among the congeneric species studied. The presence or absence of lateral lymphoid organs appears to be phylogenetically informative: the organ is absent in buthids, chaerilids and Pseudochactas Gromov, 1998. Embryo follicle morphology appears to be phylogenetically informative within the superfamily Scorpionoidea Latreille, 1802, where it supports the controversial sister‐group relationship between Urodacus Peters, 1861 and Heteroscorpion Birula, 1903. The mesosomal anatomy of Microcharmus Lourenço, 1995 (Microcharmidae Lourenço, 1996) is consistent with that of Buthidae C.L. Koch, 1837, and we therefore propose the following new synonymy: Microcharmidae Lourenço, 1996 = Buthidae C.L. Koch, 1837. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 651–675.

Phylogenomic resolution of scorpions reveals multilevel discordance with morphological phylogenetic signal

“…All scorpions bear compact digestive glands, excepting the non-bothriurid scorpionoids, which bear digitiform digestive glands [65]. However, the two characters are strongly correlated, probably owing to the physiological and/or physical requirements of katoikogenic development.…”

“…The tree topology we obtained across all analyses indicates that most of the character systems commonly used in scorpion systematics are uninformative at the superfamilial level, due to autapomorphic character state distributions with respect to superfamilies or families (electronic supplementary material, figure S25 and table S3) [19,24,65]. A handful of characters unites Iurida and supports the mutual monophyly of Buthidae, Chaerilidae and Pseudochactidae.…”

Exploring the global animal biodiversity in the search for new drugs – Spiders, scorpions, horseshoe crabs, sea spiders, centipedes, and millipedes

“…They are characterized by the pair of pedipalps modified as grasping claws and the long, segmented tail often carried in a characteristic forward curve over the back with a venomous stinger at the end [101]. Scorpions can be found in virtually every terrestrial habitat on all continents except Antarctica, in general in dry, hot environments, although some species are also encountered in forests and wet savannas [100].…”

“…The body of a scorpion is divided into a cephalothorax and an abdomen which is subdivided into a broad anterior mesosoma and a narrow metasoma [101]. The cephalothorax comprises the thick and hard carapace; two to five pairs of eyes; chelicerae pedipalps modified as grasping claws for catching prey, defense, and sensory purposes; and four pairs of walking legs [101].…”

“…The cephalothorax comprises the thick and hard carapace; two to five pairs of eyes; chelicerae pedipalps modified as grasping claws for catching prey, defense, and sensory purposes; and four pairs of walking legs [101]. The mesosoma is made up of the anterior seven segments of the abdomen and is protected by hardened dorsal and ventral plates [101]. The long metasoma or 'tail' consists of five segments, the fifth of which bears the venomous stinger for injecting venom from a pair of venom glands [101].…”