Hemolymph vascular system in scorpions as a character in taxonomy and phylogeny

The morphological characters thus far employed in analyses of scorpion phylogeny have been based almost entirely on external structures, but it has been known for many years that internal anatomy also may have an potential importance in phylogeny.

Klussmann-Fricke, Prendini and Wirkner have recently published a paper on the evolutionary morphology of the hemolymph vascular system in scorpions and its potential use in systematic studies of scorpions.

Abstract:
Phylogenetically informative characters from the internal anatomy of scorpions were first reported more than 150 years ago, but the subject received little attention after the mid-1920s. Recent investigations, using traditional dissection, illustration and histological sectioning, microscopy, and innovative new methods for investigating complex soft tissue anatomy identified a new wealth of variation. Additionally, these investigations confirmed the phylogenetic significance of previously identified structures. Building on earlier work we present a more detailed description of the hemolymph vascular system (HVS) in scorpions, based on comparison of the vascular structures of the heart and the branching pattern of the prosomal arteries among 45 exemplar species representing most of the major scorpion lineages. Using corrosion-casting, MicroCT in combination with computer-aided 3D-reconstruction, and scanning electron microscopy, we conceptualize a series of phylogenetically informative characters for the anterior aorta system and characters of the heart and associated structures (e.g. arrangement of the ostia) of scorpions. Furthermore, we optimize the possible evolution of these new characters on a previous hypothesis of scorpion phylogeny, and discuss alternative character state transformations, their evolutionary consequences, and possible underlying evolutionary mechanisms acting on the HVS.

Reference:
Klußmann-Fricke BJ, Prendini L, Wirkner CS. Evolutionary morphology of the hemolymph vascular system in scorpions: A character analysis. Arthropod Structure & Development. 2012;41(6):545-60. [Subscription required for full text]

Thanks to Roland Stockmann for informing me about this paper!