Melanism in two buthid species from Saudi Arabia

 

Body coloration is important for many animals and is assumed to play a part in part in camouflage, thermoregulation, protection against UV damage, and increased immunity to parasites. In species inhabiting dark surfaces in their habitat, dark body colors may have evolved to increase the camouflage. 

Margareta Lakusic and co-workers have recently published an article describing different levels of dark melanism in the two buthids Leiurus haenggii Lowe, Yagmur & Kovarik, 2014 and Compsobuthus manzonii (Borelli, 1915) from Saudi Arabia. The scorpions were found on dark volcanic substrate or within transition zones between light-colored substrates and dark lava flows.

Abstract:
Body colouration is involved in multiple aspects of species ecology and behaviour. Melanism, a common colour polymorphism, has been associated with camouflage and thermoregulation, particularly in diverse, high-altitude habitats of arid regions. This study reports the first case of melanism in the lacertid Acanthodactylus boskianus, two scorpions, Leiurus haenggii and Compsobuthus manzonii, and the first records of brown-black melanistic colouration in three rodent species, Acomys dimidiatus, Meriones crassus, and Sekeetamys calurus, in the dark lavafields (harrat) of north-western Saudi Arabia. Additionally, it expands observations of melanism in the endemic colubrid Rhynchocalamus hejazicus and provides the first documented records of brown-black melanistic Acomys russatus for the region, consistent with earlier predictions. These observations suggest that colour polymorphism may serve a cryptic function through background matching in both diurnal and nocturnal species, but other roles of melanism should be further investigated. Despite their extent, lava fields in arid regions remain poorly studied due to their remoteness and limited accessibility, yet they offer unique opportunities to investigate phenotypic evolution in arid ecosystems.

Reference:
Lakušić M, Roumelioti M, Licata F, Bilancioni M, Ferreira DF, Khalatbari L, et al. Melanism in scorpions, reptiles and rodents inhabiting the volcanic fields of north-western Saudi Arabia. Journal of Arid Environments. 2026;233:105548. [Full text supplied by authors]