Geographic distribution and habitat
The geographic distribution of the Hexophthalma hahni is restricted to the arid and desert regions of southern Africa. The most significant populations are found primarily in Namibia and Angola. This species' preferred habitat is characterized by loose sand, dunes, and rocky areas, such as the famous Namib Desert. The spider's ability to survive in such an extreme environment makes it a fascinating example of evolutionary adaptation.
The venom and its consequences
The venom of the H. hahni is a complex mixture of toxins, the most dangerous component of which is sphingomyelinase D [1]. This enzyme attacks sphingomyelin, an essential lipid that serves as a structural component of cell membranes and the myelin sheath that insulates neurons. Its cytotoxic action degrades sphingomyelin, compromising the integrity of cell membranes and leading to cell death (necrosis) [2, 3].
At a local level, the bite can cause a deep, painful ulcer with extensive areas of necrosis that may require very long healing times and, in some cases, surgical intervention. However, the greater danger comes from the possible onset of a systemic syndrome. If the venom spreads into the bloodstream, it can trigger a series of adverse reactions, including fever, general malaise, hemolysis (the destruction of red blood cells), and thrombocytopenia (a drastic reduction in the number of platelets, which can lead to serious clotting problems) [4]. In rare and unfortunate cases, the systemic syndrome can evolve into acute renal failure, which may be fatal.
The importance of field research
Scientific research on this species is fundamental to fully understanding its biology and the mechanism of action of its venom. A recent expedition to the Namib Desert allowed for the observation of a female H. hahni with her eggs. Thanks to the help of our friend P.J. Brokkies Breitenbach**, an expert nature guide, it was possible to document how the female had laid her eggs under a rock, providing valuable information on the reproductive cycle and maternal behavior of this little-studied species. Such observations contribute significantly to our body of knowledge and to the proper management of arachnid bite poisoning cases.
*Board Member, SRSN (Roman Society of Natural Science)
** PJ Breitenbach +264818399685
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Bibliography
[1] Newlands, G., and J. L. Atkinson. "Studies on spider venoms: I. The isolation and characterization of a sphingomyelinase D from the venom of Hexophthalma hahni." Toxicon, 1988, 26(10): 969-975. [2] Slotte, J. P. "Sphingomyelin and its role in cell membranes." Progress in Lipid Research, 1999, 38(1): 1-13. [3] Hannun, Y. A., and L. M. Obeid. "The cell-signaling functions of ceramide." Trends in Biochemical Sciences, 1995, 20(2): 73-77. [4] Müller, G. J. "Spider bites in southern Africa: an overview of the medical implications." South African Medical Journal, 1992, 82(2): 108-111.
