Perhaps you noticed the reddish hairs on the Dermestes maculatus beetles from South Africa in my previous blog post. I certainly did, and this colour variant caught my eye on multiple iNaturalist sightings from Africa. Not a singel individual from my own Dermestes maculatus colony, imported from America, show or have shown this kind of colouration noticeably. It makes me wonder.. Can this colour variation be purposely bred?
Photo below is from the iNaturalist sighting of Sammy Kernane, Algeria.
Mulsant and Rey (1867) already noticed some wild individuals with soft brown hairs on their pronotum and elytra instead of white, naming this colour variation "rattulus". Kalík (1955) described a local population with black hairs on the thorax and abdomen, a variation he called "nigropubescens". Other variations that gained a name are "pearl" for beetles with white eyes and "fuscous" for beetles that are dorsally densely covered in brown hairs (Shaw 1965).
The first researcher to look into the inheritance of genetic traits was Philip (1940). She describes multiple morphological mutations. An example of what she discovered, is that the gene for a black body is dominant over a brown body (pronotum and elytra). She also bred a variation called "orange heads" in whom the whole head of the adult beetles were covered with orange hairs.
Melanins are the most extended biological pigments, consisting of eumelanin and/or pheomelanin and are also produced by insects (Galván et al. 2015). Generally, the more melanin present, the darker the hair. Its tone depends on the ratio of black or brown eumelanin to red pheomelanin. One can make the assumption that the "rufus" variation of Dermestes maculatus contains predominantly pheomelanin in elevated concentrations in the hairs on the reddish spots.
The phaeomelanin intensity seems to be controlled by a number of different genes in other animals and is therefore not a simple Mendelian trait. After a thorough search through my Dermestes maculatus colony, I found two females that showed orange hairs at the same locations on the body as the goal: the head, middle of the base of the pronotum, the scutellum and the posterior corners of the elytra.
The two females were placed in a seperate container for experiment. Since they likely already mated with random males of the colony before being selected, it was not necessary to search for a male to pair them with. Their offspring (F1) was reared to adulthood and the majority inherited the orange hairs on the desired locations. The individuals showing the most vibrant colour were selected to continue the breeding program. These selected individuals were allowed to live in a colony to maximize the genetical combinations that result in viable offspring.
The collage above are photos from the following iNaturalist sightings:
1 (upper left): Subramanian Sevgan, Kenya
2 (upper right): Grant Reed, Botswana
3 (lower left): Glenn Stockil, Zimbabwe
4 (lower right): rguinness, Malawi
Image below: a regular looking individual from my coloniy.
Image below: one of the best two females at the start of the breeding program.
Image below: one of the F1 that was selected to continue the breeding program.
This post is on-going and will be updated with new information when available.
References:
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Galván, I., García, A. J., Edelaar, P. & Wakamatsu, K. 2015: Insects synthesize pheomelanin. Pigment Cell & Melanoma Research 28(5): 599-602. Link.
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Kalík, V. 1955: Dermestidae. In: Verheyen, R. K. (ed.): Parc National de L'Upemba. Mission, I. & G. de Witte, G. F. in collaboration with Adam, W., Janssens, A., van Meel, L. & Verheyen, R. (1946-1949) Fascicule 38(6). Institut des Parcs Nationaux de Congo Belge, Bruxelles, pp. 93-99. Link.
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Philip, U. 1940: A genetical analysis of three small populations of Dermestes vulpinus F. (Coleoptera, Dermestidae). Proceedings of the Indian Academy of Sciences 12: 133-171. Link.
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Shaw, D. D. 1966: The inheritance of two mutations, "Pearl" and "Fuscous" in Dermestes maculatus Deg. (Col. Dermestidae). Journal of Stored Products Research 1: 261-265. Link.
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