How to exploit Rhopalurus junceus populations in a sustainable way?
In the first article of the series on Rhopalurus junceus, we commented on the very marked territorial character of this species, which leads to frequent episodes of cannibalism and forces populations to be widespread and not concentrated.
We also commented that this species avoids the urban environment and can be found in dry places, or places with little humidity, they are nocturnal and rest during the day.
It is important to have these concepts clear, because one of the first challenges I faced when I started my studies on Rhopalurus junceus, at the Faculty of Biology of the University of Havana, 13 years ago, was how possible it was to breed these scorpions on a massive scale. Both then and now, there is still a great demand for the Escozulus. Unfortunately, after 20 years, we are still dependent on natural populations for their production. Therefore, it was and still is of vital importance to know what factors would influence captive breeding and what standards would have to be taken into account to develop a successful and extensive model of scorpion breeding.
Breeding Rhopalurus junceus is not simple, the multiple factors that affect this species during the captivity period require a series of measures and considerations that reveal the complexity of the matter.
1 - Humidity
Rhopalurus junceus is adapted to a dry environment, to the point that one of the interesting characteristics of this species is that in the rainy season they disappear almost completely. In laboratories, the environment is usually humid and this affects the mortality rate of Rhopalurus junceus, because, conditioned by the humidity, fungi appear that can kill the scorpion. The use of zeolite was once considered to counteract the humid environment created in such small spaces, but due to the costs associated with transportation and volume, this variant was discarded and sand and rocks were used, even though it was not the ideal solution.
2 - Diet: sugars
By studying the venom of Rhopalurus junceus, both its volume and concentration, it has been found that there is a direct relationship between the diet of this animal and the quality of the venom. Generally, in nature, the diet of Rhopalurus junceus is rich in protein from the consumption of insects, which are the basic diet of this species. However, in Cuba, under zero funding conditions, it is impossible to replicate the volume of insects for the total number of scorpions in captivity. An attempt was made with crickets in 2006, but the conditions for mass rearing were never met and it was more expensive to raise crickets than scorpions.
The current diet of Rhopalurus junceus in captivity, due to the type of food, is mainly composed of sugars and fats, which can considerably affect the quality of the venom, decreasing, over time, the concentration of proteins and peptides present in the venom, which undoubtedly affects the antitumour properties of the final product.
3 - Poison extractions.
The most efficient way to extract the venom of Rhopalurus junceus is by delivering small electric shocks to its tail. These 'milkings', as they are called, are often stressful for the body of Rhopalurus junceus, eventually causing irreversible damage to the glands that produce the venom and loss of neural connection.
Extractions are usually performed every 30 days. Over a period of 6 months it was found that the scorpion lost the mobility of its tail and its tail tended to break off. The stiffness was such that the scorpions stopped chasing prey and died within a short time.
4 - Cannibalism and living space.
Rhopalurus junceus, being so territorial, does not allow other scorpions to coexist in its environment, which forces it to breed in small plastic containers, limiting its environmental niche. The reduced confinement causes the scorpions to stop feeding over time, which, together with other factors, directly affects the mortality rate.
5 - Stress.
Scorpions are nocturnal, so while we work they sleep and vice versa. When working in hatcheries, all activities are carried out during daylight hours, exposing them to high levels of stress from sunlight. This also influences the quality of the venom, as stress can affect the appetite of Rhopalurus junceus.
6 - Handling.
On a daily basis, a technician should check the condition of the containers. He must remove dead animals, remove the base of the excrement and must decide whether or not to provide water. Since each average laboratory has more than 10,000 scorpions, this manipulation can take hours and directly exposes Rhopalurus junceus to an unusual light cycle, constantly disrupting its resting schedule and lowering venom production.
7 - Sustainable exploitation and replenishment.
For captive breeding and exploitation of Rhopalurus junceus to be sustainable, 50% of the litters would have to be successful, i.e. 50% of the hatchlings would have to survive to adulthood. However, this is impossible in practice due to the extreme care required for each small scorpion..
As a result, natural populations are subject to constant harvesting that weakens their structure and endangers the survival of Rhopalurus junceus as a species.
Rhopalurus junceus, a species endemic to Cuba, has a high mortality rate in captivity. Factors such as stress, handling, humidity and diet have a direct impact on mortality, and the quality of venom decreases over time. The ideal conditions for mass captive breeding generate a cost that is difficult to afford.
The management of Rhopalurus junceus populations is conditioned by the need to replace the loss of animals, which leads to a reduction in their size and may eventually cause their extinction. This is something that may happen in the next few years if research does not lead to the synthetic production of the venom.