Get to know the Centruroides margaritatus.

Text by Nyza Faustine Ho
Photos by Jeffrey C. Lim

The Centruroides margaritatus is one of the most researched scorpions in the world because of its wide range and availability for research. It is a species of bark scorpion which is widely distributed in the neotropical region, with species having been found to occur in Mexico, Central America, the Antillean Islands (Cuba, Jamaica, and Hispanola), Northern South America, Colombia, Ecuador, Venezuela, Peru, Sierra Leone, Gambia and Cape Verde Islands.

With this wide range covered by the Centruroides margaritatus, some variations also occur in the wild, such as with color and body proportions. However, when every distinguishing detail of the specimen is accounted for, these variations are clearly just variations and not separate species.

Scorpions are measured and aged by the number of molts or the number of times they have shed their skin in a lifetime. This is called the “instar.” They begin their life outside their mother’s body; after the gestation period of the eggs, the scorplings—who are born mobile—crawl on the mother’s back prior to their first instar; she will fend for them during this time. On their second molt, they can live on their own, but they sometimes prefer to live in groups if space permits; otherwise, cannibalism due to competition for space, food and water is inevitable.

As the scorplings continue to grow, their instars are counted and on the sixth instar for males and the seventh instar for females, they are able to reproduce. Females do not molt again after giving birth to their young, and are unable to reach the maximum number of molts, which is up to the eighth instar.

On the other hand, males can reach the seventh instar as long as they do not breed immediately when they mature. The maximum recorded size of the Centruroides margaritatus is at around 8.5 centimeters (cm) in length, including the tail. Females are capable of growing larger than males, but if they are mated before they reach their eighth instar, they cannot reach their maximum number of instars.

Generally, males can only reach 7th instar. Females can breed as young as 7th instar and males have a usable spermatophore as early as 6th instar. Scorpions will not molt any further once they mate for the first time, and this factor hinders any further growth in scorpions. Thus, early mating does not allow a male and female scorpion to reach their maximum size.

Males need time to regenerate their spermatophore after mating, and it takes a few weeks before it is able to mate once again.

How ‘Acrobats of Nature’ Communicate

Bark scorpions are considered the ‘acrobats of nature’ since they often feed upside down while holding on to bark. They also rest in this unusual position. They are very entertaining to observe, especially when they hunt and feed, as they either chase their prey or wait in ambush. This distinct feeding behavior sets bark scorpions apart from desert scorpions and forest scorpions.

Centruroides margaritatus interact with each another in communal settings. From hunting to feeding, each member of a Centruroides margaritatus colony plays a role especially during feeding; some will restrain and sting the prey while others begin to feed.

The Central American bark scorpion is one of species that uses substrate vibrations for communication purposes. This is a signal produced during a series of rapid shakings of the male’s body from front to rear and consists of multiple short pulses. These substrate vibrations make it respond to the tactile stimulus by attacking, fleeing or mating. During breeding, the males communicate with the females using shaking movements called “juddering.”

If the female is responsive, it approaches the male and they begin their courtship dance. As the courtship dance is ongoing, the female is guided by the male on a bark. The male then deposits his spermatophore (a capsule or mass containing sperm that is transferred whole to the female) on the bark and guides the female towards it so she can receive the sperm stored within.

During scorpion matings, sometimes, due to her bigger size, the female has to be stung by the male with a low dose of venom so he can guide her easily. This does not endanger the life of the female since this only makes her a bit weaker for a certain period of time for the mating to occur successfully.

The Venom Report

Very few scorpion venoms have been studied throughout the years. Most venom potency records of scorpions were compilations of sting reports from patients in hospitals. Since the Centruroides margaritatus is one of the most researched scorpions in the world, there have been studies done regarding their venom and its mechanism of action in victims.

The venom of the Central American bark scorpion is recorded as level 3 or moderate in the pet keeping hobby. Research done in western Colombia proved that venom assays were of low toxicity. If a human is stung, the most common symptoms are pain, local edema, and fever 1-20 hours after the initial exposure to the venom. There were no evidences of necrosis, permanent mutilation, or death due to the Centruroides margaritatus’ venom.

The venom of the Centruroides margaritatus is a 39-amino-acid peptide which is called the margatoxin (MgTX). The margatoxin is a selective Potassium (K+) inhibitor in the cells. The margatoxin is able to delay selected (K+) channels in the nerves and skeletal muscles of humans; in some cases, the regulation of immunoresponsiveness in human T-lymphocytes are delayed or impaired as well, depending on the location of the sting.

The margatoxin is also able to delay the immune response of a human to the venom once it binds to the cells’ receptors. This is the reason why, upon being stung, localized pain and eventually numbness occurs. This effect lasts for 24 hours at most, since the human body is able to detoxify the margatoxin without further problems and the margatoxin is not really meant to kill humans, but smaller prey creatures.

The main target of the margatoxin is the nerves and muscles of a victim, so if it is a small animal, it could mean paralysis. This allows the Centruroides margaritatus to devour its prey with less struggle, and a higher success rate during hunting, because even if prey escapes the Central American bark scorpion’s grasp and attempts to run away even after being stung, the venom will act and paralyze the prey.

Did You Know?
The Centruroides margaritatus is the only Centruroides species found outside the New World

The C. margaritatus was also introduced to Florida. This means that, originally, the C. margaritatus did not exist in Florida until it was introduced by humans and was able to successfully thrive in the area. This increased the range of the C. margaritatus and made them occur in more places in the world compared to other species of the scorpions of the same genus. It also proves that they are able to adapt to a new environment. The range of the C. margaritatus reaches up to some parts of the Old World in some parts of Africa.

Tityus carinatus and Tityus ducalis were long considered synonyms of Centruroides margaritatus—meaning, they are the same species with different scientific names, yet all three are known as Central American bark scorpions. However, sample specimens were lost in Zoologisches Museum, Berlin, so this was never confirmed.

The Centrurus edwardsii and Centruroides danieli are scientifically the same as the Centruroides margaritatus. Due to the wide range of the Centruroides species, there have been recorded variations on its physical appearance; however, when examined closely, they are the same species, after all.

SOURCES:

– Sissom, W. D. and Lourenço W.R. “The Genus Centruroides in South America” (Scorpiones, Buthidae), 1987

– Garcia-Calvo, Margarita, et. al. “Purification, Characterization, and Biosynthesis of Margatoxin, a component of Centruroides margaritatus Venom That Selectively Inhibits avoltage-Dependent Potassium Channels,”
1993

– S R.D. Briceño and F. Bonilla, “Substrate Vibrations in the Scorpion Centruroides margaritatus (Scorpiones: Buthidae) during courtship,” 2009

– Capinera J.L., “Encyclopedia of Entomology (2nd edition),” vol. 4, pp. 3311-3312, 2008

This appeared in Animal Scene’s October 2015 issue.