Science & Technology, New Zealand (Commonwealth Union) – A University of Auckland study has demonstrated the way Arachnids known as harvestmen are “trimorphic,” feature 3 types of males.
Noted for their possession of eight elongated legs, harvestmen are inhabitants of damp native forests and caves, and you might have encountered them in the Waitomo Caves. Similar to lizards detaching their tails, these creatures have the ability to shed their legs as a means of evading predators. However, unlike the lizards, harvestmen are unable to regenerate their lost appendages.
Within New Zealand’s Forsteropsalis pureora species, a distinct male sexual hierarchy exists, accompanied by the remarkable “weaponry” of the alpha and beta males. Recent research conducted by Dr. Erin Powell, a graduate at the University of Auckland, as part of her doctoral studies, has brought to light clues explaining the positioning of certain males at the lower end of this hierarchy.
While females exhibit a single type, the male population consists of three distinct categories, each characterized by a unique body size and shape. Alpha and beta males are significantly larger in size and employ their prominent chelicerae (jaws) as formidable weapons, which may constitute up to 50 percent of their overall body weight. These formidable males engage in fierce combat with one another to secure mates. On the other hand, gamma males, who are up to seven times smaller in comparison, do not engage in direct confrontations. Instead, they employ a stealthy approach, seeking out females who are undefended, allowing them to mate surreptitiously.
According to a study led by Powell and published in the academic journal Behavioral Ecology, the presence of scars on a harvestman can provide insights into whether it lost a leg during its juvenile or adult stage. The research revealed that males who experienced leg loss during their developmental phase were 45 times more inclined to mature into the smaller and weaker gamma males.
Department of Agriculture and Consumer Services indicated that this possibly due to the fact that they are unable to get sufficient food for their development due to their hunting being hindered.
“Or maybe there’s no point in investing in big fighting weapons when they’re already disadvantaged when it comes to fighting,” she says. “So, the arachnids’ resources may be invested in other things, such as testes size, sperm count, or aerobic poise, to ensure they make the most of the mating opportunities they get.”
She indicated that forming a new strategy, like scrambling to seek out undefended females, is more favourable than attempting and failing in traditional, possibly dangerous, male-male contests.
Trimorphism, or being with 3 forms, is not common in the animal kingdom. So far, scientists feel a combination of genetics along with nutrition may bring about a lot of variation inside a single species.
This study has unveiled a significant finding suggesting that environmental factors, such as interactions with predators, play a more substantial role than previously acknowledged in shaping the ultimate adult characteristics of males.
While the evolutionary reasons behind the development of alpha and beta males, both possessing large bodies and formidable weaponry, with varying shapes, remain a topic of intrigue, numerous questions persist. It is plausible that each type of weaponry offers distinct advantages in combat, with one providing greater power and the other granting superior reach in the intricate tussles involving limbs and claws. Further exploration is necessary to fully comprehend these intriguing dynamics.
“With their ridiculous towering weaponry and extreme male size variation, New Zealand harvestmen are both charming and puzzling,” explained Powell. “We still have much to learn about their fascinating biology and they have much to teach us about the evolution of mating systems across animal taxa.”
The researchers indicated that the harvestmen have closer links to scorpions than spiders and are harmless critters with no venom or silk with many native species for them in New Zealand.
