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Kingdom: Animalia
Phylum:Onychophora
Class:Udeonychophora
Order: Euonychophora VELVET WORM
Family: Peripatopsidae
Genus:Euperipatoides rowelli
Species: E. rowelli
General Description: Euperipatoides rowelli is a social species of velvet worm that is found in New South Wales and the Australian Capital. The phylum they belong to, Onychophora, means “claw-bearers” and refers to the claws on the end of their 13 to 43 pairs of legs, which helps them move around uneven terrain. The velvet worm is characterized by its velvety waterproof skin, which is covered with papillae and scales. They range in color from dark blue to grey and come in sizes of three to five centimeters. There are 110 described species of velvet worms and their appearance suggests they are living fossils that have remained unchanged for millions of years. 500 million years old fossils have been found of marine velvet worms with the earliest terrestrial velvet worm fossil dating back to approximately 300 million years old.
Foot and "Claws"
Photo by Andras Keszei, with permission.
Habitat: They have hydrostatic skeletons and are restricted to very moist environments due to their inability to retain water. Velvet worms breathe through holes along their bodies called tracheae, and aren’t able to close these holes to retain water, making them very prone to dehydration.Because of this, they live in rotting wood, among leaf litter, under stones, and sometimes in caves where moisture is high. The Phylum Onychophora is divided into two families, the Peripatidae and Peripatopsidae, each with distinct geographical distributions. Peripatidae are found in the tropics and sub-tropics of South-East Asia, the Caribbean, South and Central America and West Africa, where the Peripatopsidae are found in Chile, South Africa, Australia, New Guinea and New Zealand.
Tracheae
(https://www.flickr.com/photos/nascenthought/5516917455)
Unusual Social Behavior: Unlike many of the other species of velvet worms, Euperipatoides rowelli have been studied and it has been found that they live and hunt together in groups of up to 15 individuals that are ruled by a larger, dominant female in a hierarchal system. Through research it was found that the dominant female will eat first, and that the social hierarchy is maintained through aggression and fighting. The hierarchal system is led by the largest dominant female at top, the remaining females second, the males third, and the young at the bottom. Interestingly, it is thought that the origin of this unusual social behavior lies in kin recognition.
(http://www.abc.net.au/science/articles/2010/06/04/2917330.htm)
Predation and Feeding Habits: Euperipatoides rowelli are carnivorous predators that feed on small insects such as termites and crickets. They usually spend their time hunting at night, and aim to ambush predators using a very unique tactic. To capture their prey velvet worms shoot out a sticky, glue-like slime, out of two glands on their heads. This allows them time to approach the prey, where they then bite into it, using two fangs, and deposit digestive enzymes. This external enzymatic prey digestion then allows them to suck up the liquefied prey, without the need for mechanical digestion.
Slime Implications: The slime is very interesting because it comprises “natively disordered proteins, rather than highly-structured ones as found in spider silks, which form a gel that sets on drying into strong threads.” These highly unusual compounds are not known to be found in any other animal. The unique structure and properties of this “slime” may offer promise for biomedical and biomaterial applications upon more research in the future.
Video of High Speed Slime Cannon:https://www.youtube.com/watch?v=LY8TgD6-7kg
(https://www.researchgate.net/figure/Hunting-slime-of-Euperipatoides-rowelli-a-Ejection-of-capture-slime-by-the-animal_fig7_261924001_)
(https://www.researchgate.net/figure/Hunting-slime-of-Euperipatoides-rowelli-a-Ejection-of-capture-slime-by-the-animal_fig7_261924001_)
Hunting slime of Euperipatoides rowelli. (a) Ejection of capture slime by the animal after provoking defensive behavior. Image courtesy of Alexander Baer and Ivo de Sena Oliveira. (b) Native slime droplets contain nanoglobules (left) and form stiff fibers after mechanical shearing and drying (right). Scale bar: 500 nm.
Hunting slime of Euperipatoides rowelli. (a) Ejection of capture slime by the animal after provoking defensive behavior. Image courtesy of Alexander Baer and Ivo de Sena Oliveira. (b) Native slime droplets contain nanoglobules (left) and form stiff fibers after mechanical shearing and drying (right). Scale bar: 500 nm.
Mating and Reproduction: Mating of the Euperipatoides rowelli is very interesting in thatmales will place a spermatophore randomly onto the females skin.The spermatophore on the skin stimulates a localized breakdown of the female’s skin where the spermatophore then makes its way into the haemocoel through a lesion in the body wall to the ovaries, where fertilization occurs. Female velvet worms can store sperm for months before using them to fertilize their eggs. Once fertilization occurs, gestation can last up to another fifteen months. They will eventually give birth to live young, which appear and act almost fully developed, with no larval stage present. As a group, they will care and protect their young with males taking about a year to mature and females maturing in up to three years. A velvet worm can live up to as long as six years, and each year a female is capable of producing one to twenty three offspring.
(http://www.eartharchives.org/articles/velvet-worms-the-voracious-snipers-of-the-undergrowth/)
The Missing Link : For many years velvet worms were thought to be the missing link between the annelids and arthropods because they share similar characteristics with both phylum. However it is now thought that velvet worms are not an arthropod ancestor but rather that there arthropod characteristics are a result of parallel evolution. The main evidence supporting this is that their tracheae form numerous branches near the spiracle opening, but rarely ever branch again. Because of this, it is now believed that they evolved from the nematodes during the Cambrian Era.
Citations:
Oliveira, Ivo De Sena, et al. “Unexplored Character Diversity in Onychophora (Velvet Worms): A Comparative Study of Three Peripatid Species.” PLoS ONE, vol. 7, no. 12, 2012, doi:10.1371/journal.pone.0051220.
Monge-Nájera, Julián, and Bernal Morera-Brenes. “Velvet Worms (Onychophora) in Folklore and Art:Geographic Pattern, Types of Cultural Reference and Public Perception.” British Journal of Education, Society & Behavioural Science, vol. 10, no. 3, 2015, pp. 1–9., doi:10.9734/bjesbs/2015/18945.
Giribet, G. “On Velvet Worms and Caterpillars: Science, Fiction, or Science Fiction?” Proceedings of the National Academy of Sciences, vol. 106, no. 47, 2009, doi:10.1073/pnas.0910279106.
Kirwan, John D., et al. “Low-Resolution Vision in a Velvet Worm (Onychophora).” The Journal of Experimental Biology, vol. 221, no. 11, 2018, doi:10.1242/jeb.175802.
Reinhard, Judith, and David M. Rowell. “Social Behaviour in an Australian Velvet Worm, Euperipatoides Rowelli (Onychophora: Peripatopsidae).” Journal of Zoology, vol. 267, no. 01, 2005, p. 1., doi:10.1017/s0952836905007090.
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