My Neighbor Velvet Worm

Kelly’s Field Notes

Common Name: Velvet worms

Phylum: Onychophora (Claw-Bearers)

Family: Peripatidae and Peripatopsidae

Genera: There are currently 56 genera of velvet worms!

Species of Note Near You (There are 90 extant (living) species of velvet worm! There are only a few hundred species described, though the actual number may be higher)):

• Solórzano's velvet (Mongeperipatus solorzanoi) - the largest known velvet worm at 22 cm (8.7 in) in length.

• Ooperipatellus nanus - the smallest velvet worm species at 5 mm in length (0.2 in).

Description: 

Velvet worms are a very old taxa (group)! They have largely remained unchanged for around 500 million years. Velvet worms belong to a group of animals called “lobopods,” or segmented worm-like animals with lobe-like legs. While they may resemble worms (Annelids) they are more closely related to insects, arachnids, and other Arthropods and Tardigrades. Lobopods are important as they are part of the foundation of the predator-prey arms race where actively hunting prey is involved. Modern velvet worms very closely resemble their first ancestors that arrived on the scene during the Cambrian explosion of life (500 mya). 

They resemble a caterpillar, with long fleshy bodies but with way more legs (generally between 14 and 16 pairs). One species has 43 pairs of legs (Plicatoperipatus jamaicensis)! Their legs are very bendy, like a snail’s eyestalks, and can extend further with changes in “blood” pressure. Their hemolymph moves through a hemocoel, a body cavity filled with hemolymph. This “hydroskeleton” keeps their bodies rigid through “blood” pressure.  The ends of their legs (papilliae) have tiny hair (setae) that the velvet worms use to smell and feel their environment. Their feet are not segmented or jointed, more like fluid filled sacs.

They are usually between 1.5-7.0 cm in length (0.6-2.8 in), though there are outliers that are larger or smaller. Velvet worms are blue, grey, purple and brown, often with beautiful patterns such as chevrons, diamonds, or stripes. Their skin is covered in soft overlapping scales, which gives them a velvety feel. These scales are hydrophobic, which means they repel water. This protects the velvet worm in moist environments. 

Velvet worms have two simple eyes (lensed) and a pair of antennae. Their eyes are mostly blocked by their antenna and are likely not used in hunting. Attraction to shifting air currents due to prey movement seems to be their primary form of hunting. They also have oral tubes near their mouths that are modified legs used to capture prey. These tubes secrete a sticky slime. The oral tubes feed the prey into their mandibles, which are sickle shaped. The jaws of a velvet worm are similar to the chelicerae of a spider. While they actively hunt at night, they will abandon any prey they have caught at sunrise in order to avoid predators.

Australia is home to most of the known species of velvet worm, with 74 species calling Down Under their home. In comparison, three species live in South America, nine in South Africa,eight in New Zealand, and eight in New Guinea. A few others live in the Caribbean and Malaysia. They are mostly active at night and much like their cousins the terrestrial arthropods, they breathe through trachea. They are very sensitive to desiccation and require a high humidity environment.

Life Cycle: 

Velvet worms reproduce in two ways: through egg laying or live birth with a placenta-like attachment. Fertilization is an extra weird process! Some females have pits on their heads where males can transfer sperm, the female then touches her genitalia to that spot for fertilization. Some African species leave a packet of sperm (spermatophore) on the female’s body which causes the skin in that area to break down, then the sperm is absorbed into the body.. Once absorbed the sperm swim their way through the hemocoel to the ovaries. Other species do engage in classic genital to genital mating. Interestingly, Epiperipatus imthurni  reproduces via parthenogenesis (embryo develops from an unfertilized egg) and no males of this species have ever been observed. 

If eggs, they take about one year to hatch. In some species the eggs hatch within the female and she gives birth to them shortly after. In both cases the offspring come out looking like mini adults without all the fun colors. One female creates between 1 to 23 offspring each year. It takes between 15 and 17 months for the young to become adults, they molt like Arthropods. The entire lifespan of a velvet worm is about 6 years.

Super Powers:

• Slime - velvet worms secrete a sticky slime to trap their prey! It is also a deterrent to predators. The slime can be shot from modified limbs on the side of the head, at a speed of 3 to 5 m/s (10 to 20 ft/s).

• Digestive Juices - velvet worms poke a hole in their prey then secrete digestive juices, liquifying the prey so it can be sucked up into the velvet worm’s mouth.

• Foot Claws - velvet worms use their retractable foot claws to hold onto uneven surfaces while walking.

• Pack hunting - one species of velvet worm (Euperipatoides rowelli) is social! This velvet worm colony is run by a matriarch, with up to 14 individuals under her watch. They hunt together and when a kill happens the matriarch eats first, then the rest of the females, then males and finally their offspring.

• Parthenogenesis - one species of velvet worm from Trinidad can create offspring without fertilization. No males of this species have ever been found.

Velvet Worms in Culture:

• Velvet worms are often kept as pets but can be very difficult to keep at home as their soil and humidity requirements are fairly serious.

• There is a species of velvet worm named Eoperipatus totoro after the Studio Ghibli film.

References:

Blaxter, Mark, and Paul Sunnucks. “Velvet Worms.” Current Biology, vol. 21, no. 7, Apr. 2011, pp. R238–R240, www.cell.com/current-biology/pdf/S0960-9822(11)00208-9.pdf, https://doi.org/10.1016/j.cub.2011.02.017.

‌Colombe, Jeff. “The Velvet Worm: A Living Fossil.” American Association for the Advancement of Science, 3 Jan. 2011, www.aaas.org/taxonomy/term/9/velvet-worm-living-fossil. Accessed 24 Sept. 2024.

“Epiperipatus Imthurni.” Wikipedia, 14 Feb. 2023, en.wikipedia.org/wiki/Epiperipatus_imthurni.

‌‌Mayer, Georg, et al. “Capture of Prey, Feeding, and Functional Anatomy of the Jaws in Velvet Worms (Onychophora).” Integrative and Comparative Biology, vol. 55, no. 2, 30 Mar. 2015, pp. 217–227, https://doi.org/10.1093/icb/icv004.

‌“Mt. Hood National Forest - Nature & Science.” Usda.gov, 2024, www.fs.usda.gov/detail/mthood/learning/nature-science/?cid=fsbdev3_043042.

Reinhard, Judith, and David M. Rowell. “Social Behaviour in an Australian Velvet Worm, Euperipatoides Rowelli (Onychophora: Peripatopsidae).” Journal of Zoology, vol. 267, no. 01, 16 Sept. 2005, p. 1, https://doi.org/10.1017/s0952836905007090. Accessed 27 Sept. 2020.

“The Velvet Worm - the Strangest Worm on the Planet | Wet Tropics Management Authority.” Www.wettropics.gov.au, www.wettropics.gov.au/the-velvet-worm.

‌‌“Velvet Worm.” Australian Museum, 14 Dec. 2020, australian.museum/learn/animals/worms/velvet-worm/. Accessed 24 Sept. 2024.

Wikipedia Contributors. “Mongeperipatus Solorzanoi.” Wikipedia, Wikimedia Foundation, 4 Aug. 2024, en.wikipedia.org/wiki/Mongeperipatus_solorzanoi. Accessed 24 Sept. 2024.