Tag Archives: Acari

Friday Fellow: Rhinoceros Tick

by Piter Kehoma Boll

Parasites exist everywhere and, although most of us see them as hateful creatures, more than half of all known lifeforms live as a parasite at least in part of their life. And there are likely many more yet unknown parasites around there. Today I’m going to talk about one of them, which is found in large portions of Africa.

Its name is Dermacentor rhinocerinus, known as the rhinoceros tick. As its name suggests, it is a tick, therefore a parasitic mite, and its adult stage lives on the skin of the white rhinoceros (Ceratotherium simum) and the critically endangered black rhinoceros (Diceros bicornis).

A male rhinoceros tick attached to the skin of a rhinoceros in South Africa. Credits to iNaturalist user bgwright.**

Male and female rhinoceros ticks are considerably different. In males, the body has a black background with many large orange spots. In females, on the other hand, the abdomen is mainly black with only two round orange spots and the plate on the thorax is orange with two small dark spots. Males and females mate on the surface of rhinoceroses. After mating, the female starts to increase in size while the eggs develop inside her and then drops to the ground, laying the eggs there.

A female rhinoceros tick patiently waiting for a rhinoceros to come close. Photo by Martin Weigand.**

The larvae, as soon as they hatch, start to look for another host, usually a small mammal such as rodents and elephant shrews. They feed on this smaller host until they reach the adult stage, when they drop to the ground and climb on the surrounding vegetation, waiting for a rhinoceros to pass by and then attaching to them.

Conservation efforts to preserve biodiversity are mainly focused on vertebrates, especially mammals and birds. Rhinoceroses, which are an essential host for the rhinoceros tick to survive, are often part of conservation programs and, in order to increase their reproductive success, the practice of removing parasites from their skin is common. This is, however, bad for the rhinoceros ticks. If their host is endangered, they are certainly endangered too, and removing them worsens their condition. Are parasites less important for the planet? Don’t they deserve to live just as any other lifeform? We cannot forget that nature needs more than only what we consider cute.

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More mites and ticks:

Friday Fellow: Giant Red Velvet Mite (on 22 June 2016)

Friday Fellow: Cuban-Laurel-Thrips Mite (on 28 June 2019)

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References:

Horak IG, Fourie LJ, Braack LEO (2005) Small mammals as hosts of immature ixodid ticks. Onderstepoort Journal of Veterinary Research 72:255–261.

Horak IG, Cohen M (2001) Hosts of the immature stages of the rhinoceros tick, Dermacentor rhinocerinus (Acari, Ixodidae). Onderstepoort Journal of Veterinary Research 68:75–77.

Keirans JE (1993) Dermacentor rhinocerinus (Denny 1843) (Acari: Ixodida: Ixodidae): redescription of the male, female and nymph and first description of the larva. Onderstepoort Journal of Veterinary Research 60:59–68.

Mihalca AD, Gherman CM, Cozma V (2011) Coendangered hard ticks: threatened or threatening? Parasites & Vectors 4:71. doi: 10.1186/1756-3305-4-71

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**Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Filed under Arachnids, Conservation, Friday Fellow, Parasites, Zoology

Friday Fellow: Cuban-Laurel-Thrips Mite

by Piter Kehoma Boll

Last week I introduced the Cuban Laurel Thrips, which feeds on several fig trees, such as the Chinese Banyan and the Cuban Laurel. Today, we will continue up the food chain and talk about a mite that is a parasite of the cuban laurel thrips. Named Adactylidium gynaikothripsi, I decided to give it the common name “Cuban-Laurel-Thrips Mite”.

The Cuban-laurel-thrips mite was described only in 2011 from Cuban laurel thrips populations in Greece. This is the fourth mite of the genus Adactylidium known to parasitize the Cuban laurel thrips, the other four being Adactylidium ficorum (“fig-thrips mite”), A. brasiliensis (“Brazilian thrips mite”) and A. fletchmani (“Fletchman’s thrips mite”). As you can imagine, in order to parasitize an insect as small as the Cuban laurel thrips, these mites are even smaller, measuring about 0.1 mm in length.

An adult female of the Cuban-laurel-thrips mite. Extracted from Antonatos et al. (2011).

The life cycle of the Cuban-laurel-thrips mite, which is basically the same for all species of Adactylidium, is very bizarre. Adult females feed on the eggs of the Cuban Laurel Thrips. They start their adult life wandering over fig leaves looking for a suitable thrips egg to attack. Once finding one, they pierce the egg’s shell with their chelicerae and attach to it like ticks and start to eat. They feed on a single egg across their entire life. If they are unable to find an egg, they may also attach to an adult thrips as a last resource, or else they die of starvation in a few hours.

Once a female starts to eat, a small group of eggs, usually between 5 to 10, begins to develop inside her. The eggs grow during the first 48 hours after the female attached to the egg, making her double in size and becoming something like a spherical egg sac. The eggs hatch around this time and the mite larvae remain inside their mother. These larvae lack mouth parts, so it is believed that they absorb nutrients from her mother directly through the body surface. About 24 hours later, the larvae turn into nymphs, which remain inactive inside the shed skin of the larva. They also lack any mouth parts.

Female Cuban-laurel-thrips mites attached to eggs of the Cuban laurel thrips. Extracted from Antonatos et al. (2011).

Another 24 hours pass and the nymphs turn into adult mites. They are still inside their mother when this happens. The adults consist always of a single male and several females. This male then starts to copulate with his own sisters, still inside their mother’s abdomen, and, when copulation is finished, they start to tear their mother’s body apart to get free, killing her in the process. Once outside the body, the male dies in a few minutes, never eating anything other than his own mother. The females, on the other hand, start to look for thrips eggs on which to feed, only to be killed by her own children less than 4 days laters.

This entire life cycle may look very insane from our human perspective, but nature was never interested in following our moral rules.

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References:

Antonatos SA, Kapaxidi EV, Papadoulis, GT (2011) Adactylidium gynaikothripsi n. sp. (Acari: Acarophenacidae) associated with Gynaikothrips ficorum (Marshal) (Thysanoptera: Phlaeothripidae) from Greece. International Journal of Acarology, 37(sup1), 18–26. doi: 10.1080/01647954.2010.531763

Elbadry, EA, Tawfik, MSF (1966) Life Cycle of the Mite Adactylidium sp. (Acarina: Pyemotidae), a Predator of Thrips Eggs in the United Arab Republic. Annals of the Entomological Society of America, 59(3), 458–461. doi: 10.1093/aesa/59.3.458

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Friday Fellow: Giant red velvet mite

by Piter Kehoma Boll

While walking through an Indian market, you may end up finding something like this being sold as food:

Hmm, it looks like some sort of chips or dried seeds. Photo by Pankaj Oudhia.*

Hmm, it looks like some sort of chips or dried seeds. Photo by Pankaj Oudhia.*

It may look as some sort of crispy seed or dried fruit, some local chips, maybe? But they are actually giant mites… edible mites! They are used in India as a medicine, especially to treat paralysis and allegedly to increase sexual drive, a reason for the popular expression “Indian Viagra”.

But this edible arachnids are actually quite cute when alive. Known cientifically as Trombidium grandissimum and popularly as giant red velvet mite, they are fluffy like a piece of velvet, have a strong red color and reach up to 2 cm in length, a record for mites, which usually measure way less than a milimeter.

I would love to raise them as a pet. Wouldn't you? Photo by Brian Gratwicke.**

I would love to raise them as a pet. Wouldn’t you? Photo by Brian Gratwicke.**

As adults, the giant red velvet mites live freely and prey on small animals, mainly insects, and their eggs. The larvae, on the other hand, start their life as a parasite, attaching themselves to another invertebrate, usually an insect, but sometimes an arachnid, and suck their hemolymph (“blood”). Later, this parasitic larva develops into a free-living nymph that abandons the host and begins to live more like an adult.

The genus Trombidium has many species in the Palearctic Ecozone, so if you are wandering in a forest in Europe or Asia, you may find the giant red velvet mite or one of its cousins.

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References:

Southcott, R. V.  1986. Studies on the taxonomy and biology of the subfamily Trombidiinae (Acarina: Trombidiidae) with a critical revision of the genera. Australian Journal of Zoology, 123: 1-116.

Wikipedia. Trombidium. Available at: <https://en.wikipedia.org/wiki/Trombidium&gt;. Access on July 21, 2016.

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Filed under Friday Fellow, Zoology