Halarachne halichoeri

There are about 45000 known species of mites - these tiny arachnids can be found in a wide range of different environments, where they make a living as detritivores, predators, or of course, as parasites of plants and animals. There is a family of mites (Halarachnidae) that have evolved to live specifically in the nasal passages of marine mammals. Most of them are found up the nasal passages of seals and sea lions, though there are a few species that also live in the nasal cavities of otters.

Left: Dorsal and ventral view of adult Halarachne halichoeri mite, Right: Mite in situ in the nasal passage of a seal.
Photos from Fig. 1 and 2 of the paper. 

Halarachne halichoeri is one such mite - It was officially described in the 19th century from specimens collected from a grey seal (Halichoerus grypus), and were later found to also inhabit the nasal passage of harbour seals (Phoca vitulina). The immature stages of the mites are transmitted between hosts through coughing or during close face-to-face contact. The don't seem to really cause their host much harm, though their presence can cause some irritation to the mucus membrane - as one would expect from having tiny creepy crawlies in your nasal passage.

Due to a variety of human-related factors, including pollutants, habitat alteration, and excessive hunting, the number of grey seals and harbour seals had been dwindling in the Baltic and Wadden Sea since the start of 1960s. By the late 1970s, the number of Baltic grey seals waters were down to less than 4000 individuals. This seems to have had an effect on H. halichoeri population since no cases of these mites have been recorded from German waters since 1901, even though the mite continues to be reported from other areas where grey seals are found. In 1988, seal hunting was banned in the Baltic Sea, and the grey seal population started making a comeback - and it seems so has their nasal mites.

In a recent study, researcher examined the carcasses of six seals - four grey seals and two harbour seals - that were collected as a part of a wildlife monitoring network which screen marine mammal carcasses for various parasites. During this routine examination, they discovered that the seals were host to these nasal mites, with one of them found to have over 60 mites in its nasal passage. This was the first time that H. halichoeri has been recorded from German waters in over a century, though the authors also suggested that cases of these nasal mites are often under-reported, since the mites are very quick to escape from the nasal passage of a dead host, so many of them could have been lost while the carcasses were in transit.

Since H. halichoeri is a generalist parasite, it was able to maintain a viable population in the nasal passages of other marine mammals such other seals, sea lions, and otters during the period when the Baltic grey seals number dwindled, and were poised to make a comeback when its host population recovered. But that's not always the case for other species of parasites and symbionts. In the last decade or so, conservation biologists are starting to recognise that symbionts like parasites should also be targeted for conservation efforts, and co-extinction of symbionts along with their hosts is a major concern.

A recent report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) found that one million species are at risk of extinction due to environmental changes caused by human activities - however, that number is a vast underestimate given that all the animal and plants included that report are themselves host to a vast array of parasites and symbionts which have not been accounted for.

In this case, Halarachne halichoeri was able to remain in circulation in other marine mammals even as one of their hosts was being severely depleted, but that option might not be available for many others parasites that require multiple specific hosts to complete their life cycles, or just stick to the one host species for life - their fates are tied with that of their hosts, whether that means prosperity or extinction.

Reference:
Reckendorf, A., Wohlsein, P., Lakemeyer, J., Stokholm, I., von Vietinghoff, V., & Lehnert, K. (2019). There and back again–The return of the nasal mite Halarachne halichoeri to seals in German waters. International Journal for Parasitology: Parasites and Wildlife 9: 112-118.

Macrodinychus multispinosus

There are variety of mites which live with ants, but many of them are not well-studied. Most of them are either phoretic mites which hitch a ride on the ant's body, or detritivores that eat various substances which can be found in ant nests and in those cases, they are relatively harmless commensals. But some mites that live with ants are ectoparasites. The study being featured today is about a mite that lives (and feeds) on ants - Macrodinychus multispinosus. There are variety of other mites that also feed on ant haemolymph (a fluid which is the equivalent of blood in insects), but this vampire takes it to an another level.

Left: Ant pupa host being progressively eaten alive by the parasitoid mite.
Right (top): Adult female and male Macrodinychus multispinosus mites
Right (bottom): A M. multispinosus nymph at the stage when it is attached to the host (note the stumpy legs)
Photos from Figure 1, 3, and 5 of the paper. 

Newly hatched M. multispinosus nymphs are born with fairly long limbs which allows them to move about and find a host, but once they are attached to an ant pupa, their limbs are reduced to stumps. The mite essentially become a tiny biological pump. And whereas other blood-sucking mites that feed on insects are content with imbibing just some of the host's life blood, M. multispinosus does not hold back - it consumes all the developing ant pupa's internal tissue and literally sucks the life out of it.

Macrodinychus multispinosus can be considered as a parasitoid - even though its modus operandi is very different to parasitoid wasp which devour their host alive from the inside and burst out xenomorph-style once they are ready to pupate, the outcome is pretty much the same - a dead, empty host. The researchers behind the paper being featured in this post conducted their study at Quintana Roo, Mexico across a number of field sites where they inspected colonies of the longhorn crazy ant
(Paratrechina longicornis) - the mite's only known host.

They found this vampire mite to be relatively common - of the seventeen colonies they sampled, eight of them were infested with M. multispinosus. Overall, about a quarter (26.2%) of the ant pupae they examined were infected with these mites. In some nests, over three-quarters of all the pupae are parasitised. They noticed that M. multispinosus definitely seems to have a preference for the worker ant pupae and developing queens are usually spared. Even though by doing so, this vampire wouldn't end up killing off potential future colonies by parasitising the reproductive members of the colony, it is still killing off the developing workers and this can be quite harmful at a colony level if the mites are present in high numbers.

It seems that M. multispinosus has settled quite well into its niche as a ectoparasitoid of the longhorn crazy ant, and like other mites in the Macrodinychus genus, it is rather specific about where it attach to the host - in this case the ant pupa's abdomen. But here's the twist - whereas M. multispinosus is native to Quintana Roo, its host is not and is a relatively recent arrival to the region. Even though this vampire mite must have been parasitising ants long before the longhorn crazy ant came along, its original host is still unknown to science - in fact, even though it was described in 1973, it wasn't until now that its ecology and life cycle has been documented.

There's still a lot to learn about this little vampire. Would it be a good biological control for the invasive longhorn crazy ant? What kind of ant did M. multispinosus originally parasitised before it jumped on the invader? How was it able to take to the newly arrived host so quickly?

With so many different kinds of organisms being transported (purposefully or inadvertently) around the world, perhaps is would be useful to consider recruiting parasites are as a mean of controlling invasive species, especially if the parasite is native to the region where biological control is being considered - that way, it'll be fighting on its home turf.

Reference:
Lachaud, J. P., Klompen, H., & Pérez-Lachaud, G. (2016). Macrodinychus mites as parasitoids of invasive ants: an overlooked parasitic association. Scientific Reports 6: 29995

P.S. If you like this post and other posts like it on the blog, then you might been interested in checking out the book "The Wasp that Brainwashed the Caterpillar" by Matt Simon. It is full of funny and informative stories about wonderfully weird and bizarre animals both parasitic and non-parasitic - you should totally check it out!

Coccipolipus hippodamiae

Today we feature a guest post by Katie O'Dwyer who recently completed her PhD at the Evolutionary and Ecological Parasitology group at Otago University. She has previously written for Parasite of the Day about  Phronima - a parasitic crustacean that turns gelatinous salps into floating zombies. This time she has written a story about why "Promiscuous ladybirds pay the price when it comes to parasites".

A pair of mating two-spot ladybirds (photo by Richard001)

For most of us when we hear any mention of sexually transmitted infections (STIs) we think of humans, herpes and the variety of public service announcements we see about practicing safe methods in order to avoid contracting STIs. However STIs are rife in the animal kingdom. They can be found in any animals that require internal fertilisation for reproduction. And it seems that one group which can really benefit from advice on safe methods to avoid STIs are the ladybirds.

Who would have known (well, probably some entomologists) that these beautiful beetles are highly promiscuous and not very choosy about who they mate with? This makes them an extremely efficient host for any sexually transmitted parasite. Today’s post is about a sexually transmitted mite Coccipolipus hippodamiae and its host - an European ladybird.

These mites are transmitted when ladybirds are mating and they migrate to the wing case (called elytra) of the beetles. Here they latch on using their mouthparts and feed on the hosts blood (known as haemolymph) before metamorphosing into adults. What quickly follows is the development of a large mite colony on a single ladybird. The presence of these mites can reduce the fertility and reproductive capacity of female ladybirds.

A female Coccipolipus hippodamiae mite with eggs.
Scale bar = 100 µm (photo from here)

There are some measures that can be taken when faced with high levels of STIs, such as switching the mating system to monogamy and being choosier when it comes to potential partners. However, studies have found no evidence for C. hippodamiae having any effects on mate choice in ladybirds. Luckily for the mites, female ladybirds are unable to detect if their male partners are infected.

However, there are other factors that limit the success of these parasites. Timing is an important aspect of STI transmission in this system. Ladybirds overwinter and refrain from mating regularly during this season. Following the period of overwintering, these highly promiscuous bugs travel across plants on a mating spree, hooking up indiscriminately, and triggering an epidemic of mite infections. A key aspect in this process is the overlap between generations.  In order for the mite population to be maintained mating must occur between consecutive generations of ladybirds. The mites have evolved to take advantage of those hosts with overlapping generations and unfortunately for the two-spot ladybird, Adalia bipunctata, it has one of the longest periods of overlap between generations. Therefore it is also the most common host for these mites.

These miniature mites have also adapted to infect other ladybird species with up to four species of European ladybirds in its repertoire of hosts. Interestingly, one of these ladybird species does not have an overlap in generations because a period of diapause is required during development, whereby one generation dies off before the next one metamorphoses into adults.  Luckily for the mite, these ladybirds appear free and easy when it comes to mating, even across different species. So even this ladybird species without overlapping generations can become reinfected during such hybrid mating sessions.

This picture gets even more complicated when the invasive Asian harlequin ladybird gets involved. This beetle has invaded the UK and is out-competing the native ladybirds (of which there are up to 46 species!). As a method of control some researchers have decided it might be a good idea to introduce the mites as a biological control agent. However, up to now, C. hippodamiae has not been found in ladybirds in the UK as they do not overlap in generations in the same way that continental European ladybirds do. This is currently an active area of research and not much is known about the effect the mites could have on the UK’s naïve ladybird hosts. In their struggle against the feisty harlequin ladybird, can a foe of European ladybirds become a friend of the UK’s native ladybirds? Only further research will tell…

References:

Hurst, G.D.D., Sharpe, R.G., Broomfield, A.H., Walker, L.E., Majerus, T.M.O., Zakharov, I.A., Majerus, M.E.N. (1995) Sexually transmitted disease in a promiscuous insect, Adalia bipunctata. Ecological Entomology 20, 230-236

Webberley, K.M., Hurst, G.D.D., Husband, R.W., Schulenberg, J.H.G.V.D., Sloggett, J.J., Isham, V., Buszko, J., Majerus, M.E.N. (2004) Host reproduction and a sexually transmitted disease: causes and consequences of Coccipolipus hippodamiae distribution on coccinellid beetles. Journal of Animal Ecology 73, 1-10

Rhule, E.L., Majerus, M.E.N., Jiggins, F.M., Ware, R.L. (2010) Potential role of the sexually transmitted mite Coccipolipus hippodamiae in controlling populations of the invasive ladybird Harmonia axyridis. Biological Control 53, 243-247

Post written by Katie O'Dwyer

November 6 - Otodectes cynotis

Many people who have had a dog or a cat as a pet are probably familiar with ear mites - infections that can cause your pet to have brown, cruddy material in their ears, shake their heads, and even itch frantically at their ears. Here's a close-up look at the culprits - Otodectes cynotis. These tiny arachnids are spread from animal to animal via direct contact and then take up residence in the ear canal. The adults lay eggs in the ears and then the mites hatch out and go through a larval stage and two nymphal stage before becoming mature. If left untreated, the mites can induce secondary bacterial or yeast infections, and, in rare severe cases, even deafness in the ear as well.

October 23 - Trombidium holosericeum

The animal in the photo is not a parasite - but its offspring are. Like Eutrombicula alfreduggesi, Trombidium holosericeum is a mite that has parasitic larvae and nymphs. The larvae, commonly known as chiggers, can cause real distress to their hosts - including humans - as they feed. They do not crawl under the skin, nor do they feed on blood - what they do is attach themselves to the skin, pierce it. and inject enzymes that can break down the tissue. A hollow tube known as a stylosome forms - the chiggers will continue to "spit" in these enzymes and then suck up the nutrients. After about 3 to 5 days, they will drop off the host and transform into nymphs. They find a new host, feed in a similar way, and then drop off to molt into adults. The adults are not parasitic, but rather feed on plant juices or are predatory to other small arthropods.

August 15 - Spinturnix americanus

Spinturnix americanus is a species of mite that uses several species of vespertillionid bats as its hosts, including little brown bats (Myotis lucifugus), big brown bats (Eptisecus fuscus) and eastern pipstrelles (Pipistrellus subflavus). These mites are specialists on the wings and tail membranes of their flying hosts and have no interest in venturing into the forest of fur on those mammals.

Photo is by Christopher M. Ritzi and comes from this site.

June 9 - Orthohalarachne attenuata

Back in 1984, a 35-year old guy started feeling a pain in his eye and went to his doctor. The doctor looked under his eyelid and saw nothing. The next day, the pain was worse so he went back and asked the doctor to examine him again. During that visit, the doctor found - and removed - a single mite of the species Orthohalarachne attenuata. Ok, weird, but not that weird, right? Wrong. Orthohalarachne attenuata is a species of mite that normally is found in the nasal passages of fur seals, sea lions, and walruses. In seals, the mites can be both prevalent (as in almost every single seal has them) and abundant (as in more than 1000 mites per seal and in a few cases in one study, more than 2000!). These incredibly high infestations can cause problems for the seal's breathing, but can also do damage in the lungs and leave the seals susceptible to other infections, too. Transmission between seals occurs by -- sneezing on each other, of course. So, how did this young guy in California get a nasal mite in his eye? Turns out that two days before his first doctor's visit, he had visited Sea World - where he stood too close to some walruses and got sneezed on.

Photo contributed by Mike Kinsella. Documentation of the human case in this paper.

June 6 - Dermanyssus gallinae

Dermanyssus gallinae, or the red mite, is an ectoparasite of birds. They do not live on birds, but rather hop on them to feed on their blood at night, while they are sleeping. They can be major pests for chicken and other poultry farmers. They will occasionally take blood meals from mammals, even humans, if they work with or live near birds.

May 28 - Eutrombicula alfreddugesi

If you’ve ever had chiggers, you know they’re really, really irritating. These are the parasitic larval stages of free-living mites, and Eutrombicula (Trombicula) alfreddugesi is the most familiar in North America. Chiggers perch on foliage, climb aboard passing pedestrians, and find their way to the new host’s skin. Once there, the tiny mite positions itself atop a hair follicle or pore, and secretes highly digestive saliva that liquefies the host’s skin cells. The surrounding cells harden in defense, forming a stylostome. But it’s a poor defense – the stylostome helps the parasite by functioning as a straw for the chigger to slurp his slurry of dead cells. Moreover, the stylostome contributes to that really, really irritating inflammatory (i.e., itchy) response in the host’s skin. Thankfully, E. alfreddugesi is not a vector for disease, and the discomfort subsides after a few days.

Eutrombicula alfreddugesi isn’t picky, and infects numerable hosts besides humans. It’s a parasite of many vertebrates, including birds, mammals, and reptiles (the photo shows several chiggers on the dewlap, or throat fan, of an anole lizard). In fact, host habitat is probably more important that host taxonomy for this species. Chigger infestations usually occur in warm, shady, and moist environments, as this is best for the soil-dwelling and detritus-eating adult stages (meaning that this is where most eggs are laid). Similarly, these chiggers prefer certain areas on the host, from the undergarment areas of humans, to the “mite pockets” of some lizards. Mite pockets are small, but relatively deep, cavitations that are typically located just behind the lizard’s forelimbs. When these lizards have mites, most are in the pockets, leading some scientists to speculate (and others to dispute) that a pocketful of mites is advantageous for the lizard. The chiggers are bright red, and on a drab lizard, they present a flashy spot of color that can be turned on and off as the lizard moves its legs.

Contributed by Bryan Falk.

May 5 - Acarapis woodi

Earlier, you saw the mite Varroa destructor, that hitches rides on honeybees. Now meet Acarapis woodi, another teeny tiny little mite that also infects honeybees. But, unlike Varroa, this species gets inside the trachea (the tubes that it uses to exchange gases) of the bees. The mites pierce the trachea and suck up the hemoplymph to get their nutrients. Bees can be infected with huge numbers of these things, and even though they're tiny, it's got to be hard to fly when you've got 100 little passengers!

April 18 - Demodex folliculorum

One of the things that grosses non-parasitologists out (and probably many parasitologists!) is the fact that little tiny mites live on our eyelashes. These are Demodex folliculorum, and they can actually inhabit many different follicles on humans' faces. In fact, they're a bit social - as many as 10 of them can co-exist in a single follicle (party on the forehead - spread the word!) There are no known pathogens that they spread, but they can cause people to lose hair and they can make pores larger. They don't bite people and instead they mostly just munch up the secretions from our sebaceous glands. One of the coolest things is that they seem to be so incredibly efficient at digestion that they don't produce waste - so much so that they don't even have an excretory pore for defecation. So, if you have to deal with the fact that right now there are potentially a bunch of tiny spider-like things living on your face, at least you can take a little comfort from the knowledge that they are clean house guests.

March 25 - Sarcoptes scabei

In the aftermath of the earthquake, aid workers report that scabies has been running rampant in tent cities in Haiti. Scabies is a contagious disease caused by Sarcoptes scabiei, parasitic mites that are hosted on humans, dogs, cats, and other wild animals such as koalas, gorillas, and wild boar. Sarcoptes scabiei are Acariformes, members of the subclass Arachnida (spiders, scorpions, mites and ticks), subphylum Cheliceriformes, phylum Arthropoda. Up to 104 species are known to have been infected with Sarcoptes scabiei, producing a condition called sarcoptic mange. All four stages of the parasite’s life, egg, larva, nymph and adult, take place on the host’s epidermis. The adult female burrows under the skin and lays 2 or 3 of her eggs each day. To enter the skin, the mites use cutting mouth parts and cutting hooks on the legs. As the life cycle progresses, the mites come to the surface of the skin, then burrow into molting patches to complete the stages. Burrowing mites feed on living cells and tissue fluid. The first hosts of S. scabiei are thought to have been humans. The mites then infected domestic animals that later transferred the parasite to wild animals. The movement of the mites into and on the skin produces an allergic reaction and is extremely itchy. On humans, scabies is most common in areas of the body that come in contact with the skin of other humans, such as the hands and arms. Scabies can be treated with prescribed medical cream.

Contributed by Sara Baughn, Bucknell University.

January 10 - Varroa destructor

Many people have heard of grave concerns about the loss of honey bees, key pollinators of our crops and other important plants. One of the reasons for their trouble is the ectoparasitic mite, Varroa destructor. These tiny little arachnids climb onto bees and suck out their hemolymph - insect blood - and can also transmit dangerous viruses from bee to bee.