Monthly Archives: July 2019

New Species: July 2019

by Piter Kehoma Boll

Here is a list of species described this month. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, Mycological Progress, Journal of Eukaryotic Microbiology, International Journal of Systematic and Evolutionary Microbiology, Systematic and Applied Microbiology, Zoological Journal of the Linnean Society, PeerJ, Journal of Natural History and PLoS One, as well as several journals restricted to certain taxa.

Bacteria

SARs

Primulina cerina is a new flowering plant from China. Credits to Li et al. (2019).*
Tashiroea villosa is another new flowering plant from China. Credits to Zhou et al. (2019).*

Plants

Guatteria aliciae is a new flowering plant from Panama. Credits to Maas et al. (2019).*
Rhaptopetalum rabiense is a new flowering plant from Gabon. Credits to Kenfack & Nguema (2019).*

Fungi

Dicephalospora yunnanica is a new fungus from China. Credits to Zheng & Zhuang (2019).*
Amanita ahmadii is a new mushroom from Pakistan. Credits to Jabeen et al. (2019).

Poriferans

Rotiferans

Flatworms

Annelids

Mollusks

Sinochloritis lii is a new species of snail from China. Credits to Wu et al. (2019).*

Kinorhynchs

Nematodes

Tardigrades

Arachnids

Hyleoglomeris roukouqu is a new millipede from China. Credits to Liu & Winne (2019).*

Myriapods

Sarothrogammarus yiiruae is a new amphipod from China. Credits to Zheng et al. (2019).*
Hyalella puna is a new amphipod from Argentina. Credits to Peralta & Miranda (2019).*

Crustaceans

Geosesarma mirum is a new semi-terrestrial crab from Taiwan. Credits to Shy & Ng (2019).*
Macrobrachium laevis is a new shrimp from China. Credits to Zheng et al. (2019).*

Hexapods

Paranthrenella helvola is a new species of moth from Taiwan. Credits to Liang & Hsu (2019).*
Scolopsis lacrima is a new fish from New Caledonia. Credits to Nakamura et al. (2019).*

Actinopterygians

Cirrhilabrus wakanda is a new fish from Tanzania. Credits to Tea et al. (2019).*
Nidirana yaoica is a new frog from China. Credits to Lyu et al. (2019).*

Amphibians

Cnemaspis tarutaoensis is a new gecko from Thailand. Credits to Ampai et al. (2019).*

Reptiles

Mammals

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

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Friday Fellow: Portuguese Millipede

by Piter Kehoma Boll

Millipedes, which make up the class Diplopoda, are very cute arthropods in my opinion and include amazing species, such as the animal with the largest number of legs in the world. Many species are not well studied, though. However, one that is very well known is the Portuguese Millipede Ommatoiulus moreleti.

As its common name suggests, the Portuguese millipede is native from Portugal, more precisely from Southern Portugal and nearby areas in Spain, living in the soil of pine and oak forests. Its body, measuring about 4 cm as adults, has the typical cylindrical and elongate shape seen in most millipedes and is very dark, almost black, with legs that have a light color, usually whitish, but sometimes purplish.

A Portuguese millipede in Portugal. Photo by Romulo Arrais.*

Despite its relatively small size, the Portuguese millipede takes more than a year to reach maturity and grow for about three years. The mating period is usually during Autumn, and after having its eggs fertilized, the female lays from 60 to 80 of them in a chamber about 2 cm deep in the soil. When the eggs hatch, the first stage is a small, pupoid legless animal that remains inside a membrane until it molts into a small six-legged larva. During the first year, the juvenile molts about 8 times and the number of legs increases at each new stage. At about stage 10, they are sexually mature, but continue to molt and gaining more legs until reaching about 90 legs at the 14th stage. Males have an interesting reproductive strategy called periodomorphism, in which mature individuals molt into a “castrated” form, with reduced sexual organs, and becomes sexually mature again in the next molt, only to return to the immature form again in the next molt and so on.

The Portuguese millipede became famous after its accidental introduction in southeastern Australia, apparently in the 1950s. It soon became a very abundant species and, as a consequence, a nuisance for humans. As most millipedes, the Portuguese millipede is mainly detritivorous, feeding on dead plant material, such as rotten wood and dead leaves, so its introduction is not that much an ecological catastrophe, although it can have some negative impacts by competing with native millipede species.

A Portuguese millipede in Australia. Photo by iNaturalist user corunastylis.**

The main problems caused by the introduction of the Portuguese millipede in Australia affect mostly humans. They are attracted to weak light sources, such as those emitted by houses at night, and, as a result, end up invading residences, sometimes hundreds of them at a time. When threatened, the Portuguese millipede emits a pungent yellow secretion that can irritate the eyes and, in contact with clothes, mark them with a permanent stain. Addtionally, the Portuguese millipede sometimes can feed on some crops, especially fruits.

In Portugal, the populations of the Portuguese millipede are controlled by native predators, such as the European hedgehog Erinaceus europaeus and the beetle Ocypus olens. Released from these natural enemies, the millipede spread quickly through southeastern Australia. However, about 30 years later, its population in Australia started to decrease. Apparently some nematode parasites that infect native millipedes adapted to parasitize this invasive species as well, helping to contain its population size. Some other native Australian predators have also observed feeding on the Portuguese millipede, including the blue garden flatworm, Caenoplana coerulea.

Other than Australia, the Portuguese millipede was also introduced in several Atlantic Islands, such as the Macaronesian Islands, Bermuda and the UK, as well as in South Africa. However, it does not seem to be that much of a nuisance there.

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More millipedes:

Friday Fellow: Leggiest Millipede (on 12 February 2016)

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References:

Baker GH (1985) Predators of Ommatoiulus moreletii (Lucas) (Diplopoda: Iulidae) in Portugal and Australia. Australian Journal of Entomology 24(4): 247–252. doi: 10.1111/j.1440-6055.1985.tb00237.x

Baker GH (1978) The post-embryonic development and life history of the millipede, Ommatoiulus moreletii (Diplopoda: Iulidae), introduced in south-eastern Australia. Journal of Zoology 186: 209–228. doi: 10.1111/j.1469-7998.1978.tb03366.x

Gregory SJ, Owen C, Jones G, Williams E (2018) Ommatoiulus moreleti (Lucas) and Cylindroiulus pyrenaicus (Brölemann) new to the UK (Diplopoda, Julida: Julidae) and a new host for Rickia laboulbenioides (Laboulsbeniales). Bulletin of the British Myriapod & Isopod Group 30: 48–60.

McKillup SC, Allen PG, Skewes MA (1988) The natural decline of an introduced species following its initial increase in abundance: an explanation for Ommatoiulus moreletii in Australia. Oecologia 77:339–342. doi: 10.1007/BF00378039

Terrace TE, Baker GH (1994) The blue land planarian, Caenoplana coerulea Moseley (Tricladida: Geoplanidae), a predator of Ommatoiulus moreleti (Lucas) (Diplopoda: Julidae) in southern Australia. Australian Journal of Entomology 33(4): 371–372.

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Friday Fellow: Stonewort Seed Shrimp

by Piter Kehoma Boll

It’s time to talk about an ostracode, or seed shrimp, again and, as usual, this is a difficult time due to the little information easily accessible regarding any particular species of this group. But there is, indeed, one that is considerably well studied. Being one of the most common ostracodes in North America and Eurasia, its scientific name is Cypridopsis vidua, to which I coined the common name “stonewort seed shrimp”.

The stonewort seed shrimp is a freshwater crustacean with the typical ostracode appearance, looking like a tiny bivalve measuring about 0.5 mm in length. Its valves have a distinctive light and dark pattern.

A stonewort seed shrimp with a closed shell. Credits to Markus Lindholm, Anders Hobæk/Norsk institutt for vassforsking.*

A relatively mobile species, the stonewort seed shrimp lives at the bottom of water bodies, over the sediment, and is common in areas that are densely vegetated by stoneworts (genus Chara). This association with stoneworts gives the stonewort seed shrimp both protection from predators, which are mostly fish, and a good food source.

The main food of the stonewort seed shrimp are microscopic algae that grow on the stems of stoneworts. While foraging, the stonewort seed shrimp swims from one stonewort stem to another using its first pair of antennae and clings on the stems using the second pair of antennae and the first pair of thoracic legs. Once realocated, it starts to scrape the microscopic algae using its mandibles.

The body of a stonewort seed shrimp as seen when one of the valves (the left one here) is removed. Credits to Paulo Corgosinho.**

The stonewort seed shrimp is one more of those species in which males do not exist, not even in small quantities. During the warm months of summer, females produce the so-called subitaneous eggs, which develop immediately into new females. However, when winter is approaching, they produce another type of eggs, the so-called diapausing eggs, which remain dormant in the substrate during winter. The adult animals all die during this season and, when spring arrives, a new population appears from the hatching eggs. Since not all eggs hatch in the spring, some of them may remain in the substrate for years before hatching, which usually increases the genetic diversity every year, as it not only depends of the daughters of the last generation.

But how does genetic diversity appear if there are no males and, as a result, the daughters are always clones of the mothers? This mystery is not yet fully solved. Genetic recombination during parthenogenesis, by exchanging alleles between chromosomes, does not seem to be very common. It is possible that different populations are genetically different and that they colonize new areas very often, mixing with each other. Since males are known in closely related species, it is still possible that, some day, we will find, somewhere, some hidden males of the stonewort seed shrimp. It is also possible that, somehow, males went all extinct in the recent past, like in the last glaciation, for example. If so, only time can tell what is the destiny of the stonewort seed shrimp.

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More Ostracods:

Friday Fellow: Sharp-Toothed Venus Seed Shrimp (on 22 June 2018)

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References:

Cywinska A, Hebert PDN (2002) Origins of clonal diversity in the hypervariable asexual ostracode Cypridopsis vidua. Journal of Evolutionary Biology 15: 134–145. doi: 10.1046/j.1420-9101.2002.00362.x

Roca JR, Baltanas A, Uiblein F (1993) Adaptive responses in Cypridopsis vidua (Crustacea: Ostracoda) to food and shelter offered by a macrophyte (Chara fragilis). Hydrobiologia 262: 121–131.

Uiblein F, Roca JP, Danielpool DL (1994) Experimental observations on the behavior of the ostracode Cypridopsis vidua. Internationale Vereinigung für Theoretische und Angewandte Limnologie: Verhandlungen 25: 2418–2420.

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Instead of toxic chemicals, use helping plants to get rid of crop pests

by Piter Kehoma Boll

Finding efficient ways to deal with agricultural pests in crops is a challenging work. Currently, as we all known, the main strategy to control such pests is the use of chemical pesticides. However, this approach only serves the interests of those seeking profit over well-being, as we all know that such pesticides increase the risk of several health issues in those consuming the crops. More than that, chemical pesticides not only kill the targeted pest but many other life forms, causing a devastating effect on ecosystems.

The cross-striped cabbageworm (Evergesis rimosalis) is a common pest in plants of the genus Brassica (kale, cabbage, mustard) in the eastern United States. Photo by iNaturalist user margaridamaria.*

Fortunately, there has been an increasing interest in finding alternative, healthier ways to deal with the problem. One way is the production of genetically modified organisms (GMOs) that are naturally resistant to pests. There are, however, two main problems with this approach. The first one is that the population in general has an irrational fear of GMOs, apparently believing that they can be more harmful than the poisonous chemical pesticides, which is completely absurd. The second problem with GMOs is that the technology to create them is dominated by the same companies that produce most pesticides and, as all big companies, only seek profit and do not give a damn about the people and the environment.

A third strategy is the use of natural enemies of the pests to control them in organic farms. Although many natural enemies are great doing their job, they may also cause negative impacts by interfering with the surrounding ecosystems. Many crop pests are not native from the area where they are pests, i.e., they are invasive species and, in order to control them efficiently, a predator from its native area must be introduced as well, and this predator may end up becoming a threat to other species that it elects as food.

Coleomegilla maculata is a common predatory lady beetle in the eastern United States. They are great to control agricultural pests locally but should not be deliberately introduced elsewhere. Photo by Riley Walsh.*

Fortunately, some nice strategies have been recently developed. One of them includes the use of additional plants in the fields that change the way that pests behave without posing a threat to surrounding areas. These additional plants consists of two types: trap crops and insectary plants.

The common buckwheat Fagopyrum esculentum has been used as an insectary plant. Photo by iNaturalist user jimkarlstrom.*

A trap crop, as the name suggests, is an additional crop that is not intended to be commercially exploited, but serves as a trap for the pests. Instead of attacking the main crop (called the ‘cash crop’), the pests are attracted to the trap crop, reducing their density in the cash crop. This system is more efficient if the trap crop is similar to the cash crop, such as another plant of the same genus, or another variety of the same species, because it must be as attractive to the pest as the cash crop, or perhaps even more attractive.

Insectary plants, on the other hand, are intended to attract other insects to the plantation, especially predatory insects that prey on the agricultural pest. Insectary plants should produce flowers in abundance, thus attracting many insect species, which will increase the interest of predators in the area. However, when used alone, insectary plants will only provide predators to control the pest in crop plants that are near the insectary plants and, as they are usually planted in an area surrounding the plantation, they would not protect the plants that are near the center of the plantation.

In a recent study, Shrestha et al. (see references) decided to combine trap crops and insectary plants together with the cash crops in a strategy that they called a ‘botanical triad’. The cash crap was organic cabbage (Brassica oleracea var. capitata) planted in the eastern United States; the trap crops were three other crops of the genus Brassica: mighty mustard (Brassica juncea), kale (Brassica oleracea var. acephala) and collard (Brassica oleracea var. italica); and the insectary plants were buckwheat (Fagopyrum esculentum) and sweet alyssum (Lobularia maritima).

Kale (Brassica oleracea var. acephala). Photo by David Adreas Tønnessen.*

As a result, the number of herbivores (i.e., crop pests) was larger in the trap crops than in the cash crop. The trap crops were, therefore, more attractive than the cash crops for the pests. The presence of insectary plants increased the number of predatory and parasitoid insects, such as lady beetles and parasitoid wasps, in the trap crops when compared to treatments without insectary plants. The number of parasitized pests also increased in the presence of insectary plants.

Field layout of the study by Shrestha et al. (2019).**

In general, the “team work” of trap crops and insectary plants greatly reduced the influence of agricultural pests on the cash crops. The trap crops attracted the pests to an area close to the insectary plants, allowing the predators to reach them.

Efficient ways to raise crops organically are possible. We just have to focus on a healthy ecosystem and not on money. If we work together, we can defeat the “Big 6” corporations that dominate the food production in the world. They are the real pests.

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Reference:

Shrestha B, Finke DL, Piñero JC (2019) The ‘Botanical Triad’: The Presence of Insectary Plants Enhances Natural Enemy Abundance on Trap Crop Plants in an Organic Cabbage Agro-Ecosystem. Insects 10(6): 181. doi: 10.3390/insects10060181

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Friday Fellow: Luna Moth

by Piter Kehoma Boll

It’s been a very long time since the last time I presented a lepidopteran here, so today I decided to go back to this amazing group of insects. The species I chose for today is quite popular, maybe the most popular moth in the world. Its name is Actias luna, commonly known as the luna moth.

Adult luna moth in the Unites States. Photo by Andy Reago & Chrissy McClarren.*

The luna moth is native from Canada and the United States. It is a quite large moth, with a wingspan of about 8 to 12 cm, although some individuals can be as big as 18 cm. Its wings, covered with scales as usual in lepidopterans, have a light green color. The forewigs have a brown anterior border that connects to two eyespots (one on each wing) by a stalk. The hindwings also have one eyespot each, but they are not connected by a stalk to the border. The hindwings also have a long tail that is characteristic of the genus Actias and somewhat resembles the similar (but shorter) tails in some butterflies, such as those of the family Papilionidae. Males and females are very similar and can be often distinguished by the size of the abdomen, which is much thicker in females.

In colder climates, such as in Canada, the luna moth has one generation per year, but southern populations, in places where the climate is warmer, can have up to three. The females lay eggs on suitable plants to serve as food for the larvae. There are several identified tree species that are used as food, including birches, walnuts, hickories and persimmons. The larvae feeding on a tree never, or very rarely, reach a number that can cause significant damage to the plant.

Third instar larvae. Photo by Wikimedia user Kugamazog~commonswiki.**

The eggs are brown and laid in irregular clusters on the underside of the leaves. They usually hatch one to two weeks after being laid and originate small, green larvae. The larvae are green in all instars and pass through five of them during a period of about 7 weeks. The fifth and final instar then descends the tree in which it lives to reach the ground. There, it starts to spin a silk coccoon and, after finishing it, turns into a pupa. In warmer regions, the pupa takes about two weeks to become an adult, but in colder regions it enters into diapause over winter, taking about nine months to complete the cycle.

A fifth-instar larvae building its coccoon. Credits to Virginia State Parks staff.*

When females become adults, they search for a suitable tree of its preferred species (usually the same species in which it was born) and emits pheromones to attract males. Adults lack mouth parts and, therefore, do not eat, living only enough to mate and lay eggs. The nice long tails on the hindwings, more than just beautiful, seem to decrease the ability of bats to detect them using their echolocation.

Pupa beside an empty coccon. Photo by Wikimedia user Kugamazog~commonswiki.**

The luna moth is one of the most popular insects in North America. In fact, it was the first insect ever to be described from the continent, being named Phalaena plumata caudata by James Petiver in 1700. When Linnaeus started the binomial nomenclature for animals in 1758, he renamed it Phalaena luna as a reference to the Roman goddess of the moon.

Beautiful specimen in Canada. Photo by Alexis Tinker-Tsavalas.***

Although not considered a vulnerable species at the moment, the luna moth faces some threats caused by human interference, such as habitat loss and damage caused by invasive species. Fortunately, due to its popularity, it is likely to have considerable support from the public for its conservation when that time comes.

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References:

Lindroth RL (1989) Chemical ecology of the luna moth: Effects of host plant on detoxification enzyme activity. Journal of Chemical Ecology 15(7): 2019–2029.

Millar JG, Haynes KF, Dossey AT, McElfresh JS, Allison JD (2016) Sex Attractant Pheromone of the Luna Moth, Actias luna (Linnaeus). Journal of Chemical Ecology 42(9): 869–876.

Wikipedia. Luna moth. Available at < https://en.wikipedia.org/wiki/Luna_moth >. Access on 11 July 2019.

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Friday Fellow: Chinese Banyan Wasp

by Piter Kehoma Boll

During the past three weeks, I presented a fig tree, the Chinese Banyan, a thrips that parasitizes it, the Cuban Laurel Thrips, and a mite that parasitizes the thrips, the Cuban-Laurel-Thrips Mite. However, I haven’t wrote yet about one of the most interesting creatures that interacts with a fig tree: its pollinator.

In the case of the Chinese Banyan, its pollinator is the fig wasp Eupristina verticillata, which I named the Chinese Banyan Wasp. As all fig wasps, this species is very small and completely adapted to live with figs. They cannot survive without the exact fig species with which they interact and the fig species cannot reproduce without that exact wasp. How does this works?

Let’s start our story with an adult female Chinese banyan wasp. The females are black and very small, measuring around 1 to 1.2 mm in length only. This female is flying around looking for a young fig which will serve as her nest and her grave.

This is what a female Chinese Banyan wasp loooks like. Photo by Forest & Kim Starr.*

A fig, in case you don’t know, is not a real fruit in the botanical sense. It is actually a special kind of inflorescence called a syconium that is basically a flower-filled sack. The inner walls of a fig have many tiny male and female flowers and the only way to get to them is through a tiny hole at the fig’s appex. And this hole is only open during the initial stages of the fig’s development.

Chinese Banyan figs in their early stage. You can see the hole marked by a darker “areola” around them. That is the place through which a female fig wasp enters the fig. Credits to Wikimedia user Vinayaraj.**

When the female Chinese Banyan fig wasps is flying around, she is looking for a fig that is at this exactly stage of development. Once she finds one, she crawls inside the fig through that tiny hole. She usually loses her wings while doing that because the passage is too narrow. She evens needs to use her especially adapted mandible to help her go through. Once inside the fig, she looks for the female flowers, which are located at the base of the fig, away from the entrance. The male flowers, located right at the entrance, are not mature yet. However, the female wasps arrived with pollen that she gathered elsewhere (you will learn about that soon). When she reaches the female flowers, she introduces her ovopositor (the long structure at the end of her abdomen that is used to lay eggs) inside the female flower and lays one egg inside the flower’s ovary. Her ovopositor needs to have the exact size to reach the ovary to lay the egg. If it is too short, she is unable to complete her task. And while she is moving from flower to flower to lay eggs, she ends up pollinating them. After she has finished, she dies still inside the fig.

The ovaries that received an egg start to grow into a gall (a “plant tumor”) by influence of the insect and serve as food and shelter for the larvae that hatch from the eggs. A larva grows, pupates and turns into an adult inside a single gall. When the wasps have finally reached their adult stage, they leave the gall in which they were born. This happens when the fig reached its mature stage.

Males are the first ones to emerge. They are even smaller than the females and have a yellow to light-brown color. They gnaw their way through the gall and, once outside it (but still inside the fig) they start to look desperately for female wasps to inseminate. They do that by tearing other galls apart and, when a female is found trapped inside, they inseminate her. After that, the males dig a hole through the fig to the outside and die soon after, never experienced the external world.

A male Chinese Banyan wasp (right) compared to a female. Photo by Forest & Kim Starr.*

Female wasps then leave their galls and move towards the hole opened by the male. While doing that, they move over the now mature male flowers and become covered in polen. After leaving the fig, they search for another fig that is in its early stage of development, restarting the cycle.

When a female leaves a mature fruit, she needs to find an immature one soon after that because she will die in a couple of days. In other words, the only way for this to work is if there are figs in the right stage all year around, and that is what happens. Differently from most plant species, which produce flowers in a specific time of the year, fig trees are always flowering. Well, not exactly. One individual fig tree produces figs only in a specific period of the year. All the figs of that tree ripen at the same time, i.e., a fig tree has an intra-individual synchrony of flower maturation. However, other trees of the same species have different moments to produce flowers, i.e., there is an inter-individual asynchrony of flower maturation. This assures that a wasp will always find a fig at the suitable maturation stage when there are enough fig trees around and also assures that a fig tree will not be fertilized by its own pollen.

As I mentioned when I presented the Chinese Banyan, this tree can only produce viable figs when the wasp is present, so that populations introduced outside of their native range will only reproduce if the waps is introduced as well. However, the wasp will be unable to survive if there are not enough fig trees to provide it with figs all year round. It is a delicate relationship between a tiny, fragile and short-lived insect and a huge, resistant and long-lived tree. And they need each other to survive.

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References:

Cook J, Rasplus J-Y (2003) Mutualists with attitude: coevolving fig wasps and figs. TRENDS in Ecology and Evolution 18(5): 241–248.

Kjellberg F, Jousselin E, Hossaert-McKey M, Rasplus J-Y (2005) Biology, Ecology, and Evolution of Fig-pollinating Wasps (Chalcidoidea, Agaonidae). In Raman A, Schaefer CW, Withers TM (Eds.) Biology, ecology and evolution of gall-inducing arthropods. v.2. New Hampshire, Science, p.539-572.

McPherson JR (2005) A Recent Expansion of its Queensland Range by Eupristina verticillata, Waterston (Hymenoptera, Agaonidae, Agaoninae), the Pollinator of Ficus microcarpa l.f. (Moraceae). Proceedings of the Linnean Society of New South Wales: 126: 197–201.

Weiblen DG (2002) How to be a fig wasp. Annual Review of Entomology 47: 299–330.

Wiebes JT (1992) Agaonidae (Hymenoptera, Chalcidoidea) and Ficus (Moraceae): fig waps and their figs, VIII (Eupristina s.l.). Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen 95(1): 109–125.

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Tospovirus and thrips: an alliance that terrifies plants

by Piter Kehoma Boll

I recently presented a thrips in the Friday Fellow section, in that case a thrips that infects mostly fig trees. This group of insects, which make up the insect order Thysanoptera, is poorly known by the general public, but is certainly known by gardeners and farmers, as they can be a serious nuisance for many plant types.

We could imagine thrips as being kind of the mosquitoes of plants. They pierce the surface of plants and suck their juices just like mosquitoes do with vertebrates. And we all know that a mosquito bite may lead to much more than a small blood loss and local irritation of the skin. Many parasites use mosquitoes as vectors to travel from host to host, including protists such as Plasmodium falciparum, which causes malaria, and many types of virus, such as those of the genus Flavivirus, which cause the yellow, dengue and zika fevers.

A similar thing happens in the association of thrips with plants. A special genus of virus, called Tospovirus, infects many plant species and uses thrips as a vector. Inside the thrips bodies, the viruses reproduce after infecting the epithelial cells of the gut and, from there, travel via blood to the salivary glands and, when a thrips perforates a plant, the virus is injected in it. The cycle is basically the same used by Flavivirus in mosquitoes and ticks to infect vertebrates. Isn’t it amazing how a virus such as Tospovirus can infect both an animal and a plant? But what exactly is the disease caused by these viruses?

Basil leaf infected with the tomato spotted wilt virus. Photo by Scot Nelson.**

One of the most common Tospovirus is the so-called Tomato spotted wilt virus (TSWV), which is considered one of the most economically devastating plant viruses in the world. It can infect many crops, such as tomato, tobacco, bellpepper, peanut and basil. The symptoms vary from plant to plant, but usually include stunting, poorly developed fruits, commonly with ring spots on the surface, and necrosis of the leaves. It is transmitted to plants by thrips of the genus Frankliniella, mainly the western flower thrips Frankliniella occidentalis. Although the virus usually needs several hours to be able to reinfect a plant after infecting a thrips, in ideal conditions the time can e as short as five minutes.

The western flower thrips Frankliniella occidentalis. Photo by Dave Kirkeby.*

But why would a thrips feed on an obviously sick plant, all ugly and full of spots? They would certainly prefer a healthy plant, but that would prevent the virus to spread. As a result, the virus developed several strategies to attract the thrips. The TSWV is able to increase the amount of free aminoacids in infected plants, and these are essential nutrients for egg production in thrips. As a consequence, infected plants become more nutritious and attract more thrips. Feeding on infected plants, the thrips will certainly get infected and at the same time ingest more nutrients than non-infected thrips. Thus, a sick thrips actually has an increased fitness and usually lays more eggs. The plants would certainly get effing scared if they were able to have emotions.

The Soybean vein necrosis virus (SVNV) is another Tospovirus of economic concern. As it names suggests, it attacks mainly soy plants, and its main vector is the soybean thrips Neohydatothrips variabilis. Infected soybean thrips produce significantly more offspring than non-infected ones, although heavily infected individuals lay few viable eggs. How do thrips bypass this problem? It’s simple! Once they are infected, they stop feeding on infected plants and prefer non-infected ones, which increases their reproductive success by avoiding becoming heavily infected and at the same time they spread the virus further to non-infected plants. A nightmare for the plants once more.

Soybean thrips Hydatothrips variabilis. Photo by Even Dankowicz.***

A recent study investigated the relationship of another Tospovirus-thrips pair, this time of the iris yellow spot virus (IYSV), which commonly attacks garlic and onion plants, and its main vector, the onion thrips, Thrips tabaci. Infected thrips did not show an increased daily fecundity but had an increased lifespan, allowing them to lay more eggs simply because they lived longer.

Iris yellow spot virus lesion on an onion leaft. Extracted from https://vegetableguide.usu.edu/diseases/onion/iris-yellow-spot-virus

But the effect of Tospovirus on thrips can go further. For example, although plants infected by the TSWV release more aminoacids that attract and increase the fecundity of thrips, the infections still seems to have some deleterious effects on the insect. Infected males of Frankliniella occidentalis increase their consumption of food juices and increase the transmission of the virus. Females, on the other hand, seem to need nutrients that cannot be found in plants. As a result, they increase the consumption of eggs of the two-spotted spider mite Tetranychus urticae, with which they often coexist. Although primarily herbivorous as most thrips, the western flower thrips eventually feeds on mite eggs, and being infected by TSWV makes females become more eager to eat eggs. This is certainly not a strategy of the virus itself as the other ones, since a female that is feeding on mite eggs does not contribute for the virus’ reproductive success. Nevertheless, this is an interesting phenomenon that show us how the interactions in a trophic web can be dynamic, changing, for example, due to an uninentional side effect of a virus trying to survive.

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References:

Keough S, Han J, Shuman T, Wise K, Nachappa P (2016) Effects of Soybean Vein Necrosis Virus on Life History and Host Preference of Its Vector, Neohydatothrips variabilis , and Evaluation of Vector Status of Frankliniella tritici and Frankliniella fusca. Journal of Economic Entomology 109(5): 1979–1987. doi: 10.1093/jee/tow145

Leach A, Fuchs M, Harding R, Nault BA (2019) Iris Yellow Spot Virus Prolongs the Adult Lifespan of Its Primary Vector, Onion Thrips (Thrips tabaci) (Thysanoptera: Thripidae). Journal of Insect Science 19(3): 8. doi: 10.1093/jisesa/iez041

Shrestha A, Srinivasan R, Riley DG, Culbreath AK (2012) Direct and indirect effects of a thrips‐transmitted Tospovirus on the preference and fitness of its vector, Frankliniella fusca. Entomologia Experimentalis et Applicata 145(3): 260–271. doi: 10.1111/eea.12011

Stafford-Banks CA, Yang LH, McMunn MS, Ullman DE (2014) Virus infection alters the predatory behavior of an omnivorous vector. Oikos 123(11): 1384–1390. doi: 10.1111/oik.01148

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

** Creative Commons License This work is licensed under a Creative Commons Attribution 2.0 Generic License.

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

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