Category Archives: Ecology

A balanced diet may kill you sooner… if you are a land planarian

by Piter Kehoma Boll

There’s one thing that I should do more often here, and that is presenting my own research for the readers of the blog, so today I am going to do exactly that.

As you may know, the group of organisms with which I work is the family Geoplanidae, commonly known as land planarians. Here in Brazil, the most speciose genus is Obama, of which I have talked in previous posts. This genus became considerably famous after one of its species, Obama nungara, became invasive in Europe, which called attention of the public especially because of the curious name of this genus, even though it has nothing to do with the former president of the United States.

Anyway, during my Master’s study, it became clear that species in the genus Obama feed on soft-bodied invertebrates, mainly slugs and snails, although some species also feed on earthworms or even other land planarians. Obama nungara, for example, feeds on all three groups, although it seems to have some preference for earthworms.

A specimen of Obama anthropophila with its testicle freckles. Photo by myself, Piter K. Boll.*

One common species of Obama in urbans areas of southern Brazil is Obama anthropophila, whose name, meaning “lover of humans” is a reference to this habit precisely. This species has a uniformly dark brown dorsal color, sometimes mottled by the mature testicles appearing as darker spots on the first half of the body. The diet of this species includes snails, slugs, nemerteans and other land planarians, especially of the genus Luteostriata, and more especially of the species Luteostriata abundans, which occurs very often in urbans areas too.

Watch Obama anthropophila capture different prey species.

So I wondered… if O. anthropophila feeds on different types of invertebrates, does it mean that each type provides different nutritients, so that a mixed diet is necessary or more beneficial than one composed of a single prey type? To assess that, I divided adult specimens of O. anthropophila into three groups, each receving a different diet:

Group Dela: fed only with the common marsh slug, Deroceras laeve
Group Luab: fed only with the abundant yellow striped planarian, Luteostriata abundans
Group Mixed: fed with both prey species in an alternating way

The results were not what I expected. The Mixed group showed a lower survival rate than the groups receiving a single diet. Another interesting feature was that the Mixed group showed a tendency to skip the slug meal and eat only the planarian after some days receiving the alternating prey types.

Based on the hypothesis that a mixed diet is more nutritious, I was expecting the Mixed group to have the best performance, or at least being similar to the single-diet groups if there was no increase in nutritional value with an additional prey type. However, the results indicate that a mixed diet may be bad for the planarian, at least if the animal has to eat a different food on every meal.

We don’t know what causes this, but my idea is that maybe different prey types demand different metabolic processes, such as the production of different enzymes and stuff, and having to constantly reset your metabolism is too costly. As a result, the fitness of specimens receiving such a diet decreases and the animals start to avoid one of the food types, because eating less is less dangerous than mixing food.

A “pregnant” Obama anthropophila about to ley an egg capsule. Photo by myself, Piter K. Boll.*

Another interesting aspect is that planarians receiving a mixed diet, even though they died earlier, laid heavier egg capsules than the single-diet groups. Heavier egg capsules generally mean that they have more embryos or are more nutrient for the embryos, increasing the reproductive success. But how can a dying animal be better at reproducing than a healthy one?

Well, this may be related to the terminal investment hypothesis. It is thought, and proven in some groups, that an organism may increase its investment on reproduction when future reproductive events are not expected, i.e., when the organism “realizes” it is about to die, it puts all its effort to reproduce in order to garantee that its genes will pass successfully to future generations.

We cannot be sure about anything yet. More studies are necessary to better understand the relationship of land planarians and their food. What we can assure is that, just like Obama nungara, O. anthropophila may end up in Europe or anywhere else soon because its relatively broad diet and its proximity to humans make it a potential new species to be spread accidentally around the world.

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Reference:

Boll PK, Marques D, & Leal-Zanchet AM (2020) Mind the food: Survival, growth and fecundity of a Neotropical land planarian (Platyhelminthes, Geoplanidae) under different diets. Zoology 138: 125722.

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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 Ecology, Evolution, flatworms, worms

Should we save or should we get rid of parasites?

by Piter Kehoma Boll

Parasites are special types of organisms that live on or inside other lifeforms, slowly feeding on them but usually not killing them, just reducing their fitness to some degree. This is a much more discrete way to survive than killing or biting entire parts off, as predators (both carnivores and herbivores) do. However, different from these creatures, parasites are often regarded as unpleasant and disgusting. Yet parasitism is the most common way to get food in nature.

When I introduced the rhinoceros tick in a recent Friday Fellow, I mentioned the dilemma caused by it. Since the rhinoceros tick is a parasite of rhinoceroses, and rhinoceroses are threatened with extinction, a common practice to improve the reproductive fitness of rhinos is removing their ticks, but this may end up leading the rhinoceros tick to extinction.

This actually happened already with other parasites, such as the louse Coleocephalum californici, which was an exclusive parasite of the California condor Gymnogyps californianus. In order to save the condor, a common practice among veterinarians working with conservationists was to delouse the birds and, as a result, this louse is now extinct. The harm that the louse caused to the condor was so little, though, that its extinction was not at all necessary, being nothing more than a case of negligence and lack of empathy for a small and non-charismatic species.

The California condor louse Coleocephalum californici was extinct during a poorly managed campaign to save the California condor Gymnogyps californianus. Image extracted from https://www.hcn.org/blogs/goat/the-power-and-plight-of-the-parasite

The louse Rallicola (Aptericola) pilgrimi has also vanished forever during the conservation campaigns to save its host, the little spotted kiwi, Apteryx owenii, in another failed work.

The efforts to save the little spotted kiwi, Apteryx owenii, from extinction led to the extinction of its louse. Photo by Judi Lapsley Miller.*
The now extinct Rallicola (Aptericola) pilgrimi. Credits to the Museum of New Zealand.***

Another group of parasites that is facing extinction are fleas. The species Xenopsylla nesiotes was endemic to the Christmas Island together with its host, the Christmas Island rat, Rattus macleari. The introduction of the black rat, Rattus rattus, in the island led to a quick decline in the population of the Christmas Island rat, which went extinct at the beginning of the 20th century and, of course, the flea went extinct with it. The flea Acanthopsylla saphes has likely become extinct as well. It was a parasite of the eastern quoll, Dasyurus viverrinus, in mainland Australia. The eastern quoll today is only found in Tasmania, as the mainland Australia’s population went extinct in the mid-20th century. However, the flea was never found in the Tasmanian populations, so it is likely that it died away in mainland Australia together with the local population of its host.

The Manx shearwater flea Ceratophyllus (Emmareus) fionnus. Photo by Olha Schedrina, Natural History Museum.*

But things have been changing lately and fortunately the view on parasites is improving. A recent assessment was made on the population of another flea, the Manx shearwater flea, Ceratophyllus (Emmareus) fionnus. This flea is host-specific, being found only on the Manx shearwater Puffinus puffinus. Although the Manx shearwater is not at all a threatened species and has many colonies along the North Atlantic coast, the flea is endemic to the Isle of Rùm, a small island off the west coast of Scotland. Due to the small population of its host in this island, the flea has ben evaluated as vulnerable. If the Manx shearwater population in the Island were stable, things would be fine but, as you may have guessed already, things are not fine. Just like it happened in Christmas Island, the black rat was also introduced in the Isle of Rúm and has become a predator of the Manx shearwater, attacking its nests.

The Manx shearwater, Puffinus puffinus, is the sole host of the Manx shearwater flea. Photo by Martin Reith.**

Some ideas have been suggested to protect the flea from extinction. One of them is to eradicate the black rat from the Isle or at least manage its population near the Manx shearwater colonies. Another proposal is to translocate some fleas to another island to create additional populations in other Manx shearwater colonies.

But why bother protecting parasites? Well, there are plenty of reasons. First, they comprise a huge part of the planet’s biodiversity and their loss would have a strong impact on any ecosystem. Second, they are an essential part of their host’s evolutionary history and are, therefore, promoters of diversity by natural selection. Removing the parasites from a host would eventually decrease its genetic variability and let it more vulnerable to other new parasites. Due to their coevolution with the host, parasites are also a valuable source of knowledge about the host’s ecology and evolutionary history, helping us know their population dynamics. We can even find ways to deal with our own parasites by studying the parasites of other species, and parasites are certainly something that humans managed to collect in large numbers while spreading across the globe.

Parasites may be annoying but they are necessary. They may seem to weaken their host at first but, in the long run, what doesn’t kill you makes you stronger.

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References:

Kirst ML (2012) The power and plight of the parasite. High Country News. Available at < https://www.hcn.org/blogs/goat/the-power-and-plight-of-the-parasite >. Access on 3 November 2019.

Kwak ML (2018) Australia’s vanishing fleas (Insecta: Siphonaptera): a case study in methods for the assessment and conservation of threatened flea species. Journal of Insect Conservation 22(3–4): 545–550. doi: 10.1007/s10841-018-0083-7

Kwak ML, Heath ACG, Palma RL (2019) Saving the Manx Shearwater Flea Ceratophyllus (Emmareus) fionnus (Insecta: Siphonaptera): The Road to Developing a Recovery Plan for a Threatened Ectoparasite. Acta Parasitologica. doi: 10.2478/s11686-019-00119-8

Rózsa L, Vas Z (2015) Co-extinct and critically co-endangered species of parasitic lice, and conservation-induced extinction: should lice be reintroduced to their hosts? Oryx 49(1): 107–110. doi: 10.1017/S0030605313000628

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

**Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

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

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Filed under Conservation, Ecology, Evolution, Extinction, Parasites

Alien invasions: the resistance lies in streams

by Piter Kehoma Boll

Human activities have been introducing, either deliberately or accidentally, several species in areas outside of their native range. Many os these species, when they reach a new ecosystem, can have devastating effects on the local communities.

One common practice is the introduction of exotic fish for food production or recreation. Although the impact of exotic fish species can be severe, there are several factors that modulate this severity. However, one situation in which it can have catastrophic outcomes is when fish are introduced in water bodies that were originally fishless.

Mountain streams and lakes are usually fishless because of physical barriers, especially waterfalls, as they prevent fish from moving upstream. But fish have been introduced in many mountain lakes to provide a local food stock or for sport fishing.

One place that was plagued this way is the Gran Paradiso National Park in the Western Italian Alps. During the 1960s, the brook trout, Salvelinus fontinalis, a fish that is native from North America, was introduced in several of the park’s high-altitude lake. Later, when the area became proteced, fishing was prohibited.

Salvelinus fontinalis, the brook trout. Photo by Alex Wild.

From 2013 to 2017, a fish erradication program was conducted in four lakes of the park, namely Djouan, Dres, Leynir and Nero. Fish were captured using gillnetting and electrofishing. Since the trouts had colonized the streams that are connected to the lakes, they had to be removed from there as well.

The communities of organisms living in the lakes and streams were monitored to assess their recovery after the fish removal. The lakes showed a remarkable resilience, reaching a community structure similar to that of lakes where fish were never introduced. The streams, on the other hand, did not show a great difference before and after fish removal. The reason, however, was not that streams have low resilience. On the contrary, streams showed a great resistance to fish invasion. Trouts did not seem to have affected the macroinvertebrate communities of streams that much. But why is it so?

Dres lake in the Gran Paradiso National Park. Image extracted from the park’s website (http://www.pngp.it).

One hypothesis was that macroinvertebrates constantly colonize the streams by passive dispersion, coming from upstream waters. However, this is not applicable to streams that drain the lakes, as lake and stream communities are very different. Lower predation by trouts is not an option either, because it was shown that stream trouts actually eat more than lake trouts. Maybe stream invertebrates reproduce more quickly than lake ones? No! Studies have shown than this is similar in both environments.

The reason why stream invertebrates are less affected by the introduction of fish is still a mystery. One possible explanation is that streams present more microhabitats that are not explored by the trouts, providing refuges for the invertebrates. We need more studies to understand what is going on.

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You may also like:

Exotic species: are they always a trouble?

The New Guinea Flatworm visits France – a menace

Obama invades Europe: “Yes, we can!”

Think of the worms, not only of the whales, or: how a planarian saved an ecosystem

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References:

Tiberti R, Bogliani G, Brighenti S, Iacobuzio R, Liautaud K, Rolla M, Hardenberg A, Bassano B. (2019) Recovery of high mountain Alpine lakes after the eradication of introduced brook trout Salvelinus fontinalis using non-chemical methods. Biological Invasions 21: 875–894. doi: 10.1007/s10530-018-1867-0

Tiberti R, Brighenti S (2019) Do alpine macroinvertebrates recover differently in lakes and rivers after alien fish eradication? Knowledge & Management of Aquatic Ecosystems 420: 37. doi: 10.1051/kmae/2019029

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Filed under Conservation, Ecology, Fish

Going deep with your guts full of microbes: a lesson from Chinese fish

by Piter Kehoma Boll

All around the world, many animal species have adapted to live in cave environments, places that are naturally devoid of light, either partially or entirely, and are, therefore, nutrient-poor habitats. The lack of light makes it impossible for plants and other photosynthetic organisms to survive and, as a result, little food is available for non-photosynthetic creatures. They rely almost entirely on food that enters the cave from the surface by water or animals that move between the surface and the depths.

Due to the lack of light in caves, animals adapted to this environment are usually eyeless, because seeing is not possible anyway, and white, because there is no need for pigmentation on the skin to protect from radiation or to inform anything visually. On the other hand, chemical senses such as smell and taste are often very well developed.

All these limitations make cave environments relatively species-poor when compared to surface environments. Or at least that is what it looks like at first. There are, of course, much less macroscopic species, such as multicellular animals, but those animals are themselves an environment and they may harbor a vast and unknown diversity of microrganisms inside them.

As you may know, most, if not all, animals have mutualistic relationships with microorganisms, especially bacteria, living in their guts. Those microorganisms are essential for many digestive processes and many nutrients that animals get from their food can only be obtained with the aid of those microscopic friends. The types of microorganisms in an animal’s gut are directly related to the animal’s diet. For example, herbivores usually have a high diversity of microorganisms that are able to break down carbohydrates, especially complex ones such as cellulose.

A recent study, conducted in China with fishes of the genus Sinocyclocheilus, compared the gut microbial diversity of different species, including some that live on the surface and some that are adapted to caves. All species of Sinocyclocheilus seem to be primarily omnivores but different species may have preferences for a particular type of food, being more carnivorous or more herbivorous.

The study found that cave species of Sinocyclocheilus have a much higher microbial diversity than surface species. But how can this be possible if there is a limited number of resources available in caves compared to the surface? Well, that seems to be exactly the reason.

Sinocyclocheilus microphthalmus, one of the cave-dwelling species used in this study. Photo extracted from the Cool Goby Blog.

As I mentioned, species of Sinocyclocheilus are omnivores. On the surface, they have plenty of food available and can have the luxury of choosing a preferred food type. As a result, their gut microbiome is composed mainly by species that aid in the digestions of that specific type of food. In caves, on the other hand, food is so scarce that one cannot chose and must eat whatever is available. This includes feeding on small amounts of many different food types, including other animals that live in the cave and many different types of animal and plant debris that reach the cave through the water. Thus, a much more diverse community of gut microorganisms is necessary for digestion to be efficient.

Look how the number of different genera of bacteria is much larger in the cave group (right) than in two groups of surface species (left and center). Image extracted from Chen et al. (2019).

More than only an increased diversity by itself, the gut community of cave fish also showed a larger number of bacteria that are able to neutralize toxic compounds of several types. The reason for this is not clear yet but there are two possible explanations that are not necessarily mutually exclusive. The first states that water in caves is renewed in a much lower rate than surface waters, which promotes the accumulation of all sort of substances, including metabolic residues of the cave species themselves that can be toxic. The second hypothesis is of greater concern and suggests that this increased number of bacteria that are able to degrade harmful substances is a recent phenomenon caused by an increase in water pollutants coming from human activities, which is promoting a selective pressure on cave organisms.

The diverse gut microbiome of cave fish is, therefore, a desperate but clever strategy to survive in such a harsh environment. Nature always finds a way.

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More on cave species:

Think of the worms, not only of the wales, or: how a planarian saved an ecosystem

Don’t let the web bugs bite

Friday Fellow: Hitler’s beetle

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Reference:

Chen H, Li C, Liu T, Chen S, Xiao H (2019) A Metagenomic Study of Intestinal Microbial Diversity in Relation to Feeding Habits of Surface and Cave-Dwelling Sinocyclocheilus Species. Microbial Ecology. doi: 10.1007/s00248-019-01409-4

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Filed under Bacteria, Ecology, Evolution, Fish

The land planarian community of FLONA-SFP and how it gets along

by Piter Kehoma Boll

(First of all, I wish it were Bolsonaro, that piece of diarrhea-shaped cancer, who were dying by fire instead of the Amazon forest.)

(Now let’s go to the post itself:)

The São Francisco de Paula National Forest (FLONA-SFP) is a protected area for sustainable use in southern Brazil. Its was originally covered by Araucaria forest but currently is composed of a mosaic of the native forest and plantations of Araucaria, Pinus and Eucalyptus trees. This protection area is one of the main study areas of Unisinos’ Planarian Research Institute, where I conducted my undergradate, Master’s and PhD studies.

After studying the land planarian community of FLONA-SFP for many years, we conclude that it includes a fairly large number of species. Take a look at some of them and how cool they are:

Obama ladislavii, the Ladislau’s leaf-like flatworm. Photo by Piter Kehoma Boll.*
Obama anthropophila, the brown urban leaf-like flatworm. Photo by Piter Keehoma Boll.*
Obama josefi, the Josef’s leaf-like flatworm. Photo by Piter Kehoma Boll.*
Obama ficki, the Fick’s leaf-like flatworm. Photo by Piter Kehoma Boll.*
Obama maculipunctata, the spotted-and-dotted leaf-like flatworm. Photo by Piter Kehoma Boll.*
Cratera ochra. The ochre crater flatworm. Photo by Piter Kehoma Boll.*
Luteostriata arturi, the Artur’s yellow striped flatworm. Credits to Instituto de Pesquisas de Planárias, Unisinos.**
Luteostriata ceciliae, the Cecilia’s yellow striped flatworm. Photo by Piter Kehoma Boll.*
Luteostriata pseudoceciliae. The false Cecilia’s yellow striped flatworm. Credits to Instituto de Pesquisas de Planárias, Unisinos.**
Luteostriata ernesti, the Ernst’s yellow striped flatworm. Photo by Piter Kehoma Boll.*
Luteostriata graffi, the Graff’s yellow striped flatworm. Photo by Piter Kehoma Boll.*
Supramontana irritata, the irritated yellowish flatworm. Photo by Piter Kehoma Boll.*
Pasipha backesi, the Backes’ shiny flatworm. Photo by Piter Kehoma Boll.*
Pasipha brevilineata, the short-lined shiny flatworm. Photo by Piter Kehoma Boll.*
Matuxia tymbyra, the buried Tupi flatworm. Photo by Piter Kehoma Boll.*
Choeradoplana iheringi, the Ihering’s swollen-throated flatworm. Photo by Piter Kehoma Boll.*
Choeradoplana benyiai, the Benya’s swollen-throated flatworm. Photo by Piter Kehoma Boll.*
Choeradoplana minima, the lesser swollen-throated flatworm. Photo by Piter Kehoma Boll.*
Cephaloflexa araucariana, the Araucaria’s bent-headed flatworm. Photo by Piter Kehoma Boll.*
Paraba franciscana, the Franscican colored flatworm. Photo by Piter Kehoma Boll.*
Paraba rubidolineata, the red-lined colored flatworm. Credits to Instituto de Pesquisas de Planárias, Unisinos.**
Imbira guaiana, the Kaingang bark-strip flatworm. Photo by Piter Kehoma Boll.*

Land planarians live in the leaf litter of forest soils and prey on other invertebrates. The 22 species shown above are the ones found in FLONA-SFP that are formally described but there are still some awaiting description. We could say that there are at least 30 different species coexisting in this protected area.

How can they all persist together? Isn’t there any sort of competition for food? Thinking of that, I conducted my master’s research investigating the diet of those and other land planarians. My results suggest that, although some species share many food items, most of them have a preferred food or an exclusive food item that could be considered what Reynoldson and Pierce (1979) called a “food refuge”.

Here is what we know about the FLONA-SFP’s species until now:

  • Obama ficki feeds on slugs and snails and seems to prefer large slugs;
  • Obama ladislavii feeds on slugs and snails and seems to prefer snails;
  • Obama maculipunctata feeds on slugs and snails with unknown preference;
  • Obama anthropophila feeds on slugs, snails and other land planarians, especially of the genus Luteostriata, and prefers the latter;
  • Obama josefi apparently feeds on other land planarians only;
  • All species of Luteostriata feed exclusively on woodlice;
  • Species of Choeradoplana apparently feed on woodlice and harvestmen;
  • Cephaloflexa araucariana apparently feeds on harvestmen;
Obama ladislavii capturing a slug. Photo by Piter Kehoma Boll.*

The diet of the remaining species is still completely unknown but, based on other species of the same genera, it is likely that species of Pasipha feed on millipedes, species of Paraba feed on slugs and planarians, and Imbira guaiana feeds on earthworms.

Luteostriata ernesti near some juicy woodlice. Photo by Piter Kehoma Boll.*

There are plenty of different invertebrate groups that share the leaf litter with land planarians. Despite the apparently simple anatomy of these flatworms, they were able to adapt to feed on different types of prey and have muscular and pharyngeal adaptations for that. And attempt to relate anatomical adaptations to the diet of land planarians was part of my PhD research. As soon as it is published, I’ll make a post about it. There are some nice results!

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More on land planarians:

Friday Fellow: Abundant Yellow Striped Flatworm

Friday Fellow: Ladislau’s Flatworm

Darwin’s Planaria elegans: Hidden, extinct or misidentified?

How are little flatworms colored? A Geoplana vaginuloides analysis

Obama invades Europe: “Yes, we can!

The fabulous taxonomic adventure of the genus Geoplana

The hammerhead Flatworms: Once a mess, now even messier

The New Guinea flatworm visits France: a menace

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References:

Boll PK & Leal-Zanchet AM 2015. Predation on invasive land gastropods by a Neotropical land planarian. J. Nat. Hist. 49: 983–994.

Boll PK & Leal-Zanchet AM 2016. Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest. Zoology 119: 162–168.

Leal-Zanchet AM & Carbayo F 2000. Fauna de Planárias Terrestres (Platyhelminthes, Tricladida, Terricola) da Floresta Nacional de São Francisco de Paula, RS, Brasil: uma análise preliminar. Acta Biologica Leopoldensia 22: 19–25.

Oliveira SM, Boll PK, Baptista V dos A, & Leal-Zanchet AM 2014. Effects of pine invasion on land planarian communities in an area covered by Araucaria moist forest. Zool. Stud. 53: 19.

Reynoldson TB & Piearce B 1979. Predation on snails by three species of triclad and its bearing on the distribution of Planaria torva in Britain. Journal of Zoology 189: 459–484.

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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-NonCommercial-ShareAlike 4.0 International License.

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Filed under Ecology, flatworms, worms, Zoology

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

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

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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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*Creative Commons License This work is licensed under a Creative Commons Attribution 3.0 Unported License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

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