For a long time, culture was considered a human trait, but nowadays we recognize the existence of culture in many other species, such as other primates, whales and some birds too. Now there are some evidences of culture being found in bats too.
A group of researchers from China studied the calls of the Chinese rufous horseshoe bat (Rhinolophus sinicus) across different populations and compared them to genetic and environmental variables to determine whether the differences where linked to genetic differences between the populations or to different environments that would force the bats to change their calls in order to use them more successfully.
The results indicate that none of those two factors were strongly linked to the acoustic differences in the calls. The most likely explanation is that the differences happen due to cultural drift. The bats are teaching a way to speak to their children that is slightly different from what their neighbors speak, even if the neighbors are genetically similar and live in a similar environment.
As an animal’s call is an important variable during mating, this may eventually lead to reproductive isolation even without genetic differences. Culture can also shape evolution!
The adjective “giant” can be quite relative. When regarding microorganisms, even something with a few milimeters can be considered a giant, and that is the case with the giant amoeba Chaos carolinense (sometimes wrongly written as Chaos carolinensis).
A chaotic mess as any good amoeba. Photo by Tsukii Yuuji.
Measuring up to 5 mm in length, the giant amoeba is a freshwater organism and is easily seen with the naked eye and, since it is also easily cultivated in the laboratory, it became widely used in laboratory studies.
As with amoebas in general, the giant amoeba has an irregular cell with several pseudopods that can contract and expand. The cell has hundreds of nuclei, as it is common with species of the genus Chaos, this being the main difference between them and the closely related genus Amoeba.
The diet of the giant amoeba is variable and includes bacteria, algae, protozoan and even some small animals. In the lab, they are usually fed with ciliates of the genus Paramecium.
A specimen of Chaos carolinense feeding on several individuals of Paramecium. Photo by Carolina Biological Supply Company.*
Wouldn’t the giant amoeba make a nice unicelular pet?
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References:
Tan, O. L. L.; Almsherqi, Z. A. M.; Deng, Y. (2005) A simple mass culture of the amoeba Chaos carolinense: revisit. Protistology, 4(2): 185–190.
As the second species of today, I’m bringing a terrible but beautiful predator of the Portuguese man o’ war, the sea swallow Glaucus atlanticus, which is, in my opinion, one of the most beautiful sea creatures.
Isn’t it a magnificent creature? Photo by Sylke Rohrlach.*
Also known as blue dragon, blue glaucus and many other names, the sea swallow is a small sea slug that measures up to 3 cm in length as an adult. This species is pelagic, meaning that it lives in the open ocean, neither close to the bottom nor close to the shore. Although it is found in all three oceans, genetic evidences indicate that the populations from the Atlantic, the Pacific and the Indian oceans have diverged more than 1 million years ago.
The sea swallow has a gas-filled sac in the stomach that makes it float upside down in the water, meaning that its ventral side is directed upward. The wide blue-bordered band running along the body, as seen in the picture above, is the slug’s foot. It’s dorsal side, which is directed downward, is completely white or light gray.
Being a carnivorous species, the sea swallows feeds on several cnidarian species, especially the Portuguese man o’ war. It usually collects the cnidocytes (the sting cells) of its prey and put them on its own body, so that it becomes as stingy as or even stingier than its prey. If you find one lying on the beach, be careful.
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References:
Churchull, C. K. C.; Valdés, Á.; Foighil, D. Ó (2014) Afro-Eurasia and the Americas present barriers to gene flow for the cosmopolitan neustonic nudibranch Glaucus atlanticus. Marine Biology, 161(4): 899-910.
Wikipedia. Glaucus atlanticus. Available at < https://en.wikipedia.org/wiki/Glaucus_atlanticus >. Access on June 18, 2017.
And so we finally reached the 100th Friday Fellow! In order to commemorate, we will have two Friday Fellows today, just as we had during the 50th one. And to start I chose a cnidarian that always caught me attention.
Living in the Atlantic Ocean and known popularly as Portuguese man o’ war, its binomial name is Physalia physalis, both words derived from the Greek word for bubble, physalis. And the Portuguese man o’ war is, in fact, like a floating bubble with some stuff attached, or at least it looks like that.
A Portuguese man o’ war lying on the beach. Photo by Anna Hesser.*
Most people may think that the Portuguese man o’ war is a jellyfish due to its looks, but it is actually part of another group of cnidarians, the siphonophores. Their body is not a single individual, but rather a colony of several smaller animals, called zooids, which are speciallized to have different functions within the colony and cannot live separately. They are all derived from the same embryo, thus being clones from each other.
The upper portion of the Portuguese man o’ war has a gas-filled sack, which is called the pneumatophore and is the original organism derived directly from the embryo. Below the pneumatophore there are several different kinds of organisms, such as nectophores for swimming, dactylozooids for defense and capture of prey, gonozooid for reproduction and gastrozooids for feeding. The long tentacles, which reach more than 10 m in length, are composed by dactylozooids and fish for prey throughout the water.
As other cnidarians, the Portuguese man o’ war has nettle-like cells which sting and inject venom. In humans, the venom usually cause pain and let whip-like marks on the skin where the tentacles touched. Sometimes more severe complications will results and in rare cases it may result in death.
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References:
Stein, M. R.; Marraccini, J. V.; Rothschild, N. E.; Burnett, J. W. (1989) Fatal portuguese man-o’-war (Physalia physalis) envenomation. Annals of Emergency Medicine 18(3): 312–315.
A long, long time ago, I wrote two posts here about the definition of species, explaining briefly the most important horizontal and vertical species concepts. So we all agree that species exists, but how they emerge? How one species become two, or how one species become another?
The phenomenon by which it occurs is called speciation. Well, sort of… It all depends on how you define a species, actually (so be certain to have read the posts I mentioned above).
Model of a lineage splitting into two lineages that evolve independently and eventually become separated species. Extracted from Hawlitschek et al. (2012)*
Speciation is usually defined as the evolution of reproductive isolation, therefore it deals more with the concept of biological species, but also with the ecological concept and certainly needs some insights on the vertical concepts. If two populations are reproductively isolated, it means that the individuals of one of them are unable or unwilling to breed with those of the other. This usually arrives through genetic and ecological differences that lead to differences in behavior, morphology, physiology. And considering that, we can classify reproductive isolation into two groups: pre-zygotic and post-zygotic isolation.
In pre-zygotic isolation, the two species are reproductively isolated because they do not want or cannot mate and produce a zygote. This may happen simply because of different behaviors in which the two species occupy different places in the environment, mate at different times of the year or even because they are not sexually attracted to each other. There are several experiments using fruitflies that demonstrate how this may evolve pretty fast.
In the late 1980s, William R. Rice and George W. Salt separated individuals of Drosophila melanogaster depending on their preference for dark × light and wet × dry environments, allowing them to mate only with other specimens showing the same preferences. After several generations, the individuals of one group were unable to mate with those of other groups because of their strong habitat preferences, making them unlikely to interact. A similar experiment was performed by Diane Dodd using the species Drosophila pseudoobscura, in which one population was raised with starch as food and other with maltose as food. In this case, after several generations the flies showed a strong preference to mate with individuals of the same group and to reject those of the other group.
Evolution of reproductive isolation in fruit flies of the species Drosophila pseudoobscura after several generations fed with different sugars.
Such speciation events are called ecological speciation and are also well-documented in the wild, especially regarding fish preferring different habitats, such as shallow × deep water or still × running water. Eventually the individuals will diverge into two groups that are ecologically isolated in the same environment and consequently become reproductively isolated as well.
Post-zygotic isolation is generally a more advanced form of isolation that indicates deep genetic divergences. This is more commonly associated with the notion of biological species and is based on the inability of the individuals of the two species to produce viable offspring. They may mate with each other and even produce a zygote, but this will be unable to developed into an embryo or the offspring will be sterile or otherwise unable to survive enough to breed. A classical example is the mule, the hybrid of a mare and a donkey that is usully sterile.
A mare, Equus ferus caballus (left), a donkey, Equus africanus asinus (right) and a mule (center). Photos by ‘Little Miss Muffit’ (flickr.com/people/42562654@N00)(mare), Adrian Pingstone (donkey) and Dario Urruty (mule).
In both forms of speciation mentioned above, reproductive isolation usually arises from the accumulation of small differences due to natural selection. This may be enhanced by two phenomena, pleiotropy and genetic hitchhiking.
Pleiotropy is the phenomen by which a single gene have influence over more than one phenotypic trait. For example, a gene that influences the shape of a bird’s bill may also make it change its diet and its song. Several human genetic diseases, such as phenylketonuria (PKU), are examples of pleiotropy.
The frizzled trait in chickens, which makes the feather curl outward, also leads to delayed sexual maturity and decreased metabolism rate. Photo by flickr user Just chaos.*
Genetic hitchhiking, on the other hand, is the phenomenon by which a gene that is naturally selected carries neighbours genes that are in the same DNA chain with it. In fruitflies, for example, a gene that is linked to courtship behavior may be drawn with the gene linked to a digestive enzyme, so that flies that specialize in one kind of sugar have a different courtship behavior than others specialized in another sugar.
That’s all for now. In a future post, I’ll talk about the geographic and genetic variables in species formation.
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References and further reading:
Bolnick, D. I., Snowberg, L. K., Patenia, C., Stutz, W. E., Ingram, T. & Lau, O. L. 2009. Phenotype-dependent native habitat preference
facilitates divergence between parapatric lake and stream stickleback. Evolution, 63(8): 2004-2016.
Hendry, A. P.2009. Ecological speciation! Or the lack thereof? Canadian Journal of Fisheries and Aquatic Sciences, 66: 1383-1398.
Hoskin, C. J. & Higgie, M. 2010. Speciation via species interactions: the divergence of mating traits within species. Ecology Letters, 13: 409-420.
Maan, M. E., Hofker, K. D., van Alphen, J. J. M. & Seehausen, O. 2006. Sensory drive in cichlid speciation. The American Naturalist, 167(6):
947-954.
Nosil, P. 2008. A century of evolution: Ernst Mayr (1904-2005). Ernst Mayr and the integration of geographic and ecological factors in
speciation. Biological Journal of the Linnean Society, 95: 26-46.
Turelli, M., Barton, N. H. & Coyne, J. A. 2001. Theory and speciation. TRENDS in Ecology and Evolution, 16(7): 330-343.
A little more than a year ago I introduced the first foraminifer here, the tepid ammonia. Now it is time to bring the second one, this time a planctonic species that is rather famous and whose scientific name is Globigerina bulloides, or the bubble globigerina as I call it.
A live specimen of Globigerina bulloides. Photo extracted from Words in mOcean.
This species can be found throughout the world, but it’s more common in cold subantarctic waters and a little less common in subarctic waters. The most common areas are the North and South Atlantic and the Indian Oceans, but the tropical records are most likely a misidentification of other closely related species.
The bubble globigerina usually lives in the upper 60 m of the water column, at least while reproducing, and feeds on other planktonic organisms, especially microscopic algae. In oder to maximize the ability of their gametes to meet in the vast extension of the ocean, the bubble globigerina synchronizes its sexual cycle with the moon cycle, reproducing during the first week after the new moon. It is, therefore, a kind of biological calendar.
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References:
Bé, A. W. H.; Tolderlund, D. S. 1972. Distribution and ecology of living planktonic Foraminifera in surface waters of the Atlantic and Indian Oceans. In: Funnell, B. M.; Riedel, R. (Eds.) The Micropaleontology of Oceans, Cambridge University Press, pp. 105–150.
Schiebel, R., Bijma, J., & Hemleben, C. (1997). Population dynamics of the planktic foraminifer Globigerina bulloides from the eastern North Atlantic Deep Sea Research Part I: Oceanographic Research Papers, 44 (9-10), 1701-1713 DOI: 10.1016/S0967-0637(97)00036-8
Although I’m not much of a taxonomist, I really love taxonomy and the way it can be used to add some sort of literary art to biology. So here I am going to present a list of genera named after some Greek gods. I hope you enjoy it!
The genus of fish Zeusis named after the king of the Greek gods. The photo shows the species Zeusfaber. Photo by Wikimedia user Kleines.Opossum.*
The genus of fungi Zeus is also named after the king of the Greek gods. The photo shows the species Zeus olympius. Photo by Rossen Aleksov.*
Named after the Greek god of the sea,Poseidonused to be a genus of ribbon worms (nemerteans), but this name is currently a synonym of Lineus. The photo shows a specimen of Lineus ruber, formerly known as Poseidon ruber. Photo by Eduardo Zattara.**
The name of the god of the underworld,Hades, was given to a genus of butterflies. Here you can see an individual of the species Hades noctula. Photo by Dan Wade.
The plant genus Hestia, with a single species, Hestia longifolia, was named after the Greek goddess of the hearth. Photo by Michael Lo.
The sea mouse genus Aphrodita was so named after Aphrodite, the Greek goddess of love, sex and beauty. The photo shows the species Aphrodita aculeata. Photo by Michael Maggs.*
The fish genus Hephaestus, including the species Hephaestus tulliensis seen above, is named after the Greek god of fire and forgery. Photo by Glynn Aland.
The greek goddess of wisdom, Athena, was honored in the owl genus Athene, which includes the borrowing owl Athene cunicularia seen above. Photo by flickr user travelwayoflife.***
Ares, named after the Greek god of war, is a genus of fossil radiolarians that includes the species Ares mexicoensis shown above. Photo extracted from Whalen & Carter, 2002.
Artemis, the greek Goddess of hunt, used to be the name of a genus of clams, but currently it is a synonym of Dosinia. The species seen above, Dosinia coerulea, used to be in the genus Artemis.
The Greek god of travelers and messenger of the gods, Hermes, was honored in a genus of sea snails. Currently, it is regarded as a subgenus of the genus Conus and includes the species Conus (Hermes) nussatella seen above. Photo by Nick Zantop.*
A relative of the famous black pepper from India that is used as a spice worldwide, today’s fellow, the spiked pepper Piper aduncum, comes from South America, where it is also called by other names such as matico and higuillo de hoja menuda.
Growing as a small tree or shrub, the spiked pepper is widespread throughout the continent, being found in both the Atlantic and the Amazonian forests. Having a peppery odor as other peppers, it can be used as a substitute of them while preparing food, but its main uses are medicinal.
Close up of a branch of Piper aduncum showing the inflorescences. Photo by João Medeiros.*
It is classically used by local populations as an antiseptic applied directly on open wounds and also as an infusion or paste to treat gastrointestinal disorders and problems of the genital organs. Laboratory studies using extracts from the plant concluded that it has antibacterial and moluscidal properties, thus having the potential to be used as both an antiseptic and a pesticide against mollusks.
Outside of South America, the spiked pepper became a problematic invasive species in several islands of the Pacific, such as New Guinea and Fiji. In Papua-New Guinea, it has become so common that it was incorporated in the culture of local people, who use it as a wood source and as a medicine and pesticide.
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References:
Maia, J., Zohhbi, M., Andrade, E., Santos, A., da Silva, M., Luz, A., & Bastos, C. (1998). Constituents of the essential oil ofPiper aduncum L. growing wild in the Amazon region Flavour and Fragrance Journal, 13 (4), 269-272 DOI: 10.1002/(SICI)1099-1026(1998070)13:43.0.CO;2-A
Orjala, J., Wright, A., Behrends, H., Folkers, G., Sticher, O., Rüegger, H., & Rali, T. (1994). Cytotoxic and Antibacterial Dihydrochalcones from Piper aduncum Journal of Natural Products, 57 (1), 18-26 DOI: 10.1021/np50103a003
Potzernheim, M., Bizzo, H., Silva, J., & Vieira, R. (2012). Chemical characterization of essential oil constituents of four populations of Piper aduncum L. from Distrito Federal, Brazil Biochemical Systematics and Ecology, 42, 25-31 DOI: 10.1016/j.bse.2011.12.025
Siges, T., Hartemink, A., Hebinck, P., & Allen, B. (2005). The Invasive Shrub Piper aduncum and Rural Livelihoods in the Finschhafen Area of Papua New Guinea Human Ecology, 33 (6), 875-893 DOI: 10.1007/s10745-005-8214-7
Last week I introduced a serious plant pathogen, the gray mold, that attacks many crops and has a special role as either a bad or a good guy in wine grapes. But a plant that is never happy with an infection by the gray mold is certainly the lettuce. And in this case our juicy vegetable has an enemy that makes it susceptible to the mold, and I’m bringing it to you today.
Named Bremia lactucae, this organism is a oomycete, thus belonging to a group of organisms that was formerly classified as a fungus, but that currently is known to be more closely related to brown and golden algae. This species attacks lettuces and closely related plants, causing a disease called downy mildew.
A lettuce leaf with downy mildew. Photo by Gerald Holmes.*
The downy mildew is the most important disease affecting lettuce worldwide. The disease itself is not the main problem, although it decreases the quality of the crop. Its main problem is that it makes the vegetable more vulnerable to other infections, such as those by the gray mold, and also increases the risk of contamination by human pathogens, such as intestinal parasites.
A branch of the downy mildew under the microscope. Photo by Bruce Watt.*
The usual forms of controling the spread of the downy mildew is by using fungicides and developing mildew-resistant lettuces by hybridization with wild and naturally resistant varieties. However, as usual, the downy mildew eventually adapts to this, giving rise to fungicide-resistant strains, as well as strains able to neutralize the resistance of lettuce lineages. It’s one more evolutionary arms race.
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References:
Beharav, A., Ochoa, O., & Michelmore, R. (2013). Resistance in natural populations of three wild Lactuca species from Israel to highly virulent Californian isolates of Bremia lactucae Genetic Resources and Crop Evolution, 61 (3), 603-609 DOI: 10.1007/s10722-013-0062-5
Parra, L., Maisonneuve, B., Lebeda, A., Schut, J., Christopoulou, M., Jeuken, M., McHale, L., Truco, M., Crute, I., & Michelmore, R. (2016). Rationalization of genes for resistance to Bremia lactucae in lettuce Euphytica, 210 (3), 309-326 DOI: 10.1007/s10681-016-1687-1
Today’s Friday Fellow will show you how beauty is only a matter of perspective. Being an ascomycete fungus, it is commonly known as gray mold and is usually found growing on decaying vegetables, especially fruits such as the strawberry in the photo below:
Gray mold growing on a strawberry. Most people would not see it as a beautiful image. Photo by Wikimedia user Rasbak.*
The gray mold has a controversial biological nomenclature, as many other fungi. The most common name is Botrytis cinerea used for its asexual stage (anamorph), which is the most common. Its sexual stage (teleomorph) is known as Botryotina fuckeliana. I guess this issue, which was common in naming fungi with rare or unknown occurrences of sexual stage, has already been settled, but as I’m not a taxonomist of fungus, I cannot speak much on the subject.
More than only having a controversial name, this fungus has also a controversial interaction with humans. It is a notable pest in wine grapes and may lead to two different infections on them. One of those is called “grey rot” and happens under wet conditions, leading to the loss of the grapes. The other is called “noble rot” and is a beneficial form of the infection that happens when the wet condition is followed by a dry one and produce a fine and sweet vine due to the concentration of sugars in the grape.
Out of the vine world, however, the gray mold is not something that you want growing on your crops. As as it attacks more than 200 species, many of them being important food crops, there is a big interest in developing strategies to reduce the damage it causes. And these strategies include the use of pesticides, plant essential oils or even other organisms that may parasitize the gray mold.
But one cannot deny that if you look closer, even the gray mold is beautiful:
A beautiful tiny forest of gray mold on a strawberry. Photo by Macroscopic Solutions.**
Earthling Nature 