Sexual selection is a frequent subject of my posts here but they are usually focused on how females and males behave regarding each other. However, there is a third element that results from their interactions: the children.
Females tend to select the best males to be the father of their children because they are interested in having a healthy and strong offspring with better chances of surviving. But what happens when a female has no choice but to mate with a low-quality male? Will she take care of their children the same way?
A recent study conducted with the Honduran red point cichlid, Amatitlania siquia, investigated this question. This fish species is native from Central America and, as usually between cichlids, a female and a male form a bond and take care of their eggs and young together.
The researchers placed a female in an aquarium with transparent walls in which she was able to visually analyze two males, one placed in a chamber to the left and another in a chamber to the right. One of the males was larger than the other, both being larger than the female. After 48 hours, the female was placed randomly with either the larger or the smaller male for them to mate.
The results indicate that females produce similar egg clutches and take care of the eggs in equal amounts when mated with either larger or smaller males. However, after the eggs hatch and the larvae develop to the fry stage, the female spends more time caring for them if their father is the larger one.
They don’t seem very excited to waste their time with low-quality children. Afterall, they may meet that handsome big fish again in the future.
Today we celebrate the birthday of one of the most important Spanish naturalists of the 18th century.
Antonio José Cavanilles y Palop was born on 16 January 1745 in Valencia, Spain. He studied at the University of Valencia and obtained a master’s degree in Philosphy in 1765 and a doctorate in Theology in 1766. In 1772 he was ordained priest.
Dedicated to teaching, Cavanilles moved to Paris in 1777 to become the instructor of the children of the Duke of Infantado. There, he was introduced to botany by André Thouin and Antoine Laurent de Jussieu and became one of the first Spanish scientists to adopt the taxonomic system introduced by Linnaeus.
Cavanilles returned to Spain in 1789 due to the conflicts caused by the French Revolution. From 1790 on, he started a scheme with a Parisian bookseller, Jean-Baptiste Fournier, that introduced many forbidden books into Spain, including the Encyclopédie, which aimed to secularize learning, separating it from religious ideas.
Back in Spain, Cavanilles also increased his dedication to botany. He described many plant species from the Americas brought to Europe by Spanish expeditions. Among the several new genera described by him, we can mention the well-known Dahlia and Stevia.
In 1801, Cavanilles became director of the Royal Botanical Garden of Madrid and remained at this post until his death in 1804.
Speciation, i.e., the split of one species into two or more, usually happens when two populations become spatially isolated from each other. This separation can happen in many different ways, and sometimes a simple ecological preference can cause it.
This is what happens with a Neotropical butterfly, the banded king shoemaker Archaeoprepona demophon. Found in tropical forests from Mexico to the Northern portions of South America, this butterfly feeds on rotten fruits.
Many other butterflies feed on rotten fruits as well. Inside the forest, they usually occur only in the understory, close to the forest floor, or only in the canopy, among the tree crowns. Archaeoprepona demophon is an exception, living both in the understory and in the canopy.
A recent study, however, found out that the populations living in the understory and in the canopy are genetically distinct, indicating that they do not interbreed. The vertical distance between both populations is of about 20 m, but the degree of divergence is as high as that found between populations living in different locations about 1500 km apart.
It seems that once you ascend to the top of the forest community, you are not willing to keep in touch with the lower classes anymore. If the environmental conditions that keep this separation continue in the future, understory and canopy populations may become different species.
Everybody knows salmons, especially the Atlantic salmon, Salmo salar, and many of us love to eat this fish species as well. However, I’m not here to talk about the Atlantic salmon itself, but to talk about one of its closes companions and antagonists, the salmon fluke.
Scientifically known as Gyrodactylus salaris, the salmon fluke is a flatworm of the clade Monogenea, a group of ectoparasites that infect mainly fish. As its name suggests, the salmon fluke infects salmons, such as the Atlantic salmon, and closely related species, such as the rainbow trout Onchorhynchus mykiss.
The salmon fluke was first discovered in 1952 in salmons from a Baltic population that were kept in a Swedish laboratory. Measuring about 0.5 mm in length, the salmon fluke attaches to the skin of the fish and is too small to be seen with the naked eye. The attachment happens using a specialized organ full of tiny hooks, called haptor, located at the posterior end of the body. When feeding, the salmon fluke attaches its mouth to the surface of the fish using special glands in its head and everts its pharynx through the mouth, releasing digestive enzymes on the fish, dissolving its skin, which is then ingested. The wounds caused by the parasite’s feeding activity can lead to secondary infections that can seriously affect the salmon’s health.
Different from most parasitic flatworms, monogeneans such as the salmon fluke have a single host. During reproduction, the hermanophrodite adults release a ciliated larva called oncomiracidium that infects new fish. A single fluke can originate an entire population because it is able to self fertilize.
During the 1970’s, a massive infection by the salmon fluke occurred in Norway following the introduction of infected salmon strains. This led to a catastrophic decrease in the salmon populations in the country, affecting many rivers. Due to this evident threat to such a commercially important species, several techniques have been developed to control and kill the parasite. The first developed methods included the use of pesticides in the rivers, but those ended up having a negative effect on many species, including the salmons themselves. Currently, newer and less aggressive methods have been used.
Jansen, P. A., & Bakke, T. A. (1991). Temperature-dependent reproduction and survival of Gyrodactylus salaris Malmberg, 1957 (Platyhelminthes: Monogenea) on Atlantic salmon (Salmo salar L.). Parasitology, 102(01), 105. doi:10.1017/s0031182000060406
Johnsen, B. O., & Jenser, A. J. (1991). The Gyrodactylus story in Norway. Aquaculture, 98(1-3), 289–302. doi:10.1016/0044-8486(91)90393-l
Meinilä, M., Kuusela, J., Ziętara, M. S., & Lumme, J. (2004). Initial steps of speciation by geographic isolation and host switch in salmonid pathogen Gyrodactylus salaris (Monogenea: Gyrodactylidae). International Journal for Parasitology, 34(4), 515–526. doi:10.1016/j.ijpara.2003.12.002
Today I am going to introduce you to a German explorer that had a tragic and early death.
Adolf von Schlagintweit was born on 9 January 1829 in Munich, the second son of Rosalie Seidl and Joseph Schlagintweit, an ophthalmologist. He had four brothers, Hermann, Eduard, Robert and Emil. Joseph taught science to his sons at home and raised in them the desire to become explorers, which all five did, becoming known as The Schlagintweit Brothers.
With his older brother Hermann, Adolf studied the geography of the Alps from 1846 to 1848, publishing a study about it in 1850 entitled Untersuchungen über die physikalische Geographie der Alpen. Later, the two brothers were joined by their younger brother Robert and together the three published new studies of the Alps in 1854 in a work entitled Neuer Untersuchungen über die physikalische Geographie und Geologie der Alpen. At this time, the famous botanist and explorer Alexander von Humboldt was interested in studying the geology of the Indian subcontinent, but was too old to do it himself, so he convinced the East India Company to hire the three Schlagintweit brothers to do it.
Traveling to India, the three brothers started exploring the Deccan Plateau in central India and from there moved to the north toward the Himalayas. They did not travel together and only reunited occasionally. Their last reunion happened in the fall of 1856 and, by the beginning of 1857, Hermann and Robert returned to Europe, but Adolf decided to stay and continue exploring.
After crossing the mountains of Tibet, Adolf ended up near Kashgar, a region that is currently part of China, near the borders with Kyrgyzstan and Pakistan. This region was at the time under conflict, with the East Turkestan Khojas claiming the territory and invading it constantly. The leader of the Khojas during this period was Wali Khan, who was notorious for his brutality and tyranny.
Despite all the warnings from members of his party, who started to desert, and from people fleeing from the region, Adolf was decided to reach Kashgar, and so he did. At the city border, he was met by the Khojas and brought before the Khan. Seeing no use for Europeans explorers wandering through his territory, Wali Khan accused Adolf of being a spy working for the Chinese and had him beheaded on 26 August 1857, at the early age of 28.
In 1859, the Kazakh ethnographer Shoqan Walikhanov, disguised as a merchant, visited Kashgar and found Adolf’s notebook in a tobacco shop, where it was being used to wrap tobacco leaves. He purchased the notebook and tracked down a skull that most likely was Adolf’s. He took the notebook and the skull with him to the Russian Empire, which allowed the information about the circumstances of Adolf’s death finally reach Europe and his family.
The zebra finch, Taeniopygia guttata, is an Australian bird that is often used as a model for behavioral studies focused on their vocalization.
Recently, a research team from Australia discovered a new call in this species and named it “incubation call”. This particular vocalization was identified as occurring during the last five days of incubation when one of the birds, either the male or the female, was alone with the eggs, and only when temperatures were above 26°C. This raised the hypothesis that this call is used by the parents to communicate to the embryos that the environmental temperature is high and that this information would be used by the nestlings to adapt their behavior and metabolism to higher temperatures.
An experimental study was conducted where eggs were kept in incubators under a constant temperature and exposed (test) or not (control) to recorded incubation calls. The results indicated that nestlings that were exposed to incubation calls grew faster in high temperatures than those that were not exposed to the calls. The mean difference in nestling mass between different temperatures and treatments was of about 2 g only, although the difference in mass between two randomly selected nestlings could be as much as 6 g. Additionally, the R² value of the analyses, which tells how much of the variation is explained by the measured variable, was only 0.1, i.e., temperature explained only 10% of the growth differences between different temperatures in both treatments.
One of the most intriguing aspects, however, was the fact that the incubation call was produced at temperatures as low as 26°C, which is not particularly hot in the natural environment of the zebra finch. Thus, another team conducted new studies to understand better how and when the “incubation call” was produced. They decided to rename this call as the “v-call” because their shape is an inverted V in spectrograms. They discovered that the v-call is related to panting, when the birds breathes quickly with its bill open to help reduce body temperature and is likely a side effect of panting and not a deliberate directed call. It is also not produced only during the last 5 days of incubation, but during the whole incubation period and the chick rearing, and some birds are more likely to v-call than others. The results suggest that the v-call is unlikely to have evolved as an incubation call and is more likely a side effect of panting. There is, however, the possibility that embryos can use this information to modulate their growth, although more studies are needed.
Other recent studies with the zebra finch indicate that elevated temperatures can have negative effects on the bird’s reproductive fitness. Temperatures around 40°C reduce sperm quality in male zebra finches and reduce the ability of females to discriminate between songs produced by males of the same species and males of different, distantly related species. A combination of these two effects can lead to a severe decrease in reproductive success by reducing the mating events and reducing sperm ability to fertilize eggs.
A physiological modulation in embryos to deal with the adverse effects of higher temperatures, as suggested by the use of the v-calls, would be certainly benefitial. Maybe this is a behavior still under selection? Let’s see what further studies tell us.
Hurley LL, McDiarmid CS, Friesen CR, Griffih SC, Rowe M (2018) Experimental heatwaves negatively impact sperm quality in the zebra finch. Proceedings of the Royal Society B: Biological Sciences 285(1871): 20172547. https://doi.org/10.1098/rspb.2017.2547
Mariette MM, Buchanan KL (2016) Prenatal acoustic communication programs offspring for high posthatching temperatures in a songbird. Science 353(6301): 812–814. https://doi.org/10.1126/science.aaf7049
McDiarmid CS, Naguib M, Griffith SC (2018) Calling in the heat: the zebra finch “incubation call” depends on heat but not reproductive stage. Behavioral Ecology 29(6): 1245–1254. https://doi.org/10.1093/beheco/ary123
Previously, we saw that Linnaeus classified animals into 6 classes: Mammalia, Aves, Amphibia, Pisces, Insecta and Vermes and retained that system in future editions of Systema Naturae. At the same time that Linnaeus was publishing the 10th edition of Systema Naturae, which is the first work to use binomial nomenclature for animals, Brisson, a French zoologist, was creating his own system of classification.
Brisson decided to classify animals into 9 classes: Quadrupeda, Cetacea, Aves, Reptilia, Pisces cartilaginosi, Pisces proprie dicti, Insecta, Crustacea and Vermes. He describes the characters of animals in each class in his work “Regnum animale in classes IX. Distributum sive synopsis methodica”.
hairy body, at least in some areas, and four feet.
naked and elongate body, fleshy fins, horizontally flat tail.
3. Aves: body
covered by feathers, corneous bill, two wings, two feet.
either naked body and four feet or scaly body and either four or no feet, and
breathing through lungs.
5. Pisces cartilaginei: cartilaginous fins and breathing through openings to naked gills.
6. Pisces proprie dicti: fins consisted of little bones and breathing with gills covered by a
movable and partially ossified cover.
head equipped with antennae, and eight or more feet.
before last metamorphosis, with several stigmata or breathing organs; after
last metamorphisis, head equipped with antennae, and six feet.
9. Vermes: the
body, or at least part of it, retractile, without antennae, feet or stigmata.
same work, he describes in detail the first two classes. The class Aves is
described in a separate work, “Ornithologia, sive, synopsis methodica sistens
avium divisionem in ordines, sectiones, genera, species, ipsarumque varietates”,
but the remaining classes are never presented, so I will have to deal with
those three only.
This class is composed by all mammals known at the time, except for the cetaceans, which were in the following class, Cetacea. Brisson divided quadrupeds into 18 orders, but did not gave them names, only described them based on the number of teeth and types of nails. Linnaeus used dentition as the main character to classify mammals, but did it using different criteria.
This class was composed by the cetaceans and was divided into 4 orders, each with a single genus. The orders were based on the (apparent) distribution of teeth.
In the following image you can see the classification of both Quadrupeda and Cetacea and their comparison to Linnaeus’ 1767 system.
Some curiosities when we compare mammals in
1. Linnaeus’ genus Trichechus included manatees
and walruses. Brisson classified walruses into a separate genus, Odobenus,
but included manatees in the genus Phoca, together with seals and sea
2. Linnaeus included weasels and otters in the
genus Mustela and civets in the genus Viverra. Brisson, on the
other hand, put civets in the genus Mustela,
together with weasels, but put otters in a separate genus, Lutra.
3. While Linnaeus put hyaenas with dogs in the
genus Canis and badgers with bears in the genus Ursus, Brisson
had separate genera for hyaenas and badgers, named Hyaena and Meles.
4. Brisson put mice and rats in the genus Mus,
dormice in the genus Glis and South-American short-tailed rodents, such
as cavies and pacas, in the genus Cuniculus. Linnaeus had them all in Mus.
5. Brisson separated giraffes in their own
genus, Giraffa, while Linnaeus classified them in the genus Cervus
Brisson’s classification of birds was very different from that of Linnaeus. There were many more orders and genera. In fact, some genera used by Linnaeus in 1767 were created by Brisson. See below how complex the relationship of one system to the other is:
Unfortunately, Brisson never published his classification of other animals, so we must move on to the next authors in the following posts.
– – –
Brisson M-J (1762). Regnum animale in classes IX. Distributum, sive, Synopsis methodica. Lugduni Batavorum apud Theodorum, Haak. 316 pp.
Brisson M-J (1763a). Ornithologia, sive, synopsis methodica sistens avium divisionem in ordines, sectiones, genera, species, ipsarumque varietates. Apud Theodorum Haak, Lugduni Batavorum : 534 pp.
Brisson M-J (1763b). Ornithologia, sive, Synopsis methodica sistens avium divisionem in ordines, sectiones, genera, species, ipsarumque varietates. Apud Theodorum Haak, Lugduni Batavorum : 542 pp.