Isn’t it great to know that at least half of your genome is a winner? This part of you won the race of the sperm to the egg cell. Regarding the genetic/epigenetic variation among the sperm of your father, this part of you was the fastest and robustest your father could produce. The question is, if this race between the haploid sperms of the same man, results in a sort of selection which is important for the Darwinian fitness. In other words: Does Darwin’s “The survival of the fittest” describe not only the selection among the diploid organisms but also the selection among the haploid sperm? And does this selection between the gamete phenotypes of the same man have a fitness consequence for the created offspring? Ghazal Alavioon et al. say “yes”. They selected zebrafish sperm for their longevity, and indeed, the offspring of this longevity sperm had a better survival rate and the sons which were created by longevity sperm produced significantly faster-swimming sperm compared to the sons of short living sperm. Also the fitness of the fertilized egg cell seems enhanced with longevity sperm compared to short living sperm. This fitness effect was still valid in the second generation. "Haploid selection within a single ejaculate increases offspring fitness."
Ghazal Alavioon, et al. Proceedings of the National Academy of Sciences(2017): 201705601.
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As you may noticed, it is some time since the last "Paper of the Day". The main point of it, was a decreasing motivation in reading old papers. Of course there are some hidden diamonds between them, but I am not a person who lives in the past. So I changed my focus to newly published papers. I created email alerts for a lot of different journals and I must say: I love it. I will not say that the quality is better as in papers from around 1950... . The only benefit of reading new published paper is the knowledge that the problem discussed in the paper is a topic/question/problem which brings restless nights to at least one scientist in the world in this moment. This is a comfort thought, at least when you are a PhD student like I am :D Sometimes, problems which experimentalists are dealing with, are so general that it is sort of funny to write about it. This is why this paper from Peter Elliott et al., published in PLOS ONE (5. July), caught my attention. It describes a new method to detect mouse scratching. For all the readers which like me think “What? Mouse scratching?”, let me explain: yes indeed, I mean the behaviour mice (and other animals including humans) are doing when they feel itchy. There are a lot of illnesses in humans, which can lead to (chronic) itching. And of course there are some scientists doing animal experiments (with mice) in order to find better treatment for affected individuals. For such experiments it is important to analyse the scratching behaviour of the mice, because it is the strongest clue for itchy feeling in the mice. Normally these means a lot of videos and a lot of work analysing them… by a human who watches the videos or paw movement tracking algorithms. But videos need light and as mice are nocturnal animals this creates the problem that the light induces stress in the mice which may affect the scratching behaviour. So the question is: How can we detect a mice scratching without light? One possibility is “to place a metal ring around the mouse’s hind paws and track perturbations in an electromagnetic field in the cage”, but this would detect ANY paw movement. The paper I present today, investigates the value of sound analyzation in the problem of detecting mouse scratches. A mouse scratching consists of a small set of rapid paw movements (of around 50 ms). These typical rhythmic pattern of the often 200- 500ms long sets of scratches, can be identified in by applying a filter to a time-frequency representation of the audio recording. Together with some supervised supervised learning algorithm, which helps to distinguish scratching sound from environmental noise and other animal behaviour sounds, they managed to quantify the chloroquine-induced scratching behaviour of a certain mice model (C57BL/6) with reasonable accuracy (85% sensitivity, 75% positive predictive value). Congratulation. "Automated acoustic detection of mouse scratching."
Peter Elliott et al. PloS one 12.7 (2017): e0179662. In my opinion, science is the ability to ask questions which either can't be answered or which answers just raise new questions. The paper today is from the first kind. It asks "are gorillas right-handed or not?" and the result is: We don't know. In 1992, there were just 22 published studies about hand preferences in gorillas. Although, McGrew and Marchant analyzed and compared the study results, the number of studies was not enough to conclude if gorillas are left-, right- or ambi-preferent. Therefore, based on the knowledge from 1992, I can not answer you the question. But today... in the time where everybody can access the world-wide knowledge everytime with his smartphone, laptop or tablet... today it is different, isn't it? So many people had now so much time to observe gorillas and to share their observations with the rest of the world. So today we have to know the answer, right? No. Unfortunately wrong. You still find contradictory answers to this simple question. Some webpages claim gorillas to be right-handed (http://phys.org/news/2012-10-predominance-right-handed-uniquely-human-trait.html) and some others claim them to be ambi-prefered (http://scienceblogs.com/developingintelligence/2007/10/16/why-animals-dont-show-handedne/). So if you always asked yourself: is there any question which science can not answer?... here you have an example :-D "Are gorillas right-handed or not?"
W. C. McGrew and L. F. Marchant Human Evolution 8.1 (1993): 17-23. The word “cephalopod” has its origin in Greek and means as much as “head foot”. Consequently, the class cephalopods includes octopuses, squid, cuttlefish and nautiluses, which are all characterized by their arms/tentacles (“feet”) which are directly connected to their head. Since at least the movie “Finding Dory”, we all know again why cephalopods are such fascinating animals. Their ability to change their colors and body shape, “ink” production, three hearts,… . Moreover they are found “in all oceans of the world, from the tropics to the poles, the intertidal to the abyss.” (http://www.thecephalopodpage.org) So, of course, they also exist in the nort-western Mediterranean and Roger Villanueva published a paper in 1992 in which he looked at the distribution of cephalpalopods in the bathybenthic zone (700-2000m) of the nort-western Mediterranean. He mainly found the octopus Bathypolypus sponsalis and the squid Neorossia caroli. In both species, young and small individuals could be found in a wider range of depths as old and large individuals. The large individuals are nearer to the surface while the small individuals can also be found in larger depths. So if you are afraid of meeting large cephalopods while diving, you have to dive deeper. "Deep-sea cephalopods of the north-western Mediterranean: Indications of up-slope ontogenetic migration in two bathybenthic species."
Roger Villanueva Journal of Zoology 227.2 (1992): 267-276. Collagenous tissues which have different passive mechanical properties in response to different environmental and mechanical stimuli are called mutable collagenous tissues (MCTs). The rapid changes of their mechanical properties are nervously mediated. It is assumed that the tissue properties are regulated by certain molecules which secretion is controlled by nerve terminals connected to the secretory cells. The secretory cells associated with MCTs are called juxtaligamental cells. They are characterized “by the presence in their cytoplasm of numerous electron-dense, membrane-bound granules.” There is no known MCT that lacks these cells, whereas they are absent from the few definitely non-mutable collagenous structures examined. It has always been suggested that the tube feet of sea urchin and sea star are MCTs, but proof was missing until 2005. In 2005, Romana Santos et al. published a paper in which they showed that the tube feet tissue indeed (I) contains juxtaligamental cells and (II) shows differences in stiffness/elasticity in response to environmental stimuli. The mechanical properties of the tube feet from both species were influenced by the environmental calcium concentration. They both became more flexible in an low calcium environment. However, stiffness response to cell-disrupting treatments was more prominent in the sea urchin compared to the sea star. This may be based on their different function (and structure). The feet of the sea urchin are flexible. Their task is mainly “pulling” the sea urchin to the ground and even movement is based on a pulling process. Therefore, cell stress (e.g. because of waves pushing the sea urchin) induces the secretion of molecules which increase the stiffness of the feet which may be helpful for an energy-sparing maintenance of position. Sea stars have a different method of movement, compared to the sea urchin. Instead of pulling, their feet are like little columns which lift the body up. Therefore, they are already quite stiff and cell stress can not significantly increase this stiffness further. "The tube feet of sea urchins and sea stars contain functionally different mutable collagenous tissues."
Romana Santos, et al. Journal of experimental biology 208.12 (2005): 2277-2288. Length and duration,… these are important parameters for sexual success. That refers not only to the sexual act itself but also to the sperm traits. Longer and faster spermatozoa with longer life-duration are expected to have an advantage in competitive interactions between ejaculates. However, there is little evidence for this sperm competition theory. The sperm competition theory claims that (I) increasing sperm competition leads to faster spermatozoa and (II) this increase of speed is related to an increase in sperm length. However, both, that sperm competition promotes evolution of faster-swimming sperm across species, and link between sperm morphology and swimming speed, is weakly supported by just a handful of studies and even neglected by other studies. For example: the only clear evidence for the length-speed correlation of sperm within a species comes from the roundworm C.elegans and its sperm has, unlike the sperm of the most animals, an amoeboid form (lacking a flagellum). In order to prove that theory, species are needed which relatedness are well studied and which show a high diversity of mating behaviour, like the cichlid fishes of the Lake Tanganyika. Therefore, John L. Fitzpatrick et al. (2009) tested the sperm competition theory in 29 closely related species of cichlid fishes from Lake Tanganyika. They proved both hypotheses of the sperm competition theory by slitting fish testes and comparing sperm traits across the species (inside a species proof of the hypotheses mainly failed). They showed that:
"Female promiscuity promotes the evolution of faster sperm in cichlid fishes".
John L. Fitzpatrick, et al. Proceedings of the National Academy of Sciences 106.4 (2009): 1128-1132. Leeches are fascinating animals. They can be found everywhere, from ponds to streams, from polar seas to desert oases. Many of the about 300 species of leeches feed on small invertebrates, only some species are parasitic blood suckers. The leech’s spittle does not only contain enzymes which prevent blood clotting but also an anesthetic. So the host is not aware of the attack by the blade-like jaws or secreted enzymes that digest a hole through the skin. It is no accident that the most famous leech species is called Hirudo medicinalis. Leeches have a long tradition in medical treatment. Before using it for treatment, the leech needs to be washed and the gut content needs to be squeezed, because leeches just “attack” when their gut is empty. Interestingly, H.medicinalis does not produce any gut enzymes. Symbiotic bacteria, principally Aeromonas hydrophila, which are living in the leech’s gut, carry out the digestion. The medical treatment with leeches is a sort of improvement of the much older tradition of bloodletting, which origins are suspected to go back as far as the Stone Age. The advantage of leeches is that it is less painful and easier to use for body parts which are hard/dangerous to access with blades like eyes and rectum. This usage of leeches in medicine in mind, it seems logical that, in the past, the word “leech” had a second meaning as medical practitioner. However, as Robert N. Mory et al. (2000) pointed out, this is an example of folk etymology: a “type of linguistic development, in which an apparently logical connection is used to explain (or is understood as) the development of one meaning from another”. In reality, "leech" and "leech", the worm and the physician, have two different origins. Both are based on the Old English word “leace”. However, while the worm “leech” came from the Middle Dutch lieke, the physician “leech” has its origin in Germanic languages including Old Frisian letza, Old Saxon laki, and Old High German lakki. So, even if leeches and leeches worked together in the past, the origins of their names are not connected. Today the word “leech” for physician is outdated. Today, “leech” is used to describe people which download from file-sharing sites without uploading anything. There the logical connection to the worm “leech” is obvious. Both are parasites: taking without giving something back. "The leech and the physician: biology, etymology, and medical practice with Hirudinea medicinalis."
Robert N. Mory, David Mindell, and David A. Bloom World journal of surgery 24.7 (2000): 878-883. Which factors determine micro-arthropods (like mites and springtails) abundance and diversity in the soil? Stef Bokhorst et al. addressed this question in a paper which was published in 2014. They analyzed the effect of plant removals in pine forest sectors in Sweden which differ in their age (time scince last forest fire) on the micro-arthropod community living in the soil. With increasing forest age, the soil fertility and amount of fast growing plant species decreases while the humus layer and amount of slow growing plant species increases. The forest sectors in this experiments were between 44 and 364 years old. In each sector, Bokhorst et al. did the same two experiments: I) removal of feather mosses and dwarf shrubs as the two main understory functional groups (understory = plant life on the ground of the forest) and II) removal of specific dwarf shrub species. While feather mosses are thought to have a large effect on the soil ecosystem because of its temperature and humidity regulation effects, dwarf shrubs (something between herb and bush) influence the soil with their litter production. However, as leaves are also produced by trees, it doesn’t wonder that the removal of moss had larger influence on the abundance of micro-arthropods as the removal of dwarf shrubs (in experiment I). All in all, the dwarf shrubs species had just minor effects on the micro-arthropods abundance and diversity, independent of their litter quality (experiment II). So mites and springtails care mainly about moss. But what about the age of the forest which affects the properties of the soil? Interestingly, only a few groups of micro-arthropods were affected by the forrest age. The others don’t care. And this is already the summary of this article: Plant removal, forest age? If you don’t touch the moss, the micro-arthropods don’t care so much what you are doing there on the surface. "Impact of understory mosses and dwarf shrubs on soil micro-arthropods in a boreal forest chronosequence."
Stef Bokhorst, et al. Plant and soil 379.1-2 (2014): 121-133. The neotropic ecozone covers a small tropical part of North America and complete South America. The birds there are called neotropical birds and the flavescent warbler ( Basileuterus flaveolus) is one of them. It inhabits forests and forest edges as well as woody savanna and desert vegetation and eats mainly beetles. In 2005, Charles Duca and Miguel Â. Marini published a paper about the territory size of the flavescent warbler in South Brazil. Previous studies suggest a correlation between territory size and habitat structure. The ‘ecological trap hypothesis’ predicts that on the one hand more insects are accessible for the birds at the forrest edge. On the other hand the nest predator rate is higher at the forest edges. However, the study of Duca and Marini does not support this hypothesis. Neither the insect biomass nor the nest predation vary significant between forest interior and forest edge. The territory size also does not depend on the distance to the forest border and vary little during the season. Nevertheless, the flavescent warbler seems to prefer living on the edge. “Males defending territories closer to the forest edge were more successful in pairing than those in the forest interior.” Territory size of the Flavescent Warbler, Basileuterus flaveolus (Passeriformes, Emberizidae),
in a forest fragment in Southeastern Brazil Charles Duca and Miguel Â. Marini Lundiana, Belo Horizonte 6.1 (2005): 29-33 According to the challenge hypothesis, the testosterone level correlates with the mating related aggression in seasonal breeders. In the breeding season, the testosterone level baseline is higher compared to the non-breeding season. The high baseline in breeding season is said to be necessary for successful reproductive behavior. While this seasonal change is due to environmental clues, social clues from conspecifics can additional increase the testosterone level in the begin of breeding season leading to more aggressive behavior in defending territory or finding mating partners. But how is that in non-aggressive species like the tufted capuchin monkey? Jessica W. Lynch, Toni E. Ziegler and Karen B. Strier published 2002 a study were they analyzed the seasonal changes in fecal testosterone levels of wild male tufted capuchin monkeys. As expected, all male individuals had their highest testosterone level in the period when the adult females were fertile. However, despite the high testosterone level, the aggression level in the group was low. Interestingly, the highest aggression level could be seen in the non-breeding season when the testosterone level was low in all individuals, but these aggressions were not mating related but related to food competition. Moreover, the testosterone level of the top-ranked male, who is favored as mating partner by the females, did not differ from the other males. However, the alpha male just achieved the position three month before the begin of the study. Therefore, it is not sure if on long timescale the alpha male will produce more testosterone as the others. Sure is that there are exceptions to the challenge hypothesis and a high testosterone level does not have to lead to higher aggression levels... at least in tufted capuchin monkeys. Individual and Seasonal Variation in Fecal Testosterone and Cortisol Levels of Wild Male Tufted Capuchin Monkeys, Cebus apella nigritus
Jessica W. Lynch, Toni E. Ziegler and Karen B.Strier Hormones and Behavior 41, 275–287 (2002) doi:10.1006/hbeh.2002.1772 |
IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
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