Öğretirken eğlendiren eğitim sistemleri

Öğretirken eğlendiren eğitim sistemleri

FROG’S TONGUE ‘CAN LIFT THREE TIMES OWN BODY WEIGHT’

11 MONTHS AGO BY RESISTGEZI IN ECOLOGY, ECOLOGY


“It’s not like having a liquid glue, it’s rather like a sticky tape.”Dr Thomas KleinteichUniversity of Kiel.

According to new research, the pulling force of a frog’s tongue can be up to three times the animal’s own weight. Zoologists placed the horned frog, a predator known to swallow whole mice, in front of a glass slide and tempted it with a tasty cricket. Stronger pulling forces were measured when contact with the glass was briefer and less mucus was left behind. The study suggests that the action of the tongue is similiar to sticky tape.

“It’s the first time we’ve ever measured how well frog tongues stick,” said Dr Thomas Kleinteich, who performed the experiments at the University of Kiel in Germany.

Dr Kleinteich works in a group that studies biological adhesives, including gecko and beetle feet, with a view to finding new designs for sticky applications like boot soles, tapes and parcel closures.

“The thing that’s interesting about frog tongues is that they’re really fast,” he told BBC News. “It only takes milliseconds.” The South American horned frog in particular, a popular pet, is known for its ability to snatch morsels up to half its own size – from locusts and fish to other amphibians and small rodents. In the wild, they lurk half-buried in wait for their prey, and then “they swallow pretty much everything that fits into their mouths,” Dr Kleinteich said.

On average, these forces were larger than the weight of the frog itself, and in the case of one young amphibian more than three times larger. After each trial, the equipment was removed and the frog got its treat. Dr Kleinteich ultimately needed twenty measurements from each frog, so the predators had to be kept happy. Looking at the slides afterwards, the “tongue print” left behind on the glass slide offered more insights, including massive variation in the proportion of the contact area that was covered by mucus. The tongue prints left behind showed varying degrees of mucus coverage

“The common belief is… that the mucus acts as some sort of superglue,” Dr Kleinteich explained. “But what we found was actually that we got higher adhesive forces in trials where we found less mucus. That was quite interesting.”

The mucus appeared to build up over time, so that cases where the tongue touched the glass for longer left more mess behind. “But during the initial contact, the mucus coverage was rather low,” said Dr Kleinteich. “So to actually establish the contact, there might be very little mucus involved.”

“It plays a role. It’s definitely a wet adhesive system, it’s not just structure and friction, because there is some fluid involved. But the key is the structure plus the mucus.

“It’s not like having a liquid glue, it’s rather like a sticky tape.”

Reference: http://www.bbc.com/

http://biologypop.com/frogs-tongue-can-lift-three-times-own-body-weight/

Platypus (Ornithorhynchus anatinus)

The platypus is a semiaquatic egg-laying mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth. It is one of the few venomous mammals, the male platypus having a spur on the hind foot that delivers a venom capable of causing severe pain to humans.  The fur is waterproof, and the texture is akin to that of a mole. The platypus uses its tail for storage of fat reserves. It has webbed feet and a large, rubbery snout; these features appear closer to those of a duck than to those of any known mammal. Monotremes are the only mammals known to have a sense of electroreception: they locate their prey in part by detecting electric fields generated by muscular contractions. The platypus is a carnivore: it feeds on annelid worms, insect larvae, freshwater shrimps, and freshwater yabby that it digs out of the riverbed with its snout or catches while swimming. It uses cheek-pouches to carry prey to the surface, where it is eaten.

photo credits: wiki, creatures etranges, gifte, TwoWings, zoochat

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Similar but different, the fascinating mimicry

These two frogs are so similar that you might think are of the same species, but in fact they are not, they are different species, but one, Ranitomeya imitator (below), whose name could not be more appropriate, is a master of camouflage, and mimics Ranitomeya summersi (above) with remarkable accuracy.

Ranitomeya imitator, commonly referred to as Mimic Poison Frog, is known for its variety of phenotypes (morphs) even in a single population, however, at the Huallaga Canyon, R. imitator exhibits only the phenotype mimic of the sympatric and Endangered R. summersi, known from only a few localities in central Peru near the Huallaga river valley.

References: [1] - [2] - [3]

Photo credit: ©Brad Wilson | Locality: San Martin, Peru (2010)

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Algae invade amphibian egg masses

The establishment of symbiotic systems requires one organism to live in or on a host. For some North American amphibians, these symbionts are algae and they associate with their aquatic egg masses. Researchers have begun to speculate that these smaller organisms initially invade embryonic host tissues and cells and then transfer to the next generation of hosts.

In a previous study, one of the authors of the current study was part of a team that discovered single-celled algae were invading the embryonic cells of their salamander hosts. This was the first report of such an organism in a vertebrate host, and it led the researchers to question why a photosynthetic organism like algae would invade the tissues of an opaque host that will, as yellow spotted salamanders do, spend virtually all of its life underground. They hypothesized that the algae are invading the embryos as part of a system of intergenerational symbiont transfer.

However, it was still very possible, and in fact likely, based upon work done in the 1940s that the algae that invaded egg masses were present in pond water at the time that the egg masses were laid and simply migrated in, thereby becoming acquired environmentally.

The authors of an article published in the current issue of the journalPhycologia investigate the possibility of environmental symbiont acquisition on yellow spotted salamanders and their symbionts, a type of single-celledgreen algae called Oophila (egg lover) amblystomatis. 

Salamander embryos growing inside egg capsules covered with and often infiltrated by Oophila algae.  Image Credit: Roger Hangarter.

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Holywood Lignum Vitae - Guaiacum sanctum

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Commonly referred to as Holywood Lignum Vitae in English, and Guayacán, Guayacán Real and Palo Santo in Spanish, Guaiacum sanctum (Zygophyllales - Zygophyllaceae) is an evergreen tree that grows up to 25-30 m in height and 60 cm diameter at breast height. It has a very slow growth rate and it has been known to live for up to 1,000 years

The very attractive flowers have blue-violet petals and yellow stamens. Fruits are capsules 1.5-2.0 cm long, with four or five lobes and are bright orange-yellow when mature. They open to expose red, fleshy arils (seed coverings) which contain the hard, black, rounded seeds. 

Both the timber and medicinal resin of this tree are of commercial use and have been traded for several centuries. The wood is highly sought after for its desirable qualities of strength, toughness and density. The wood is largely used as a building material.

Currently, Guaiacum sanctum is listed as Endangered species on the IUCN Red List. It is native to Mexico, Nicaragua, Puerto Rico, the Dominican Republic, the United States (Florida), Costa Rica, Guatemala, Bahamas (national tree), Haiti, Cuba, Honduras, El Salvador, Trinidad and Tobago, and the Turks & Caicos Islands. However, in some of these countries, G. sanctum has become rare or is virtually extinct.

References: [1] - [2] - [3]

Photo credits: ©Keith A Bradley | Locality: Homestead, Florida, United States (2006, 2007) | [Top] - [Bottom]

A practical approach for assessing the melanin and blood content of the skin

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Many factors can change skin pigmentation, including aging, exposure to UV light, certain drugs, as well as certain diseases. A simple technique for measuring skin pigmentation could be a helpful tool for research and diagnostics. The same goes for measuring the skin blood content. Alteration of blood flow in the skin can, for example, be linked to skin irritations, inflammatory disorders, or diseases, such as psoriasis and rosacea. In addition, some systemic diseases, such as rheumatoid arthritis, atherosclerosis, and asthma, have shown to be associated with peripheral microvascular modifications.

Steven L. Jacques, Oregon Health & Science University, Portland, OR/USA now presents a practical approach for assessing the melanin and blood content of the skin from total diffuse reflectance spectra. It is based on the 1985 work of Kollias and Baquer who proposed using the slope of the optical density (OD) versus wavelength, OD(λ) = –log (R(λ)), between 620 nm and 720 nm as a metric for the epidermal melanin content. Jacques’ method offers a quick spectral analysis using just three wavelengths, namely 585 nm, 700 nm, and 800 nm.

More information: “Quick analysis of optical spectra to quantify epidermal melanin and papillary dermal blood content of skin,” J. Biophotonics 8:4, 309-316 (2015); doi: dx.doi.org/10.1002/jbio.201400103