Moles also have additional fingers. In their case, however, the irregularity compared to the five-finger formula of land vertebrates is the norm. An international team of researchers headed by paleontologists from the University of Zurich has now uncovered the background to the development of the mole’s extra “thumb”: A bone develops in the wrist that stretches along the real thumb, giving the paw a bigger surface area for digging.
Computer-tomographical representation of the paw skeleton of a mole (Talpa occidentalis); the sickle-shaped extra “thumb” is clearly visible.
Paw of a mole embryo (Talpa occidentalis) with the Sox9 molecules marked, which reveal the early development of the skeleton.
Most pawed animals have ten fingers. One of the main exceptions is the little mole: It has an extra “thumb”, which it rests upon while digging and thus increases the size of its digging apparatus. Polydactyly – the presence of supernumerary fingers – is a phenomenon that has already been observed in various land animals in Devon and is also fairly common in humans, dogs and cats. Land vertebrates appear to possess a silent developmental program for polydactyly, which is only activated under certain conditions. In moles, however, polydactyly is the norm, which means the program is constantly activated during embryogenesis.
An international team of researchers headed by Marcelo Sánchez-Villagra, a professor of paleontology at the University of Zurich, has studied the molecular-genetic origin and development of the extra thumb in moles. As the scientists reveal in their recent article published in the journal Biology Letters, the additional thumb develops later and differently during embryogenesis than the real fingers. The studies were funded by the Swiss National Science Foundation.
Unlike the other fingers on the mole’s hand, the extra thumb does not have moving joints. Instead, it consists of a single, sickle-shaped bone. Using molecular markers, the researchers can now show for the first time that it develops later than the real fingers from a transformed sesamoid bone in the wrist. In shrews, however, the mole’s closest relative, the extra thumb is lacking, which confirms the researchers’ discovery.
Male hormones linked to polydactyly
The researchers see a connection between the species-specific formation of the extra thumb in the mole and the peculiar “male” genital apparatus of female moles. In many mole species, the females have masculinized genitals and so-called “ovotestes”, i.e. gonads with testicular and ovary tissue instead of normal ovaries. Androgenic steroids are known to influence bone growth, transformation and changes, as well as the transformation of tendons in joints. A high level of maternal testosterone is also thought to be one of the causes of polydactyly in humans.
Beat Müller | Universität Zürich
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy