The mechanism of cellular migration mode switching

When faced with difficult terrain, off-road vehicles can switch from two- to four-wheel drive to keep moving forward. Similarly, cell migration can be driven either by protrusion-directed crawling, or by contractile pulling ...

How cytoplasm separates from yolk

The segregation of yolk from the surrounding cytoplasm in the very early fish embryo is a key process for the development of fish larva. To identify its underlying mechanisms, biologists at the Institute of Science and Technology ...

Too-tight membrane keeps cells from splitting

Cells divide to grow new tissues or patch up damaged ones, but when cell division goes wrong, it can cause more harm than good. To avoid dire consequences, namely disease and unwanted cell death, cells employ a suite of failsafes ...

Acoustic waves can monitor stiffness of living cells

MIT engineers have devised a new, noninvasive way to measure the stiffness of living cells using acoustic waves. Their technique allows them to monitor single cells over several generations and investigate how stiffness changes ...

Biology of our ancient ancestor takes shape

The recent discovery of a new lineage of microbes has overturned biologists' understanding of the evolution of complex life on Earth. Genomic studies of Asgard archaea revealed that they carry many genes previously thought ...

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Actinopterygii

The Actinopterygii /ˌæktɨnɒptəˈrɪdʒi.aɪ/ or ray-finned fishes constitute a class or sub-class of the bony fishes.

The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii which also, however, possess lepidotrichia. These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the link or connection between these fins and the internal skeleton (e.g., pelvic and pectoral girdles).

In terms of numbers, actinopterygians are the dominant class of vertebrates, comprising nearly 96% of the 25,000 species of fish. They are ubiquitous throughout fresh water and marine environments from the deep sea to the highest mountain streams. Extant species can range in size from Paedocypris, at 8 millimetres (0.31 in), to the massive Ocean Sunfish, at 2,300 kilograms (5,100 lb), and the long-bodied Oarfish, to at least 11 metres (36 ft).

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