27th September 2019
Today we are learning all about Flying Fish (Family: Exocoetidae) and their amazing ability to flee predators by leaping out of the water and gliding above the ocean's surface. These fish will usually fly for distances of around 50 m (164 ft), but if they catch an up-draft they can reach 400 m, that's 8 x the length of an Olympic swimming pool!
Flying fish have a multitude of morphological adaptations to allow them to fly, including a strong rigid vertebral column and fin connections, this inflexibility increases aerodynamics, speed, and aim, and ensures that the fish doesn't weaken mid-leap.
As can be seen in the BBC Earth video above flying fish glide close to the water, using their tails to propel off the surface to lift for another glide. But how do they stay aloft?
Korean researchers, Haecheon Choi and Hyungmin Park, studied the flying fish's lift-to-drag ratio – a measure of the horizontal distance travelled relative to the descent in height during a glide. By studying models in wind tunnels they found that flying fish are incredibly well adapted to gliding, even better than insects and some species of bird. They also found that by gliding within close proximity to a flat surface the model's lift-to-drag ratio increased, and this was increased again when the flat surface was replaced by a tank of water, thereby allowing the fish to glide even further. Check out the video to view this feat for yourself and you can read a summary of the study in the Journal of Experimental Biology, and access the full article, here.
Friday 20th September
Today we are looking at the extremely well-adapted teeth of Sea Urchins (class: Echinoidea). Although as adults sea urchins have five side symmetry their larval stage is actually bilaterally symmetrical, and this shows that they are actually part of the phylum bilateria.
A sea urchins entire chewing organ is known as Aristotle's lantern, the jaw consists of five symmetrical calcium carbonate teeth called 'pyramids' with a tongue-like structure. These pyramids come to a point, like a beak, which is perfect for gripping onto the rock and scraping off their primary food item, algae. Scientists have recently discovered that sea urchin's teeth only chip on one side, meaning that they are actually self-sharpening. The reason this happens is that one side of each tooth is formed of strong calcite fibers, whereas the other is formed of brittle inclined calcite plates, whenever the calcite material is lost a sharp edge remains.
You can read more about the discovery here.
Photo attribution: Philippe Bourjon [CC BY-SA 3.0 ( https://creativecommons.org/licenses/by-sa/3.0) ]
13th September 2019
Earlier in the year we featured a story about Hammerhead sharks (family Sphyrnidae) and their amazing sensory abilities. We can't stay away from sharks for very long so today we are looking at their complex mating rituals.
A group of sharks is called a gam, herd, frenzy, school or shiver. Although at night they are solitary hunters, during the day hammerheads often form (primarily female) schools. These usually number 10-20 individuals, but sometimes 100 or more.
The largest and therefore most sexually mature females will often be found at the center of the school. Males must make their way through to her and swim in a particular pattern to signal that they are ready to mate. We rather wish we could then say the male whispers sweet nothings in her ear, but in fact they bite onto her pectoral fin and use this as an anchor until she becomes receptive, romantic! As hammerheads, like many sharks, are negatively buoyant, during this act they sink. The female later gives birth to live young, which immediately separate from the mother to form schools with other pups.
Why not check out the footage in BBC Earth 's documentary above.
6th September 2019
Today we are looking at the Chain Catshark and Swell Shark, both catsharks from the family Scyliorhinida. Many of us are aware of catfish from our first visits to the beach as children, as many of the species within the family are oviparous and lay eggs in tough egg cases, colloquially known as 'mermaid's purses'.
What's particularly cool about these two species is that they are the only known sharks to give off a vibrant green glow when exposed to the blue light below the ocean's surface. There are many species in the ocean which are able to fluoresce using particular proteins, however, these two species use an α-amino acid. Tryptophan is broken down into a compound called kynurenine which, when combined with bromine, creates the glow that can be seen below.
Read more via this link and learn why it is thought that these species glow.
Photo attribution: D Ross Robertson [Public domain]
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