Top Tweets for #25daysofFishmas
The official state fish of Texas takes the stage for the 7th day of Fishmas. Typically, Guadalupe bass are found in flowing water and are only in Texas. They do not grow to large size because they are adapted to small streams. #25DaysofFishmas
#25DaysOfFishmas
Topic 5 - Wildcards
Day 25 - Argyropelecus olfersii (Cuvier, 1829)
Olfers' Hatchetfish
So there we are, that's #25DaysOfFishmas done for the year. Merry Fishmas to all and, for those that celebrate, Merry Christmas. Here's to 2025 - who knows what fish we'll see!
And there it was! Forgive me for being sincere ('tis the season) - I've done a lot of cool stuff, but few moments this year were as enchanting. I've loved deep sea fish since I was a kid, and getting the opportunity to finally see this was a surreal privilege #25DaysOfFishmas
Indeed, during a cruise earlier this year, we caught a bunch. One evening, I had the bright idea of scooping up a fresh one and taking it into the darkest place I could find - the ship's walk-in freezer... #25DaysOfFishmas
A very special fish for #25daysofFishmas with Anaecypris hispanica aka saramugo (in PT). Endemic to Guadiana and Guadalquivir, it faces severe population reduction. Short lived, inhabits small intermittent streams. More at Archiv für Hydrobiologie 149 569-586, 2000 @MAREscience
So, why leave this quite mundane little mesopelagic fish for the end? It's nice, but is it Fishmas Day material? Well, as mentioned, they're really very abundant and common, and I've had the chance to sample a few for my research project and PhD #25DaysOfFishmas
A very special fish for #25daysofFishmas with Anaecypris hispanica aka saramugo (in PT). Endemic to Guadiana and Guadalquivir, it faces severe population reduction. Short lived, inhabits small intermittent streams. More at Archiv für Hydrobiologie 149 569-586, 2000 @MAREscience
As far as bioluminescence goes, hatchetfish are pretty standard counterilluminators. They do, though, have a neat trick - they use a light organ facing the eye to check how bright their camouflage is, allowing them to match the sunlight better #25DaysOfFishmas
Argyropelecus are "classic" and very common mesopelagic fish, showing off a number of traits common to the community - large mouth, vertically-oriented (and beautiful!) eyes, silvery skin, and very thin body shape (to minimise silhouette) #25DaysOfFishmas
Fishmas Day! Every year it takes a lot of thought to decide which species to end #25DaysOfFishmas. Thanks to how diverse bioluminescence is in fishes, this year it's been particularly tricky. Today, we're talking about a classic - Argyropelecus olfersii, Olfer's hatchetfish.
On day 24 of Fishmas, we bring you the freshwater drum. Freshwater drum are silvery in color and lack the distinctive tail fin spot of red drum. In Texas the rod and reel record exceeds 40 pounds, and the trotline record is 55 pounds! #25DaysofFishmas
Iberian barbel - Luciobarbus bocagei - is probably the most common native cyprinid in Portugal and Spain. #25daysofFishmas @MAREscience
#25DaysOfFishmas
Topic 5 - Wildcards
Day 24 - Opisthoproctus soleatus Vaillant, 1888
Barrel-eye
Inside the sole there is a highly reflective layer which bounces this light back down for counterillumination. The fish can change how wide this membrane is, altering the amount of light emitted downwards to match the sunlight, perfectly hiding the fish! #25DaysOfFishmas
Opisthoproctus hosts luminous symbiotic bacteria in a little organ just next to the anus, charmingly called a "rectal bulb". This light then shines forwards along the flat underside of the fish, termed a "sole" - like a shoe! #25DaysOfFishmas
In life these eyes are covered by a protective transparent dome and scan the waters above for their preferred prey - bioluminescent siphonophores. But what about predators looking up from below at the barreleyes? #25DaysOfFishmas
The Opisthoproctidae are a family with 22 species, but within that there is a surprising level of morphological diversity. One feature they almost all share, though, is th presence of huge, upwards-facing, tubular eyes - hence the "barreleye" moniker #25DaysOfFishmas
Can you believe it's Fishmas Eve already? Only two more fish to go... 🥲
Today we've got our last fish that uses bacterial bioluminescence, an absolute deep-sea icon and a previous #25DaysOfFishmas Alum. This is the Barrel-Eye, Opisthoproctus soleatus.
Atlantic cutlassfish are also known as a ribbonfish in Texas. They do not have any scales, but their long, tapered bodies are covered with shiny, metallic silver skin. The body conformation is cutlass-like, tapering from the head to a pointed tail. #25DaysofFishmas
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