Biomedical Ephemera, or: A Frog for Your Boils

Top left: Hippocampus sp. internal structure Top right: Short-snouted seahorse - Hippocampus hippocampus Center: 1. Syngnathus hippocampus [now Hippocampus hippocampus] 2. Pegasus draconis [now Eurypegasus draconis] - the Little Dragonfish (*unrelated to Syngnathidae family*) 3. Syngnathus pelagicus - the Sargassum pipefish Bottom: Phyllopteryx taeniolatus -the Weedy Sea Dragon

Despite their remarkable appearance, seahorses are true ray-finned bony fishes (class Actinopterygii, infraclass Teleostei), along with bass, mullets, eels, salmon, and lanternfish.

Many people know of the male seahorse incubating the eggs and giving "birth" to 100-1000 offspring after they hatch, but reproduction is similar throughout the order Syngnathidae (including the seahorses, leafy and weedy sea dragons, and pipefish). There's a persistent myth that seahorses are monogamous, but that's not strictly true. The majority of species are serially monogamous, and remain together throughout the mating season (until the male births the babies).

Another remarkable thing about seahorses (Hippocampus spp.) is that they're the only fish with prehensile tails - even their close relatives, the sea dragons and pipefish, don't have this adaptation. However, since the seahorses are the only ones that swim upright, and they have the poorest locomotive skills, they need to be able to anchor themselves to the sea flora in order to not be swept away. The Guinness Book of World Records has named Hippocampus zosterae, the dwarf seahorse, the slowest fish in the world, moving less than 5 ft [150 cm] an hour.

Aside from the seahorses, the razorfish (Aeoliscus strigatus) is the only other fish to swim "upright".

Images: Bulletin of the United States Fish Commission, Vol 1. 1881. Arcana; or, The Museum of Natural History. George Perry, 1811.

Dear Early Morning Anon: I still have no idea, nor am I sure I want to have an idea, of what you were talking about. But perhaps these helpful onlookers can lend a hand - these were the three most common structures suggested. That said, I have absolutely no clue how the corpus callosum would function as a "sex toy" (if I were forced to choose...), as it's just a band stretching from one hemisphere to the other, essentially.

Top right: Fornix of the brain Bottom left: Corpus callosum Bottom right: Medulla oblongata (aka the lower brain stem)

There are also two structures in the vagina known as a fornix, but as "fornix" simply means "arch" or "vault" in Latin, I'm not sure that's incredibly relevant.

Fucus-like sea-horse. "Fucus" is a genus of brown algae...it's not like a slimy algae you'd find in a pool, but what most people call a "seaweed". Many seahorses that live in cooler environs are shaped and colored similarly to endemic plant life. More tropical seahorses tend to be the more brightly colored ones, just like other bony fishes.

The Royal Natural History. Richard Lydekker, 1897.

Cigarette card of a seahorse, 1903.

1. & 2. Pegasus draconis, The Sea-Dragon 3.  Sygnathus hippocampus, The Sea-Horse 4.  Sygnathus pelagicus, The Sea-Pipe

1785 illustration of some fused-jaw bony fishes