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Behold Aplysia californica–an extremely large sea slug which grazes on red algae along the California coast. The mollusk is rarely found at depths deeper than 20 meters. It grows to seventy-five cm (thirty inches) in length and weighs a whopping 7kg (15.4 lbs). Aplysia californica belongs to a family of sea slugs known as the sea hares –so called because the two rhinophores (smelling organs) atop the creatures’ heads are fancifully said to resemble a rabbit’s ears.
Although this Pacific gastropod is interesting in its own right, the slug is of greatest importance to humankind as a research animal (like the regenerating axolotl). Aplysia has only 20,000 neuron cells–as opposed to a human brain which contains between ten and a hundred billion–and the slug’s neurons are extremely large. This allows neuroscientists to easily observe and assess physiological and molecular changes which take place in the cells when the slug learns something. Aplysia research is thus at the cutting edge of neuroscience. Nearly everything we know about the molecular basis of memory and learning started out as research with the humble gastropod.
A news piece on CNN today featured Dr. Eric Kandel of Columbia University who won the 2000 Nobel Prize in Medicine & Physiology for neural research (mainly on these slugs) and made immense headway on what is probably the great cellular biology mystery of our time. It is a pleasure to see a science article on CNN online but it was also somewhat dismaying to see how many comments were basically “why are we wasting money on studying slugs?” In case it is not self-evident why we are trying to discover the fundamental molecular mechanisms of memory and cognition, here is a brief and not-at-all comprehensive list.
Understanding these underlying biological processes would probably help us find therapy for neuro-degenerative disorders (such as Parkinson’s disease, multiple sclerosis, and Alzheimer’s disease). It might also allow us to comprehend a number of psychiatric conditions, such as schizophrenia and depression. At some point in the future, understanding the molecular basis of memories and thoughts might also allow for the engineering of some sort of bioimplant for the nervous system. You could learn Sanscrit by popping a chip in your head or record your nightmares via wire! Beyond such science fiction concepts, knowing about how the brain works is an end into itself—understanding the most complicated known structure in the universe is a necessary step to building structures of greater complexity.
Although perhaps the politically polemicized commenters who object to studying the sea hare actually reject the creature’s sex life–which is indeed somewhat at odds with traditional notions of romance and propriety.
Like all sea hares, Aplysia californica is a hermaphrodite with both male and female reproductive organs. Because of its physiology it can (and does!) use both sets of organs simultaneously during mating. Multiple Aplysia have been known to form chains of more than 20 animals (somewhat like pop beads) where each animal simultaneously acts as a male and female at the same time with its fore and aft partners. Copulation lasts for many hours (or sometimes for days). One can see how the creatures’ amorous predilections might not sit well with puritans and fundamentalists, however for providing a window into molecular neurophysiology we owe this gentle sea slug a big round of thanks.
In terms of taxonomical diversity the gastropods are second most diverse class of animals on Earth (outnumbered only by the teeming class Insecta of the other great invertebrate phylum Arthropoda). This means that there are some deeply strange arthropods out there. While we traditionally think of gastropods as snails and slugs there are odd subcategories of these creatures, like the subject of today’s post, sea angels (of the clade Gymnosomata).
Sea angels consist of six different families of pelagic marine opisthobranch gastropod molluscs. Gastropods are named for their famous foot (the name means “stomach-foot”–a misnomer since gastropods all have true stomachs elsewhere) however the name is even more inappropriate for sea angels. In these free-smimming predators, the gastropod foot, so familiar to us as seen on snails, has evolved into a pair of delicate wings for swimming through the water. Sea angels are very small: the largest species only reach 5 cm (2 inches) in length and most varieties are much more miniscule. They prey on other tiny creatures swimming among the plankton—particularly other smaller slower species of gelatinous mollusks.
Adult sea angels lack any sort of shell—which they discard when they metamorphose into adulthood. Their feeding apparatuses can be strangely complicated—pseudoarms and tentacles which recall their cousins the cephalopods. Sea angels are numerous in the oceans but some scientists are concerned that the acidification of the world’s oceans will cause substantial problems for the tiny translucent gastropods.
The Portuguese man o’ war (Physalia physalis) is not a jellyfish, in fact it is not a discreet animal at all, but instead a siphonophore—a colonial medusoid made up of specialized animal polyps working together as an organism. These siphonophores have stinging tentacles which typically measure 10 metres (30 ft) in length but can be up to 50 metres (165 ft) long. Being stung by a man o’ war does not typically cause death, but sailors and mariners who have survived the experience assert that it taught them a new definition of agony.
But the fearsome man o’ war is not the subject of this post. Instead we are concentrating on the animal which feeds on the man ‘o war (as well as other siphonophores which drift in the great blue expanses of the open ocean). One is inclined to imagine that men o’ war are eaten only by armored giants with impervious skins and great shearing beaks (and indeed the world’s largest turtles, the loggerheads, are the main predators of siphonophores), however another much less likely predator is out there in the open ocean gnawing away at the mighty stinging colonies. Glaucus atlanticus, the blue sea slug, is a tiny shell-free mollusk which lives in the open ocean. The little nudibranch only grows up to 3 cm in length but it hunts and eats a variety of large hydrozoans, pelagic mollusks, and siphonophores (including the man o’ war).
Although not quite as gaudy as its lovely cousins from tropical coral reefs, Glaucus atlanticus is a pretty animal of pale grey, silver, and deep blue with delicate blue appendages radiating out from its six appendages. The little mollusks live in temperate and tropical oceans worldwide. They float at the top of the water thanks to a swallowed air bubble stored in a special sack in their gastric cavity. Because of this flotation aid, the slug is able to cling upside down to the surface tension of the waves. Since it is entirely immune to the venomous nematocysts of the man o’ war, the sea slug can store some of the man o’ wars venom for its own use. The tendrils at the edge of Glaucus atlanticus’ body can produce an extremely potent sting (so it is best to leave the tiny creatures alone, if you happen to somehow come across them).
Each and every Glaucus atlanticus is a hermaphrodite with a complete set of sex organs for both genders. Incapable of mating with themselves they ventrally (and thoroughly) embrace another blue sea slug during breeding, and both parties then produce strings of eggs. The hatchling nudibranchs have a shell during their larval stages, but this vestige quickly disappears as they mature into hunters of the open ocean.
This blog has featured replicas of two ancient sailing ships–the Greek trireme Olympias and the Norwegian Viking ship Dragon King Harald—however the prettiest modern replica of an ancient ship is a reconstruction of a much older vessel. The ship Min of the Desert was hand built by 4 men and 2 teenage boys in the modern Hamdi Lahma & Brothers shipyard in Rashid, Egypt (which was called Rosetta in classical times). The builders used traditional tools and original techniques to craft the Min after a sea-going Egyptian trade ship from 3500 years ago.
Archaeologists know a great deal about the boats which sailed the Nile–since they have the actual ships (which were preserved in tombs in order that Pharaohs could sail in the next world). However sea-faring ships were not preserved in the same way and only trace evidence from underwater archaeological sights survives. To build the Min, the modern shipwrights looked to river ships from tombs for technique, but they looked at ancient Egyptian art for a design. A 3,500-year-old bas relief from the pharaoh Hatshepsut ‘s funerary temple at Deir el-Bahri near Thebes, provided the basic design for the Min of the Desert.
The ships pictured on the bas relief were trade ships which participated in Hatshepsut ‘s trade expedition to Punt, which took place in the ninth year of her reign (Hatshepsut was a lady pharaoh who lived in the 15th century B.C. and reigned as the fifth pharaoh of the eighteenth dynasty). From the time of the old kingdom onward, Egyptians had launched expeditions to the land of Punt, a kingdom rich in gold, frankincense, myrrh, and exotic timber. Numerous ancient Egyptian sources mention Punt (which was a trade destination for the Egyptians for over a thousand years) but none actually mention where it is—apparently everyone back then just knew. The actual location has eluded Egyptologists for 150 years. To get to Punt, ships were carried in pieces across the desert to the Red Sea port of Saww. Then the vessels sailed on the Red Sea…to where? Modern day Somalia and Arabia are the best guesses, but the issue remains in doubt.
When completed Min of the Desert measured 20 meters (66 ft) long and nearly 5 meters (16 ft) wide with a cargo capacity of about 17 tons. Held together entirely by mortise-and-tenon joints, the ship proved to be surprisingly seaworthy and fast. Sailors rowed the Min in to position to raise the sail (a labor which required substantial physical strength) and then traveled along at speeds between 5 and 9 knots. The ship handled 25 knot winds and 3 meter swells with ease. The modern sailors were surprised by the excellence of the 3500 year old ship.
Saint Patrick’s Day spirit is beginning to pervade the land and the mind turns to all things Hibernian. Last week, Ferrebeekeeper investigated Leprechaun tattoos and, though visually interesting, that subject quickly turned dark and scary. This week, we plunge into the green forests of ancient Celtic Ireland to pursue the roots of Ogham, the mysterious tree alphabet of the Druids. Get out your golden sickles and put on your mistletoe haloes, the nature and origin of Ogham are shadowed by primeval mystery and this whole journey could easily veer off into the fantastic realms of pre-Christian myth.
To begin with the basics, Ogham was a runic alphabet from early medieval times which was in use throughout the lands ringing the Irish Sea, but which seems to have been most prevalent in Munster (Southern Ireland). Ancient objects inscribed in Ogham are most commonly found in Kerry, Cork, and Waterford, but are also known in Wales, Scotland, the Orkney Isles, the Isle of Man, and the Devon coast. Stone monuments inscribed in Ogham are usually written in Old Irish or an unknown Brythonic tongue—probably Pictish. The alphabet seems to have been primarily used from the 4th century AD to the 8th century AD (although correct dates are a subject of contention).
There are many historical theories explaining the origin of Ogham, but none are conclusive. Some scholars hold that the script originated during the Roman conquest of Britain as a sort of non-Roman code language used between Celtic people. Others assert that the language grew up as a means for denoting Celtic sounds—which the Roman alphabet is not well suited for—and became more complex and complete only as Christian scholars set up communities in Ireland. Wilder theories involve ancient primitive peoples as diverse as Mesolithic hunter-gatherers, the lost tribes of Israel, and the mysterious Sea People who destroyed Minoan palace civilization in the Mediterranean (please, please don’t tell my Irish history professor that I let you know about any of these hare-brained ideas). My favorite mythical (as in “not-real”) story of the origin of Ogham involves the legendary Scythian king, Fenius Farsa, who invented the Gaelic language and then crafted Ogham out of scraps recovered from the fallen Tower of Babel (there’s more than a soupçon of world-famous Irish blarney in this folktale).
Whatever the actual origins of Ogham were, a large number of inscribed stones have been found in what were once Celtic lands. Most of these were territorial markers and memorials—the oldest of which come from Ireland (although it is believed there was a heritage of inscribing the lines on sticks and bark which predated stone inscriptions). Some scholars believe the Welsh, Manx, Scotish, British, and Orkadian Ogham stones date from Post-Roman Irish incursion/invasions. Ancient tradition assigns the names of trees or shrubs to each of the letters of Ogham (although such a naming convention may only date from the tenth century). A comprehensive glossary of letter names can be found here along with a translation of an ascetic Ogham joke (of sorts).
The coral reef is a super-competitive ecosystem where every surface hides a hidden mouth, a poison dart, or a camouflaged hunter. However the reef is also a place rich in resources where it is possible to make a good living. It is sort of the New York City of ocean habitats. Some animals have been part of reef-like ecosystems for a tremendously long time, but one of my favorite reef animals, the banded sea snake or yellow-lipped sea krait (Laticauda colubrina) is a latecomer. Like the coral reef catfish (which descended from freshwater river fish ancestors but evolved into a saltwater coral reef dweller), the krait has put its land-dwelling roots behind it and moved out into the ocean—although it remains an air-breather like all snakes and it must also come ashore to drink freshwater since it has not yet evolved the super kidneys necessary for dealing with saltwater. Yellow-lipped sea kraits are widespread throughout the Indo-Pacific Ocean. They grow up to 2.2 meters (6 and a half feet long).
An accomplished hunter, the banded sea snake lives on cuttlefish, squid, fish, fish eggs, and small arthropods which throng the shallow reef. The krait’s venom is among the most poisonous on earth, but fortunately the creatures have easy going dispositions (and small fangs) and they rarely bite humans. Their closest relatives among the land snakes are the cobras.
Yellow-lipped sea kraits shed their skin far more often than do land snakes in order to protect themselves from parasites: sometimes they change skins as often as every fortnight. Kraits are viviparous and do not bear eggs but rather give birth to completely autonomous baby snakes which are born with their parents’ swimming and hunting ability. The snakes are such gifted swimmers thanks not just too their sinuous bodies but also to laterally compressed tails which they use like paddles to propel themselves through the water. Another feature which the kraits possess to deal with their watery habitat is nostrils which clamp shut
The kraits are extremely beautiful: their bodies are banded with black and pale blue rings. They have a balck head with a yellow snout. Their beauty gives them a special place in art and literature. I like to imagine that the yellow-lipped krait was one of the mysterious beautiful “water-snakes” who caused the ancient mariners unconscious epiphany which broke the curse he labored under and marked the climax of Coleridge’s The Rime of the Ancient Mariner (a profoundly beautiful miniature epic about the importance of treating animals kindly):
Beyond the shadow of the ship,
I watched the water-snakes:
They moved in tracks of shining white,
And when they reared, the elfish light
Fell off in hoary flakes.
Within the shadow of the ship
I watched their rich attire:
Blue, glossy green, and velvet black,
They coiled and swam; and every track
Was a flash of golden fire.
O happy living things! no tongue
Their beauty might declare:
A spring of love gushed from my heart,
And I blessed them unaware:
Sure my kind saint took pity on me,
And I blessed them unaware.
In Norse folklore the universe was envisioned as Yggdrasil an immense tree with roots and branches winding through many different worlds and realms. An immense serpent, Níðhöggr, forever gnawed at the roots of the tree thus threatening to bring the entire universe down– however Níðhöggr was not the only gigantic serpent in the Norse pantheon.
Between the chthonic roots of the tree and its lofty branches (at ground level, as it were) lay the world of humankind, called Midgard. Midgard was protected by the gods and, to a lesser extent, by humankind, from the ice giants who were always attacking and from Loki, the strange trickster god, who was forever plotting. Loki knew the ice giantess, Angrboða, and together the pair had three children. One was Hel, who went down to icy Niflheim to rule over the damned and lost (our word “Hell” comes from her name and her realm). Another was Fenris Wolf, the all-devouring giant wolf who was chained by magic fetters to an immense stone thrust deep into the roots of Yggrasil. The last of the three children of Loki and Angrboða was Jörmungandr, a colossal sea serpent also known as the Midgard Serpent. When Odin perceived how quickly the serpent was growing, he cast it into ocean which the Norse believed ringed the whole world. There the serpent grew to colossal size, eventually surrounding the entire world and swallowing its tail. In some ways the monster became synonymous with the world-girding ocean.
Jörmungandr is ever opposed by the god Thor. Twice the two met in the Norse mythical canon. The first time, Thor was fooled into thinking the world-sized ocean monster was a large indolent housecat (it should be noted that Thor was not only drinking heavily but also being magically fooled by a trickster king of the Jötnar). Despite using all his divine strength, Thor was unable to lift the cat off the floor and only managed to heft one paw up for a moment. The seemingly trivial feat of strength was revealed as more impressive when the nature true of the cat was manifested (the entire story is a very amusing one). Thor again encountered the serpent when he was fishing for monsters with the giant Hymir. Thor had struck the head off the great ox belonging to the giant in order to catch two whales. Against Hymir’s protests, the two proceeded farther out to sea, towards the edge of the world. Thor hooked the Midgard serpent and dragged the creature’s head to the surface. The monster’s fanged mouth was dripping with poison and blood and it was moving towards the boat to finish the two off. Before Thor could lift his hammer to kill the serpent (or the serpent could devour the two fishermen), Hymir cut the line and the creature escaped.
Thor is slated to encounter the monster one last time at Ragnarök. When the last battle comes, the serpent will swim towards land poisoning everything it touches and causing huge tidal waves. This will be the signal for Naglfar to sail, bringing the hordes of walking dead back to the world of the living. Thor will finally fight the serpent and, after a great battle, the thunder god will triumphantly kill the mighty creature. Thor will then walk nine steps before dying from his poisoned wounds as the mortally wounded Fenris Wolf swallows the sun and the world comes to an end.
The Siphonophorae are a group of marine animals closely related to jellyfish and corals. Like jellyfish, siphonophores are free to move around the ocean. They hunt and capture fish and crustaceans by means of stinging tentacles. However, like adult coral, siphonophores are colony animals. A single siphonophore consists of multiple living animals–some of which are quite different from each other, since they serve different functions in the overall colony. Their unusual nature makes them a focus of the scientific (and philosophical) question of what constitutes an individual organism as opposed to a group of organisms.
The best known siphonophore, the fearsome Portuguese man-of-war, possesses a gas filled bladder from which long colonies of stinging animals hang. Most siphonophores however are not found near the surface. Siphonophore colonies form delicate chains which can be quite long. Some have been recorded to be 130 feet or more in length—substantially longer than the mighty blue whale. Additionally some siphonophores are bioluminescent.
Marine biologists are beginning to think that siphonophores are more prevalent and important than initially believed. Scientists once used nets and tows to capture specimens and calculate overall biomass. These methods broke delicate siphonophores into unidentifiable pieces. Now that biologists are using unmanned submarines to study the ocean, they have been finding many more siphonophores than they expected.