You are currently browsing the tag archive for the ‘round’ tag.
Earth’s oceans today are defined by the disasters and exigencies of the past. When you dip a net in a shallow tropical sea it does not emerge from the waves seething with conodonts…because they died out completely during the Triassic. You could fish from the beach every night from now until the sun burns out and never catch another belemnite nor see an Archelon drag her 5 meter carapace from the sea to lay her eggs. Past disasters (and the constant ebb and flow of evolution) have removed some of the core cast from the great drama. Yet the oceans are vast: sometimes we find that an organism known only from fossils and presumed long lost has been swimming around the Comoro Islands or living in an ancient grove in Hubei. Today’s post involves a “living fossil” of this sort, but this creature was presumed lost for longer than the lobe-fin fishes or the purple frog.
This is a fossil monoplacophoran, a strange ancient superclass of single shelled mollusks which thrived in the ancient oceans of the Palaeozoic (or earlier) but then was known only through fossils. I can understand if you are shrugging about some primitive snail/limpet thing–but, my friend this is no gastropod–it is an entirely different class of mollusk which was presumed to have died out 380 million years ago. A look at the (long and complicated) taxonomy of monoplacophorans on Wikipedia is like looking at a World War I cemetery (extinct taxa are noted with a funereal superscript cross).
Yet, scientists came to discover that not every name on the list had a cross. The monoplacophorans never fully died out. They just moved to the bottom of the oceans and stayed there for the long ages as continents drifted across the world and dinosaurs came and went. As mammals scurried out of burrows and across the world, the monoplacophorans lived their ascetic lives upon the floor of the ocean. They are still there right now, as you read these words! If you look at a picture of the colorless gray ocean bottom, you will see colorless gray ovals–the monoplacophorans (their very name makes them sound like some implacable cthulu-ish monk)
It is funny to me that ancient fossils in 400 million year old rocks were more accessible to scientists than the bottom of the ocean up until about the time I was born. Yet, since then, the bottom of the ocean has become closer as humankind’s ever-grasping arms have become longer. Lately our robot probes have reported a bit of summery warmth at the cold ocean bottom. And mining cartels are eagerly pushing to vacuum of nodules of precious ore upon the distant seabed. I truly wonder if we could look 380 million years into the future whether we will still find these tough little eremites still going about their business in the crushing depths? Or will the field of taxonomical crosses finally be complete, with these ultimate living fossils turning into yet another victim of our insatiable appetite?
After last week, you are probably thinking one thing: “what about these gobies?”
Last week Ferrebeekeeper featured a post on the invasive round gobies from the Black Sea which have showed up in the Great Lakes. The blobtastic little fish sneaked into the lakes by means of ballast water carried across the great oceans in international freighters and now they are wrecking up the place. The gobies are outcompeting larger fish for resources. They are devouring native mussels. To quote the USGS website, “This species has been found to prey on darters, other small fish, and Lake Trout eggs and fry in laboratory experiments. They also may feed on eggs and fry of sculpins, darters, and Logperch (Marsden and Jude, 1995) and have also been found to have a significant overlap in diet preference with many native fish species.” Particularly hard hit are mottled sculpins, little round pebble-looking native fish which occupy(ied?) the ecological niche which the gobies are now taking over. the fish horror stories contain some rather sad anecdotes of gobies biting sculpins and chasing them away and taking their lunch money and otherwise bullying them on the lake bed. It is a rough world out there.
This mottled sculpin looks disgruntled
So are we just fated to dwell in a gobified dystopia from now on? Well, actually, there are some positive things which the gobies are accomplishing and not everybody is sad they are here. I was joking about gobies eating zebra mussels, the horrible invasive freshwater mussels which are filling up the Great Lakes and causing havoc to power plant and shipping infrastructure, however, it turns out the gobies do happily eat zebra mussels. Additionally the gobies are not just eating other animals: they are also being eaten by them. Because of the proliferation of round gobies, the previously endangered Lake Erie water snakes (Nerodia sipedon insularum) have become more prolific in number and the snakes are much fatter and happier (insomuch as we have records for these reptilian parameters). The water snakes have been so successful at hunting gobies that they have been removed from the endangered species list (back before the act was watered down).
Why, here’s a great writing mass of ’em! The world is getting better!
Larger gamefish like walleye, yellow perch, and bass and are eating the gobies, as are piscivorous birds like gulls, cormorants, plovers, and bald eagles(!). Unfortunately there is downside to this as well. Zebra mussels filter decaying cladophora algae out of the water. This algae contains C. botulinum, a bacteria which contains the infamously dangerous botulism toxin. If the predatory birds eat too many gobies they can be killed by the botulism and several mass die-offs have occurred.
What is the point of all of this (other, than, you know, the fact that it is happening in the world)? I suppose this article is really about ecosystems–the complex webs of life we depend upon. they are fragile in unexpected ways and resilient in unexpected ways. We need to think about them more and learn more about them (witness what happened in all of my aquariums). Thanks for the mindfulness lesson, ugly invasive goby!
Opah?
In all of entertainment, no figure is more beloved than Opah! Her networks make the most money. Her endorsements confer instant fame and wealth. Her personal life is the subject of profound fascination and scrutiny. She is what all Americans aspire to be…a veritable queen who transcends…
Opah!
Wait…Opah? That’s a big orange fish! Also known as moonfish, opahs consist of two species (Lampris guttatus and Lampris immaculates) which are alone in their own small family the Lampridae. Their closest relatives are the magnificent ribbonfishes like the crestfishes and oarfish! They are discoid fish with orange bodies (speckled with white) and with bright vermillion fins. Opahs do not give away cars or support quack psychiatrists and physicians, but, they are much in the news right now anyway. To the immense surprise of ichthyologists and zoologists, a research team from the NOOA has discovered that Opahs are warm-blooded—in a way. They are the only endothermic fish known to science.
Lampris guttatus (NOAA)
Being warm-blooded allows animals in the deep ocean to think and move more swiftly than the more ascetic and staid dwellers of the deep (most creatures of the ocean bottom are usually slow and placid in order to conserve energy–like the tripod fish). Ocean birds and marine mammals have long used this to their advantage. They gulp air from the surface and then dive deep to catch slower moving fish, squid, and invertebrates from the cold depths.
A stamp from French Southern and Antarctic Territories showing Lampris immaculatus
Other high-speed predatory fish (certain species of sharks and sportsfish) can warm key muscle groups using heat exchanging blood vessels in order to gain a burst of super speed, but these fish rapidly lose their heat—and the related speed advantages–as their blood circulates through their gills. This is one of the reasons sharks and marlins lunge and then return to slow measured swimming.
The opah appears to produce the majority of its heat by constantly flapping its pectoral fins. The warmth thus generated is not lost through the opahs’ gills. Critically, these fish possess unique insulated networks of blood vessels between their hearts and gills. The residual heat is removed from blood headed through the gills and then restored as it goes back through the heart. Their weird circular shape and comparatively large size are additional adaptations to help them conserve this warmth.
An opah near San Clemente Island (Jane J. Lee for National Geographic)
Marine biologists know surprisingly little about opahs (especially considering that the fish have long been known to fishermen and diners). Opahs live in the mesopelagic depths 50 to 500 meters (175 to 1650 feet) beneath the surface but it now seems they might make deeper hunting forays into the true depths. They are solitary hunters which live on shrimp, krill, and small fish. Opahs are approximately the size of vehicle tires. The smaller species (Lampris immaculatus) is like a big car tire and reaches a maximum of 1.1 m (3.6 ft). The larger species, Lampris guttatus, can become as large as an industrial lorry tire and can attain a length of 2 m (6.6 ft). the largest opahs weight up to 270 kg (600 lb).
Spotted Opah larva (Lampris guttatus)
Larval opahs resemble the larvae of oarfish (they are long and ribbonlike with strange protuberances. The main predators of Opahs are the great sharks…and humankind. Because of predation from this latter species which is endlessly hungry the survival of the opahs has grown less certain. It is believed that they have a low population resilience, but this…like their numbers and their lifestyle is unknown to science. We only just found they were warm-blooded earlier this month!
ferrebeekeeper 