The world is decorated with an astonishing diversity of animals. Here are some new discoveries about a few of them.
Squid rangefinder: Why are portions of the squid eyeball out of focus? Scientists noticed the squid bobbing their heads, and deduced that the “defect” has a purpose. In the low-contrast deep waters of their hunting grounds, the retina and behavior provides them a kind of rangefinder, allowing them to “catch prey with remarkable speed and precision,” a new paper in Current Biology says.
Mantis shrimp eyes : The weirdly-patterned eyes of the mantis shrimp, moving atop stalks, look like something out of science fiction. What are the vertical bands and spots in the centers of the eyes? Nature News and Live Science talked about a new paper in Science Magazine that analyzes how the physiology and 12 kinds of photoreceptors gives the crustaceans “extraordinary color vision” (see also the Perspective article in the same issue that says these eyes that see “color in a fundamentally different way” are “unique in the animal kingdom”). The vertical bands are designed for detecting circularly polarized light and ultraviolet, as well as sharpening color spectrum in 12 spectral channels. “The upper and lower halves of each eye also have overlapping visual fields, so that each eye can act as a stereoscopic rangefinder, at least for close distances.” Live Science posted a gallery of different species of clown-colored mantis shrimp with their “googly eyes.” Nature News included a video clip that shows the mantis shrimp rotating and moving its eyes on the stalks.
Under the sea ice: Add this to the list of unexpected places to find life. A robotic submersible measuring ocean currents under the Ross Ice Shelf in Antarctica. When its camera looked under the sea ice, it made “a startling discovery,” reported Live Science. “Clinging upside-down from crannies in the ice shelf with their tentacles dangling into the icy water were thousands and thousands of tiny sea anemones.” They must feed on nutrients upwelling in currents. How they live without freezing is not known; Live Science added a video from the NSF that shows the creatures. That’s not all they found: “fish that swim upside down, marine worms that live in the icy melt, crustaceans called amphipods and a strange creature resembling a sea cucumber, which they nicknamed ‘the eggroll.’”
Hookworm genes: The hookworm parasite undergoes a “fantastic voyage” once inside the body, Live Science relates. “These parasites start their lives in soil, and enter the human body through the foot, where they embark on a fantastic voyage through the blood vessels, to the heart, then into the lungs and trachea before being coughed up and swallowed and carried to their final home in the small intestine.” There, they feed on blood, causing host symptoms including anemia and lassitude. The genome of the hookworm has just been published, providing hope for understanding their lifestyles to reduce infections in poor countries with inadequate sanitation. The infections are not all bad: usually not deadly, they give the victim’s immune system a “vigorous workout,” reducing risk of allergies and autoimmune diseases. In fact, some medical researchers are finding good success with “helminth therapy” for treating these diseases (7/13/04, 2/04/12).
Spots & stripes: Scientists may just be beginning to get a grip on how animal patterns arise. Science Magazine has a video clip that shows two types of skin cells, dark melanophores and light xanthophores, having a kind of race in the embryos of zebrafish. When they make contact, one type moves and the other follows in “hot pursuit.” This may lead to the colored bands in the adult.
Dinosaur gigantism: Imagine the problems of being an animal weighing 80 tons. Scientists are trying to figure out how the big sauropods regulated their body temperature, Science Daily says. “The gigantism of these vertebrates, unique in the history of Earth, raises many questions, such as why no other land creatures have ever achieved this size and what their bauplan, physiology, and life cycle would have been like.” The story includes links to three open-access papers in PLoS ONE exploring the physiology of dinosaur gigantism.
Sloth-fulness: The sloth truly deserves its name, PhysOrgs says. It nibbles on its own fur when too lazy to hunt, and only comes down out of the tree once a week to defecate on the ground. The animal almost acts like a hanging terrarium. Cracks in its hair catch rainwater, providing a microhabitat for algae growth. Moths lay their eggs in its fur to live off the algae. “This complex (symbiosis)… reinforces fundamental aspects of the sloth’s behaviour and life history, and may reinforce the slothfulness of sloths,” scientists said.
Bat olympics: The BBC reported on a bat that crossed the English Channel – an “incredible journey” for a bat. It’s the first time the crossing has been documented. The little creature is the size of a human thumb. One scientist remarked, “it’s incredible to think that this little bat has flown a distance of at least 600km, avoiding hazards like roads and wind turbines, and for it to safely cross the sea is remarkable.”
Dog paddle: What could be more common than the dog paddle? Yet Live Science called it a “mystery” that scientists are diving into. Frank Fish at West Chester University (Pennsylvania) is taking underwater videos (see sample in the article) of various breeds swimming to understand this instinctive behavior of dogs, armadillos, and some humans. It’s kind of like an underwater trot, he found; “Despite all these different dogs having different terrestrial gaits, they all basically focus in on one gait when they’re swimming.” Then came an evolution commercial:
Fish says he’s trying to understand what natural selection factors were in play for animals that were just beginning to swim. Although dogs aren’t direct predecessors of cetaceans — the category that includes dolphins, whales and porpoises — aquatic mammals did evolve from longed-legged quadrupeds that moved into the water, and over time dropped their paws in favor of fins.
Scientists estimate that the first aquatic mammals probably flopped into the water around 60 million years ago, and it took 20 million years for them to evolve flukes and flippers like modern-day whales and dolphins.
In between factual observations with tanks and flumes, Fish says “I still want to know what animals have to give up as they’re going along evolutionarily from terrestrial to aquatic.” He’s even pondering what it would take for a dolphin to evolve the ability to move on land.
The strangest creature of all is the human evolutionary scientist. He can look at design all around and attribute it to blind, unguided processes. From there he turns his imagination into overdrive and wanders into mythical worlds with walking dolphins. This is called “going along evolutionarily.” It’s like stumbling in the dark.