FIELD NOTES
The Nictitating MembraneBald eagles, like other birds, have incredible eyesight. To help their vision stay sharp, they have the help of an inner eyelid called the nictitating membrane or plica semilunaris. This membrane is clearly visible, mid-blink, in the picture above and can be captured with a fast shutter speed camera. Eagles and other birds have three eyelids: top, bottom and horizontal. As the bird blinks, the nictitating membrane slides horizontally across the eye beginning in the inside corner, closest to the beak, then moves across to the outside corner. In addition to protection while attacking prey, this membrane keeps the eye moist and clear of dust. And, because the membrane is transparent, eagles never lose sight of their prey when the membrane draws across the eye. In most mammals, there is only a small vestigial remnant of the nictitating membrane in the corner of the eye. However, polar bears, aardvarks, camels, seals, marsupials and monotremes do have fully functional membranes. A good video of a crocodile's nictitating membrane in slow motion can be viewed here: The first anatomical description of the nictitating membrane in the eye was made by an English biologist named Richard Owen in 1866. In the context of human evolution, we, too, have a remnant of this membrane in the corners of our eyes. If you look in a mirror at the inner corner of your eye, you will see a small fold of pink tissue which is the vestigial remnant of the nictitating membrane. Vestigial organs are things in our anatomy like our appendix and wisdom teeth that are left over remnants from a time in early human evolution when we needed them for survival for grinding leaves and digesting our food. The reason that primates lost the real function of this membrane is because evolution, by natural selection, takes away functions and organs that are no longer necessary for survival. There have been rare cases of persistent nictitating membranes found in our species which you can read about and see here: A rare case report And the same report with pictures in the 2017 Indian Journal of Ophthalmology can be viewed here: Persistent unilateral nictitating membrane in a 9‑year‑old girl: A rare case report To read about other interesting human vestigial organs and functions, please see here. 7 Vestigial Features of the Human Body | |
Know Your Flies | |
Glass gem corn is a unique variety of rainbow-colored cornYou can learn all about Nicole's homegrown gem corn featured on Dr. Jerry Coyne's website: Why Evolution is True. | |
Crystal RiverEvery winter West Indian manatees travel into the warm 74-degree waters of Crystal River, Florida. The Crystal River National Wildlife Refuge is a unique refuge that preserves the last unspoiled and undeveloped habitat that forms the headwaters of Crystal River. It is also home to a variety of wildlife including otters, alligators, bald eagles, raptors, and another 200 species of birds. Despite their massive size, manatees are graceful swimmers in the coastal waters and rivers. Manatees are air-breathing, water-dwelling mammals related to elephants and they can grow up to 12 feet long and weigh up to 3500 pounds. These large animals are herbivores and adult manatees are voracious grazers eating weeds, water grasses and algae. Manatees have an average life span of 40 years but can live 60 years or more. Manatees are endangered and are often accidently hit by motorboats and sometimes become entangled in fishing nets. Ultimately, loss of habitat is the most serious threat facing manatees. Our friends at River Ventures in Crystal River, Florida provided us with an unforgettable experience and connection with these amazing animals. River Ventures is a family owned and operated manatee swim tour company and educational facility. Special focus is placed on educating the public on safety, conservation, history and behaviors of manatees and the federal and state laws regarding swimming with these beautiful animals. If you have ever wanted to see these fascinating, shy and gentle creatures, consider a tour with River Ventures. Visit our friends at: www.riverventures.com Tell them we sent you! | |
How Elephants Listen with Their Feet | |
Beekeeping in winterIn winter, honeybees gather in a central area of the hive and form a "winter cluster". A winter cluster is much like a huddle you may have seen at a football game-except it lasts all winter. Bees have one main job in the winter-to keep the queen safe and warm. In order to do so, worker bees surround the queen and form a cluster with their bodies. The worker bees then flutter their wings and shiver. The constant motion keeps the temperature of the hive warm. Though the queen is always at the center of the cluster, worker bees rotate from the outside to the inside of the cluster, so no individual bee gets too cold. |
Video written by Nicole Reggia, Produced by Dave Bock, Now That's Wild.com
- Red foxes live around the world in many diverse habitats including deserts, mountains, grasslands and forests. The red fox's resourcefulness has earned it a legendary reputation for intelligence and cunning. |