Retinal anatomy of hatchling loggerhead (left), leatherback (middle) and green turtle (right).
Loggerheads, in contrast, hunt along the bottom for their hard- shelled preyįigure 6. Those plants must live in shallow water where they are exposed to adequate levels of sunlight. Green turtles, for example, are herbivores that feed on algae and seagrasses. Sea turtles usually search for food visually during the daylight hours, but different species most commonly feed at different depths. Blue light at ~ 475 nm (nanometers, or 10-9 m) is transmitted best through clear seawater while with depth, light wavelengths shorter or longer gradually disappear. The eyes of oceanic animals like marine turtles function in an environment where the available light not only fluctuates between night and day, but also with depth (Figure 3). Light consists of a range of wavelengths transmitted from the sun to the earth’s atmosphere that penetrate the sea as downwelling energies. Oceanic Light Transmission and Spectral Sensitivity Their names and thesis titles are cited at the end of this article.
I’m proud to say that much of this information has been recently provided by biology graduate students at Florida Atlantic University. With these generalizations in mind, let’s explore how sea turtles use one sense organ, their eyes (Figures 1 and 2), to better understand why their visual world differs from ours. A proper understanding of that perceptual world requires knowing not only where each species lives (on land or under water), but also what it needs to know to survive in a hostile world. That window is modified through evolution to detect what each species needs to know. The common denominator is that each complement of sense organs provides a perceptual “window” into the external world.
Collectively, those discoveries led to the realization that how we view the world is unique to us, but not a “better” version than one possessed by another species. Those aspects sometimes included information that we can’t detect, such as the earth’s magnetic field or high-frequency “ultrasound”. Those differences were caused by the unique properties of their sense organs (eyes, ears, touch, smell, etc.) used to inform them about their environment. I was particularly interested in studies showing that animals differed in how they perceived their world.
#SEATURTLE EYE HOW TO#
His class was an introduction to the entire field and covered a wide range of topics in two general areas: (i) what we knew (at the time) about what animals did and why they did it, and (ii) how to design proper experiments to find out more. All that uncertainty disappeared two weeks after I enrolled in an Animal Behavior class taught by the professor who ultimately guided my studies toward an advanced degree. be they marshes, bays or the open ocean, was where I was happiest, especially when observing the amazing activities of their inhabitants. A head-on view of a juvenile green turtle, showing its large eyes.