And the other is from livescience.com, and it won't upload into this post, so you'll have to go view it here.
Author: Matthew
First, from the ever-indefatigable xkcd: It's easy to forget how much biodiversity there is in the ocean and how much really is going on down there, especially within the halos of activity that surround any exposed land masses.
And the other is from livescience.com, and it won't upload into this post, so you'll have to go view it here. Author: Matthew
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Pfeffer's Flamboyant Cuttlefish (Metasepia pfefferi). Giant Australian Cuttlefish (Sepia apama) Cuttlefish are most closely related to the squids (order Teuthida), and while they are similar to squid in many ways, they are also totally unique and amazing in their own right. Instead of tails, cuttlefish have a continuous rippling fin surrounding their mantle, a muscular yet highly flexible construction that allows cuttlefish speed and maneuverability; with their fin, cuttlefish can move backwards, forwards, even flip over. Cuttlefish ink contains dopamine and dopamine chemical precursors that may suppress predators' sense of of smell. The pigments in the cuttlefish's ink were the original source for the shade of brown known as sepia and were once used in the art world for paints, inks and dyes. Cuttlefish possess aptly-named cuttlebones, calcareous internalized shells with tiny layered chambers connected by a strand of tissue called a siphuncle that regulates the cuttlebone's gas-to-liquid ratio (and, in doing so, the animal's buoyancy) through osmoregulation (this is really very similar to the nautilus's camerae system). Cuttlefish have venom in their suckers that can poison or kill prey, and one species – Pfeffer's Flamboyant Cuttlefish, an intelligent and aggressive cuttlefish that is almost constantly dramatically modifying its body structure, skin texture and color – is one of the few toxic cephalopods, with toxins as lethal as a Blue-Ringed Octopus's. Their eyes, with mustache-shaped pupils, allow them high-resolution perception of the angles at which light is reflected and polarized. And then, of course, there's the color-changing thing: Cuttlefish have the most advanced chromatophores (pigmentous cells that aid in color-changing) of any cephalopod, allowing them to perform mind-boggling changes of skin color and texture in the span of a couple seconds. The Reef Cuttlefish (Sepia latimanus) seen in the video above can also look like this: And this: The chromatophore Cuttlefish chromatophores are neurally controlled, directly innervated rather than dependent on hormones for instructions. This allows cuttlefish their rapidity in color changes. An individual cuttlefish has about 10-20 million chromatophores in its skin (200 per square millimeter). Radial muscles encircle the cell. These can change the shape of the cytoelastic sacculus within the cell, and in doing so translocate the sacculus's pigment granules, changing the skin's color. Pigments in cuttlefish chromatophores can be red, orange, yellow, brown, or black. In addition to chromatophores, cuttlefish have additional layers of cells that aid in color-changing: iridiphores, reflective columns of platelets with a protein-based structure (sometimes chitinous) that use thin-film interference to produce green, blue and gold. The plates reflect light, and change orientation in order to change the wavelength of light reflected. In addition to allowing nuance in color-changing that allows for extensive camouflage and communication, iridophores help cuttlefish disguise vulnerable organs like eyes and the ink sac. Cuttlefish skin includes another layer of color-changing cells, known as leucophores. These are flattened, elongated cells with an array of reflective granules (leucosomes) embedded in the cellular membrane. Leucophores enable cuttlefish (and the many shallow-water octopus species that have these cells) to engage in a form of passive camouflage. Leucophores reflect and scatter ambient light, without color discrimination or wavelength modification through cell orientation. Thus, these cells allow cuttlefish to automatically match the ambient lighting of their surroundings. This is especially important as cuttlefish eyes, while remarkably advanced in some respects, cannot see color very well. In addition to their psychedelic color-changing skills, cuttlefish can also change the texture of their skin to match the surrounding substrate. They use circular concentric muscles to force up liquid beneath the mantle into spikes or nodes, varying in size. These folds of skin, known as papillae, allow cuttlefish to blend in with the ocean bottom. Many species, including the Giant Australian Cuttlefish, use their papillae not only in camouflage but in communication. S. Apama spends most of its time carefully concealed amongst rocks and vegetation on the seafloor, as seen in the footage above. They live exclusively off the southern coast of Australia, at depths of 5-230 ft., where the ~60 F water temperature and many muddy seagrass beds and rocky reef crevices provide a perfect habitat for a cuttlefish. Their bioenergetic strategy is more similar to that of an octopus than that of squids or other cuttlefish - about 95% of a Giant Australian Cuttlefish's day is spent resting and hiding from predators like the Indo-Pacific Bottlenose Dolphin (Tursiops aduncus), with short hunting periods during both day and night where the cuttlefish sates its diverse dietary desires consuming crabs, lobsters, prawns and a variety of small and mid-size reef fish, ensnaring them with the long, concealed, decapodal tentacles it shares with its squid cousins. It is thought that this is how S. apama is able to grow to such extreme size – at the largest, they are almost three feet in total length (20 inches in mantle length alone) and nearly 30 pounds. G'day, mate! The exception to all of this is a few weeks in austral fall (May-July), when Giant Australian Cuttlefish shed their cryptic coloration for lurid colors and patterns and congregate by the thousands to mate. The largest and most colorful males usually win females first, the two entwining their tentacles and male placing spermatophores in an opening near the female's mouth. As most cuttlefish are male, competition is intense, and male cuttlefish often fight over females, with bites found on male cuttlefish evidencing the viciousness of these struggles. The polyandrous females have receptacles where they can store sperm from multiple males. Recently, it has been discovered that small males find mating success by adopting the size, texture and coloration of a female, swimming close to a mating couple, and depositing his own spermatophores in the female's buccal opening; the larger male, meanwhile, may be distracted by large male competitors, or even interested in the "cross-dressed" male as a potential mate. This provides a fascinating insight into cephalopod sexual selection. While the animal kingdom is rife with examples of females choosing showy, colorful, ostentatious mates with well-developed secondary sexual characteristics – these organisms most likely have higher relative fitness and would pass those genes on to her offspring – the female Giant Australian Cuttlefish, like organisms in other species with advanced intelligence, are equally willing to mate with physically well-developed indidviduals and individuals that have exhibited intelligence. Females lay their eggs on the underside of rocks and ledges. A female may lay up to hundreds of eggs each mating season. The 12-mm eggs take about 3-5 months to hatch. Young cuttlefish grow rapidly, reaching sexual maturity at 7 months. They continue to grow into their second year of life. Cuttlefish, like most cephalopods are semelparous; mating at one or two years of age, they die soon afterward. Like all cuttlefish, S. apama has complex eyes that can see the polarization of light. Polarization, the reflection of multiple scattered rays of light off a large surface os that the light is conentrated into a single plane, is usually experienced by humans as the glare seen on metal or large surfaces of water on a sunny day. Cuttlefish can actually see the angles at which various rays of light are reflected and polarized, and respond to changes in angle as little as 1.05 degrees. They also have photosensory organs that allow them to, in a sense, look behind themselves. Giant Australian Cuttlefish have no osmoregulatory mechanisms and are overall very senstitive to changes in temperature, salinity, and other aspects of water chemistry. As they have have 100% mortality at 50 ppt salinity (28-38 ppt is their preferred range), recent plans to construction desalination facilities that would discharge 120 megalitres (32 million US gallons) of brine into the water every day have been met with opposition from scientists and conservationists. S. apama populations have also been affected by hydrocarbon processing and other industrial activities along Australia's southern coast. Learn more about the Giant Australian Cuttlefish:
Author: Matthew |
WelcomeWith Every Drop is a Chicago-based blog, published by CR² team members, that focuses on the biodiversity, ecology, and conservation of marine and freshwater ecosystems. “Even if you never have the chance to see or touch the ocean, the ocean touches you with every breath you take, every drop of water you drink, every bite you consume. Everyone, everywhere is inextricably connected to and utterly dependent upon the existence of the sea.” – Dr. Sylvia Earle Archives
July 2015
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