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Fish retinas generally have both rod cells and cone cells (for scotopic and photopic vision), and most species have colour vision. Some fish can see ultraviolet and some are sensitive to polarised light. Among jawless fishes, the lamprey [1] has well-developed eyes, while the hagfish has only primitive eyespots. [2]
Vision is an important sensory system for most species of fish. Fish eyes are similar to those of terrestrial vertebrates like birds and mammals, but have a more spherical lens. Their retinas generally have both rod cells and cone cells (for scotopic and photopic vision), and most species have colour vision.
Freshwater fish are fish species that spend some or all of their lives in bodies of fresh water such as rivers, lakes and inland wetlands, where the salinity is less than 1.05%. These environments differ from marine habitats in many ways, especially the difference in levels of osmolarity. To survive in fresh water, fish need a range of ...
Freshwater ecosystems are a subset of Earth's aquatic ecosystems. They include lakes, ponds, rivers, streams, springs, bogs, and wetlands. [1] They can be contrasted with marine ecosystems, which have a larger salt content. Freshwater habitats can be classified by different factors, including temperature, light penetration, nutrients, and ...
Resting small fish are still vulnerable to attack by crevice predators, so many fish, such as triggerfish, squeeze into a small hiding place and wedge themselves by erecting their spines. [2] As an example of the adaptations made by reef fish, the yellow tang is a herbivore which feeds on benthic turf algae. They also provide cleaner services ...
Aquatic respiration. Sea slugs respire through a gill (or ctenidium) Aquatic respiration is the process whereby an aquatic organism exchanges respiratory gases with water, obtaining oxygen from oxygen dissolved in water and excreting carbon dioxide and some other metabolic waste products into the water.
Aquatic locomotion. A great cormorant swimming. Aquatic locomotion or swimming is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella. Swimming has evolved a number of times in a range of organisms including arthropods, fish, molluscs, amphibians, reptiles, birds, and mammals.
An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms — aquatic life —that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. [1]