Aquatic Animals Video Download

Reactive oxygen species (ROS) are an unenviable part of aerobic life. Their steady-state concentration is a balance between production and elimination providing certain steady-state ROS level. The dynamic equilibrium can be disturbed leading to enhanced ROS level and damage to cellular constituents which is called "oxidative stress". This review describes the general processes responsible for ROS generation in aquatic animals and critically analyses used markers for identification of oxidative stress. Changes in temperature, oxygen levels and salinity can cause the stress in natural and artificial conditions via induction of disbalance between ROS production and elimination. Human borne pollutants can also enhance ROS level in hydrobionts. The role of transition metal ions, such as copper, chromium, mercury and arsenic, and pesticides, namely insecticides, herbicides, and fungicides along with oil products in induction of oxidative stress is highlighted. Last years the research in biology of free radicals was refocused from only descriptive works to molecular mechanisms with particular interest to ones enhancing tolerance. The function of some transcription regulators (Keap1-Nrf2 and HIF-1) in coordination of organisms' response to oxidative stress is discussed. The future directions in the field are related with more accurate description of oxidative stress, the identification of its general characteristics and mechanisms responsible for adaptation to the stress have been also discussed. The last part marks some perspectives in the study of oxidative stress in hydrobionts, which, in addition to classic use, became more and more popular to address general biological questions such as development, aging and pathologies.

An aquatic animal is any animal, whether vertebrate or invertebrate, that lives in water for all or most of its lifetime.[1] Many insects such as mosquitoes, mayflies, dragonflies and caddisflies have aquatic larvae, with winged adults. Aquatic animals may breathe air or extract oxygen from water through specialised organs called gills, or directly through the skin. Natural environments and the animals that live in them can be categorized as aquatic (water) or terrestrial (land). This designation is polyphyletic.

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The term aquatic can be applied to animals that live in either fresh water or salt water. However, the adjective marine is most commonly used for animals that live in saltwater, i.e. in oceans, seas, etc.

Aquatic animals (especially freshwater animals) are often of special concern to conservationists because of the fragility of their environments. Aquatic animals are subject to pressure from overfishing, destructive fishing, marine pollution, hunting, and climate change. Many habitats are at risk which puts aquatic animals at risk as well.[2] Aquatic animals play an important role in the world. The biodiversity of aquatic animals provide food, energy, and even jobs.[3]

Fresh water creates a hypotonic environment for aquatic organisms. This is problematic for some organisms with pervious skins or with gill membranes, whose cell membranes may burst if excess water is not excreted. Some protists accomplish this using contractile vacuoles, while freshwater fish excrete excess water via the kidney.[4] Although most aquatic organisms have a limited ability to regulate their osmotic balance and therefore can only live within a narrow range of salinity, diadromous fish have the ability to migrate between fresh water and saline water bodies. During these migrations they undergo changes to adapt to the surroundings of the changed salinities; these processes are hormonally controlled. The European eel (Anguilla anguilla) uses the hormone prolactin,[5] while in salmon (Salmo salar) the hormone cortisol plays a key role during this process.[6]

In addition to water breathing animals, e.g., fish, most mollusks, etc., the term "aquatic animal" can be applied to air-breathing aquatic or sea mammals such as those in the orders Cetacea (whales) and Sirenia (sea cows), which cannot survive on land, as well as the pinnipeds (true seals, eared seals, and the walrus). The term "aquatic mammal" is also applied to four-footed mammals like the river otter (Lontra canadensis) and beavers (family Castoridae), although these are technically amphibious or semiaquatic. There are up to one million types of aquatic animals and aquatic species.[10]

Amphibians, like frogs (the order Anura), while requiring water, are separated into their own environmental classification. The majority of amphibians (class Amphibia) have an aquatic larval stage, like a tadpole, but then live as terrestrial adults, and may return to the water to mate.

Most mollusks have gills, while some fresh water ones have a lung instead (e.g. Planorbidae) and some amphibious ones have both (e.g. This depends on the animals.Ampullariidae). Many species of aquatic animals lack a backbone or are invertebrates.[10]

Aquatic animals play an important role for the environment as well as human's daily usage. The importance of aquatic animals comes from the fact that they are organisms that provide humans with sources such as food, medicine, energy shelter, and raw materials that are used for daily life.

Let's remember: virtual animals do not suffer, hence, having orcas or dolphins isn't unethincal. The real issue is having them in real-life zoos or aquariums. So people who attend those places are the real problem.

Given their dormancy capability (long-term resistant stages) and their ability to colonise and reproduce, microscopic aquatic animals have been suggested having cosmopolitan distribution. Their dormant stages may be continuously moved by mobile elements through the entire planet to any suitable habitat, preventing the formation of biogeographical patterns. In this review, I will go through the evidence we have on the most common microscopic aquatic animals, namely nematodes, rotifers, and tardigrades, for each of the assumptions allowing long-distance dispersal (dormancy, viability, and reproduction) and all the evidence we have for transportation, directly from surveys of dispersing stages, and indirectly from the outcome of successful dispersal in biogeographical and phylogeographical studies. The current knowledge reveals biogeographical patterns also for microscopic organisms, with species-specific differences in ecological features that make some taxa indeed cosmopolitan with the potential for long-distance dispersal, but others with restricted geographic distributions.

The inclusion of microscopic animals in the discussion on the ubiquity hypothesis makes comparisons with larger organisms more obvious: microscopic and macroscopic animals have common physiology, similar ecology, and shared evolutionary trajectories [10]. Yet, biogeographical patterns seem to be different between microscopic and large animals, because of the differences in size and the ecological consequences of being microscopic [1, 6].

Three assumptions should be met in order to allow long-distance dispersal in microscopic aquatic animals: dormancy capability, long-term resistance of dormant stages, and ability to colonise and reproduce quickly. Here I review these assumptions and the direct and indirect evidence we have for long-distance dispersal. The review is not meant to be exhaustive on each of the topics, but is designed to introduce the subject and its relevance for our general understanding of movement ecology and biogeography of microscopic aquatic animals, focusing on nematodes, rotifers, and tardigrades, the most notorious microscopic animals with high potentials for long-distance dispersal.

Nematodes, rotifers, and tardigrades independently evolved adaptations to survive adverse periods without water [16,17,18,19]: as soon as conditions are not favourable with liquid water becoming unavailable because of evaporation or of freezing, some animals are able to produce dormant stages to allow the following generation to recover a viable population when liquid water becomes available again [16]. Such dormant stages are known as resting eggs in rotifers and in tardigrades [20, 21], and eggs in nematodes [22]. They are dormant embryos and not actual eggs [23], and they are produced both by parthenogenesis and by sexual reproduction. There is an ample literature on the triggers that drive the production of resting stages, and also on the mechanisms that are put in place to maximise the efficacy of such stages to maintain viable populations through bet-hedging strategies, especially for microscopic zooplankton animals [24]. The production of dormant stages that accumulate at the bottom of an ephemeral water body is also considered the main mechanism that structures community and population dynamics for microscopic animals with high genetic differentiation at the local and landscape level [25], in what was named monopolisation hypothesis [26]. These communities, structured by the interplay between the buffering effect of dormant stages acting against new colonisers and the dispersal of dormant propagules from other populations [27, 28], are one of the most studied examples within the metacommunity framework [29, 30]. The research output of community ecology connected to dispersal in microscopic aquatic animals is highly productive, but will be only marginally considered in this review, given that it involves local or landscape-level settings, and not proper long-distance dispersal across continents.

Dormancy may be attained several times during the life span of an organism: for example, meiofauna living on a lichen patch on a tree trunk at temperate latitudes may desiccate every day under the sun in the morning and resume activity every evening when moisture levels increase again with enough water in the thin layers surrounding the lichen to allow the animals to move and feed. Given that the life span of these animals is usually more than a month [20, 22, 41, 42], they may experience several tens of cycles of desiccation and resurrection during their life. Desiccated dormant animals can be easily moved by wind through the landscape, and this is considered the main mechanism that strictly asexual bdelloid rotifers use to survive their arm-race against fungal parasites in a hide-and-seek continuous movement to new lichen patches temporarily without parasites [43]. 006ab0faaa