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Retrieved 12 October The digestive system and nutrition mollusks In mollusk: For example, passive absorption of nutrients such as fat-soluble vitamins is not subject to modulation by diet. University of Washington Course Descriptions gencat u. Have the kids make their own labels and tape them to toothpicks. Fish anatomy Fish physiology Age determination Anguilliformity Bone dermal intramembranous ossification Cleithrum Chromatophore Fins dorsal fin Gill branchial arch gill raker gill slit pharyngeal arch pharyngeal slit pseudobranch Glossohyal Jaw hyomandibula pharyngeal jaw Leydig's organ Mauthner cell Meristics Operculum papillare Papilla Photophore Root effect Shark cartilage Scales ganoine Spiral valve Suckermouth Swim bladder physoclisti physostome Teeth pharyngeal teeth shark teeth Teleost leptins Digital Library.

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Today, you will learn how you can find out if you have a problem with your gut though many of you won't need me to tell you — your gut will speak for itself!

Fixing your digestion is the fourth key of the 7 Keys to UltraWellness or functional medicine, and it is absolutely essential that you heal this critical system in your body if you want to achieve optimum health. The health of your gut determines what nutrients are absorbed and what toxins, allergens, and microbes are kept out.

It is directly linked to the health of your whole body. Intestinal health could be defined as the optimal digestion, absorption, and assimilation of food. But that is a big job that depends on many other factors. Let's look at a few of them. First, there are bugs in your gut that form a diverse and interdependent ecosystem like a rainforest. In fact, there are species and 3 pounds of bacteria in your gut which form a HUGE chemical factory that helps you digest your food, regulate hormones, excrete toxins, and produce vitamins and other healing compounds that keep your gut and your body healthy.

Too many of the wrong bacteria, like parasites and yeasts, or not enough of the good ones, like Lactobacillus or Bifidobacteria, can seriously damage your health. It's important to understand that many diseases that seem to be totally unrelated to the gut — such as eczema or psoriasis or arthritis — are actually CAUSED by gut problems. Second, there is your gut-immune system. Your entire immune system — and the rest of your body — is protected from the toxic environment in your gut by a lining that is only ONE cell-thick layer.

If spread out, this lining would take up a surface area the size of a tennis court, and the entire thing is covered by a sewer! If that barrier is damaged, you can become allergic to foods you may normally be able to digest perfectly well, you will get sick, your immune system will become overactive, and it will begin producing inflammation throughout your body. Filtering out the good molecules from the bad molecules and protecting your immune system is yet another important factor in gut health.

Third, there is your second brain — your gut's nervous system. Did you know your gut, actually contains MORE neurotransmitters than your brain? In fact, the gut has a brain of its own. It is called the "enteric nervous system" and it is a very sophisticated piece of your biology that is wired to your brain in intricate ways. Messages constantly travel back and forth between your gut-brain and your head-brain, and when those messages are interfered with in any way your health will suffer.

Fourth, your gut also has to get rid of all the toxins produced as byproducts of your metabolism , which your liver dumps into bile. If things get backed up when you are constipated, you will become toxic and your health will suffer.

And last but not least, your gut must break down all the food you eat into its individual components, separate out the vitamins and minerals, and shuttle everything across the one cell-thick layer mentioned above so it can get into your bloodstream and nourish your body and brain.

Your gut has quite a lot to manage. Even in perfect world it is hard to keep all of this in balance. But in our modern world there are endless insults that can knock our digestive systems off balance; it is that much more difficult to maintain excellent digestive health.

To fix your digestion, you first need to understand what is sending your gut out of balance in the first place. The list is short:. But what's important to understand is that many diseases that seem to be totally unrelated to the gut — such as eczema or psoriasis or arthritis — are actually CAUSED by gut problems. By focusing on the gut, you can get better.

Here is an example …. In the third type, the oocytes are conveyed to the exterior through the oviduct. Cystovaries characterize most teleosts, where the ovary lumen has continuity with the oviduct. Oogonia development in teleosts fish varies according to the group, and the determination of oogenesis dynamics allows the understanding of maturation and fertilization processes.

Changes in the nucleus , ooplasm, and the surrounding layers characterize the oocyte maturation process. Postovulatory follicles are structures formed after oocyte release; they do not have endocrine function, present a wide irregular lumen, and are rapidly reabsorbed in a process involving the apoptosis of follicular cells. A degenerative process called follicular atresia reabsorbs vitellogenic oocytes not spawned.

This process can also occur, but less frequently, in oocytes in other development stages. Some fish, like the California sheephead , are hermaphrodites , having both testes and ovaries either at different phases in their life cycle or, as in hamlets , have them simultaneously.

Examples of oviparous fish include salmon , goldfish , cichlids , tuna , and eels. In the majority of these species, fertilisation takes place outside the mother's body, with the male and female fish shedding their gametes into the surrounding water. However, a few oviparous fish practice internal fertilization, with the male using some sort of intromittent organ to deliver sperm into the genital opening of the female, most notably the oviparous sharks, such as the horn shark , and oviparous rays, such as skates.

In these cases, the male is equipped with a pair of modified pelvic fins known as claspers. Marine fish can produce high numbers of eggs which are often released into the open water column. The eggs have an average diameter of 1 millimetre 0. Egg of catshark mermaids' purse. The newly hatched young of oviparous fish are called larvae. They are usually poorly formed, carry a large yolk sac for nourishment , and are very different in appearance from juvenile and adult specimens.

The larval period in oviparous fish is relatively short usually only several weeks , and larvae rapidly grow and change appearance and structure a process termed metamorphosis to become juveniles. During this transition larvae must switch from their yolk sac to feeding on zooplankton prey, a process which depends on typically inadequate zooplankton density, starving many larvae. In ovoviviparous fish the eggs develop inside the mother's body after internal fertilization but receive little or no nourishment directly from the mother, depending instead on the yolk.

Each embryo develops in its own egg. Familiar examples of ovoviviparous fish include guppies , angel sharks , and coelacanths. Some species of fish are viviparous.

In such species the mother retains the eggs and nourishes the embryos. Typically, viviparous fish have a structure analogous to the placenta seen in mammals connecting the mother's blood supply with that of the embryo. Examples of viviparous fish include the surf-perches , splitfins , and lemon shark. Some viviparous fish exhibit oophagy , in which the developing embryos eat other eggs produced by the mother.

This has been observed primarily among sharks, such as the shortfin mako and porbeagle , but is known for a few bony fish as well, such as the halfbeak Nomorhamphus ebrardtii. This behavior is also most commonly found among sharks, such as the grey nurse shark , but has also been reported for Nomorhamphus ebrardtii. Aquarists commonly refer to ovoviviparous and viviparous fish as livebearers. Fish can produce either stridulatory sounds by moving components of the skeletal system, or can produce non-stridulatory sounds by manipulating specialized organs such as the swimbladder.

There are some species of fish that can produce sounds by rubbing or grinding their bones together. These noises produced by bone-on-bone interactions are known as 'stridulatory sounds'. An example of this is seen in Haemulon flavolineatum , a species commonly referred to as the 'French grunt fish', as it produces a grunting noise by grinding its teeth together. In a study conducted by Oliveira et al. The sounds emitted by the H.

Some fish species create noise by engaging specialized muscles that contract and cause swimbladder vibrations. Oyster toadfish produce loud grunting sounds by contracting muscles located along the sides of their swim bladder, known as sonic muscles [51] Female and male toadfishes emit short-duration grunts, often as a fright response. The red drum, Sciaenops ocellatus , produces drumming sounds by vibrating its swimbladder.

Ocellatus can produce different calls depending on the stimuli involved. Like other animals, fish suffer from diseases and parasites. To prevent disease they have a variety of defenses. Non-specific defenses include the skin and scales, as well as the mucus layer secreted by the epidermis that traps and inhibits the growth of microorganisms.

If pathogens breach these defenses, fish can develop an inflammatory response that increases blood flow to the infected region and delivers white blood cells that attempt to destroy pathogens.

Specific defenses respond to particular pathogens recognised by the fish's body, i. Some species use cleaner fish to remove external parasites. The best known of these are the Bluestreak cleaner wrasses of the genus Labroides found on coral reefs in the Indian and Pacific oceans. These small fish maintain so-called "cleaning stations" where other fish congregate and perform specific movements to attract the attention of the cleaners.

Immune organs vary by type of fish. These fish rely on regions of lymphoid tissue within other organs to produce immune cells. For example, erythrocytes , macrophages and plasma cells are produced in the anterior kidney or pronephros and some areas of the gut where granulocytes mature. They resemble primitive bone marrow in hagfish. Cartilaginous fish sharks and rays have a more advanced immune system. They have three specialized organs that are unique to Chondrichthyes ; the epigonal organs lymphoid tissue similar to mammalian bone that surround the gonads, the Leydig's organ within the walls of their esophagus, and a spiral valve in their intestine.

These organs house typical immune cells granulocytes, lymphocytes and plasma cells. They also possess an identifiable thymus and a well-developed spleen their most important immune organ where various lymphocytes , plasma cells and macrophages develop and are stored. Chondrostean fish sturgeons, paddlefish, and bichirs possess a major site for the production of granulocytes within a mass that is associated with the meninges membranes surrounding the central nervous system.

Their heart is frequently covered with tissue that contains lymphocytes, reticular cells and a small number of macrophages. The chondrostean kidney is an important hemopoietic organ; where erythrocytes, granulocytes, lymphocytes and macrophages develop. Like chondrostean fish, the major immune tissues of bony fish or teleostei include the kidney especially the anterior kidney , which houses many different immune cells.

Much like the mammalian immune system, teleost erythrocytes, neutrophils and granulocytes are believed to reside in the spleen whereas lymphocytes are the major cell type found in the thymus. Although not confirmed as yet, this system presumably will be where naive unstimulated T cells accumulate while waiting to encounter an antigen.

B and T lymphocytes bearing immunoglobulins and T cell receptors , respectively, are found in all jawed fishes. Indeed, the adaptive immune system as a whole evolved in an ancestor of all jawed vertebrate.

However, freshwater fish seem particularly threatened because they often live in relatively small water bodies. Overfishing is a major threat to edible fish such as cod and tuna. Such commercial extinction does not mean that the species is extinct, merely that it can no longer sustain a fishery. One well-studied example of fishery collapse is the Pacific sardine Sadinops sagax caerulues fishery off the California coast.

The main tension between fisheries science and the fishing industry is that the two groups have different views on the resiliency of fisheries to intensive fishing.

In places such as Scotland, Newfoundland, and Alaska the fishing industry is a major employer, so governments are predisposed to support it. A key stress on both freshwater and marine ecosystems is habitat degradation including water pollution , the building of dams, removal of water for use by humans, and the introduction of exotic species.

Introduction of non-native species has occurred in many habitats. One of the best studied examples is the introduction of Nile perch into Lake Victoria in the s. Nile perch gradually exterminated the lake's endemic cichlid species. Some of them survive now in captive breeding programmes, but others are probably extinct. Throughout history, humans have utilized fish as a food source. Historically and today, most fish protein has come by means of catching wild fish.

However, aquaculture, or fish farming, which has been practiced since about 3, BCE. Overall, about one-sixth of the world's protein is estimated to be provided by fish. In a similar manner, fish have been tied to trade. Catching fish for the purpose of food or sport is known as fishing , while the organized effort by humans to catch fish is called a fishery. Fisheries are a huge global business and provide income for millions of people. However, the term fishery is broadly applied, and includes more organisms than just fish, such as mollusks and crustaceans , which are often called "fish" when used as food.

Fish have been recognized as a source of beauty for almost as long as used for food, appearing in cave art , being raised as ornamental fish in ponds, and displayed in aquariums in homes, offices, or public settings. Recreational fishing is fishing for pleasure or competition; it can be contrasted with commercial fishing , which is fishing for profit. The most common form of recreational fishing is done with a rod , reel , line , hooks and any one of a wide range of baits. Angling is a method of fishing, specifically the practice of catching fish by means of an "angle" hook.

Anglers must select the right hook, cast accurately, and retrieve at the right speed while considering water and weather conditions, species, fish response, time of the day, and other factors. Fish themes have symbolic significance in many religions. In ancient Mesopotamia , fish offerings were made to the gods from the very earliest times.

In the Book of Jonah , a work of Jewish literature probably written in the fourth century BC, the central figure, a prophet named Jonah , is swallowed by a giant fish after being thrown overboard by the crew of the ship he is travelling on. In the dhamma of Buddhism , the fish symbolize happiness as they have complete freedom of movement in the water. Often drawn in the form of carp which are regarded in the Orient as sacred on account of their elegant beauty, size and life-span.

The astrological symbol Pisces is based on a constellation of the same name , but there is also a second fish constellation in the night sky, Piscis Austrinus. Fish feature prominently in art and literature, in movies such as Finding Nemo and books such as The Old Man and the Sea. Large fish, particularly sharks, have frequently been the subject of horror movies and thrillers , most notably the novel Jaws , which spawned a series of films of the same name that in turn inspired similar films or parodies such as Shark Tale and Snakehead Terror.

Piranhas are shown in a similar light to sharks in films such as Piranha ; however, contrary to popular belief, the red-bellied piranha is actually a generally timid scavenger species that is unlikely to harm humans.

Though often used interchangeably, in biology these words have different meanings. Fish is used as a singular noun, or as a plural to describe multiple individuals from a single species. Fishes is used to describe different species or species groups.

But if the pond contained a total of fish from three different species, it would be said to contain three fishes. The distinction is similar to that between people and peoples. A random assemblage of fish merely using some localised resource such as food or nesting sites is known simply as an aggregation.

When fish come together in an interactive, social grouping, then they may be forming either a shoal or a school depending on the degree of organisation. A shoal is a loosely organised group where each fish swims and forages independently but is attracted to other members of the group and adjusts its behaviour, such as swimming speed, so that it remains close to the other members of the group. Schools of fish are much more tightly organised, synchronising their swimming so that all fish move at the same speed and in the same direction.

Shoaling and schooling behaviour is believed to provide a variety of advantages. While the words "school" and "shoal" have different meanings within biology, the distinctions are often ignored by non-specialists who treat the words as synonyms.

Thus speakers of British English commonly use "shoal" to describe any grouping of fish, and speakers of American English commonly use "school" just as loosely. From Wikipedia, the free encyclopedia. For fish as eaten by humans, see Fish as food. For other uses, see Fish disambiguation. For the similar monophyletic clade, see Vertebrata. Giant grouper swimming among schools of other fish. Head-on view of a red lionfish.

Fish anatomy and Fish physiology. Fish reproduction and Spawn biology. Egg of bullhead shark. Fish diseases and parasites. Environmental impact of fishing. Fishing industry , Aquaculture , and Fish farming. Fishkeeping , Recreational fishing , and Angling.

For a topical guide to sharks, see Outline of sharks. Angling sport fishing Aquaculture Aquarium Catch and release Deep sea fish Fish acute toxicity syndrome Fish anatomy Fish as food Fish development Fishing fishing for food Fish intelligence Fishkeeping Forage fish Ichthyology List of fish common names List of fish families Marine biology Marine vertebrates Mercury in fish Otolith Bone used for determining the age of a fish Pregnancy fish Seafood Walking fish.

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