Sea cucumbers are echinoderms from the class holothuroidea. They are marine invertebrates with a leathery skin and an elongated bod. Sea cucumbers are found on the sea floor worldwide. The number of holothurian species worldwide is about 1250 with the greatest number being in the Asia Pacific region.

Many of these are gathered for human consumption and some species are cultivated in aquaculture systems.  Sea cucumbers serve a useful purpose in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter after which bacteria can continue the degradation process.

Like all echinoderms, sea cucumbers have an endoskeleton  just below the skin, calcified structures that are usually reduced to isolated microscopic ossicles (or sclerietes) {say that three times fast!} joined by connective tissue. In some species these can sometimes be enlarged to flattened plates, forming an armour.

All puffin species have predominantly black or black and white plumage, a stocky build, and large beaks. They shed the colourful outer parts of their bills after the breeding season, leaving a smaller and duller beak. Their short wings are adapted for swimming with a flying technique under water. In the air, they beat their wings rapidly (up to 400 times per minute) in swift flight, often flying low over the ocean’s surface.  (The Wiki)

The one above has a mouth full of lunch!

Like many auks, puffins eat both fish and zooplankton, but feed their chicks primarily with small marine fish several times a day.  The prey species of the Atlantic Puffin include the sandeel, herring and capelin.   The puffins are distinct in their ability to hold several (sometimes over a dozen) small fish at a time, crosswise in their bill, rather than regurgitating swallowed fish. This allows them to take longer foraging trips, since they can come back with more food energy for their chick than a bird that can only carry one fish at a time. This behaviour is made possible by the unique hinging mechanism of their beak, which allows the upper and lower biting edges to meet at any of a number of angles.

A fish may love a bird, but where would they live?

{Drew Barrymore}

Fish are friends, not food.

 {Bruce, Finding Nemo}

Shark

From Wikipedia, the free encyclopedia

Sharks are a group of fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (orSelachii), and are the sister group to the rays. However, the term “shark” has also been used for extinct members of the suborder Elasmobranchii outside the Selachimorpha, such as Cladoselache and Xenacanthus. Under this broader definition, the earliest known sharks date from more than 420 million years ago.[1]

Since that time, sharks have diversified into over 400 species. They range in size from the small dwarf lanternshark(Etmopterus perryi), a deep sea species of only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (39 ft). Despite its size, the whale shark feeds only on plankton, squid, and small fish by filter feeding. Sharks are found in all seas and are common down to depths of 2,000 metres (6,600 ft). They generally do not live in freshwater although there are a few known exceptions, such as the bull shark and the river shark that can survive in both seawater and freshwater.   They breathe through five to seven gill slits. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They also have several sets of replaceable teeth.

Well-known species such as the great white shark, tiger shark, blue shark, mako shark, and the hammerhead sharkare apex predators—organisms at the top of their underwater food chain. Their predatory skill fascinates and frightens humans, even though their survival is threatened by human-related activities.

Etymology

Until the 16th century,  sharks were known to mariners as “sea dogs”.   The etymology of the word “shark” is uncertain. One theory is that it derives from theYucatec Maya word xok, pronounced ‘shok’.  Evidence for this etymology comes from the OED, which notes the name “shark” first came into use after Sir John Hawkins‘ sailors exhibited one in London in 1569 and used the word “sharke” to refer to the large sharks of the Caribbean Sea.

An alternate etymology states that the original sense of the word was that of “predator, one who preys on others” from the German Schorck, a variant ofSchurke ”villain, scoundrel” (cf. card shark, loan shark, etc.), which was later applied to the fish due to its predatory behaviour.

Anatomy

General anatomical features of sharks

Teeth

The teeth of tiger sharks are oblique and serrated to saw through flesh

Shark teeth are embedded in the gums rather than directly affixed to the jaw, and are constantly replaced throughout life. Multiple rows of replacement teeth grow in a groove on the inside of the jaw and steadily move forward in comparison to a conveyor belt; some sharks lose 30,000 or more teeth in their lifetime. The rate of tooth replacement varies from once every 8 to 10 days to several months. In most species, teeth are replaced one at a time as opposed to the simultaneous replacement of an entire row, which is observed in the cookiecutter shark.

Tooth shape depends on the shark’s diet: those that feed on mollusks and crustaceans have dense and flattened teeth used for crushing, those that feed on fish have needle-like teeth for gripping, and those that feed on larger prey such as mammals have pointed lower teeth for gripping and triangular upper teeth with serrated edges for cutting. The teeth of plankton-feeders such as the basking shark are small and non-functional.

Skeleton

Shark skeletons are very different from those of bony fish and terrestrial vertebrates. Sharks and other cartilaginous fish (skates and rays) have skeletons made of cartilage and connective tissue. Cartilage is flexible and durable, yet is about half the normal density of bone. This reduces the skeleton’s weight, saving energy.  Because sharks do not have rib cages, they can easily be crushed under their own weight on land.

Jaw

Jaws of sharks, like those of rays and skates, are not attached to the cranium. The jaw’s surface (in comparison to the shark’s vertebrae and gill arches) needs extra support due to its heavy exposure to physical stress and its need for strength. It has a layer of tiny hexagonal plates called “tesserae“, which are crystalblocks of calcium salts arranged as a mosaic.  This gives these areas much of the same strength found in the bony tissue found in other animals.

Generally sharks have only one layer of tesserae, but the jaws of large specimens, such as the bull shark, tiger shark, and the great white shark, have two to three layers or more, depending on body size. The jaws of a large great white shark may have up to five layers.  In the rostrum (snout), the cartilage can be spongy and flexible to absorb the power of impacts.

Fins

Fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling the horny keratin in hairand feathers.  Most sharks have eight fins. Sharks can only drift away from objects directly in front of them because their fins do not allow them to move in the tail-first direction.

 

What is your favorite shark and why?

Antiquity

In the Roman Empire, the first fish to be brought indoors was the sea barbel, which was kept under guest beds in small tanks made of marble. Introduction of glass panes around the year 50 allowed Romans to replace one wall of marble tanks, improving their view of the fish. In 1369, the Chinese Emperor, Hóngwǔ, established a porcelain company that produced large porcelain tubs for maintaining goldfish; over time, people produced tubs that approached the shape of modern fish bowls.  Leonhard Baldner, who wrote Vogel-, Fisch- und Tierbuch (Bird, Fish, and Animal Book) in 1666, maintained weather loaches andnewts.

Nineteenth century

In 1836, soon after his invention of the Wardian case, Dr. Nathaniel Bagshaw Ward proposed to use his tanks for tropical animals. In 1841 he did so, though only with aquatic plants and toy fish. However, he soon housed real animals. In 1838, Félix Dujardin noted owning a saltwater aquarium, though he did not use the term. In 1846, Anne Thynne maintained stony corals and seaweed for almost three years, and was credited as the creator of the first balanced marine aquarium in London.  At about the same time, Robert Warington experimented with a 13-gallon container, which contained goldfish, eelgrass, and snails, creating one of the first stable aquaria. He published his findings in 1850 in the Chemical Society’s journal.

The keeping of fish in an aquarium became a popular hobby and spread quickly. In the United Kingdom, it became popular after ornate aquaria in cast iron frames were featured at the Great Exhibition of 1851. In 1853, the first large public aquarium opened in the London Zoo and came to be known as the Fish House. Philip Henry Gosse was the first person to actually use the word “aquarium”, opting for this term (instead of “aquatic vivarium” or “aqua-vivarium”) in 1854 in his book The Aquarium: An Unveiling of the Wonders of the Deep Sea. In this book, Gosse primarily discussed saltwater aquaria. In the 1850s, the aquarium became a fad in the United Kingdom.^[10] Tank designs and techniques for maintaining water quality were developed by Warington, later cooperating with Gosse until his critical review of the tank water composition. Edward Edwards developed these glass-fronted aquaria in his 1858 patent for a “dark-water-chamber slope-back tank”, with water slowly circulating to a reservoir beneath.

Germans soon rivaled the British in their interest. In 1854, an anonymous author had two articles published about the saltwater aquaria of the United Kingdom: Die Gartenlaube(The Garden House) entitled Der Ocean auf dem Tische (The Ocean on the Table). However, in 1856, Der See im Glase (The Lake in a Glass) was published, discussing freshwater aquaria, which were much easier to maintain in landlocked areas. During the 1870s, some of the first aquarist societies were appearing in Germany.  The United States soon followed. Published in 1858, Henry D. Butler’s The Family Aquarium was one of the first books written in the United States solely about the aquarium.  According to the July issue of The North American Review of the same year, William Stimson may have owned some of the first functional aquaria, and had as many as seven or eight.  The first aquarist society in the United States was founded in New York City in 1893, followed by others.   The New York Aquarium Journal, first published in October 1876, is considered to be the world’s first aquarium magazine.

In the Victorian era in the United Kingdom, a common design for the home aquarium was a glass front with the other sides made of wood (made watertight with a pitch coating). The bottom would be made of slate and heated from below.  More advanced systems soon began to be introduced, along with tanks of glass in metal frames.  During the latter half of the 19th century, a variety of aquarium designs were explored, such as hanging the aquarium on a wall, mounting it as part of a window, or even combining it with a birdcage.

Twentieth century

Circa 1908, the first mechanical aquarium air pump was invented, powered by running water, instead of electricity.   The introduction of the air pump into the hobby is considered by several historians of the hobby to be a pivotal moment in its development.

Aquaria became more widely popular as houses had an electricity supply afterWorld War I.  Electricity allowed artificial lighting as well as aeration, filtration, and heating of the water.  Initially, amateur aquarists kept native fish (with the exception of goldfish); the availability of exotic species from overseas further increased the popularity of the aquarium.  Jugs made from a variety of materials were used to import fish from overseas, with a bicycle foot pump for aeration.  Plastic shipping bags were introduced in the 1950s, making it easier to ship fish.   The eventual availability of air freight allowed fish to be successfully imported from distant regions.  In the 1960s metal frames made marine aquaria almost impossible due to corrosion, but the development of tar and silicone sealant allowed the first all-glass aquaria made by Martin Horowitz in Los Angeles, CA. The frames remained, however, though purely for aesthetic reasons.

In the United States, as of 1996, aquarium keeping is the second-most popular hobby after stamp collecting.  In 1999 it was estimated that over nine million U.S. households own an aquarium. Figures from the 2005/2006 APPMA National Pet Owners Survey report that Americans own approximately 139 million freshwater fish and 9.6 million saltwater fish.  Estimates of the numbers of fish kept in aquaria in Germany suggest at least 36 million.  The hobby has the strongest following in Europe, Asia, and North America. In the United States, 40 percent of aquarists maintain two or more tanks.  (The Wiki)