THE OCEAN DEEP

Cuttlefish are much more closely related to garden slugs and snails than they are to fish! They belong to the same group of animals as the octopuses, squid and nautilus and like a snail they are all molluscs. Cuttlefish are unique within this group in that they have a gas filled bone within their bodies which allows them to be buoyant... you may have seen cuttlebones before, sticking out from the bars on a budgie's cage? The bone is within the body part of the animal called the mantle and attached to the mantle is a head with eight arms and two feeding tentacles. he cuttlefish is an ambush predator and a master of disguise. Its skin is covered with special cells called chromatophores, iridophores and leucophores that reflect light in many different colours enabling the cuttlefish to blend into its background almost perfectly. Some say it's like a chameleon but it is far superior in its ability to change colour and even the texture of its skin! A cuttlefish will steadily, using its camouflage, sneak up on its prey. Their preferred diet is crabs or fish, and when it is close enough it opens apart its eight arms and out shoots two deceptively long feeding tentacle. On the end of each is a pad covered in suckers that grasp hold of the prey and quickly pull it close to the cuttlefish's mouth that looks like a parrot's beak. The scientific name for a cuttlefish is Sepia. In years gone by sepia ink, which is derived from cuttlefish, was used by artists for their paintings. For the cuttlefish this ink is a decoy, a means of escape from predators. If a large fish were to attack a cuttlefish it would eject a cloud of dark brown, almost black ink towards its attacker! The predator would get a mouthful of ink that tastes nasty and coats its nostrils. Meanwhile the cuttlefish is hidden from view and propels itself away backwards by using its own jet propulsion system, its siphon.
The eggs of cuttlefish are laid in clumps together and are often coated in ink from the mother; this serves as camouflage for the eggs. They hatch at a much further developed stage than an octopus does and immediately start feeding on suitably small shrimps. Many people would like to keep cuttlefish as pets. This is quite easy in the UK and Europe as species of cuttlefish like Sepia officinalis the 'European cuttlefish' are found there.
In the USA however, there are no naturally found species and the most commonly imported species is from Bali called Sepia bandensis which is a poor traveller and normally arrives as a four-inch adult with perhaps only weeks to live. It is not recommended as a pet. One day someone will be captive breeding Sepia officinalis for the American hobby!
Cuttlebone
Cuttlefish possess an internal structure called the cuttlebone, which is porous and composed of aragonite, to provide the cuttlefish with buoyancy. Buoyancy can be regulated by changing the gas-to-liquid ratio in the chambered cuttlebone via the ventral siphuncle. Each species has a distinct shape, size, and pattern of ridges or texture on the cuttlebone. The cuttlebone is unique to cuttlefish, one of the features contrasting them with their squid relatives. Cuttlebones are traditionally used by jewelers and silversmiths as moulds for casting small objects. They are probably better known today as the tough material given to parakeets and other caged birds and snails as a source of dietary calcium
Changing color
Cuttlefish are photochromic, and are sometimes referred to as the chameleon of the sea because of their remarkable ability to rapidly alter their skin color at will. Their skin flashes a fast-changing pattern as communication to other cuttlefish and to camouflage them from predators. This color-changing function is produced by groups of red, yellow, brown, and black pigmented chromatophores above a layer of reflective iridophores and leucophores, with up to 200 of these specialized pigment cells per square millimeter. The pigmented chromatophores have a sac of pigment and a large membrane that is folded when retracted. There are 6-20 small muscle cells on the sides which can contract to squash the elastic sac into a disc against the skin. Yellow chromatophores (xanthophores) are closest to the surface of the skin, red and orange are below (erythrophores), and brown or black are just above the iridophore layer (melanophores). The iridophores reflect blue and green light. Iridophores are plates of chitin or protein, which can reflect the environment around a cuttlefish. They are responsible for the metallic blues, greens, golds, and silvers often seen on cuttlefish. All of these cells can be used in combinations. For example, orange is produced by red and yellow chromatophores, while purple can be created by a red chromatophore and an iridophore. The cuttlefish can also use an iridophore and a yellow chromatophore to produce a brighter green. As well as being able to influence the color of the light that reflects off their skin, cuttlefish can also affect the light's polarization, which can be used to signal to other marine animals, many of which can also sense polarization.
Eyes
Cuttlefish eyes are among the most developed in the animal kingdom. The organogenesis of cephalopod eyes differs fundamentally from that of vertebrates like humans. Superficial similarities between cephalopod and vertebrate eyes are thought to be examples of convergent evolution. The cuttlefish pupil is a smoothly-curving W shape. Although they cannot see color, they can perceive the polarization of light, which enhances their perception of contrast. They have two spots of concentrated sensor cells on their retina (known as fovea), one to look more forward, and one to look more backwards. The lenses, instead of being reshaped as they are in humans, are pulled around by reshaping the entire eye in order to change focus.
Scientists have speculated that cuttlefish's eyes are fully developed before birth and start observing their surroundings while still in the egg. One team of French researchers has additionally suggested that cuttlefish prefer to hunt the prey they saw before hatching.
Blood
The blood of a cuttlefish is an unusual shade of green-blue because it uses the copper-containing protein hemocyanin to carry oxygen instead of the red iron-containing protein hemoglobin that is found in mammals. The blood is pumped by three separate hearts, two of which are used for pumping blood to the cuttlefish's pair of gills (one heart for each gill), and the third for pumping blood around the rest of the body. A cuttlefish's heart must pump a higher blood flow than most other animals because hemocyanin is substantially less capable of carrying oxygen than hemoglobin.
Ink
Cuttlefish have ink, like squid and octopuses. This ink was formerly an important dye, called sepia. Today artificial dyes have replaced natural sepia. However, there is a modern resurgence of Jewish people using the ink for the techelet dye on their Tallit strings.

The gobies form the family Gobiidae, which is one of the largest families of fish, with more than 2,000 species in more than 200 genera. Most are relatively small, typically less than 10 cm (4 in) in length. Gobies include some of the smallest vertebrates in the world, like species of the genera Trimmaton and Pandaka, which are under 1 cm (3/8 in) long when fully grown. There are some large gobies, such as some species of the genera Gobioides or Periophthalmodon, that can reach over 30 cm (1 ft) in length, but that is exceptional. Although few are important as food for humans, they are of great significance as prey species for commercially important fish like cod, haddock, sea bass, and flatfish. Several gobies are also of interest as aquarium fish, such as the bumblebee gobies of the genus Brachygobius.
The most distinctive aspect of goby morphology are the fused pelvic fins that form a disc-shaped sucker. This sucker is functionally analogous to the dorsal fin sucker possessed by the remoras or the pelvic fin sucker of the lumpsuckers, but is anatomically distinct: these similarities are the product of convergent evolution. Gobies can often be seen using the sucker to adhere to rocks and corals, and in aquariums they will happily stick to glass walls of the tank as well.
Triplefin goby on a wire coral from East Timor
Gobies are primarily fish of shallow marine habitats including tide pools, coral reefs, and seagrass meadows; they are also very numerous in brackish water and estuarine habitats including the lower reaches of rivers, mangrove swamps, and salt marshes. A small number of gobies (unknown exactly, but in the low hundreds) are also fully adapted to freshwater environments. These include the Asian river gobies (Rhinogobius spp.), the Australian desert goby (Chlamydogobius eremius), and the European freshwater goby Padogobius bonelli. Most gobies feed on small invertebrates, although some of the larger species eat other fish, and a few eat planktonic algae.
Reproduction
Gobies attach their eggs to a substrate, such as vegetation, coral, or a rock surface. They can lay anything from five to a few hundred eggs, depending on species. After fertilising the eggs, the male remains to guard them predators and keep them free from detritus. The eggs hatch after a few days. The larvae are born transparent, developing their colouration after dispersing to find a suitable habitat. The larvae of many freshwater species are carried downstream to the brackish waters of estuaries, or even to the sea, and only return to fresh water weeks or months later.
Gobies in warmer waters reach adulthood in a matter of months, while those in cooler environments may take up to two years. The total lifespan of gobies varies from a single year to up to ten years, again with the temperate species generally living longer. A few species of goby are known to be able to change sex from female to male, although most do not do this. In such species, most individuals are born female, and the male must expend considerable effort in guarding the eggs of the multiple females with which he breeds.
Symbiosis
Gobies sometimes form symbiotic relationships with other species. Some goby species live in symbiosis with burrowing shrimps. The shrimp maintains a burrow in the sand in which both the shrimp and the goby fish live. The shrimp has poor eyesight compared to the goby, but if it sees or feels the goby suddenly swim into the burrow, it will follow. The goby and shrimp keep in contact with each other, the shrimp using its antennae, and the goby flicking the shrimp with its tail when alarmed. These gobies are thus sometimes known as watchmen or prawn gobies. Each party gains from this relationship: the shrimp gets a warning of approaching danger, and the goby gets a safe home and a place to lay its eggs in. Only the alpha male and female reproduce, other fish in colony eat sparingly to resist being eaten by alpha male or female. This way only the largest and fittest are able to reproduce.
Another example of symbiosis is demonstrated by the neon gobies (Elacatinus spp.). These gobies are known as "cleaner gobies", and remove parasites from the skin, fins, mouth, and gills of a wide variety of large fish. The most remarkable aspect of this symbiosis is that many of the fish that visit the gobies' cleaning station would otherwise treat such small fish as food (for example, groupers and snappers). Again, this is a relationship where both parties gain: the gobies get a continual supply of food as bigger fish visit their cleaning stations, and the bigger fish leave the cleaning stations healthier than they were when they arrived.

Coelacanth, adaptation of Modern Latin Cœlacanthus: cœl-us + acanth-us from Greek κοῖλ-ος [hollow] + ἄκανθ-α [spine]) is the common name for an order of fish that includes the oldest living lineage of gnathostomata known to date. The coelacanths, which are related to lungfishes and tetrapods, were believed to have been extinct since the end of the Cretaceous period, until the first Latimeria specimen was found off the east coast of South Africa, off the Chalumna River in 1938. They are, therefore, a Lazarus taxon. Since 1938, Latimeria chalumnae have been found in the Comoros, Kenya, Tanzania, Mozambique, Madagascar, and in iSimangaliso Wetland Park, Kwazulu-Natal in South Africa. The second extant species, L. menadoensis, was described from Sulawesi, Indonesia in 1999. The coelacanth has no real commercial value, apart from being coveted by museums and private collectors. As a food fish the coelacanth is almost worthless as its tissues exude oils even when dead, imparting the tough flesh with a foul flavour.
An amazing discovery
A few days before Christmas in 1938, a Coelacanth was caught at the mouth of the Chalumna River on the east coast of South Africa. The fish was caught in a shark gill net by Captain Goosen and his crew, who had no idea of the significance of their find. They thought the fish was bizarre enough to alert the local museum in the small South African town of East London.
The Director of the East London Museum at the time was Miss Marjorie Courtney-Latimer. She alerted the prominent south African ichthyologist Dr J.L.B. Smith to this amazing discovery. The Coelacanth was eventually named (scientific name: Latimeria chalumnae) in honour of Miss Courtney-Latimer.
This Coelacanth specimen led to the discovery of the first documented population, off the Comoros Islands, between Africa and Madagascar. For sixty years this was presumed to be the only Coelacanth population in existence.
Zanzibar Coelacanth
On 14th July 2007, a Coelacanth was caught by fishermen off Nungwi, Northern Zanzibar. Researchers from the Institute of Marine Sciences, Zanzibar (IMS) led by Dr Narriman Jiddawi were contacted and arrived on site to identify the fish as Latimeria chalumnae.
In 2003 the IMS joined efforts with the African Coelacanth Project (ACEP) programme to search for Coelacanths. On 6th September 2003 the first coelacanth was caught in the southern part of Tanzania at Songo Mnara making Tanzania the 6th country to record the presence of the L. chalumnae. Since then, 35 coelacanths have been recorded in Tanzania ranging from Tanga in the north, south to Mtwara. The Nungwi specimen is the 36th coelacanth to be caught in Tanzania and the first for Zanzibar.
Narriman Jiddawi is acknowledged for providing this information and the image.
Sulawesi Coelacanth
On July 30 1998, a Coelacanth was caught in a deep-water shark net by local fishers off the volcanic island of Manado Tua in northern Sulawesi, Indonesia. This is about 10 000 km east of the Western Indian Ocean Coelacanth population. The fisher brought the fish to the house of American biologist Mark Erdmann who along with his wife Arnaz had seen a specimen in the outdoor markets the previous September. The local people were familiar with the Coelacanth and called it raja laut or 'king of the sea'.
When the Coelacanth from Sulawesi was first documented, the only obvious difference between it and the Coelacanth from the Comoros Islands was the colour. The Comoros Coelacanth is renowned for its steel blue colour, whereas fish from the Sulawesi population were reported to be brown. In 1999 the Sulawesi Coelacanth was described as a new species, Latimeria menadoensis by Pouyaud, Wirjoatmodjo, Rachmatika, Tjakrawidjaja, Hadiaty and Hadie.
The discovery of a new species of Coelacanth in Sulawesi, opens up the possibility that Coelacanths may be more widespread and abundant than was previously assumed.
Living fossil
The Coelacanth specimen caught in 1938 is still considered to be the zoological find of the century. This 'living fossil' comes from a lineage of fishes that was thought to have been extinct since the time of the dinosaurs.
Coelacanths are known from the fossil record dating back over 360 million years, with a peak in abundance about 240 million years ago. Before 1938 they were believed to have become extinct approximately 80 million years ago, when they disappeared from the fossil record.
How could Coelacanths disappear for over 80 million years and then turn up alive and well in the twentieth century? The answer seems to be that the Coelacanths from the fossil record lived in environments favouring fossilisation. Modern Coelacanths, both in the Comoros and Sulawesi were found in environments that do not favour fossil formation. They inhabit caves and overhangs in near vertical marine reefs, at about 200 m depth, off newly formed volcanic islands.
The discovery by science of the Coelacanth in 1938 caused so much excitement because at that time Coelacanths were thought to be the ancestors of the tetrapods (land-living animals, including humans). It is now believed that Lungfishes are the closest living relative of tetrapods. The Coelacanth may still provide answers to some very interesting evolutionary questions.
Coelacanth characteristics
Coelacanths are quite different from all other living fishes. They have an extra lobe on the tail (see bottom image), paired lobed fins, and a vertebral column that is not fully developed. Coelacanths are the only living animals to have a fully functional intercranial joint, which is a division separating the ear and brain from the nasal organs and eye. The intercranial joint allows the front part of the head to be lifted when the fish is feeding. One of the most interesting features of the Coelacanth, is that it has paired fins which move in a similar fashion to our arms and legs.
The Australian Museum Coelacanth
The Australian Museum collection contains one Coelacanth specimen (AMS IB.7555). It was captured off the Comoros Islands, and purchased by the Trustees of the Australian Museum in 1965. The fish was transported to the Western Australian Museum by the US RV Atlantis, where it starred briefly in the Perth media. It was then sent by air to the Australian Museum. Once on display it became affectionately known as the 'wishing fish'. Visitors dropped coins through a small crack in the holding case of the tank and made a wish. Unfortunately after a time the coins discoloured the liquid in the tank, and the practice was stopped. The Coelacanth has been on display in several different exhibitions.