Cuttlefish

Cuttlefish

Cuttlefish or cuttles^[1] are marineanimals of the order Sepiida. They belong to the class Cephalopoda, which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone. Despite their name, cuttlefish are not fish but molluscs.

CuttlefishScientific classificationKingdom:AnimaliaPhylum:MolluscaClass:CephalopodaSuperorder:DecapodiformesOrder:Sepiida
Zittel, 1895Suborders and Families†Vasseuriina†Vasseuriidae†BelosepiellidaeSepiina†BelosaepiidaeSepiadariidaeSepiidae

Cuttlefish have large, W-shaped pupils, eight arms, and two tentacles furnished with denticulated suckers, with which they secure their prey. They generally range in size from 15 to 25 cm (6 to 10 in), with the largest species, Sepia apama, reaching 50 cm (20 in) in mantlelength and over 10.5 kg (23 lb) in mass.^[2]

Cuttlefish eat small molluscs, crabs, shrimp, fish, octopus, worms, and other cuttlefish. Their predators include dolphins, sharks, fish, seals, seabirds, and other cuttlefish. The average life expectancy of a cuttlefish is about one to two years. Recent studies indicate cuttlefish are among the most intelligentinvertebrates.^[3] Cuttlefish also have one of the largest brain-to-body size ratios of all invertebrates.^[3]

The 'cuttle' in 'cuttlefish' comes from the Old English name for the species, cudele, which may be cognate with the Old Norse koddi ('cushion') and the Middle Low German Kudel ('rag').^[4] The Greco-Roman world valued the cuttlefish as a source of the unique brown pigment the creature releases from its siphon when it is alarmed. The word for it in both Greek and Latin, sepia, now refers to a brown pigment in English.

Range and habitatEdit

S. mestus swimming (Australia)

The family Sepiidae, which contains all cuttlefish, inhabit tropical/temperate ocean waters. They are mostly shallow-water animals, although they are known to go to depths of about 600 m (2,000 ft).^[5] They have an unusual biogeographic pattern: they are present along the coasts of East and South Asia, Western Europe, and the Mediterranean, as well as all coasts of Africa and Australia but are totally absent from the Americas. By the time the family evolved, ostensibly in the Old World, the North Atlantic possibly had become too cold and deep for these warm-water species to cross.^[6] The common cuttlefish (Sepia officinalis), is found in the Mediterranean, and North and Baltic Seas, although it has been suggested populations occur as far south as South Africa. They are found in sublittoral depths, between the low tide line and the edge of the continental shelf, to about 180 m (100 fathoms)."^[7] The cuttlefish is listed under the Red List category of "Least Concern" by the IUCN Red List of Threatened Species. This means that while there has been some over-exploitation of the marine animal in some regions due to large-scale commercial fishing, their wide geographic range prevents them from being too threatened. Ocean acidification, however, caused largely by higher levels of carbon dioxide emitted into the atmosphere, is cited as a potential threat.^[8]

Anatomy and physiologyEdit

CuttleboneEdit

Main article: Cuttlebone

Top and bottom view of a cuttlebone, the buoyancy organ and internal shell of a cuttlefish

Cuttlefish possess an internal structure called the cuttlebone, which is porous and is made of aragonite. The pores provide it with buoyancy, which the cuttlefish regulates by changing the gas-to-liquid ratio in the chambered cuttlebone via the ventral siphuncle.^[9]Each species' cuttlebone has a distinct shape, size, and pattern of ridges or texture. The cuttlebone is unique to cuttlefish, and is one of the features that distinguish them from their squid relatives. Jewellers and silversmiths traditionally use cuttlebones as moulds for casting small objects,^[10] but they are probably better known as the tough material given to parakeets and other caged birds as a source of dietary calcium.

EyesEdit

The characteristic W-shape of the cuttlefish eye

Play media

Pupil expansion in Sepia officinalis

Cuttlefish, like other cephalopods, have sophisticated eyes. The organogenesisand the final structure of the cephalopod eye fundamentally differ from those of vertebrates such as humans.^[11]Superficial similarities between cephalopod and vertebrate eyes are thought to be examples of convergent evolution. The cuttlefish pupil is a smoothly curving W-shape.^[12][13]Although cuttlefish cannot see color,^[14]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 foveae), one to look more forward, and one to look more backward. The eye changes focus by shifting the position of the entire lens with respect to the retina, instead of reshaping the lens as in mammals. Unlike the vertebrate eye, there is no blind spot, because the optic nerve is positioned behind the retina.

It has been speculated that cuttlefish's eyes are fully developed before birth, and that they start observing their surroundings while still in the egg. In consequence they may prefer to hunt the prey they saw before hatching.^[15]

SuckersEdit

The suckers of cuttlefish extend most of the length of their arms and along the distal portion of their tentacles.

CirculationEdit

The blood of a cuttlefish is an unusual shade of green-blue because it uses the copper-containing protein haemocyaninto carry oxygen instead of the red, iron-containing protein haemoglobin found in vertebrates' blood. The blood is pumped by three separate hearts: two branchial hearts pump blood to the cuttlefish's pair of gills (one heart for each), and the third pumps blood around the rest of the body. Cuttlefish blood must flow more rapidly than that of most other animals because haemocyanin carries substantially less oxygen than haemoglobin.

InkEdit

See also: Cephalopod ink

Cuttlefish have ink, like squid and octopus species, which they use to help evade predators.^{[citation needed]} This ink is stored inside an ink sac.

Venomosity and toxicityEdit

Some cuttlefish are venomous. The genes for venom production are thought to be descended from a common ancestor.^[16]

The muscles of the flamboyant cuttlefish (Metasepia pfefferi) contain a highly toxic, unidentified compound^[3] as lethal as that of a fellow cephalopod, the blue-ringed octopus.^[17]

ReproductionEdit

Interacting cuttlefish

Male cuttlefish challenge one another for dominance and the best den during mating season. During this challenge, no direct contact is usually made. The animals threaten each other until one of them backs down and swims away. Eventually, the larger male cuttlefish mate with the females by grabbing them with their tentacles, turning the female so that the two animals are face-to-face, then using a specialized tentacle to insert sperm sacs into an opening near the female's mouth. The male then guards the female until she lays the eggs a few hours later.^[18]

On occasion, a large competitor arrives to threaten the male cuttlefish. In these instances, the male will first attempt to intimidate the other fish. If the competitor does not flee, the male will eventually attack it to force it away, and the confrontation turns physical. The cuttlefish that can paralyze the other first, by forcing near its mouth, wins the fight and the female. Since there are, on average, four or five ( and sometimes as many as ten) males for every female, this kind of behavior is inevitable.^[19]

Cuttlefish are indeterminate growers, so smaller cuttlefish always have a chance at finding a mate the next year, when they are bigger.^[20] Additionally, cuttlefish unable to win in a direct confrontation with a guard male have been observed employing several other tactics to acquire a mate. The most successful of these methods is camouflage; smaller cuttlefish will use their camouflage abilities to disguise themselves as a female cuttlefish. Changing their body color, concealing their extra arms (males have four pairs, females only have three), and even pretending to be holding an egg sack, disguised males are able to swim past the larger guard male and mate with the female.^[19][21][22]

CommunicationEdit

Cephalopods are remarkable for how quickly and diversely they can communicate visually. To produce these signals, cephalopods can vary four types of communication element: chromatic (skin coloration), skin texture (e.g. rough or smooth), posture and locomotion. Changes in body appearance such as these is sometimes called polyphenism. The common cuttlefish can display 34 chromatic, six textural, eight postural and six locomotor elements, whereas flamboyant cuttlefish use between 42 and 75 chromatic, seven textural, 14 postural, and seven locomotor elements. For the Caribbean reef squid(Sepioteuthis sepioidea), it is thought they have a "language" with up to 35 distinct signalling states, i.e. "words".^[23][24]

Visual signals of the common cuttlefish^[23]Chromic - lightChromic - darkTexturePostureLocomotorWhite posterior triangleAnterior transverse mantle lineSmooth skinRaised armsSittingWhite squarePosterior transverse mantle lineCoarse skinWaving armsBottom suctionWhite mantle barAnterior mantle barPapillate skinSplayed armsBuriedWhite lateral stripePosterior mantle barWrinkled first armsDrooping armsHoveringWhite fin spotsPaired mantle spotsWhite square papillaeExtended 4th armJettingWhite fin lineMedian mantle stripeMajor lateral papillaeFlattened bodyInkingWhite neck spotsMantle margin stripeRaised headIridescent ventral mantleMantle margin scallopingFlanged finWhite zebra bandsDark fin lineWhite landmark spotsBlack zebra bandsWhite splotchesMottleWhite major lateral papillaeLatero-ventral patchesWhite head barAnterior head barWhite arm trianglePosterior head barPink iridophore arm stripesPupilWhite arms spots (males only)Eye ringDark arm stripesDark arms

ChromaticEdit

This broadclub cuttlefish (Sepia latimanus) can change from camouflage tans and browns (top) to yellow with dark highlights (bottom) in less than one second.

Cuttlefish are sometimes referred to as the "chameleons of the sea" because of their remarkable ability to rapidly alter their skin color – this can occur within one second. Cuttlefish change color and pattern (including the polarization of the reflected light waves), and the shape of the skin to communicate to other cuttlefish, to camouflage themselves, and as a deimatic display to warn off potential predators. Under some circumstances, cuttlefish can be trained to change color in response to stimuli, thereby indicating their color changing is not completely innate.^[25]

As well as being able to influence the color of light as it 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.^[26] It has been suggested that although cuttlefish (and most other cephalopods) lack color vision, high-resolution polarisation vision may provide an alternative mode of receiving contrast information that is just as defined.^[27]

There are three broad categories of color patterns - Uniform, Mottle and Disruptive.^[28] Some researchers have suggested that cuttlefish can display 12 to 14 patterns,^[23] 13 of which have been categorized as 7 "acute" (relatively brief) and 6 "chronic" (long-lasting) patterns.^[29] although other researchers suggest the patterns occur on a continuum.^[28]

Patterns of the common cuttlefish^[23]ChronicAcuteUniform lightUniform blanchingStippleUniform darkeningLight mottleAcute disruptiveDisruptiveDeimaticDark mottleFlamboyantWeak zebraIntense zebraPassing cloud

The color-changing ability of cuttlefish is due to multiple types of cell. These are arranged (from the skin's surface going deeper) as pigmented chromatophoresabove a layer of reflective iridophoresand below them, leucophores.^[30][31]

ChromatophoresEdit

The chromatophores are a sac containing hundreds of thousands of pigment granules and a large membrane that is folded when retracted. There are hundreds of muscles radiating from the chromatophore. These are under neural control and when they expand, they reveal the hue of the pigment contained in the sac. Cuttlefish have three types of chromatophore; yellow/orange (the uppermost layer), red, brown/black (the deepest layer). The cuttlefish can control the contraction and relaxation of the muscles around individual chromatophores, thereby opening or closing the elastic sacs and allowing different levels of pigment to be exposed.^[24] Furthermore, the chromatophores contain luminescent protein nanostructures; there are tethered pigment granules which modify light through absorbance, reflection, and fluorescence between 650 and 720 nm.^[32][33]

For cephalopods in general, the hues of the pigment granules are relatively constant within a species but can vary slightly between species. For example, the common cuttlefish and the opalescent inshore squid (Loligo opalescens) have yellow, red and brown, the European common squid (Alloteuthis subulata) has yellow and red and the common octopus has yellow, orange, red, brown and black.^[24]

In cuttlefish, activation of a chromatophore can expand its surface area by 500%. There may be up to 200 chromatophores per mm² of skin. In Loligo plei, an expanded chromatophore may be up to 1.5 mm in diameter, but when retracted, it can measure as little as 0.1mm.^[32][34][35]

IridophoresEdit

Retracting the chromatophores reveals the iridophores and leucophoresbeneath them, thereby allowing cuttlefish to use another modality of visual signalling brought about by structural coloration.

Iridophores are structures that produce iridescent colors with a metallic sheen. They reflect light using plates of crystalline chemochromes made from guanine. When illuminated, they reflect iridescent colors because of the diffraction of light within the stacked plates. Orientation of the schemochrome determines the nature of the color observed. By using biochromes as colored filters, iridophores create an optical effect known as Tyndall or Rayleigh scattering, producing bright blue or blue-green colors. Iridophores vary in size but are generally smaller than 1 mm. It has been shown that squid at least are able to change their iridescence. This takes several seconds or minutes and the mechanism is not understood.^[36]However, iridescence can also be altered by expanding and retracting the chromatophores above the iridophores. Because chromatophores are under direct neural control from the brain, this effect can be immediate.

Cephalopod iridophores polarize light. Cephalopods have a rhabdomeric visual system which means they are visually sensitive to polarized light. Cuttlefish use their polarization vision when hunting for silvery fish (their scales polarize light). Female cuttlefish exhibit a greater number of polarized light displays than males and also alter their behavior when responding to polarized patterns. The use of polarized reflective patterns has led some to suggest that cephalopods may communicate intraspecifically in a mode that is "hidden" or "private" because many of their predators are insensitive to polarized light.^[36][37][35]

LeucophoresEdit

The white spots and bands on this cuttlefish are produced by leucophores.

Leucophores, usually located deeper in the skin than iridophores, are also structural reflectors utilizing crystalline purines, often guanine, to reflect light. Unlike iridophores, however, leucophores have more organized crystals that reduce diffraction. Given a source of white light, they produce a white shine, in red they produce red and in blue they produce blue. Leucophores assist in camouflage by providing light areas during background matching (e.g. by resembling light-colored objects in the environment) and disruptive coloration (by making the body appear to be composed of high-contrasting patches).^[36]

The reflectance spectra of cuttlefish patterns and several natural substrates (stipple, mottle, disruptive) can be measured using an optic spectrometer.^[36]

Intraspecific communicationEdit

Cuttlefish sometimes use their color patterns to signal future intent to other cuttlefish. For example, during agonistic encounters, male cuttlefish adopt a pattern called the Intense Zebra Pattern, considered to be an honest signal. If a male is intending to attack, it adopts a "dark face" change, otherwise, it remains pale.^[38]

Females react to other females and their own reflection in a mirror with a display called Splotch. However, they do not use this display in response to males, inanimate objects or prey. This indicates they are able to discriminate same-sex conspecifics, which is noteworthy because humans are unable to make the same discrimination.^[39]

Female cuttlefish signal their receptivity to mating using a display called Precopulatory Grey.^[39] Male cuttlefish sometimes use deception toward guarding males to mate with females. Small males hide their sexually dimorphic fourth arms, change their skin pattern to the mottled appearance of females, and change the shape of their arms to mimic those of non-receptive, egg-laying females.^[22]

Displays on one side of a cuttlefish can be independent of the other side of the body; males can display courtship signals to females on one side while simultaneously showing female-like displays with the other side to stop rival males interfering with their courtship.^[40]

Interspecific communicationEdit

The Deimatic Display (a rapid change to black and white with dark ‘eyespots’ and contour, and spreading of the body and fins) is used to startle small fish that are unlikely to predate the cuttlefish, but use the Flamboyant Display towards larger, more dangerous fish^[41] and give no display at all to chemosensory predators such as crabs and dogfish.^[42]

One dynamic pattern shown by cuttlefish is dark mottled waves apparently repeatedly moving down the body of the animals. This has been called the Passing Cloud pattern. In the common cuttlefish, this is primarily observed during hunting and is thought to communicate to potential prey – “stop and watch me”^[24] – which some have interpreted as a type of "hypnosis".

CrypsisEdit

Further information: Camouflage and Animal coloration

Juvenile cuttlefish camouflaged against the seafloor

External video Kings of Camouflage

– Nova documentary

Cuttlefish ^[43] are able to rapidly change the color of their skin^[42] to match their surroundings and create chromatically complex patterns, despite their inability to perceive color, through some mechanism which is not completely understood.^[43] They have been seen to have the ability to assess their surroundings and match the color, contrast and texture of the substrate even in nearly total darkness.^[34]

The color variations in the mimicked substrate and animal skin are very similar. Depending on the species, the skin of cuttlefish responds to substrate changes in distinctive ways. By changing naturalistic backgrounds, the camouflage responses of different species can be measured.^[44] Sepia officinalis changes color to match the substrate by disruptive patterning (contrast to break up the outline), where as S. pharanonis matches the substrate by blending in. Although camouflage is achieved in different ways, and in an absence of color vision, both species change their skin colors to match the substrate. Cuttlefish adapt their own camouflage pattern in ways that are very specific for a particular habitat. An animal could settle in the sand and appear one way, with another animal a few feet away in a slightly different microhabitat, settled in algae for example, will be camouflaged quite differently.^[34]

Cuttlefish are also able to change the texture of their skin. The skin contains bands of circular muscle which as they contract, push fluid up. These can be seen as little spikes, bumps or flat blades. This can help with camouflage when the cuttlefish becomes visually similar to objects in its environment such as kelp or rocks.^[34]

DietEdit

Play media

Video of S. mestus in Sydney waters, hunting and catching prey

While the preferred diet of cuttlefish is crabs and fish, they feed on small shrimp shortly after hatching.^[45]

Cuttlefish use their camouflage to hunt and sneak up on their prey.^[46] They swim at the bottom, where shrimp and crabs are found and shoot out a jet of water to uncover the prey buried in the sand. Then when the prey tries to escape, the cuttlefish open their eight arms and shoot out two long feeding tentacles to grab them. Each arm has a pad covered in suckers which grabs and pulls prey toward its beak, paralyzing it with venom before eating it.^[45] In order to achieve a hypnotic effect and stun prey before catching them, cuttlefish are also known to change color rapidly.^{[citation needed]}

TaxonomyEdit

Wikispecies has information related to: Sepiida

Play media

Video of a cuttlefish in its natural habitat

Over 120 species of cuttlefish are currently recognised, grouped into five genera. Sepiadariidae contains seven species and two genera; all the rest are in Sepiidae.

Class CephalopodaSubclass Nautiloidea: nautilusSubclass Coleoidea: squid, octopus, cuttlefishSuperorder OctopodiformesSuperorder DecapodiformesOrder BoletzkyidaOrder Spirulida: Ram's horn squidOrder Sepiida: cuttlefishSuborder VasseuriinaFamily VasseuriidaeFamily BelosepiellidaeSuborder SepiinaFamily BelosaepiidaeFamily SepiadariidaeFamily SepiidaeOrder Sepiolida: bobtail squidOrder Teuthida: squid

The common cuttlefish (Sepia officinalis) is the best-known cuttlefish species

The giant cuttlefish, (Sepia apama) is the largest cuttlefish species

Hooded cuttlefish (Sepia prashadi)

Engravings by the Dutch zoologist Albertus Seba, 1665–1https://en.m.wikipedia.org/wiki/Cuttlefish

Sponge

Porifera

PoriferaAplysina fistularis (Spons tabung kuning)Klasifikasi ilmiahKingdom:AnimaliaFilum:Porifera
Grant in Todd, 1836Kelas†Archaeocyathida * Calcarea(Calcarea) * Hexactinellida(Hexactinellida) * Demospongiae(Demospongiae) * Sclerospongiae(Sclerospongiae)

Porifera (Latin:"berpori") atau Sponsadalah organisme multiseluler, yang mempunyai banyak pori sehingga air dapat melewatinya. Tubuh mereka terdiri dari mesohil yang diapit dua lapisan tipis sel. Spons memiliki sel yang tak terspesialisasi (tdk memiliki tugas khusus) dan dapat berubah menjadi tipe sel lain serta dapat berpindah antara lapisan sel utama dan mesohil. Spons tidak memiliki sistem saraf, pencernaan maupun sistem peredaran darah. Sebaliknya, sebagian besar mengandalkan aliran air melalui pori-pori tubuh mereka untuk mendapatkan makanan dan oksigen dan untuk membuang limbah.

Gambaran umum

Struktur tubuh

KlasifikasiSunting

Euplectella aspergillum , contoh spons kaca

Spons dapat dibagi berdasarkan struktur rangkanya^[3]:

Calcarea : Disebut juga spons kapur, karakteristiknya adalah spikula yang terbuat dari kalsium karbonat dalam bentuk mineral kalsit dan aragonit.Hexactinellida : Disebut juga spons kaca, karakteristiknya adalah spikula yang tersusun dari silika (kaca).Demospongiae: 80% dari semua spons di dunia merupakan anggota kelas ini, rangkanya terbuat spikula dan benang spongin.Homoscleromorpha: Sebelumnya bagian dari Demospongiae, tetapi baru-baru ini diakui sebagai kelas tersendiri, tidak ada perbedaan mendasar dengan demospongia, tetapi hanya berbeda secara genetik

Dalam berbagai buku pelajaran, Sclerospongia (spons karang) masih dianggap sebagai kelas tersendiri karena karakteristiknya yang berbeda dengan spons lainnya, yaitu memiliki rangka luar dari kalsium karbonat sehingga bentuknya mirip karang seperti namanya, akan tetapi secara genetik Sclerospongia dapat dimasukkan dalam Calcarea atau Hexactinellida.

Fungsi vital

Ekologi

Peran Porifera dalam kehidupanhttps://id.m.wikipedia.org/wiki/Porifera#/editor/2

Flamboyant cuttlefish

The Flamboyant Cuttlefish (Metasepia pfefferi)

by Lauren Siba & Sascha Janson, July 03, 2014

 

 

Geographic Range:

Metasepia pfefferi is a cephalopod commonly known as the flamboyant cuttlefish (sometimes abbreviated to ‘flambo’). It is found in tropical South-East Asia (Indonesia, Malaysia, PNG and northern Australia). There is one other similar cuttlefish in the genus, Metasepia tullbergi or ‘paint-pot cuttlefish’, which is found from Hong Kong to southern Japan.

Environment:

Flambos are benthic or bottom-dwelling creatures and prefer mud, sand or coral rubble substrates, at a range of depths from 3m+.

Skin and colouration

Like many cephalopods, the appearance of the flamboyant is highly variable (and beautiful) thanks to a sophisticated system involving chromatophores, iridophores and leucophores, which allow for instantaneous appearance changes. 
Flambos can be camouflaged to match their surroundings or flash yellow, pink, purple, black & white in a rippling pattern. They can change both the colour and texture of their skin. Check out this link if you want to know more about how cephalopods change colour.
Bright colours can indicate fear but also excitement when hunting and probably also serve as means of communication between mates as well as to warn predators that they are toxic. At the moment when a flambo catches something to eat, it often flashes bright colours, perhaps as an expression of its delight.
Despite their beautiful colours and astounding ability to change their skin tone to blend in with their surroundings, it is thought that flamboyant cuttlefish, along with most other cephalopods, are colour-blind.

Size:

Males are much smaller than females. Females reach a maximum length of about 10 cm, compared to males which are usually 4-6cm long. Newborns are about 1cm long (3/8 inch) and are immediately able to hunt, walk, squirt ink, etc.
Their growth is rapid and they reach adult size approximately 4-6 months after hatching.

 

Male (left - about 3cm) and female (right - about 10cm) moments before mating

 

Morphology

In the middle of eight arms, there is a small beak, which cuttlefish use to break open the shells of mollusks, crabs, and other crustaceans. 
Like all cuttlefish, they also have two longer tentacles, whose ends are called tentacle clubs.  Tentacle clubs have flat surfaces with suckers, 3-4 of which are large and located in the centre of the clubs. They use these two elongated tentacles to grab their prey and they work in tandem, appearing to the casual observer like one unit.

 

Flambo feeding on a fish

 

In this picture the two tentacles are clearly visible

 

close-up of a tentacle club

Like all cephalopods, they have 3 hearts; one pumps blue blood throughout the body, and the other two, called branchial hearts, pump blood to the gills where they absorb oxygen as water flows into the mantle. This water is then pushed out of a tube called the siphon.

 

Diet:

They eat crustaceans and bony fishes and are formidable hunters. They need to eat a lot to sustain their rapid growth, and later, to provide energy for egg production. 
Once the tentacles have caught something and the cuttlefish has its prey firmly in its arms, the prey is brought to a beak-like mouth and a rasping tongue called a radula, both of which help reduce the prey to an appropriate size to be eaten.  Reducing the food size is critical because the esophagus runs through the middle of the cuttlefish’s ring-shaped brain; swallowing something too big might damage the brain.

 

Flambo hunting a small fish (tentacle clubs appear to be one unit)

Lifespan:

Like most cephalopods, they are short-lived and have a lifespan of about a year in captivity. Although we don’t know for sure, it is probably similar in the wild based on research on other small cephalopods.

Reproduction:

According to studies done at Monterey Bay Aquarium by Bret Grasse on aquarium-raised individuals, sexual maturity is reached at around 3 months and females begin laying eggs aged about four months. The older females lay larger clutches of eggs. Males have a modified left ventral (lower) arm called a hectocotylus for holding and transferring spermatophores. The male transfers sperm into the female’s buccal cavity and they mate head-to-head. The female takes the sperm with her arms and wipes them onto her eggs in order to fertilize them. She will then find a place to lay eggs, doing so one by one. They prefer to hide the eggs under coral, shells, rocks or on the underside of empty coconut halves. The eggs are initially opaque, white and round and become larger and more transparent as they develop. With immature embryos you can see the attached yolk sac (see photo), and if you are lucky enough to find embryos which are almost ready to hatch, you can even see them change colour.

 

Flambo with yolk sack (the chromatophores are already clearly visible)

 

Flambos changing colour just before hatching

 

Flambos changing colour while hatching

The incubation period usually takes between 3 to 4 weeks with an average of 25 days. 
Flamboyant cuttlefish are polyandrous meaning the females usually mate with more than one male. One study (Metasepia pfefferi was not used in this study, but results may be similar) suggests that female dumpling squid which mated with more than one male had more offspring and larger, healthier offspring. Click here to find out more about this study)

 

We once had the honour of witnessing flamboyant cuttlefish courtship and mating. We first saw a large female and then located a male a few meters away. At first he seemed unaware of her presence and was walking slowly but suddenly he sensed the female and rushed directly over to her, flashing alternately white and bright colours. She seemed amenable and without much preamble, they quickly mated several times, each time lasting a short duration of just a second or two. After this, she ambled off to find a place to lay her eggs and started doing this immediately. She took several minutes to lay each egg individually, in this case on the underside of a shell.

 

Flambos mating. See the difference in size between female (left) and male (right)

 

Flambos mating. See the difference in size between female (left) and male (right)

 

Female flambo placing an egg under a shell

 

New eggs, no shape of flambo yet

Defense:

Flambos, like other cephalopods, can produce a small, thick ink cloud when threatened to confuse predators. If this happens in response to you taking photos, back off - it means the animal is highly stressed.
It is widely believed that flamboyant have poisonous or toxic flesh, and if this is the case, its bright colours may serve as a warning to potential predators. However, to date, there are no scientific studies or evidence to prove this theory. Nonetheless, it is wise to exercise caution and never allow a flambo to touch your skin or bite you.

Predators:

Unknown. I have not been able to find any references to what their predators in the wild are. I have never seen anything attack an adult, and even when I questioned some of Lembeh's most experienced guides with many thousands of dives each, none of them had ever witnessed an attack on an adult. We have however personally observed hermit crabs and sea snails eating flamboyant cuttlefish eggs.

Movement/Locomotion:

Unlike most cuttlefish, they walk along the bottom using two arms and specially adapted flaps on the bottom of their mantle instead of swimming. This is because Metasepia pfefferi has a smaller than normal cuttlebone. All cuttlefish have a cuttlebone made of calcium carbonate containing several chambers the cuttlefish can empty or fill with gas in order to adjust its buoyancy. Because the flamboyant has a small cuttlebone, they find it more difficult to adjust their buoyancy and cannot swim long distances.

 

Flambo "walking"

Behaviour:

Flambos are active during the day and are effective hunters. If you are patient, you can easily watch an individual capture and eat several ‘meals’ within a relatively short period of time.
They are solitary animals and only seem to associate with others of their species in order to mate, similar to octopuses.

Photography tips:

The best lens to use is the 60mm macro as some of the females get quite big, so you can still get fairly close to the subject to avoid backscatter and particles between the lens and the flambo. For shooting baby flambos and eggs, we would recommend using the 100mm/105mm to give you a little more working distance (for getting the tiny babies you might consider an extra diopter like SubSee/SMC), or stick to the 60mm and shoot the whole coconut half or the whole coral with the eggs attached.

These animals are relatively unafraid of divers and if given a bit of space and are not harassed, they can be observed, photographed and videoed engaging in fascinating natural behaviours such as hunting, mating and laying eggs. Avoid stressing the animal by forcing it to flash colours with hand movements, and discourage your guide from doing so too, and you will be rewarded with fascinating glimpses into this most beautiful animal’s life. If they are stressed they just freeze and don't do anything (they only flash the color for a few seconds), but once they start hunting, they often hunt several fishes/shrimps in a row and observing/photographing/videoing this behaviour is much more rewarding than just getting a shot of the nice colours (btw, they often show their colours just moments before striking to distract their pray). The bigger females are usually more camouflaged and not as photogenic as the smaller individuals, so especially there it's even more crucial to be patient and get a behaviour shot. The most colourful ones are the newborns, they look just like a very nice candy :-).

 

A juvenile flambo (2cm) feeding

 

Flambo close-up. Note the beautiful colours.

 

Watch this movie about the flamboyant cuttlefish

The Flamboyant Cuttlefish (Metasepia pfefferi) from uw-pix.com on Vimeo.

 

 

References:

animaldiversity
reefsmagazine.com
marinebio.org 
advancedaquarist.com 
science20.com
plosone.org
Columbuszoo.org

 

This article was researched at Lembeh Resort, all photos and videos where taken while diving with Critters@Lembeh.http://uw-pix.com/articles/flambo.html

Spanish dancer nudibranch

Hexabranchus sanguineus
(Ruppell & Leuckart, 1828)

Order:NUDIBRANCHIA
Suborder:DORIDINA
Family:Hexabranchidae

DISTRIBUTION

Tropical Indo-West Pacific

PHOTO

UPPER RIGHT: Colour forms from Philippines (upper) and Red Sea (lower). PHOTOS: Erwin Koehler.
BELOW: Yellow colour form, right photo showing start of swimming sequence. Fungu Yasin, Dar es Salaam, Tanzania, February 1979. PHOTOS: Bill Rudman.

The species was first described from the Red Sea and based on a red colour form. The mottled form (Philippines photo) is the most common colour form, although yellow animals have been reported from Hawaii and here from Tanzania. Thanks to Erwin Koehler for the upper two photos. Apart from being able to swim, Hexabranchus is an unusual member of the Superfamily Eudoridoidea in that its gills do not have a gill pouch into which the gills can retract. Also each gill is inserted separately into the body wall. Hexabranchus sanguineus is one of the largest of all nudibranchs with animals being recorded at over 40cm in length. See Wayne Ellis' photo of an animal swimming.

See References on biology and natural history.
See Hexabranchus sanguineusPage 2.

Authorship details
Rudman, W.B., 1999 (March 31) Hexabranchus sanguineus (Ruppell & Leuckart, 1828). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/hexasang

Related messages

Hexabranchus sanguineus from Pemba

November 20, 2002
From: Paul Young

Dear Bill,
Here is another nudibranch that Charlotte and I found at Pemba Island, off the coast of Tanzania, western Indian Ocean, in November/December 2001. This one was seen on 1 December. It was from the west coast of Pemba where we dived with the Fundu Lagoon Resort to small nearby islands. Night dive
Best wishes,
Paul Young

young@underwater.org

Young, P., 2002 (Nov 20) Hexabranchus sanguineus from Pemba. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/8417

Napoleon wrasse

Ikan Napoleon

Ikan NapoleonIkan NapoleonStatus konservasi

Terancam (IUCN 2.3)

Klasifikasi ilmiahKingdom:AnimaliaFilum:ChordataKelas:ActinopterygiiOrdo:PerciformesFamili:LabridaeGenus:CheilinusSpesies:C. undulatusNama binomialCheilinus undulatus'
(Rüppell, 1835)

Ikan Napoleon atau Ikan Napoleon Wrasse (Cheilinus undulatus) merupakan ikan karang berukuran besar anggota dari familia Labridae, dengan ukuran bisa mencapai 2 m dan berat 190 kg. Ikan Napoleon terutama ditemukan di terumbu karang di kawasan samudra hindia dan samudra pasifik. Ikan ini mempunyai pola reproduksi hermafrodit protogini dengan sebaran di wilayah perairan india-pasifik. Ikan napoleon merupakan jenis ikan karang yang mempunyai daya tarik menarik bagi para penyelam untuk menikmati wisata alam bawah laut.

DeskripsiSunting

Ikan napoleon mempunyai ponokmasuk dalam keluarga ikan wrasse

Ikan ini disebut orang Australia dengan nama Hump Head Maori Wrasse, yang dibedakan karena bagian mukanya mempunyai guratan-guratan yang menyerupai hiasan muka orangMaori.Guratan-guratan tersebut berwarna krem (kuning susu) yang saling tumpang tindih pada bagian hidung dan pipi, kemudian meluas ke atas badan dan seberang ujung sirip dada. Badannya disepuh dengan warna hijau cerah dan di bagian atas seluruh seluruh sirip-siripnya berwarna coklat. Panjang ikan ini bisa mencapai 1.5 meter. Dan beberapa ikan bisa mencapai ukuran sampai 180 kg pada usia 50 tahun. Ketika muda, ikan napoleon terlihat pucat dengan garis-garis vertikal lebih gelap. Begitu dewasa, warna tubuhnya menjadi hijau kebiru-biruan dengan garis-garis lebih jelas. Bibirnya menebal macam bibir Mick Jagger. Bagian atas kepalanya pun, di atas mata, menjadi benjol ke depan. Karena ponoknya itu, orang pun menamainya Wrasse kepala berponok (Humphead wrasse). Wajahnya memiliki garis-garis tak beraturan. Di belakang matanya terdapat dua garis pendek berwarna hitam. “Goresan” hitam ini menyerupai ornamen wajah suku Maori di Selandia Baru. Maka, ikan napoleon pun mendapat julukan lain, Maori wrasse.

HabitatSunting

Ikan Napoleon berenang di terumbu karang

Ikan Napoleon (Cheilunus undulatus) merupakan salah satu ikan karang besar yang hidup pada daerah tropis Kehidupan hewan ini umumnya sama dengan ikan karang lain yang hidup secara soliter. Para penyelam biasanya menemukan ikan ini berenang sendiri pada daerah sekitar karang. Dan biasanya sangat jinak dengan para penyelam. Ikan ini biasanya tidak terusik dengan aktivitas para penyelam. Kebiasaan hidup sendiri pada kedalaman tertentu membuat hewan ini sangat dinantikan oleh para penyelam untuk melihat atau bahkan memotret hewan ini. Biasanya ikan berenang sendiri mencari makan didaerah dekat karang, karena makanannya yang berupa beberapa jenis sea urchin,molusca dan crustacean memang banyak berada pada daerah sekitar karang.

Cara makanSunting

Cara makannya adalah dengan membongkar karang mati dengan gigi besarnya untuk mencari siput dan cacing-cacingan yang terkubur. Mereka gemar sekali makan kerang-kerang yang berukuran besar seperti Triton. Ikan ini sanggup memecahkan cangkang kerang-kerangan tersebut dengan mudah untuk diambil dagingnya. Bunyi gerusan mulutnya ketika makan, sangat menarik bagi para penyelam sehingga diibaratkan seperti sekelompok anak-anak yang sedang memakan kembang gula. Kadang-kadang juga ikan besar ini mengasah giginya pada karang massif (padat) sehingga meninggalkan bekas goresan yang menakjubkan.

ReproduksiSunting

Ikan ini mempunyai pola reproduksi yang Hermafrodit protogini. Biasanya ikan ini lahir sebagai hewan jantan dan akan berubah menjadi betina saat menjelang dewasa. Sehingga kadang ditemukan dominasi jantan pada satu populasi ikan kecil sampai ukuran sedang dan akan berubah menjadi dominasi populasi betina saat mendekati matang gonad. Ini memang fenomena unik dialam yang merupakan salah satu strategi sebagian besar hewan laut utntuk mempertahankan kehidupan populasi mereka. Di sini ikan napoleon jantan ada dua tipe, yakni mereka yang terlahir sebagai jantan dan tetap sebagai jantan sejati sampai akhir hayat, dan mereka yang memulai hidup sebagai betina dan dalam masa kehidupan berikutnya berubah fungsi sebagai jantan! Perubahan menjadi betina biasanya terjadi setelah berumur 5 – 10 tahun atau berbobot badan kurang dari 10 – 15 kg. Namun, pergantian kelamin dan bagaimana perubahan kelamin terjadi masih menyimpan misteri. Ada sejumlah faktor yang diperkirakan bisa mendorong perubahan jenis kelamin tadi. Yakni hubungan antarikan napoleon jantan dan dominasi sosial, atau dalam hal lebih spesifik, ukuran tubuhnya. Ikan napoleon betina bertelur sepanjang tahun di pinggir atau bagian luar lereng terumbu karang. Proses bertelur ini terjadi dalam kelompok maupun berpasangan. Kegiatan bertelur dalam kelompok sungguh dramatis. Aktivitas itu dimulai dengan berkeliling bersama secara perlahan membentuk suatu kelompok. Saat anggota kelompok bertambah, mereka berenang lebih cepat dan lebih cepat lagi, akhirnya makin rapat membentuk kelompok besar. Pada puncak hiruk-pikuk tadi, seluruh kelompok naik ke arah permukaan laut kemudian secepat kilat berbalik arah dan meninggalkan sebuah massa telur dan sperma di belakang yang segera terbawa oleh arus. Jika proses bertelur dilakukan secara pasangan, yang jantan menyiapkan tempat bertelur pada seonggok karang atau batu yang menyolok. Dari sini dia menarik perhatian betina yang lewat, yang kira-kira bisa memberi harapan. Caranya, di atas calon pasangan dia bergerak ke atas dan ke bawah dan menggetarkan tubuhnya sembari berenang kembali. Kalau siap menerima pinangannya, si betina akan membalasnya dengan memberi sinyal ke ikan jantan yang meminangnya. Dengan bangga si betina melengkungkan tubuhnya membentuk huruf “S” sembari mempertontonkan perut buncitnya yang berisi telur. Mereka kemudian bertelur dalam suatu gerakan naik turun secara cepat ke permukaan. Proses bertelur ini berlangsung singkat dalam suatu hari, tergantung pada kondisi setempat. Di areal dengan arus pasang surut yang kuat, bertelur terjadi hanya setelah puncak pasang naik, keadaan yang ideal untuk memindahkan telur ke luar terumbu karang.

KonservasiSunting

Akibat dampak penangkapan berlebih untuk perdagangan ikan karang hidup, ikan napoleon mengalami penurunan populasinya di alam. Penangkapan ikan napoleon umumnya menggunakan racun sianida dan merusak ekosistem terumbu karang. Ikan Napoleon merupakan ikan yang memerlukan waktu lama untuk mencapai usia matang reproduktif.Ikan napoleon menjadi matang seksual pada usia 5 sampai 7 tahun (pada ukuran 40–60 cm). Ikan Napoloen di Negara Malaysia, dan Filipina ,sudah tidak boleh ditangkap dan diperdagangkan. Australia melarang semua mengambil dan memiliki Ikan Napoleon. Indonesia memungkinkan memancing hanya untuk penelitian, marikultur, dan memancing rakyat berlisensi. PenelitianIUCN tahun 2005 di Sulut, Bali, Raja Ampat, dan NTT menunjukan bahwa di habitat yang mendapat tekanan (target penangkapan) sangat tinggi, ikan napoleon sangat jarang ditemukan, akan tetapi pada saat ikan tersebut tidak menjadi ikan target nelayan para penyelam masih dapat menemukan spesies tersebut. Hasil survei menunjukan bahwa tingkat kepadatan napoleon di kangean-Bali hanya 0,04 per ha, Bunaken-Sulut 0, 38 per ha, Raja Ampat 0,86 per ha, NTT 0,18 per ha, maratua 0,15 per ha, Banda 1,6 per ha. Menurut Sadovy dalam pemaparannya, akibat dampak penangkapan berlebih untuk perdagangan ikan karang hidup, ikan napoleon rentan (vulnerable) mengalami kepunahan. Oleh karena itu akibat penurunan drastis diberbagai tempat menyebabkan ikan napoleon dimasukkan ke dalam daftar merah IUCN (Endangered) pada tahun 2004 dan appendix II CITES pada tahun 2005.

ReferensiSunting

Randall, J.E., et al. (1978). Food habits of the giant humphead wrasse, Cheilinus undulatus (Labridae). Env. Biol. Fish 3:235-238Russell (2004). Cheilinus undulatus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 10 May 2006.https://id.m.wikipedia.org/wiki/Ikan_Napoleon

Penyu

Penyu

Masalah halaman

PenyuPenyu hijau HawaiiStatus konservasi

Terancam

Klasifikasi ilmiahKingdom:AnimaliaFilum:ChordataKelas:SauropsidaOrdo:TestudinataSubordo:CryptodiraSuperfamili:Chelonioidea
Bauer, 1893GeneraFamilia Cheloniidae (Oppel, 1811)CarettaCheloniaEretmochelysLepidochelysNatatorFamilia DermochelyidaeDermochelysFamilia Protostegidae (hanya fosil)Familia Toxochelyidae (hanya fosil)Familia Thalassemyidae (hanya fosil)

Penyu adalah kura-kura laut yang ditemukan di semua samudra di dunia. Menurut data para ilmuwan, penyu sudah ada sejak akhir zaman Jura (145 - 208 juta tahun yang lalu) atau seusia dengan dinosaurus. Pada masa ituArchelon, yang berukuran panjang badan enam meter, dan Cimochelys telah berenang di laut purba seperti penyu masa kini.

Penyu memiliki sepasang tungkai depan yang berupa kaki pendayung yang memberinya ketangkasan berenang di dalam air. Walaupun seumur hidupnya berkelana di dalam air, sesekali hewan kelompok vertebrata, kelas reptilia itu tetap harus sesekali naik ke permukaan air untuk mengambil napas. Itu karena penyu bernapas dengan paru-paru. Penyu pada umumnya bermigrasidengan jarak yang cukup jauh dengan waktu yang tidak terlalu lama. Jarak 3.000 kilometer dapat ditempuh 58 - 73 hari.

Masa bertelurSunting

Penyu mengalami siklus bertelur yang beragam, dari 2 - 8 tahun sekali. Sementara penyu jantan menghabiskan seluruh hidupnya di laut, betina sesekali mampir ke daratan untuk bertelur. Penyu betina menyukai pantai berpasir yang sepi dari manusia dan sumber bising dan cahaya sebagai tempat bertelur yang berjumlah ratusan itu, dalam lubang yang digali dengan sepasang tungkai belakangnya. Pada saat mendarat untuk bertelur, gangguan berupa cahaya ataupun suara dapat membuat penyu mengurungkan niatnya dan kembali ke laut.

Penyu yang menetas di perairan pantaiIndonesia ada yang ditemukan di sekitar kepulauan Hawaii. Penyu diketahui tidak setia pada tempat kelahirannya.

Tidak banyak regenerasi yang dihasilkan seekor penyu. Dari ratusan butir telur yang dikeluarkan oleh seekor penyu betina, paling banyak hanya belasantukik (bayi penyu) yang berhasil sampai ke laut kembali dan tumbuh dewasa. Itu pun tidak memperhitungkan faktor perburuan oleh manusia dan pemangsaalaminya seperti kepiting, burung dantikus di pantai, serta ikan-ikan besar begitu tukik tersebut menyentuh perairan dalam.

Di tempat-tempat yang populer sebagai tempat bertelur penyu biasanya sekarang dibangun stasiun penetasan untuk membantu meningkatkan tingkat kelulushidupan (survival). Di Indonesia misalnya terdapat stasiun penetasan di:

Pantai selatan Jawa Barat (Pangumbahan, Cikepuh KSPL Chelonia UNAS)pantai selatan Bali (di dekat Kuta)Kalimantan Tengah (Sungai CabangFNPF)pantai selatan LombokJawa Timur (Alas Purwo)Bengkulu (Retak ilir Mukomuko)Pulau Cangke Kabupaten Pangkep Prov. Sulawesi selatanPulau Jemur Kabupaten Rokan Hilir Provinsi Riau (Info Selengkapnya kunjungi Website Resminya)Pulau Sangalaki, Kabupaten Berau, Kalimantan TimurKabupaten Bintan, Provinsi Kepulauan Riau (Pantai Sakerah, Pantai Trikora, Tanjung Uban, Bintan Timur, Desa Mepar, Kepulauan Tambelan)Kabupaten Karimun, Provinsi Kepulauan Riau (Pulau Karimun)Kabupaten Kepulauan Anambas, Provinsi Kepulauan Riau (Pulau Damar, Pulau Mangkai, Pulau Durai, Pulau Pahat)Kabupaten Natuna, Provinsi Kepulauan Riau (Pulau Senoa, Pulau Sekatung)

JenisSunting

Penyu belimbing adalah jenis penyu terbesar bisa mencapai panjang 2,75 meter

Di dunia saat ini hanya ada tujuh jenis penyu yang masih bertahan, yaitu:

Penyu hijau (Chelonia mydas)Penyu sisik (Eretmochelys imbricata)Penyu Kemp’s ridley (Lepidochelys kempi)Penyu lekang (Lepidochelys olivacea)Penyu belimbing (Dermochelys coriacea)Penyu pipih (Natator depressus)Penyu tempayan (Caretta caretta)

Dari ketujuh jenis ini, hanya penyu Kemp's ridley yang tidak pernah tercatat ditemukan di perairan Indonesia.

Dari jenis-jenis tersebut, penyu belimbing adalah yang terbesar dengan ukuran panjang badan mencapai 2,75 meter dan bobot 600 - 900 kilogram. Penyu lekang adalah yang terkecil, dengan bobot sekitar 50 kilogram. Namun demikin, jenis yang paling sering ditemukan adalah penyu hijau.

Penyu, terutama penyu hijau, adalah hewan pemakan tumbuhan yang sesekali memangsa beberapa hewan kecil.

Isu konservasiSunting

Tukik (anak) penyu hijau di dalam penangkaran.

Dalam laporan Conservation International (CI) yang diumumkan pada simposium tahunan ke-24 mengenai usaha pelestarian penyu di Kosta Rikadisebutkan, banyaknya penyu belimbing turun dari sekitar 115.000 ekor betina dewasa menjadi kurang dari 3.000 ekor sejak tahun 1982. Penyu belimbing telah mengalami penurunan 97% dalam waktu 22 tahun terakhir. Selain itu, lima spesies penyu juga beresiko punah, meski tidak dalam jangka waktu yang singkat seperti penyu belimbing.

Hampir semua jenis penyu termasuk ke dalam daftar hewan yang dilindungi olehundang-undang nasional maupuninternasional karena dikhawatirkan akan punah disebabkan oleh jumlahnya makin sedikit. Di samping penyu belimbing, dua spesies lain, penyu Kemp’s Ridley dan penyu sisik juga diklasifikasikan sebagai sangat terancam punah oleh The World Conservation Union (IUCN). Penyu hijau (Chelonia mydas), penyu lekang atau penyu abu-abu (Lepidochelys olivacea), dan penyu tempayan atau loggerhead(Caretta caretta) digolongkan sebagai terancam punah. Hanya penyu pipih (Natator depressus) yang diperkirakan tidak terancam.

Sebagian orang menganggap penyu adalah salah satu hewan laut yang memiliki banyak kelebihan. Selaintempurungnya yang menarik untukcendramata, dagingnya yang lezat ditusuk jadi Sate penyu berkhasiat untukobat dan ramuan kecantikan. Terutama di Tiongkok dan Bali, penyu menjadi bulan-bulanan ditangkap, disantap, tergusur dari pantai, telurnyapun diambil. Meski sudah ada Peraturan Pemerintah Nomor 7 tahun 1999tentang Pelestarian Jenis Tumbuhan dan Satwa, yang melindungi semua jenis penyu, perburuan terhadap hewan yang berjalan lamban ini terus berlanjut. Untuk mencegah kepunahan penyu, terutama penyu belimbing, beberapa negara telah melindungi tempat bertelur penyu. Salah satunya adalah diJamursba Medi, yang terletak di pantai utara Irian. Pantai itu baru-baru ini ditetapkan sebagai wilayah konservasi.
https://id.m.wikipedia.org/wiki/Penyu

Hiu "sang predator"

Ikan Hiu
Rentang fosil: Devonian awal – Baru-baru iniHiu samudra berujung putih, Carcharhinus longimanusKlasifikasi ilmiahKingdom:AnimaliaFilum:ChordataSubfilum:VertebrataKelas:ChondrichthyesSubkelas:ElasmobranchiiSuperordo:SelachimorphaOrdo

Carcharhiniformes
Heterodontiformes
Hexanchiformes
Lamniformes
Orectolobiformes
Pristiophoriformes
Squaliformes
Squatiniformes

Ikan Hiu adalah sekelompok (superordoSelachimorpha) ikan dengan kerangka tulang rawan yang lengkap ^[1] dan tubuh yang ramping. Mereka bernapas dengan menggunakan lima liang insang (kadang-kadang enam atau tujuh, tergantung pada spesiesnya) di samping, atau dimulai sedikit di belakang, kepalanya. Hiu mempunyai tubuh yang dilapisi kulit dermal denticles untuk melindungi kulit mereka dari kerusakan, dari parasit, dan untuk menambah dinamika air.^[1] Mereka mempunyai beberapa deret gigi yang dapat digantikan.

Hiu mencakup spesies yang berukuran sebesar telapak tangan. Hiu pigmi, Euprotomicrus bispinatus, sebuah spesies dari laut dalam yang panjangnya hanya 22 cm, hingga hiu paus, Rhincodon typus, ikan terbesar yang mampu tumbuh hingga sekitar 12 meter dan yang, seperti ikan paus, hanya memakan plankton melalui alat penyaring di mulutnya. Hiu banteng, Carcharhinus leucas, adalah yang paling terkenal dari beberapa spesies yang berenang di air laut maupun air tawar (jenis ini ditemukan di Danau Nikaragua, di Amerika Tengah) dan di delta-delta.^[2]

Ciri-ciri fisikSunting

Artikel utama untuk bagian ini adalah: Ciri-ciri fisik hiu

KerangkaSunting

Kerangka hiu sangat berbeda dibandingkan dengan ikan-ikan bertulang seperti misalnya ikan kod, karena terbuat dari tulang muda (tulang rawan), yang sangat ringan dan lentur, meskipun tulang muda di ikan-ikan hiu yang lebih tua kadang-kadang sebagian bisa mengapur, sehingga membuatnya lebih keras dan lebih seperti tulang. Rahang hiu beraneka ragam dan diduga telah berevolusi dari rongga insang yang pertama. Rahang ini tidak melekat pada cranium dan mempunyai deposit mineral tambahan yang memberikannya kekuatan yang lebih besar.^[3]

Hiu umumnya lambat mencapai kedewasaan seksualnya dan menghasilkan sedikit sekali keturunan dibandingkan dengan ikan-ikan lainnya yang dipanen. Ini telah menimbulkan keprihatinan di antara para biologiwan karena meningkatnya usaha yang dilakukan untuk menangkapi ikan hiu selama ini, dan banyak spesies yang kini dianggap terancam punah.

Beberapa organisasi, seperti misalnya Shark Trust, melakukan kampanye untuk membatasi penangkapan hiu.

Hiu dalam mitologiSunting

Hiu sangat menonjol dalam mitologiHawaii. Ada cerita-cerita tentang manusia hiu yang mempunyai rahang hiu di belakang mereka. Mereka dapat berubah bentuk antara hiu dan manusia pada waktu-waktu yang mereka inginkan. Sebuah tema umum dalam cerita-cerita ini adalah bahwa manusia-manusia hiu ini akan memperingatkan orang-orang yang ke pantai bahwa di perairan itu terdapat hiu. Orang-orang yang ke pantai itu akan menertawai dan mengabaikan peringatan-peringatan mereka dan akan tetap berenang, dan karena itu kemudian mereka dimakan oleh manusia hiu yang sama, yang memberikan peringatan kepada mereka agar tidak turun ke air.

Mitologi Hawaii juga mengandung banyak dewa hiu. Mereka percaya bahwa hiu adalah penjaga samudra, dan mereka disebut Aumakua:^[4]

Kamohoali'i – Dewa hiu yang paling terkenal dan dihormati. Ia lebih tua dan menyukai saudara dari Pele,^[5] dan menolong serta berjalan bersamanya ke Hawaii. Ia mampu mengambil rupa manusia dan ikan. Sebuah tebing yang tinggi di kawah Kilauea dianggap sebagai salah satu tempatnya yang paling suci. Di salah satu tempat itu, ia mempunyai sebuah he'iau (kuil) yang dipersembahkan baginya di setiap potong tanah yang menjorok ke laut di pulau Moloka'i.Ka'ahupahau – Dewi ini dilahirkan sebagai manusia, dengan ciri khasnya karena rambutnya yang merah. Ia belakangan berubah ke dalam bentuk hiu dan diyakini melindungi rakyat yang hidup di O'ahu dari ikan-ikan hiu. Ia juga diyakini hidup dekat Pearl Harbor.Kaholia Kane – Ini adalah dewa hiu dari ali'i Kalaniopu'u dan diyakini tinggal di sebuah gua di Puhi, Kaua'i.Kane'ae – Dewi hiu yang berubah menjadi manusia agar dapat mengalami suka cita menari.Kane'apua – Yang paling umum, ia diyakini sebagai saudara laki-laki dari Pele dan Kamohoali'i. Ia adalah dewa yang suka mempermainkan orang yang melakukan banyak tindakan kepahlawanan, termasuk menenangkan dua bukit legendaris yang konon bertabrakan sehingga menghancurkan perahu-perahu yang berusaha melewatinya.Kawelomahamahai'a – Asalnya manusia, ia kemudian diubah menjadi hiu.Keali'ikau 'o Ka'u – Ia adalah sepupu dari Pele dan anak laki-laki dari Kua. Ia disebut pelindung rakyat Ka'u. Ia pernah mengadakan hubungan dengan seorang gadis manusia, yang melahirkan seekor hiu hijau.Kua – ini adalah dewa hiu yang utama dari rakyat Ka'u, dan diyakini merupakan nenek moyang mereka.Kuhaimoana – Ia adalah saudara laki-laki dari Pele dan tinggal di pulau Ka'ula. Panjangnya konon 55 m dan merupakan suami dari Ka'ahupahau.Kauhuhu – Ia adalah raja hiu yang kejam yang hidup di sebuah gua di Kipahulu di pulau Maui. Kadang-kadang ia pindah ke gua yang lain di sisi angin bertiup dari pulau Moloka'i.Kane-i-kokala – Sejenis dewa hiu yang menyelamatkan orang-orang yang karam kapalnya dengan membawa mereka ke pantai. Orang-orang yang menyembahnya tidak mau memakannya, menyentuh atau melintasi asap kokala, ikannya yang suci.

Dalam budaya-budaya Samudra Pasifik lainnya, Dakuwanga adalah dewa hiu yang juga merupakan pemakan jiwa-jiwa yang tersesat.

Di Yunani kuno, orang dilarang makan daging hiu pada festival-festival perempuan.

MitosSunting

Ada mitos yang populer bahwa hiu kebal terhadap penyakit dan kanker; namun hal ini tidak benar. Ada penyakit dan parasit yang memengaruhi hiu. Bukti bahwa hiu setidak-tidaknya tahan terhadap kanker dan penyakit boleh dikatakan hanya anekdot dan kalaupun ada, sedikit sekali studi ilmiah atau statistik yang membuktikan bahwa hiu dapat meningkatkan kekebalan terhadap penyakit. Namun sekarang sudah ada beberapa perusahaan obat-obatan yang memproduksi minyak hati ikan hiu (Squalene) untuk meningkatkan kesehatan hati dan jantung.^[6]

FilmSunting

Jaws (1975)Deep Blue Sea (1999)Open Water (2003)Shark Tale (2004)Soul Surfer (2011)

Lihat pula

ReferensiSunting

^ ^a b Budker, Paul (1971). The Life of Sharks. London: Weidenfeld and Nicolson. SBN 297003070.^ Allen, Thomas B. (1999). The Shark Almanac. New York: The Lyons Press. ISBN 1-55821-582-4.^ Hamlett, W. C. (1999). Sharks, Skates and Rays: The Biology of Elasmobranch Fishes. Johns Hopkins University Press. ISBN 0-8018-6048-2.^ "Hawaiian Mitologi". Diakses tanggal 13 Sept. 2006.^ "Pele, Goddess of Fire (Pele, Dewi Api)". Diakses tanggal 13 Sept. 2006.^ "Do Sharks Hold Secret to Human Cancer Fight?". National Geographic. Diakses tanggal 8 Sept. 2006.

Referensi umumSunting

Castro, Jose (1983). The Sharks of North American Waters. College Station: Texas A&M University Press. ISBN 0-89096-143-3.Stevens, John D. (1987). Sharks. New York: NY Facts on File Publications. ISBN 1-858052-49-4.Pough, F. H.; Janis, C. M. & Heiser, J. B. (2005). Vertebrate Life. 7th Ed. New Jersey: Pearson Education Ltd. ISBN 0-13-127836-3.https://id.m.wikipedia.org/wiki/Hiu