''Dichotomyctere ocellatus'' ( syn. ''Tetraodon biocellatus''), commonly the figure 8 puffer or eyespot puffer, is a

pufferfish Tetraodontidae is a family of marine and freshwater fish in the order Tetraodontiformes. The family includes many familiar species variously called pufferfish, puffers, balloonfish, blowfish, blowers, blowies, bubblefish, globefish, swellfis ...

found in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

. It is known from the lower reaches of the

Mekong The Mekong or Mekong River ( , ) is a transboundary river in East Asia and Southeast Asia. It is the world's twelfth-longest river and the third-longest in Asia with an estimated length of and a drainage area of , discharging of wat ...

(Cambodia), the

Peninsular Malaysia Peninsular Malaysia, historically known as Malaya and also known as West Malaysia or the Malaysian Peninsula, is the western part of Malaysia that comprises the southern part of the Malay Peninsula on Mainland Southeast Asia and the list of isla ...

as well as

Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...

(

Sarawak Sarawak ( , ) is a States and federal territories of Malaysia, state of Malaysia. It is the largest among the 13 states, with an area almost equal to that of Peninsular Malaysia. Sarawak is located in East Malaysia in northwest Borneo, and is ...

Kalimantan Kalimantan (; ) is the Indonesian portion of the island of Borneo. It constitutes 73% of the island's area, and consists of the provinces of Central Kalimantan, East Kalimantan, North Kalimantan, South Kalimantan, and West Kalimantan. The non-Ind ...

Characteristics

Figure 8 puffers grow to about

total length Fish measurement is the measuring of individual fish and various parts of their anatomies, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured f ...

(TL). They are colourful fish, with greenish yellow patterns on their backs. These patterns vary greatly from fish to fish, but the markings either side of the caudal fin resemble the number eight, or eye-spots (earning the species another common name as "eyespot puffer"). Figure 8 puffers are relatively peaceful among

Tetraodontidae Tetraodontidae is a family of marine and freshwater fish in the order Tetraodontiformes. The family includes many familiar species variously called pufferfish, puffers, balloonfish, blowfish, blowers, blowies, bubblefish, globefish, swellfish, ...

, and have been kept successfully with other fish such as bumblebee gobies and mollies, but as with all pufferfish there is a risk that tankmates will not be tolerated. Like all members of its family, the figure 8 puffer is capable of inflating itself with water or air when stressed or otherwise frightened.

In freshwater

Like the closely related green pufferfish, the figure 8 exhibits euryhalinity, and undergoes

epithelial Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

remodeling and changes in the

kidneys In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and right in the retro ...

and

gills A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

when exposed to changes in salinity. Accordingly, the figure 8 puffer is often mistakenly regarded as an entirely freshwater fish, and has considerable resistance to freshwater exposure. In a marine environment, it exhibits typical saltwater fish morphological features in its gills, allowing it to secrete

sodium chloride Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs a ...

across the gill epithelium like a typical saltwater fish. However, acclimated to freshwater, the figure 8 puffer will exhibit specialized cells that do not match any gill

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

-regulating cell of a freshwater fish. The other fish known to have these types of cells is the

Mozambique tilapia The Mozambique tilapia (''Oreochromis mossambicus'') is an oreochromine cichlid fish native to southeastern Africa. Dull colored, the Mozambique tilapia often lives up to a decade in its native habitats. It is a popular fish for aquaculture. Due ...

(''O. mossambicus'').

In the aquarium

In captivity, figure 8 puffers require a 15 US gallon tank with temperatures between 24 °C and 28 °C. They are sensitive to

nitrites The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...

and

nitrates Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insol ...

and must be introduced into a fully cycled aquarium. Over-filtration is recommended as well as frequent partial water changes. Water pH will reflect the brackish environment to which these fish are best suited; the addition of marine salt will buffer the pH to a range between 7.8 and 8.3. With a

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

of between 1.005 and 1.008

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

(S.G.), the lifespan of this species has been as long as 15 years.The Puffer Forum, http://www.thepufferforum.com/forum/ug.php/v/PufferPedia/Brackish/T_Biocellatus/ (Retrieved 25 July 2007) As with all puffer fish, they require a complex aquarium set up consisting of many nooks and crannies. This helps figure 8 puffers to behave as they would in nature, and reduce boredom.

Diet

Pufferfish are classed as

molluscivore A molluscivore is a carnivorous animal that specialises in feeding on molluscs such as gastropods, bivalves, brachiopods and cephalopods. Known molluscivores include numerous predatory (and often cannibalistic) molluscs, (e.g. octopuses, murexes, ...

s and feed mainly on

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

organisms which may include

mussels Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, whic ...

, cockles,

oysters Oyster is the common name for a number of different families of Seawater, salt-water bivalve molluscs that live in Marine (ocean), marine or Brackish water, brackish habitats. In some species, the valves are highly Calcification, calcified, a ...

and

krill Krill ''(Euphausiids)'' (: krill) are small and exclusively marine crustaceans of the order (biology), order Euphausiacea, found in all of the world's oceans. The name "krill" comes from the Norwegian language, Norwegian word ', meaning "small ...

, though some puffers will take other foods, such as flake, it is not recommended that their primary food is flake. Their teeth, a beak formed from two plates, are capable of crushing shells in order to feed on prey. In captivity many fishkeepers feed snails as a substitute for the aforementioned foods as snails help keep the beak trim; it would otherwise be susceptible to overgrowth.

References

Bibliography

Ebert, K. (2001), ''The Puffers of Fresh and Brackish Water'', p 19. Aqualog, . {{Taxonbar, from=Q28599195 Tetraodontidae Taxa named by Franz Steindachner Fish described in 1885 Fish of the Mekong Basin Freshwater fish of Borneo Fish of Cambodia Freshwater fish of Indonesia Freshwater fish of Malaysia