Kissing gouramis, also known as kissing fish or kissers (''Helostoma temminckii''), are medium-sized tropical

freshwater fish Freshwater fish are fish species that spend some or all of their lives in bodies of fresh water such as rivers, lakes, ponds and inland wetlands, where the salinity is less than 1.05%. These environments differ from marine habitats in many wa ...

comprising the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

labyrinth fish The Anabantoidei are a suborder of anabantiform ray-finned freshwater fish distinguished by their possession of a lung-like labyrinth organ, which enables them to breathe air. The fish in the Anabantoidei suborder are known as anabantoids or la ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Helostomatidae (from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''elos'' tud, nail ''stoma'' outh. These fish originate from

Mainland Southeast Asia Mainland Southeast Asia (historically known as Indochina and the Indochinese Peninsula) is the continental portion of Southeast Asia. It lies east of the Indian subcontinent and south of Mainland China and is bordered by the Indian Ocean to th ...

, the

Greater Sundas The Greater Sunda Islands (Indonesian language, Indonesian and Malay language, Malay: ''Kepulauan Sunda Besar'') are four tropical islands situated within the Indonesian Archipelago, in the Pacific Ocean. The islands, Borneo, Java, Sulawesi and S ...

and nearby smaller islands, but have also been introduced outside their native range. They are regarded as a

food fish Many species of fish are caught by humans and consumed as food in virtually all regions around the world. Their meat has been an important dietary source of protein and other nutrients in the human diet. The English language does not have a s ...

and they are sometimes

farmed Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created f ...

. They are used fresh for

steaming Steaming is a method of cooking using steam. This is often done with a food steamer, a kitchen appliance made specifically to cook food with steam, but food can also be steamed in a wok. In the American Southwest, steam pits used for cooking ha ...

baking Baking is a method of preparing food that uses dry heat, typically in an oven, but it can also be done in hot ashes, or on hot Baking stone, stones. Bread is the most commonly baked item, but many other types of food can also be baked. Heat is ...

, broiling, and

pan frying Pan frying or pan-frying is a form of frying food characterized by the use of minimal cooking oil or fat (compared to shallow frying or deep frying), typically using just enough to lubricate the pan. In the case of a greasy food such as bacon, ...

. The kissing gourami is a popular aquarium fish.

Description

Typical of gourami, the body is deep and strongly compressed laterally. The long-based

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

(16–18 spinous rays, 13–16 soft) and

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

s (13–15 spinous rays, 17–19 soft) mirror each other in length and frame the body. The posterior most soft rays of each of these fins are slightly elongated to create a trailing margin. The foremost rays of the jugular

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

s are also slightly elongated. The

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

s are large, rounded, and low-slung. The

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

is rounded to concave. The

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

is divided in two, with the posterior portion starting below the end of the other; there are a total of 43–48 scales running the line's length. The most distinctive feature of the kissing gourami is its mouth. Other than being terminal (forward-facing) rather than superior (upward-facing) as in other

gourami Gouramis, or gouramies , are a group of fresh water, freshwater Anabantiformes, anabantiform fish that comprise the family (biology), family Osphronemidae. The fish are native to Asia—from the Indian Subcontinent to Southeast Asia and northeas ...

families, the kissing gourami's mouth is highly protrusible as its family name suggests, the lips are lined with horny

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

. However, teeth are absent from the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

dentaries In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

palatine A palatine or palatinus (Latin; : ''palatini''; cf. derivative spellings below) is a high-level official attached to imperial or royal courts in Europe since Roman Empire, Roman times.

, and

pharynx The pharynx (: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates ...

. The

gill raker Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of th ...

s are also well-developed and numerous. The visible scales of the body are

ctenoid A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as w ...

, whereas the scales of the top of the head are

cycloid In geometry, a cycloid is the curve traced by a point on a circle as it Rolling, rolls along a Line (geometry), straight line without slipping. A cycloid is a specific form of trochoid and is an example of a roulette (curve), roulette, a curve g ...

. Kissing gourami reach a maximum of in

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 ...

. There is no outward

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

and is difficult to almost impossible to distinguish the sexes. Two colour morphs are encountered: greenish-silvery, which have lengthwise spotty stripes on the body and opaque, dark brown fins; and pink, which have a rose to orangy pink body and silvery scales, with transparent pinkish fins. While it has been claimed that the greenish fish originate from Thailand and pinkish fish originate from

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

, the greenish is the wild form and the pinkish is a

leucistic Leucism () is a wide variety of conditions that result in partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. It is occasionally spelled ''leu ...

form achieved through

selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant m ...

in captivity.>

Jaw and mouth

It is important to emphasize the particularity that this species has in its mouth: it has an additional joint between its jaw and the rest of the joints, known as intramandibular joint. This type of joint is also present in other species of fish that feed on nutrients attached to the substrate. By increasing the angle of opening of the jaw, this joint allows kissing gourami access to these nutrients. ''H. temminkii'', however, is the only species known that uses this articulation in this way. The intramandibular joint divides the jaw into two independent elements so that it increases the degrees of freedom and the potential number of ways of getting food. This articulation, although its mechanism and anatomy are still being studied, results in an adaptation of ''H. temminkii'' and its feeding.

Habitat and ecology

Shallow, slow-moving, and thickly vegetated backwaters are the kissing gourami's natural

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

. They are midwater

omnivore An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize t ...

s that primarily graze 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". ...

alga Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, suc ...

e and

aquatic plant Aquatic plants, also referred to as hydrophytes, are vascular plants and Non-vascular plant, non-vascular plants that have adapted to live in aquatic ecosystem, aquatic environments (marine ecosystem, saltwater or freshwater ecosystem, freshwater ...

s, with

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s taken from the surface. They are also

filter feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a s ...

s, using their many gill rakers to supplement their diet with

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

. The fish use their toothed lips to rasp algae from stones and other surfaces. This rasping action, which (to humans) looks superficially like kissing, is also used by males to challenge the dominancy of conspecifics.

Intraspecific behaviour

The kissing gourami present a kind of behavior associated with their characteristic jaw and mouth: two individuals approach their mouths in both mediolateral and dorsoventral planes and press for a few seconds. This type of "kiss" has given ''H. temminkii'' the common name of kissing gourami. This has been considered an intraspecific aggressive behavior also known as "mouth fight" due to the contraction of the jaw muscles. However, it is not completely confirmed that it is an aggressive behavior and is rather understood as a ritualized form of aggression.

Ecosystem roles

''Helostoma temminkii'' can become the host to some parasitic algal species. These

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

are able to survive under kissing gourami skin and look like color spots. Some hypothesis affirm that these algae communities receive some nutrients required for photosynthesis from the ''H. temminkii.'' The individuals which have these parasites in their bodies are commonly less healthy than those which have not any algae parasites. ''H. temminkii'' are able to communicate between each other due to their complex inner ear: it has a suprabranchial air-breathing chamber which gives these fishes the capacity to modulate their hearing through air bubbles in this area. Kissing gouramis are also able to emit sounds to other individuals of their own species through the movement of their teeth.

Reproduction

''Helostoma temminkii'' are

oviparous Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

and dioecious and have external

fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise, -ize (-isation, -ization), spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give ...

Spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...

occurs from May to October in Thailand, at the beginning of the rainy season. Kissing gouramis are open-water

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

scatterers; spawning is initiated by the female and takes place under cover of floating vegetation. The eggs, which the adults do not guard, are spherical, smooth, and buoyant. Initial development is rapid: the eggs hatch after one day, and the fry are free-swimming two days thereafter. The kissing gourami does not care for its young. Adults migrate through the rivers to shallow lagoons or into flooded forests to spawn. A female starts mating and the male simultaneously shed the eggs and sperm to the outside. Females release an average of 1000 eggs. The eggs are spherical and small compared to other freshwater species and have a drop of oil to increase buoyancy. Fertilized eggs float to the surface and usually bind to floating vegetation, becoming larvae. Biting fish reach sexual maturity of three to five years.

Feeding

The kissing gourami is an

omnivorous An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...

microphagic

filtering Filtration is a physical process that separates solid matter and fluid from a mixture. Filter, filtering, filters or filtration may also refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Fil ...

fish, whose nutrition is based on a wide variety of food sources, such as insects, algae, larvae from other species and other microorganisms found on submerged species. The mouth, teeth, gills and especially the intramandibular joint described above make this fish a very well adapted species: it is able to find nutrients in places where other species cannot be such as algal-covered surfaces.

In the aquarium

Kissing gouramis are also popular with

aquarists An aquarist is a person who manages aquariums, either professionally or as a hobby. They typically care for aquatic animals, including fish and marine invertebrates. Some may care for aquatic mammals. Aquarists often work at public aquariums. They ...

for the fish's peculiar "

kiss A kiss is the touching or pressing of one's lips against another person, animal or object. Cultural connotations of kissing vary widely; depending on the culture and context, a kiss can express sentiments of love, passion, romance, sex ...

ing" behavior of other fish, plants, and other objects. Kissers of both sexes will often spar by meeting mouths and pushing each other through the water. Large quantities of these fish are exported to

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, and other parts of the world for just this reason. Kissing gouramis need a roomy tank to thrive; they grow rapidly, and juvenile fish will quickly outgrow smaller aquaria. Kissing gouramis are territorial; some are tolerant towards fish of similar size, but others will bully, chase, and torment, causing significant stress on tank mates. Male kissers will occasionally challenge each other; however, the "kissing" itself is never fatal, but the constant bullying can stress the other fish to death. They often do in fact kill other fish by sucking the

mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...

off their skin as food, which opens the victim fish up to infections. These fish may be useful as

algae eater Algae eater or algivore is a common name for any bottom-dwelling or filter-feeding aquatic animal species that specialize in feeding on algae and phytoplanktons. Algae eaters are important for the fishkeeping hobby and many are commonly kept by aq ...

s to control algae growth. To prevent digging and to present enough surface area for algae growth, the substrate should consist of large-diameter gravel and stones. The aquarium's back glass should not be cleaned during regular maintenance, as the gouramis will feed on the algae grown there. Most plants will not survive the fish's grazing, so inedible plants such as

Java fern ''Leptochilus pteropus'' (synonym ''Microsorum pteropus'') is a species of aquatic or semi-aquatic fern, commonly known as Java fern (after the Indonesian island of Java). It is predominantly known from Malaysia, Thailand, Northeastern India and ...

Java moss Java moss is a common name for multiple plants and may refer to: *'' Taxiphyllum barbieri'' *'' Vesicularia dubyana'' Hypnaceae {{Short pages monitor