Tag Archive: air breathing fishes

Kingdom: Animalia
Phylum: Chordata
Superclass: Osteichthyes
Class: Actinopterygii (ray-finned fishes)
Order: Gymnotiformes (Knifefishes)
Family: Gymnotidae (Naked-back knifefishes)

Genus/species: Electrophorus electricus

GENERAL CHARACTERISTICS: This eels (knifefishes) body is elongated and cylindrical, almost without scales; head flattened; mouth large with one row of conical teeth on each jaw; presence of three abdominal pairs of electric organs. The color is dark with anterior ventral part yellowish. They have a very long anal fin.

Large up to 2.5 m (8 feet). Weight up to 20 kg (44 pounds)


DISTRIBUTION/HABITAT: Tropical. Amazon Basin: Orinoco, and related areas in northern South America. Found in lowland backwaters and muddy river bottoms, never fast-flowing waters. During daylight, retreats to recessed hiding places shared with conspecifics.

DIET IN THE WILD: E. electricus juveniles eat invertebrates such as shrimp; adults prey on fish and small mammals.

MORTALITY/LONGEVITY: Life span: in captivity males to 15 years, females to 20+


REPRODUCTION: E. electricus  males construct foam nests and guard the growing larvae. First-born larvae prey on other eggs and embryos coming from late spawning batches. In mid-January when the first seasonal rains flood the breeding area, causing the about 10 cm long young eels to disperse.

REMARKS: NOT A TRUE EEL. True eels lack pectoral and pelvic fins. Unlike “true” eels in the Order Anguilliformes, they are obligate air breathers, taking up to 80% of their oxygen directly from the air, an adaptation for survival in poorly oxygenated water. The long undulating anal fin allows the electric eel to move backwards or forwards.

Though not an aggressive fish, can produce enough voltage to severely injure humans. If an electric eel fires a series of charges, each successive charge is less powerful. Aquarists stimulate several discharges before attempting to handle the animal safely. These eels also have two other, much smaller sets of electric organs, used for orientation, finding prey.
Active nocturnally.

The long undulating anal fin allows the electric eel to move backwards or forwards. About half the musculature has been converted into electric organs which produce up to 650 V. These eels use their electricity to stun the fish they prey upon, as well as for defense.

As the eel (knifefish) matures it develops cataracts leading to blindness relying only on its electrical senses. (Similar to the elephant fish with poor vision).

CONSERVATION: IUCN Red List; Least Concern.


California Academy of Sciences Steinhart Aquarium Flooded Amazon 2018

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Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii (Ray-finned fishes)
Order: Elopiformes (Tarpons and tenpounders)
Family: Megalopidae (Tarpons).

Genus/species: Megalops atlanticus

GENERAL CHARACTERISTICS: The Tarpon has a large, elongated, moderately deep and compressed body. Sides and belly are silvery and back blue-gray. The caudal fin is deeply forked. They “roll” at the water surface taking in air into their lunglike swimbladder which is attached to the esophagus allowing it to fill directly with air permitting the fish to live in oxygen-poor waters.

Length up to 2.5 m (8 ft) and weight up to 160 kg (350 lbs)

DISTRIBUTION/HABITAT: Nova Scotia south to Brazil, including the Gulf of Mexico, Caribbean and the West coast of Africa. Though the majority of its life is spent in the open ocean, M. atlanticus tolerates fluctuating salinities and may be found in coastal waters, bays, estuaries, mangrove-lined lagoons, and rivers, such as the Amazon.

Some populations of M. atlanticus may complete their life cycle in freshwater lakes or as in the California Academy of Sciences flooded Amazon.

DIET IN THE WILD: They feed on sardines, anchovies, and other fishes as well as shrimp, crabs, and other crustaceans.

REPRODUCTION and DEVELOPMENT:  Spawn offshore. High fecundity; a 2.3 m (7.5 ft) female is estimated to produce over 12 million eggs. Spawn in waters which can be temporarily isolated from the open sea. Larvae develop inshore and are leptocephalic in shape (flattened, transparent, and eel-like).

PREDATORS: Natural predators are sharks.

REPRODUCTION: They spawn offshore and exhibit high fecundity, a 2.3 m (7.5 ft) female is estimated to produce over 12 million eggs. They can also spawn in waters that are temporarily isolated from the open sea. Larvae develop inshore and are leptocephalic in shape (flattened, transparent, and eel-like). Life span: at least 55 years.

CONSERVATION: IUCN Red list; Vulnerable

REMARKS: Tarpon are among the most “primitive” existent bony fish.

It is a popular game fish of sportfishers, due to its dynamic reaction once hooked. Since the flesh is of poor quality, they are usually released, though another source states, “The flesh is highly appreciated despite its being bony.” It is marketed fresh or salted.

Their large (up to 8 cm (3 in) diameter) silvery scales are fashioned into jewelry.


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“It’s Easy Being Green” Docent Course. California Academy of Sciences 2014 

 fishbase fishbase.org/summary/1079

 Encyclopedia of Life  eol.org/pages/339927/details


Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii (ray-finned fishes)
Order: Osteoglossiformes (Bony tongues)
Family: Arapaimidae (Bonytongues)

Genus/species: Arapaima gigas

GENERAL CHARACTERISTICS: Usually grey to green in color with red flecks on the scales towards the tail and reddish-orange color of the filleted flesh. They are heavy with an elongated body with very large scales. There are also two symmetrical fins on either side of the body at the posterior end. The arapaima has a tongue with sharp, bony teeth that together with teeth on the roof of its palate are involved in disabling and shredding prey

It is one of the largest freshwater fishes in the world (length up to 450cm (14 feet in the 1800’s) Common length 200 cm (6.75 feet). Weight up to 133 kg. (292 lbs) In the 1800s specimens to 200 kg (440 lbs) were reported. 

DISTRIBUTION/HABITAT: Tropical. Amazon River and its tributaries in freshwater flooded areas dense with aquatic vegetation and shore plants. Much of the water that comprises the pirarucu’s habitat is also oxygen deficient, as it is located in swampy areas of the rainforest.

DIET IN THE WILD: Specialized for surface feeding with their up turned mouths. Adults prey on fish at the surface; suck smaller fish into the mouth, then crush pre against the roof of its mouth using its tooth-covered bony tongue. Like its close relative the arawana, it can leap from the water to snatch a bird or even a monkey from an overhanging branch.


REPRODUCTION: Sexually mature at the age of five years old. Builds a nest of about 15 cm (6 inches) depth and 50 cm (20 inches) width in sandy bottoms. Guards the eggs and the young. Adults have the ability to exude a pheromone from their head to attract offspring and keep them in close proximity.

MORTALITY and LONGEVITY: Preyed upon by humans. Life spans of 15 to 20 years in captivity .

CONSERVATION: IUCV Red List Data deficient. CITES Appendix II. Heavily exploited as a commercial fish throughout the Amazon. Populations have been greatly reduced during the past 200 years Commercial fishing of arapaima was banned in Brazil outside of a limited number of sustainable reserves, but illegal fishing still continues.

REMARKS: Indigenous people utilize the scales and bones. The bony or toothed tongue was once used as a seed grater to make drink powders. Its scales were used as scrappers.

In addition to gills, it has a modified and enlarged swim bladder, composed of lung-like tissue, which enables it to extract oxygen from the air. It is an obligate air breather, well adapted to oxygen-deficient waters gulping air every 10–15 minutes when oxygen levels are low.

Often referred to as the largest freshwater fish; some freshwater catfishes and sturgeon may challenge this “record.”


California Academy of Sciences Steinhart Aquarium Amazon Flooded Tunnel, 2018

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 fishbase  www.fishbase.org/summary/Arapaima-gigas.html

Arkive www.arkive.org/arapaima/arapaima-gigas/

 U. of Michigan Animal Diversity Web  animaldiversity.ummz.umich.edu/accounts/Arapaima_gigas/

National Geographic. www.nationalgeographic.com/environment/freshwater/arapaima/

 Encyclopedia of Life  eol.org/pages/204868/details




Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii (ray-finned fishes)
Order: Perciformes (Perch-likes)
Family: Osphronemidae (Gouramies)

Genus/species: Trichogaster trichopterus

GENERAL CHARACTERISTICS: Usually silvery blue in color but their colors can change significantly with their moods, as well as during spawning, when they obtain a much deeper blue hue.The three-spot gourami displays only two spots, one in the center of the body and a second on the caudal peduncle. The eye is actually the third “spot”. T. trichopterus has many different colour forms and varieties, all of which have been selectively bred for the aquarium trade. These are seen much more often than the natural form, which is the blue-grey three spotted fish. They include gold, opaline, cosby, marbled and silver forms. Length to 15 cm (6 inches).

DISTRIBUTION/HABITAT: Southeast Asia: Mekong River basin in Laos, Yunnan, Thailand, Cambodia, and Viet Nam. Preference is thickly vegetated fresh water in ditches, canals, ponds, swamps, rivers or lakes.

DIET IN THE WILD: Omnivore. Eats insects, crustaceans, and zooplankton.

REPRODUCTION and DEVELOPMENT: Typical of gouramis, male builds bubble nest, usually under a large leaf, after which he displays to female. Their courtship ends with her releasing eggs, which the male fertilizes and then collects in his mouth and “spits” into the bubble nest, where he guards them until they hatch in 2–3 days.

CONSERVATION: IUCN Red List; Least Concern (LC) Abundant to common in suitable habitats throughout its range.

REMARKS: Like all labyrinth fish, the moonlight gourami has a special lung-like organ that allows it to breathe air directly from above the water line. This allows gouramis to survive in pools with a low oxygen.

Processed into salted, dried fish in Java.

LOCATION: BO09 Rainforest Borneo, Southeast Asia Community 


fishbase  www.fishbase.org/summary/Trichopodus-trichopterus.html

Encyclopedia of Life  eol.org/pages/222297/details

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Kingdom: Animalia
Phylum: Chordata
Class: Actinoptergii
Order: Pecifomes
Family: Osphronemidae (Gouramis)

Genus/species: Trichogaster microlepis

GENERAL CHARACTERISTICS: It has a greenish hue similar to moonlight glow, hence its name, and a distinctive concave head. Males can be identified by the orange to red color of the pelvic fins and the long, pointed dorsal fins. The female’s pelvic fins are colorless to yellow, while the dorsal fins are shorter and rounder. Length: 12–15 cm  (4.66 – 6 inches)

DISTRIBUTION/HABITAT: Thailand and Cambodia. Found in ponds, lakes and swamps with shallow, sluggish or standing water and abundant vegetation.

DIET IN THE WILD: Omnivorous. Eats insects, crustaceans, and zooplankton.

REPRODUCTION: Oviparous; a bubble nest builder. The bubble nest does not contain much plant matter so the bubbles float around freely. The male performs a courtship dance beneath the nest, culminating with the male wrapping itself around the female and turning her on her back as she releases her eggs. Up to 2000 eggs may be laid during the spawning. The male fertilizes the eggs as they float up to the prepared bubble nest. Eggs incubate in the nest for 2–3 days before hatching.

CONSERVATION: IUCN: Least Concern (LC)  No major threats to this species have been reported, however, pollution in wetlands, infrastructure and draining water may impact the species.

REMARKS: Like all labyrinth fish, T. microlepis has a special lung-like organ that allows it to breathe air directly from above the water line. This allows gouramis to survive in pools with a low oxygen.

LOCATION: BO09 Rainforest Borneo, Southeast Asia Community 


fishbase www.fishbase.org/summary/4729

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