The pajama cardinalfish, spotted cardinalfish, coral cardinalfish, or polkadot cardinalfish (''Sphaeramia nematoptera'') is a species of fish belonging to the family

Apogonidae Cardinalfishes are a family, Apogonidae, of ray-finned fishes found in the Atlantic, Indian, and Pacific Oceans; they are chiefly marine, but some species are found in brackish water and a few (notably '' Glossamia'') are found in fresh water. ...

. It is a popular

aquarium fish Lists of aquarium life include lists of fish, amphibians, invertebrates and plants in freshwater, brackish and marine aquarium An aquarium (: aquariums or aquaria) is a vivarium of any size having at least one transparent side in which aquat ...

. It grows to a total length around and features distinctive red eyes and a broad, dark, vertical 'waistband' with scattered red spots toward the tail. It is considered to be of low vulnerability, and is distributed throughout much of the western

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

, 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 ...

Fiji Fiji, officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about ...

, and from the

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Geography of Taiwan, Taiwan: the Ryukyu Islands are divided into the Satsunan Islands (Ōsumi Islands, Ōsumi, Tokara Islands, Tokara and A ...

south to the

Great Barrier Reef The Great Barrier Reef is the world's largest coral reef system, composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, ...

. The male pajama cardinalfish incubates the eggs in his mouth until they hatch.

Description

Pajama cardinalfish display a rainbow of colors. They have greenish-yellow faces, bright orange eyes, and silver-based bodies dressed with a bold black scalar margin and posteriors dotted with orange polka dots. Though their bold coloration may stand out, ''S. nematoptera'' fish have a peaceful nature that lets them blend perfectly into most community saltwater aquaria. Like many other schooling fish, pajama cardinalfish form a strict hierarchy when kept in small groups within the aquarium. However, unlike some social fish, this member of the family Apogonidae does not use aggression to exert dominance over other cardinalfish.

Reproduction

''Sphaeramia nematoptera'' is

socially monogamous Monogamy ( ) is a relationship of two individuals in which they form a mutual and exclusive intimate partnership. Having only one partner at any one time, whether for life or serial monogamy, contrasts with various forms of non-monogamy (e.g., ...

, meaning that any individual male fish will form a long-term bond with just a single female. The two fish stay close to one another and mate with each other for several breeding cycles, though extra-pair fertilizations have been observed in the species. If one partner dies or is otherwise removed, the widowed fish is likely to form another bond. Both males and females prefer to mate with fish that are of similar size to themselves. Copulation occurs year-round and throughout the day, but is more common at night. While mating, the two fish may become aggressive towards

conspecifics Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organism ...

. To mate, the female will deposit eggs directly into the water column. Then, the male will quickly fertilize the eggs and scoop them into its mouth. Like other

cardinalfish Cardinalfishes are a family, Apogonidae, of ray-finned fishes found in the Atlantic, Indian, and Pacific Oceans; they are chiefly marine, but some species are found in brackish water and a few (notably '' Glossamia'') are found in fresh water. A ...

, male ''Sphaeramia nematoptera'' are

mouthbrooders Mouthbrooding, also known as oral incubation and buccal incubation, is the care given by some groups of animals to their offspring by holding them in the mouth of the parent for extended periods of time. Although mouthbrooding is performed by a va ...

; holding the fertilized eggs in their mouths for 8–31 days. This practice occurs even if the eggs are not all related to the male (though this is uncommon). In these cases, the male will be carrying an average of 18% of genetically unrelated eggs. Both males and females have been recorded to mate outside their bonded pair, leading to males carrying eggs from multiple partners. In total, only around 70% of all egg clutches will be the result of monogamy with bonded social partners.

Gallery

File:2016, wakatobi, allegra's wall, pyjama cardinal twins (30657541103).jpg, Pyjama cardinal twins at

Wakatobi National Park Wakatobi National Park is a marine national park in Southeast Sulawesi, Indonesia. It was established in 2002. The name of Wakatobi is a portmanteau of the four main Tukangbesi Islands: Wangi-wangi, Kaledupa, Tomia, and Binongko. Since 2005 t ...

Indonesia, 2016 File:Pajama Cardinalfish - Sphaeramia nematoptera.jpg, Pajama Cardinalfish at South Komodo Island, Indonesia, 2015 File:Pajama cardinalfish (Sphaeramia nematoptera) (40701335192).jpg, Pajama Cardinalfish at

Lembeh Lembeh is an island off the north east coast of Sulawesi near the city of Bitung. Lembeh Island is 25 km long and 2 km wide. Lembeh Island is separated from the mainland of Sulawesi by a narrow stretch of water known as the Lembeh Stra ...

, Indonesia, 2018

References

External links

nemoptera ''Nemoptera'' is a Palearctic genus of insects of the spoonwing family, Nemopteridae. All species are diurnal with an exclusively floral diet, preferring to fly in open spaces in full sunshine while visiting flowers. They can be recognized by th ...

Fish of Southeast Asia Fish of Indonesia Taxa named by Pieter Bleeker Fish described in 1856 {{Kurtiformes-stub