Osmeriformes
Encyclopedia
Osmeriformes is an order
of ray-finned fish that includes the true or freshwater smelts and allies, such as the galaxiid
s and noodlefishes; they are also collectively called osmeriforms. They belong to the teleost superorder Protacanthopterygii
, which also includes pike and salmon
, among others. The order's name means "smelt-shaped", from Osmerus
(the type genus
) + the standard fish
order suffix
"-formes". It ultimately derives from Ancient Greek
osmé (ὀσμή, "pungent smell") + Latin
forma ("external form"), the former in reference to the characteristic aroma of the flesh of Osmerus.
In the classification used here, the order Osmeriformes contains 2 suborders, 6 families
, some 20 genera and about 90 species
. Other authors choose a slightly different arrangement, but whether treated as suborders (Galaxoidei and Osmeroidei) or superfamilies (Galaxoidea and Osmeroidea), the division in two lineages is generally maintained.
The "marine" smelts and allies (e.g. the odd-looking barreleye
s) were formerly included here as suborder Argentinoidei; they are now usually considered more distantly related than it was believed and treated as order Argentiniformes
. When the marine smelts were included here, the subdivisions of the Osmeriformes were down-ranked
by one.
is usually included in the mouth's gape, and most of them have an adipose fin as is often found in the Protacanthopterygii
. Their pterosphenoid usually has a ventral flange, and the vomer
has a short posterior shaft. They have reduced or even missing articular and mesopterygoid teeth, and the basisphenoid and orbitosphenoid bones are entirely absent. Their scale
s lack radii.
Despite the term "freshwater
smelts", the members of the Osmeriformes are generally marine
, or amphidromous or anadromous migrants. Even the sedentary freshwater species in this family are usually tolerant of considerable changes in salinity
. Almost all osmeriforms spawn
in fresh water, thus the marine species are generally anadromous. They are found in temperate
oceans worldwide and in temperate freshwater
of the Holarctic
and around the South Pacific
region; only a handful of species
occur in tropical waters. The egg
s are surrounded by an adhesive membrane
.
separated as a distinct order, the remaining Osmeriformes appear to be a monophyletic group. Their placement in the Protacanthopterygii is not entirely clear, but may well be the closest living relatives of the Esociformes
(pikes and mudminnows). Others consider them closer to the Salmoniformes (trout
s, salmon
s and relatives). A closer relationship to the Stomiiformes
than previously assumed is supported by anatomical and DNA sequence
data. But this can be simply taken to suggest that the superorder "Stenopterygii
" ought to be included in the Protacanthopterygii, rather than a particularly close relationship between the two orders.
The classification of the Osmeriformes as approached here is:
A possible fossil
osmeriform is Spaniodon, a piscivore
from Late Cretaceous
seas. The group originated probably somewhat earlier, but a Cretaceous
age – maybe about 110 million years ago or so – is likely.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of ray-finned fish that includes the true or freshwater smelts and allies, such as the galaxiid
Galaxiid
The Galaxiidae, also known by the anglicised name as galaxiids, are a family of mostly small freshwater fish in the southern hemisphere. The majority of species live in Australia or New Zealand, some are also found in South Africa, South America, Lord Howe Island, New Caledonia and the Falkland...
s and noodlefishes; they are also collectively called osmeriforms. They belong to the teleost superorder Protacanthopterygii
Protacanthopterygii
Protacanthopterygii is a ray-finned fish taxon ranked as a superorder of the infraclass Teleostei. They inhabit both marine and freshwater habitat...
, which also includes pike and salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
, among others. The order's name means "smelt-shaped", from Osmerus
Osmerus
Osmerus is a genus of fish in the Osmeridae family.It contains the following species:* Pygmy smelt * Rainbow smelt * European smelt...
(the type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
) + the standard fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
order suffix
Suffix
In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns or adjectives, and verb endings, which form the conjugation of verbs...
"-formes". It ultimately derives from Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
osmé (ὀσμή, "pungent smell") + Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
forma ("external form"), the former in reference to the characteristic aroma of the flesh of Osmerus.
In the classification used here, the order Osmeriformes contains 2 suborders, 6 families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
, some 20 genera and about 90 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. Other authors choose a slightly different arrangement, but whether treated as suborders (Galaxoidei and Osmeroidei) or superfamilies (Galaxoidea and Osmeroidea), the division in two lineages is generally maintained.
The "marine" smelts and allies (e.g. the odd-looking barreleye
Barreleye
Barreleyes, also known as spook fish , are small deep-sea osmeriform fish comprising the family Opisthoproctidae...
s) were formerly included here as suborder Argentinoidei; they are now usually considered more distantly related than it was believed and treated as order Argentiniformes
Argentiniformes
Argentiniformes is an order of ray-finned fish whose distinctness was recognized only fairly recently. In former times, they were included in the Osmeriformes as suborder Argentinoidei. That term refers only to the suborder of marine smelts and barreleyes in the classification used here, with the...
. When the marine smelts were included here, the subdivisions of the Osmeriformes were down-ranked
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
by one.
Description and ecology
Osmeriformes are small to mid-sized slender fish. Their maxillaMaxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
is usually included in the mouth's gape, and most of them have an adipose fin as is often found in the Protacanthopterygii
Protacanthopterygii
Protacanthopterygii is a ray-finned fish taxon ranked as a superorder of the infraclass Teleostei. They inhabit both marine and freshwater habitat...
. Their pterosphenoid usually has a ventral flange, and the vomer
Vomer
The vomer is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones.-Biology:...
has a short posterior shaft. They have reduced or even missing articular and mesopterygoid teeth, and the basisphenoid and orbitosphenoid bones are entirely absent. Their scale
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
s lack radii.
Despite the term "freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
smelts", the members of the Osmeriformes are generally marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
, or amphidromous or anadromous migrants. Even the sedentary freshwater species in this family are usually tolerant of considerable changes in salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
. Almost all osmeriforms spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
in fresh water, thus the marine species are generally anadromous. They are found in temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
oceans worldwide and in temperate freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
of the Holarctic
Holarctic
The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...
and around the South Pacific
Oceania
Oceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...
region; only a handful of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
occur in tropical waters. The egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
s are surrounded by an adhesive membrane
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...
.
Systematics
With the ArgentiniformesArgentiniformes
Argentiniformes is an order of ray-finned fish whose distinctness was recognized only fairly recently. In former times, they were included in the Osmeriformes as suborder Argentinoidei. That term refers only to the suborder of marine smelts and barreleyes in the classification used here, with the...
separated as a distinct order, the remaining Osmeriformes appear to be a monophyletic group. Their placement in the Protacanthopterygii is not entirely clear, but may well be the closest living relatives of the Esociformes
Esociformes
Esociformes is a small order of ray-finned fish, with two families, the Umbridae and the Esocidae . The pikes of genus Esox give the order its name. There are ten species — five in each family....
(pikes and mudminnows). Others consider them closer to the Salmoniformes (trout
Trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
s, salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
s and relatives). A closer relationship to the Stomiiformes
Stomiiformes
Stomiiformes is an order of deep-sea ray-finned fishes of very diverse morphology. It includes for example dragonfishes, lightfishes, loosejaws, marine hatchetfishes and viperfishes. The order contains 4 families with more than 50 genera and almost 400 species...
than previously assumed is supported by anatomical and DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
data. But this can be simply taken to suggest that the superorder "Stenopterygii
Stenopterygii
Stenopterygii are a superorder of ray-finned fish in the infraclass Teleostei. Their validity is somewhat doubtful, as the group was established to separate, out of a large group of closely related Teleostei, a mere two rather peculiarly autapomorphic orders at best...
" ought to be included in the Protacanthopterygii, rather than a particularly close relationship between the two orders.
- Suborder Galaxoidei
- Family Galaxiidae – galaxiid
- Family Lepidogalaxiidae – West Australian Salamanderfish
- Family RetropinnidaeRetropinnidaeRetropinnidae is a family of bony fish that contains the southern hemisphere smelts and graylings. They are quite closely related to the northern smelts , which they greatly resemble, but not to the northern graylings . Species from this family are only found in southeastern Australia and New Zealand...
– Australian-New Zealand smelts and graylings
- Suborder Osmeroidei
- Family Osmeridae – freshwater smelts, typical smelts
- Family Plecoglossidae – Ayu
- Family SalangidaeSalangidaeIcefishes or noodlefishes are a family, the Salangidae, of osmeriform fish, related to the smelts. They are found in freshwater environments in Southeast Asia, although a few species are anadromous, spending most of their life in coastal waters, and only visiting fresh water to spawn.They have...
– noodlefishes, "icefishes"
A possible fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
osmeriform is Spaniodon, a piscivore
Piscivore
A piscivore is a carnivorous animal which eats primarily fish. Piscivory was the diet of early tetrapods , insectivory came next, then in time reptiles added herbivory....
from Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
seas. The group originated probably somewhat earlier, but a Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
age – maybe about 110 million years ago or so – is likely.