The
halfbeaks (
familyIn 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...
Hemiramphidae) are a geographically widespread and numerically abundant
familyIn 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...
of epipelagic
fishA fish is any aquatic vertebrate animal that is typically ectothermic , covered with scales, and equipped with two sets of paired fins and several unpaired fins...
inhabiting warm waters around the world. The family Hemiramphidae is divided into two subfamilies, the primarily marine Hemiramphinae and the
freshwaterFresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
or
estuarineAn estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries are thus subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of...
Zenarchopterinae. The halfbeaks are named for their distinctive jaws, in which the lower jaws are significantly longer than the upper jaws. The halfbeaks are remarkable for showing an exceptionally wide range of
reproductiveReproduction is the biological process by which new individual organisms are produced. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction...
modes. These include
egg-layingOviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, reptiles, all birds, the monotremes, and most insects and arachnids....
,
ovoviviparityOvoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch...
, and true
viviparyA viviparous animal is an animal employing vivipary: the embryo develops inside the body of the mother, as opposed to outside in an egg . The mother then gives live birth....
where the mother is connected to the developing embryos via a
placentaThe placenta is an organ unique to mammals that connects the developing fetus to the uterine wall. The placenta supplies the fetus with oxygen and food, and allows fetal waste to be disposed of via the maternal kidneys...
-like structure. In some of the
livebearingLive-bearing aquarium fish, often simply called livebearers, are fish that retain the eggs inside the body and give birth to live, free-swimming young.-Common aquarium livebearers:...
species, developing
embryoAn embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s are also known to exhibit
oophagyOophagy is the practice of embryos feeding on eggs produced by the ovary while still inside the mother's uterus.Oophagy is thought to occur in all sharks in the order Lamniformes and has been recorded in the bigeye thresher , the pelagic thresher Oophagy (egg eating) is the practice of embryos...
or
intrauterine cannibalismIntrauterine Cannibalism is the first studio album by American brutal death metal band Malignancy.-Track listing:# "Rotten Seed" — 3:16# "Intrauterine Cannibalism" — 1:42# "Intestinal Sodomy" — 2:22# "Internal Corruption" — 1:48...
, where developing embryos feed on eggs or other embryos within the uterus.
Though not
commercially importantFishing is the activity of catching fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
themselves, these are
forage fishForage fish are small fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food chain on plankton, often by filter feeding...
which support
artisanal fisheriesArtisan fishing is a term sometimes used to describe small scale commercial or subsistence fishing practises. The term particularly applies to coastal or island ethnic groups using traditional techniques such as rod and tackle, arrows and harpoons, throw nets and drag nets, and maybe traditional...
and local markets worldwide. They are also fed upon by other commercially important predatory fishes, such as
billfishThe term billfish is applied to a number of different large, predatory fish characterised by their large size and their long, sword-like bill. Billfish include the sailfish and marlin, which make up the family Istiophoridae, and the swordfish, sole member of the family Xiphiidae...
es,
mackerelMackerel is a common name applied to a number of different species of fish, mostly, but not exclusively, from the family Scombridae. They may be found in all tropical and temperate seas. Most live offshore in the oceanic environment but a few, like the Spanish mackerel , enter bays and can be...
s, and
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs....
s. Some halfbeaks are maintained as
aquariumAn aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
fish in the
fishkeepingFishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond.- Types of fishkeeping :The hobby can be broadly divided into three specific disciplines, freshwater, brackish, and marine fishkeeping....
hobby.
Taxonomy
The first halfbeak to be scientifically described was
EsoxEsox is a genus of freshwater fish, the only living genus in the family Esocidae — the esocids which were endemic to North America, Europe and Eurasia during the Paleogene through present from 65—0 mya, existing for approximately ....
brasiliensis, by
Carolus LinnaeusCarl Linnaeus was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature...
in 1758. Two more species were described as
Esox,
Esox far and
Esox marginatus, by
Peter ForsskålPeter Forsskål, sometimes spelled Pehr Forsskål, Peter Forskaol, Petrus Forskål or Pehr Forsskåhl, was a Swedish explorer, orientalist and naturalist.-Early life:...
in 1775. It was not until 1816 that
Georges CuvierGeorges Léopold Chrétien Frédéric Dagobert Cuvier was a French naturalist and zoologist. Of humble working class origins, he belonged to a new class of self-made scholars who worked their way to the top of academe...
created the genus
Hemiramphus; from then on, these three species were classified as
Hemiramphus species. Hemiramphidae was erected by Gill in 1859, deriving its name from
Hemiramphus, the family's
type genusIn biology, a type is that which fixes a name to a taxon. Depending on the nomenclature code which is applied to the organism in question, a type may be a specimen, culture, illustration, description or taxon....
. The name comes from the
GreekAncient Greek is the historical stage in the development of the Greek language spanning across the Archaic , Classical , and Hellenistic periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek...
hemi, meaning half, and
rhamphos, meaning a beak or bill.
The family Hemiramphidae is currently divided into two subfamilies, the Hemiramphinae and the Zenarchopterinae, each containing about half the known species. In a 2004 review of the family, two subfamilies, 13 genera, and 117 species and subspecies were recognised. More recently, Hemiramphidae has been listed to include 12 genera and about 109 species, with the genus
Oxyporhamphus moved to Exocoetidae.
The Hemiramphinae are primarily
marineMarine biology is the scientific study of living organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment...
and found in the Atlantic, Pacific, and
Indian OceanThe Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by South Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean...
s, though some inhabit
estuariesAn estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries are thus subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of...
and
riverA river is a natural watercourse, usually freshwater, flowing toward an ocean, a lake, a sea or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water...
s. The Zenarchopterinae are confined to the
Indo-West PacificThe Indo-West Pacific, or IWP, is a zoogeographical region spanning the entire Indian Ocean including the Red Sea and the Pacific Ocean as far as the Caroline Islands but short of the Marshall Islands...
zoogeographicZoogeography is the branch of the science of biogeography that is concerned with the geographic distribution of animal species and their attributes...
region, an area running from
East AfricaEast Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
to the
Caroline IslandsThe Caroline Islands form a large archipelago of widely scattered islands in the western Pacific Ocean, northeast of New Guinea. Politically they are divided between the Federated States of Micronesia in the eastern part of the group, and Palau at the extreme western end...
. The Zenarchopterinae are remarkable for exhibiting strong
sexual dimorphismSexual dimorphism is the systematic difference in form between individuals of different sex in the same species. Examples include colour , size, and the presence or absence of parts of the body used in courtship displays or fights, such as ornamental feathers, horns, antlers or tusks.-Examples:In...
, practicing internal fertilisation, and in some cases being ovoviviparous or viviparous. Three genera in this subfamily are exclusively
freshwater fishFresh water fish are fish that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 0.05%. These environments differ from marine conditions in many ways, the most obvious being the difference in levels of salinity...
and several, such as the
wrestling halfbeakThe wrestling halfbeak, Dermogenys pusilla, also known as Malayan halfbeak is a member of the halfbeak family found in the fresh and brackish waters of rivers and coastal regions in South-East Asia, in Singapore, Thailand, Indonesia, Thailand, Malaysia, Borneo and Sumatra...
, have become commonly traded
aquarium fishFishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond.- Types of fishkeeping :The hobby can be broadly divided into three specific disciplines, freshwater, brackish, and marine fishkeeping....
. It is believed by some authors that the recognition of Zenarchopterinae as a separate family (Zenarchopteridae) probably should be accepted.
Evolution
The fossil record of the halfbeaks extends into the Lower Tertiary. The earliest known halfbeak is
Brachyrhamphus bolcensis from the
EoceneThe Eocene epoch, lasting from 55.8 ± 0.2 to 33.9 ± 0.1 Ma , is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era. The Eocene spans the time from the end of the Paleocene epoch to the beginning of the Oligocene epoch. The start of the...
at Monte
BolcaBolca is a village in the Veneto, on the southern margin of the Italian Alps. It is a frazione of the comune of Vestenanova, in the province of Verona. The area is famous for the marine fossils from the lagerstätte of Monte Bolca...
, Italy. Apart from differences in the length of the upper and lower jaws,
recentThe Holocene is a geological epoch which began approximately 11 700 years ago . According to traditional geological thinking, the Holocene continues to the present. The Holocene is part of the Neogene and Quaternary periods. Its name comes from the Greek words and , meaning "entirely...
and fossil halfbeaks are distinguished by the fusion of the third pair of upper pharyngeal bones into a plate.
Phylogeny
Phylogeny of the halfbeaks. The halfbeak familyIn 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...
Hemiramphidae (Zenarchopterinae + Hemirhamphinae) is paraphyletic.
The phylogeny of the halfbeaks is controversial and currently in a state of flux.
On the one hand, there is little question that they are most closely related to three other families of streamlined, surface water fishes: the
flyingfishExocoetidae aptly known as flying fish are a marine fish family comprising about 64 species grouped in seven to nine genera.Flying fish are found in all of the major oceans, particularly in the warm tropical and subtropical waters of the Atlantic, Pacific, and Indian oceans...
es,
needlefishNeedlefish are piscivorous fishes primarily associated with very shallow marine habitats or the surface of the open sea. Some genera include species found in marine, brackish, and freshwater environments while a few genera are confined to freshwater rivers and streams, including Belonion,...
es, and
sauriesSauries are fish of the family Scomberesocidae. There are two genera, each containing two species. The name Scomberesocidae is derived from the Greek, skombros = tunny/mackerel, and esox = nursery of salmon....
. Traditionally, these four families have been taken to together comprise the order
BeloniformesThe Beloniformes are an order of five families of freshwater and marine ray-finned fish: the Adrianichthyidae ; Belonidae ; Exocoetidae ; Hemiramphidae : and the Scomberesocidae...
. The halfbeaks and flyingfishes are considered to form one group, the superfamily Exocoetoidea, and the needlefishes and sauries another, the superfamily Scomberesocoidea.
On the other hand, recent studies have demonstrated that rather than forming a single monophyletic group (a
cladeA clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[The term "monophyletic group" is used in this article...]
), the halfbeak family actually includes a number of lineages ancestral to the flyingfishes and the needlefishes. In other words, as traditionally defined, the halfbeak family is paraphyletic.
Within the subfamily Hemiramphinae, the "flying halfbeak" genus
Oxyporhamphus has proved to be particularly problematical; while
morphologicallyIn biology morphology is the form, structure and configuration of an organism.This includes aspects of the outward appearance as well as the form and structure of the internal parts like bones and organs...
closer to the flyingfishes, molecular evidence places it with
Hemiramphus and
Euleptorhamphus. Together, these three genera form the
sister groupCladistics is a form of biological systematics which classifies living organisms on the basis of shared ancestry...
to the flyingfish family. The other two hemiramphine genera
Hyporhamphus and
Arrhamphus form another clade of less clear placement.
Rather than being closely related to the flyingfishes, the subfamily Zenarchopterinae appears to be the sister group of the
needlefishNeedlefish are piscivorous fishes primarily associated with very shallow marine habitats or the surface of the open sea. Some genera include species found in marine, brackish, and freshwater environments while a few genera are confined to freshwater rivers and streams, including Belonion,...
es and
sauriesSauries are fish of the family Scomberesocidae. There are two genera, each containing two species. The name Scomberesocidae is derived from the Greek, skombros = tunny/mackerel, and esox = nursery of salmon....
. These is based on the pharyngeal jaw apparatus, sperm ultrastructure, and molecular evidence. However, this hypothesis has awkward implications for how the morphological evolution of the group is understood, because the fused pharyngeal plate has been considered reliably diagnostic of the halfbeak family. Furthermore, the existing theory that because juvenile needlefish pass through a
developmentalDevelopmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis," which is the process that gives rise to tissues, organs and anatomy.Developmental biology is that...
stage where the lower jaw is longer than the upper jaw (the so-called "halfbeak stage") the theory that halfbeaks are
paedomorphicIn developmental biology, pedomorphosis or juvenification is a phenotypic and/or genotypic change in which the adults of a species retain traits previously seen only in juveniles. Peramorphosis is change in the reverse direction. Pedomorphosis was first proposed by Walter Garstang in 1922...
needlefish is untenable. In fact the unequal lengths of the upper and lower jaws of halfbeaks appears to be the
basalIn phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
condition, with needlefish being relatively
derivedIn phylogenetics, a trait is derived if it is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary loss...
in comparison.
Morphology
The halfbeaks are elongate, streamlined fish adapted to living in open water. Halfbeaks range in size from 4
centimetreA centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the current SI base unit of length. Centi is the SI prefix for a factor of...
s (1.6
inAn inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...
)
standard length (SL)Fish measurement refers to the measuring of the length of individual fish and of various parts of their anatomy. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.-Overall length:...
in
Hemirhamphodon tengah to over 40 cm (16 in) SL in the case of
Euleptorhampus viridisEuleptorhamphus is a genus of halfbeaks in the order Beloniformes. It includes two species, the flying halfbeak, E. velox, and the ribbon halfbeak, E. viridis.Both of these species are marine. E...
. The
scalesIn 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...
are relatively large, cycloid (smooth), and easily detached. There are no spines in the fins. A peculiarity shared by all halfbeaks that distinguishes them from the other fishes in the Beloniformes is that the third pair of upper pharyngeal bones are anklylosed (fused) into a plate. Halfbeaks are one of a number of fish families that lack a
stomachIn most mammals, the stomach is a hollow, muscular organ of the gastrointestinal tract , between the esophagus and the small intestine. It is involved in the second phase of digestion, following mastication . The word stomach is derived from the Latin stomachus, which derives from the Greek word...
, all of which possess a pharyngeal jaw apparatus (pharyngeal mill). Most species have an extended lower jaw, at least as juveniles, though this feature may be lost as the fish mature, as with
Chriodorus, for example.
As is typical for surface dwelling, open water fish, most species are silvery, and darker above and lighter below, an example of
countershadingCountershading, or Thayer's Law, is a form of camouflage. Countershading, in which an animal’s pigmentation is darker dorsally, is often thought to have an adaptive effect of reducing conspicuous shadows cast on the ventral region of an animal’s body...
. The tip of the lower jaw is bright red or orange in most species. Small patches of colour, particularly among males, are only found on the fins and the tip of the beak.
Halfbeaks demonstrate a number of adaptations to feeding at the surface of the water. The eyes and nostrils are at the top of the head and it is the upper jaw that is mobile, not the lower jaw. Combined with their streamlined shape and the concentration of fins towards the back (similar to that of a
pikeEsox is a genus of freshwater fish, the only living genus in the family Esocidae — the esocids which were endemic to North America, Europe and Eurasia during the Paleogene through present from 65—0 mya, existing for approximately ....
), these adaptations allow halfbeaks to locate, catch, and swallow food items very effectively.
Sexual dimorphism
Sexual dimorphismSexual dimorphism is the systematic difference in form between individuals of different sex in the same species. Examples include colour , size, and the presence or absence of parts of the body used in courtship displays or fights, such as ornamental feathers, horns, antlers or tusks.-Examples:In...
is apparent in some species of halfbeak. Males of the ovovivaparous and vivaparous species all have a modified anal fin, the
andropodium, similar to the gonopodium of poecilid livebearers, used to deliver sperm to the females. Although most of the egg laying species mate by shedding the
miltMilt is the seminal fluid of fish, mollusks, and certain other water-dwelling animals who reproduce by spraying this fluid, which contains the sperm, onto roe .-Milt as food:...
externally, as is typical for bony fish, at least some egg-laying species practise internal fertilisation: male
ZenarchopterusZenarchopterus is a genus of fish in the Hemiramphidae family.It contains the following species:* Allen's river garfish * Buffon's river garfish...
use a modified anal fin to direct sperm into the genital opening of the female prior to spawning.
Besides modifications to the anal fin, other differences include size, colouration, and the length or shape of the beak. Female
Normorhamphus are much larger than males but aren't as brightly coloured and have shorter beaks. By contrast, male
Hemirhamphodon are larger than the females, and some species, such as
Hemirhamphodon pogonognathus, also have a long beard-like tassle on the end of the beak.
Distribution
Halfbeaks are found in warm seas, predominantly at the surface, occurring in the Atlantic,
IndianThe Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by South Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean...
, and Pacific oceans. A small number are found in estuaries and some species, including all the species in the genera
DermogenysThe freshwater and brackish water halfbeaks of the genus Dermogenys are widely distributed in South and South East Asia from India to Indonesia. They are all viviparous, producing small clutches of up to 30 fry that closely resemble the adults except that they are much smaller, around 10 to 15 mm...
,
HemirhamphodonHemirhamphodon is a genus of halfbeak found in peaty and lowland forest streams in Southeast Asia. Six species are known, all relatively small, the largest species being about 10 cm in length. These fish are viviparous and are sometimes kept as aquarium fish, but otherwise have no commercial...
,
NomorhamphusThe freshwater halfbeaks of the genus Nomorhamphus are widely distributed in South East Asia, in particular the islands of the Philippines, Indonesia, and Sulawesi. They are all viviparous, producing small clutches of around a dozen fry about 10 to 15 mm long at birth. Females are generally larger...
, and
Tondanichthys are confined to freshwaters. Most species of marine halfbeaks are known from continental coastlines, but some extend into the western and central Pacific, and one species is endemic to
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori named New Zealand Aotearoa, commonly translated as The Land of the Long White Cloud...
.
Hemiramphus is a worldwide marine genus.
The freshwater halfbeaks all occur in freshwater or estuaries in the
Indo-West PacificThe Indo-West Pacific, or IWP, is a zoogeographical region spanning the entire Indian Ocean including the Red Sea and the Pacific Ocean as far as the Caroline Islands but short of the Marshall Islands...
region. There is a particularly high concentration of species on the island of
CelebesSulawesi is one of the four larger Sunda Islands of Indonesia and is situated between Borneo and the Maluku Islands.- Etymology :...
.
Diet
Marine halfbeaks are
omnivoreOmnivores are species that eat both plants and animals as their primary food source...
s feeding on
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in...
; marine plants such as
seagrassSeagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully-saline environments.-Ecology:These unusual marine flowering plants are called seagrasses because the leaves are long and narrow and are very...
es;
planktonPlankton consist of any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. Plankton are defined by their ecological niche rather than their phylogenetic or taxonomic classification...
; invertebrates such as
pteropodsSea butterflies, also known as Thecosomata or flapping snails, are a taxonomic suborder of small pelagic swimming sea snails. These are holoplanktonic opisthobranch gastropod mollusks in the informal group Opisthobranchia....
and crustaceans; and smaller fishes. For some subtropical species at least, juveniles are more predatory than adults. Some tropical species have been observed to feed on animals during the day and plants at night, while other species alternate between carnivory in the summer and herbivory in the winter. They are in turn eaten by many ecologically and
commercially importantFishing is the activity of catching fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
predatory fish, such as
billfishThe term billfish is applied to a number of different large, predatory fish characterised by their large size and their long, sword-like bill. Billfish include the sailfish and marlin, which make up the family Istiophoridae, and the swordfish, sole member of the family Xiphiidae...
,
mackerelMackerel is a common name applied to a number of different species of fish, mostly, but not exclusively, from the family Scombridae. They may be found in all tropical and temperate seas. Most live offshore in the oceanic environment but a few, like the Spanish mackerel , enter bays and can be...
, and
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs....
s, and so are a key link between
trophic levelIn ecology, trophic dynamics is the system of trophic levels , which describes the position that an organism occupies in a food chain — what an organism eats, and what eats the organism.- Energy economy :...
s.
The freshwater species are more predatory than the marine species, and typically orient themselves into the water current and take aquatic insect larvae, such as
midgeA midge is a very small, two-winged flying insect. "Midge" may also refer to:* Midge Hadley, a fictional character in the Barbie line of dolls by Mattel* Midge Klump, a fictional character from Archie Comics...
larvae, and small insects, such as
fliesTrue flies are insects of the order Diptera , possessing a single pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax....
that have fallen on the surface of the water, particularly
mosquitoMosquito is a common insect in the family Culicidae...
es and
spiderSpiders are air-breathing chelicerate arthropods that have eight legs, and chelicerae modified into fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s.
Behaviour
Marine halfbeaks are typically pelagic
schoolingIn biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
forage fishForage fish are small fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food chain on plankton, often by filter feeding...
that swim close to the surface of the sea. The southern sea garfish
Hyporhamphus melanochir for example is found in sheltered bays, coastal seas, estuaries around southern Australia in waters down to a depth of 20
mThe metre or meter is the basic unit of length in the International System of Units . Historically, the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent one ten-millionth of the distance from the Equator...
(66 ft). These fish form schools near the surface at night but swim closer to the sea floor during the day, particularly among beds of
seagrassSeagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully-saline environments.-Ecology:These unusual marine flowering plants are called seagrasses because the leaves are long and narrow and are very...
es. Genetic analysis of the different
sub-populationsPopulation biology is a study of populations of organisms, especially the regulation of population size, life history traits such as clutch size, and extinction...
of the eastern sea garfish
Hyporhamphus melanochir in South Australian coastal waters reveals that there is a small but consistent migration of individuals between each sub-population, sufficient to keep them genetically homogenous.
Freshwater halfbeaks vary in social behaviour from open water schooling fish similar to the marine halfbeaks, as with species of
Zenarchopterus, through to much more aggressive and combative fishes, as is best known with the "wrestling" halfbeaks of the genus
Dermogenys. These non-schooling freshwater halfbeaks prefer to lurk among aquatic plants such as
reedsReed is a generic botanical term used to describe numerous tall, grass-like plants of wet places, which are the namesake vegetation of reed beds...
, dead trees, and artificial structures of various types; from there they will wait for small prey animals to drift by or alight on the surface, and then the halfbeak will dart out of their hiding place to capture its prey. Notably, these freshwater halfbeaks feed extensively on female mosquitoes that are laying their eggs in the water, making them much better at mosquito control that species like guppies and
mosquitofishThe mosquitofish is a species of freshwater fish, also commonly known simply by its generic name, gambusia, although such usage is ambiguous. It is sometimes called the western mosquitofish, to distinguish it from the eastern mosquitofish . It is a member of the family Poeciliidae of order...
that only take mosquito larvae.
Some marine halfbeaks, including
Euleptorhamphus velox and
Euleptorhamphus viridis, are know for their ability to jump out of the water and glide over the surface for considerable distances, and have consequently sometimes been called
flying halfbeaks.
Reproduction
Halfbeaks exhibit a remarkably wide variety of reproductive modes ranging from straightforward egg-laying (oviparity) through to various form of
livebearingLive-bearing aquarium fish, often simply called livebearers, are fish that retain the eggs inside the body and give birth to live, free-swimming young.-Common aquarium livebearers:...
(
ovoviviparityOvoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch...
and viviparity). There is a taxonomic split in this however: all Hemiramphinae are egg-layers, while many of the Zenarchopterinae are either ovoviviparous or viviparous.
Oviparity in the Hemiramphinae
Hemiramphinae species are all external fertilizers. They are usually egg-layers and often produce relatively small numbers of fairly large eggs for fish of their size, typically in shallow coastal waters, such as the
seagrassSeagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully-saline environments.-Ecology:These unusual marine flowering plants are called seagrasses because the leaves are long and narrow and are very...
meadows of
Florida BayFlorida Bay is the bay located between the southern end of the Florida mainland and the Florida Keys. Its area is variously stated to be , or , or . Nearly all of Florida Bay is included in Everglades National Park. The southern edge, along the Florida Keys is in the Florida Keys National Marine...
. The eggs of
Hemiramphus brasiliensis and
H. balao are typically 1.5–2.5
millimetreThe millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the current SI base unit of length.Equal to 1000 micrometres.Equal to 1000000 nanometres....
s (0.059–0.098 in) in diameter and have attaching filaments. They hatch when they are about 4.8–11 mm (0.19–0.43 in) in diameter.
Hyporhamphus melanochir eggs are slightly larger, around 2.9
millimetreThe millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the current SI base unit of length.Equal to 1000 micrometres.Equal to 1000000 nanometres....
s in diameter, and are unusually large when they hatch, being up to 8.5
millimetreThe millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the current SI base unit of length.Equal to 1000 micrometres.Equal to 1000000 nanometres....
s in size.
Relatively little is known about the ecology of juvenile marine halfbeaks after hatching, though estuarine habitats seem to be favoured by at least some species. The southern sea garfish
Hyporhamphus melanochir grows rapidly at first, attaining a length of up to 30
centimetreA centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the current SI base unit of length. Centi is the SI prefix for a factor of...
s in the first three years, after which point growth slows down. This species lives for a maximum age of about 9 years, at which point the fish will be up to 40
centimetreA centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the current SI base unit of length. Centi is the SI prefix for a factor of...
s and weigh about 0.35 kilogrammes.
Viviparity in the Zenarchopterinae
The freshwater halfbeaks of the genera
Dermogenys,
Hemirhamphodon, and
Nomorhamphus are all livebearers, that is, they do not lay eggs but instead produce well-developed free-swimming young. However, there is a great deal of variation in the details. Meisner and Burns identified no fewer than five distinct modes of viviparity and
ovovivparityOvoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch...
in the freshwater halfbeaks:
- Type 1: Fertilised eggs retained within the ovarian follicle
Ovarian follicle is the basic unit of female reproductive biology and is composed of roughly spherical aggregations of cells found in the ovary. They contain a single oocyte . These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single competent...
. SuperfetationSuperfetation is the formation of a fetus from a different menstrual cycle while another embryo is already present in the uterus. When there are two separate instances of fertilisation during the same cycle, it is known as superfecundation.Superfetation is claimed to be common in some species of...
, that is storage of sperm, does not occur. The eggs are provided with a large yolk sacThe yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
and have little or no connection to the maternal blood supply. Example: Southeast Asian populations of Dermogenys pusilla.
- Type 2: Fertilised eggs retained within the ovarian follicle. Superfetation does occur, with up to three broods resulting from a single mating. The eggs are provided with a small yolk sac but the embryos instead have a connection to the maternal supply through the coelomic cavity
By the broadest definition, a body cavity is any fluid filled space in a multicellular organism. However, the term usually refers to the space, located between an animal’s outer covering and the outer lining of the gut cavity, where internal organs develop...
and pericardial sacThe pericardium is a double-walled sac that contains the heart and the roots of the great vessels.-Layers:There are two layers to the pericardial sac: the fibrous pericardium and the serous pericardium...
. Examples: Dermogenys pusilla from Sabah and Dermogenys orientalis.
- Type 3: Fertilised eggs retained within the ovarian follicle only for the early stages of development, with the embryos later developing along the full length of the ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in females are homologous to testes in males, in that they are both gonads and endocrine glands.-Human anatomy:...
. Superfetation does occur, and up to two broods can develop simultaneously in the ovary. The eggs are provided with a small yolk sac but the embryos have a connection to the maternal supply through an expanded belly sac. Example: Dermogenys viviparus.
- Type 4: Fertilised eggs retained within the ovarian follicle only for the early stages of development, with the embryos later developing along the full length of the ovary. Superfetation does not occur. The eggs are provided with a large yolk sac and the embryos have no connection to the maternal blood supply. Examples: Nomorhamphus megarrhamphus, Nomorhamphus weberi, and Nomorhamphus towoetii.
- Type 5: Fertilised eggs retained within the ovarian follicle only for the early stages of development, with the embryos later developing along the full length of the ovary. Superfetation does occur, and embryos of different ages can be found in the ovaries. The eggs are provided with a small yolk sac and the embryos only have a connection to the maternal blood supply for only part of their development. Late-stage embryos appear to eat eggs and small embryos in ovary. Note that embryos eating eggs and other embryos has been observed in a few other fishes, most notably sharks (see article on oophagy
Oophagy is the practice of embryos feeding on eggs produced by the ovary while still inside the mother's uterus.Oophagy is thought to occur in all sharks in the order Lamniformes and has been recorded in the bigeye thresher , the pelagic thresher Oophagy (egg eating) is the practice of embryos...
). Example: Nomorhamphus ebrardtii.
As with other livebearing fish, freshwater halfbeaks produce small broods of large offspring compared with egg-laying species of similar size, with broods of around ten to twenty, 10–15 mm long offspring being typical.
Halfbeak fisheries
Halfbeaks are not a major target for
commercial fisheriesFishing is the activity of catching fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
, though small fisheries for them exist in some places, for example in
South AustraliaSouth Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories....
where fisheries target the southern sea garfish (
Hyporhamphus melanochir). and the eastern sea garfish (
Hyporhamphus australis). Halfbeaks are caught by a variety of methods including seines and pelagic trawls, dip-netting under lights at night, and with haul nets. They are utilized fresh, dried, smoked, or salted, and they are considered good eating. However, even where halfbeaks are targeted by fisheries, they tend to be of secondary importance compared with other edible fish species.
In some localities significant
bait fishBait fish are small fish caught for use as bait to attract large predatory fish, particularly game fish. Species used are typically those that are common and breed rapidly, making them easy to catch and in regular supply. Examples of marine bait fish are anchovies, halfbeaks such as ballyhoo, and...
eries exist to supply
sport fishermenGame fish are fish pursued for sport by recreational anglers. They can be freshwater or marine fish. Game fish can be eaten after being caught, though increasingly anglers practise catch and release to improve fish populations. Some game fish are also targeted commercially, particularly...
. One study of a bait fishery in Florida that targets
Hemiramphus brasiliensis and
Hemiramphus balao suggests that despite increases in the size of the fishery the population is stable and the annual catch is valued at around $500,000.
In the aquarium
Some of the smaller freshwater species are kept as
aquariumAn aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
fish in the ornamental
fishkeepingFishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond.- Types of fishkeeping :The hobby can be broadly divided into three specific disciplines, freshwater, brackish, and marine fishkeeping....
hobbyA hobby is an activity or interest that is undertaken for pleasure or relaxation in one's spare time.- Etymology :A hobby horse is a wooden or wickerwork toy made to be ridden just like a real horse...
. Species of the genera
Dermogenys and
Nomorhamphus are quite commonly kept as aquarium fish; species of
Hemirhamphodon and
Zenarchopterus are rather less commonly seen. They are small and generally peaceful towards other species, although males can be aggressive to one another. Male
Dermogenys pusillius in particular fight vigorously and sometimes these battles end in injuries; this fish has therefore become known as the
wrestling halfbeakThe wrestling halfbeak, Dermogenys pusilla, also known as Malayan halfbeak is a member of the halfbeak family found in the fresh and brackish waters of rivers and coastal regions in South-East Asia, in Singapore, Thailand, Indonesia, Thailand, Malaysia, Borneo and Sumatra...
and in some
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
n countries fights between males are used for betting purposes in much the same way as the
Siamese fighting fishBetta is a large genus of small, often colorful, freshwater ray-finned fishes in the gourami family . There are 28 known species of betta. The type species is B. picta, the spotted betta....
.
To be kept successfully, halfbeaks require an aquarium with plenty of space at the surface. Depth is not critical, so a tank that is wide is better than one that is deep. They are sensitive to low
oxygen levelsOxygen saturation or dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.-Medical science:In medicine, oxygen...
but are otherwise relatively hardy, with one important exception: they are intolerant to sudden changes in
salinitySalinity 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...
,
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
,
hardnessHard water is water that has high mineral content . Hard water minerals primarily consist of calcium , and magnesium metal cations, and sometimes other dissolved compounds such as bicarbonates and sulfates...
, or
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
. Consequently, they must be introduced to a new aquarium gently, and subsequent water changes are best small but frequent so the water chemistry does not change suddenly. A few species, most notably
Dermogenys pusillius, have traditionally been kept in slightly brackish water, though some authors disputer this and suggest that reports that these fish come from brackish water come from the misidentification of juvenile estuarine and marine halfbeaks as adult freshwater halfbeaks. Most of the traded species of
Nomorhamphus and
Hemirhamphodon are known to prefer soft, neutral to slightly acid, freshwater conditions.
Halfbeaks are nervous fish and shocks like sudden changes in illumination can cause them to swim around the tank frantically. They may hit themselves on the glass, injuring their beaks, or jump out of the tank completely. Injuries to the beak usually heal within a few weeks. They will eat insect larvae such as bloodworms readily, as well as crustacean eggs, shrimps, fruit flies, and even small pieces of chopped white fish. Halfbeaks sometimes eat flake foods as well. Some aquarists also offer them tiny pieces of algae wafer on the basis that most species are omnivorous in the wild, and so a certain amount of green food probably does them good.
Halfbeaks will breed in captivity, but despite being
livebearersLive-bearing aquarium fish, often simply called livebearers, are fish that retain the eggs inside the body and give birth to live, free-swimming young.-Common aquarium livebearers:...
they are not particularly easy to breed. Miscarriages are common, particularly if the females are stressed or shocked (for example, by being moved to another aquarium). Once the fry have been born, things get much simpler, as the baby halfbeaks are quite big and will eat newly hatched
brine shrimpBrine shrimp is the English name of the genus Artemia of aquatic crustaceans. Artemia, the only genus in the family Artemiidae, have evolved little since the Triassic period...
s, small live foods such as
daphniaDaphnia are small, planktonic crustaceans, between 0.2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style...
, and powdered
flakeA fish flake is a platform built on poles and spread with boughs for drying cod-fish on the foreshore of fishing villages and small towns in rural Newfoundland, Canada. Spelling variations for fish flake in Newfoundland include flek, fleyke, fleake, flaik and fleack...
.
Conservation status
A small number of freshwater halfbeaks are listed in various categories on the IUCN
Red ListThe IUCN Red List of Threatened Species , founded in 1948, is the world's most comprehensive inventory of the global conservation status of plant and animal species. The International Union for the Conservation of Nature and Natural Resources is the world's main authority on the conservation...
defining their risk of extinction. None of these species are traded as aquarium fish. Most are simply rare in the wild, and consequently at particular risk from
habitat destructionHabitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms which previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose...
.
- Dermogenys megarramphus – Lower Risk, Near Threatened
- Dermogenys weberi – Vulnerable
- Nomorhamphus celebensis – Data Deficient
- Nomorhamphus towoeti – Vulnerable
- Tondanichthys kottelati – Vulnerable
- Zenarchopterus alleni – Data Deficient
- Zenarchopterus robertsi – Lower Risk, Least Concern
See also
- Live-bearing aquarium fish
Live-bearing aquarium fish, often simply called livebearers, are fish that retain the eggs inside the body and give birth to live, free-swimming young.-Common aquarium livebearers:...
- USS Halfbeak (SS-352)
USS Halfbeak , a Balao-class submarine, was a ship of the United States Navy named for the halfbeak, a garlike fish with a beak formed by an extension of the lower jaw, found in warmer seas....
American submarineA submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has only limited underwater capability...
named after these fish