Nepomorpha
Encyclopedia
Nepomorpha is an infraorder of insect
s in the "true bug" order
(Hemiptera
). They belong to the "typical" bugs of the suborder Heteroptera
. Due to their aquatic
habits, these animal
s are known as true water bugs. They occur all over the world outside the polar region
s, with about 2,000 species
altogether. The Nepomorpha can be distinguisted from related Heteroptera by their missing or vestigial ocelli. Also, as referred to by the obsolete name Cryptocerata ("the hidden-horned ones"), their antenna
e are reduced, with weak muscles, and usually carried tucked against the head.
Most of the species
within this infraorder live in freshwater
habitat
s. The exceptions are members of the superfamily
Ochteroidea, which are found along the water's edge. Many of these insects are predators of invertebrate
s and in some cases – like the large water scorpions (Nepidae) and giant water bug
s (Belostomatidae) – even small fish
and amphibian
s. Others are omnivore
s or feed on plant
s. Their mouthparts
form a rostrum
as in all Heteroptera and most Hemiptera. With this, they pierce their foodstuffs to suck out fluids; some, like the Corixidae, are also able to chew their food to some extent, sucking up the resulting pulp. The rostrum can also be used to sting in defence; some, like the common backswimmer (Notonecta glauca
) of the Notonectidae
can easily pierce the skin of humans and deliver a wound often more painful than a bee
's sting.
, some . As evidenced by fossil
s such as the rather advanced Triassocoridae or the primitive water boatman Lufengnacta, the radiation establishing today's superfamilies seems to have been largely complete by the end of the Triassic
. There are a large number of fossil genera, but except those placed in Triassocoridae they can at least tentatively be assigned to the extant superfamilies.
Though the systematics
and phylogeny
of the higher taxa
of Nepomorpha were long controversial, cladistic analysis
of mitochondrial 16S and nuclear
28S rDNA sequence
data and morphology
has more recently resolved to near-perfection. The long-accepted superfamilies are all monophyletic, with the exception of the Naucoroidea, which is now monotypic with the Aphelocheiridae and Potamocoridae being split off in a new superfamily Aphelocheiroidea. The Cibariopectinata, a proposed clade
established on the presence of cibariopectine structures in the food-sucking pump of some of the most advanced true water bugs (Tripartita), might indeed be monophyletic. Alternatively it might be synonymous with the Tripartita, the Ochteroidea having lost the cibariopectines again due to the different requirements of their (for Nepomorpha) unusual lifestyle.
The following list arranges of superfamilies in evolution
ary sequence, from the most ancient to the most modern lineage:
Infraorder Nepomorpha
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s in the "true bug" order
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...
(Hemiptera
Hemiptera
Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
). They belong to the "typical" bugs of the suborder Heteroptera
Heteroptera
Heteroptera is a group of about 40,000 species of insects in the Hemiptera. Sometimes called "true bugs", that name more commonly refers to Hemiptera as a whole, and "typical bugs" might be used as a more unequivocal alternative since among the Hemiptera the heteropterans are most consistently and...
. Due to their aquatic
Aquatic insects
Aquatic insects live some portion of their life cycle in the water. They feed in the same ways as other insects. Some diving insects, such as predatory diving beetles, can hunt for food underwater where land-living insects cannot compete.-Breathing:...
habits, these animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s are known as true water bugs. They occur all over the world outside the polar region
Polar region
Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...
s, with about 2,000 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...
altogether. The Nepomorpha can be distinguisted from related Heteroptera by their missing or vestigial ocelli. Also, as referred to by the obsolete name Cryptocerata ("the hidden-horned ones"), their antenna
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
e are reduced, with weak muscles, and usually carried tucked against the head.
Most of the 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...
within this infraorder live in 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...
habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s. The exceptions are members of the superfamily
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...
Ochteroidea, which are found along the water's edge. Many of these insects are predators of invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s and in some cases – like the large water scorpions (Nepidae) and giant water bug
Giant water bug
Belostomatidae is a family of insects in the order Hemiptera, known as giant water bugs or colloquially as toe-biters, electric-light bugs and Alligator Ticks . They are the largest insects in the order Hemiptera, and occur worldwide, with most of the species in North America, South America,...
s (Belostomatidae) – even small 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...
and amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s. Others are omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
s or feed on plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s. Their mouthparts
Insect mouthparts
Insects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...
form a rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
as in all Heteroptera and most Hemiptera. With this, they pierce their foodstuffs to suck out fluids; some, like the Corixidae, are also able to chew their food to some extent, sucking up the resulting pulp. The rostrum can also be used to sting in defence; some, like the common backswimmer (Notonecta glauca
Notonecta glauca
Notonecta glauca is a species of backswimmer. It the most widespread and abundant of the four British notonectids....
) of the Notonectidae
Notonectidae
Notonectidae is a cosmopolitan family of aquatic insects in the order Hemiptera, commonly called backswimmers because they swim upside down. They are all predators, up to nearly 2 cm in size. They are similar in appearance to Corixidae , but can be separated by differences in their...
can easily pierce the skin of humans and deliver a wound often more painful than a bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
's sting.
Systematics
The Nepomorpha probably originated around the start of the Early TriassicEarly Triassic
The Early Triassic is the first of three epochs of the Triassic period of the geologic timescale. It spans the time between 251 ± 0.4 Ma and 245 ± 1.5 Ma . Rocks from this epoch are collectively known as the Lower Triassic, which is a unit in chronostratigraphy...
, some . As evidenced by fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s such as the rather advanced Triassocoridae or the primitive water boatman Lufengnacta, the radiation establishing today's superfamilies seems to have been largely complete by the end of the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
. There are a large number of fossil genera, but except those placed in Triassocoridae they can at least tentatively be assigned to the extant superfamilies.
Though the systematics
Systematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
and phylogeny
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
of the higher taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
of Nepomorpha were long controversial, cladistic analysis
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
of mitochondrial 16S and nuclear
Nuclear DNA
Nuclear DNA, nuclear deoxyribonucleic acid , is DNA contained within a nucleus of eukaryotic organisms. In mammals and vertebrates, nuclear DNA encodes more of the genome than the mitochondrial DNA and is composed of information inherited from two parents, one male, and one female, rather than...
28S rDNA 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 and morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
has more recently resolved to near-perfection. The long-accepted superfamilies are all monophyletic, with the exception of the Naucoroidea, which is now monotypic with the Aphelocheiridae and Potamocoridae being split off in a new superfamily Aphelocheiroidea. The Cibariopectinata, a proposed clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
established on the presence of cibariopectine structures in the food-sucking pump of some of the most advanced true water bugs (Tripartita), might indeed be monophyletic. Alternatively it might be synonymous with the Tripartita, the Ochteroidea having lost the cibariopectines again due to the different requirements of their (for Nepomorpha) unusual lifestyle.
The following list arranges of superfamilies in evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
ary sequence, from the most ancient to the most modern lineage:
Infraorder Nepomorpha
- Superfamily Nepoidea
- Family Belostomatidae – giant water bugs
- Family NepidaeNepidaeNepidae is a family of insects in the order Hemiptera, suborder Heteroptera. They are commonly called waterscorpions for their superficial resemblance to a scorpion, which is due to the raptorial forelegs and the presence of a long slender process at the posterior end of the abdomen, simulating a...
– water scorpions
- Superfamily Corixoidea
- Family Corixidae – water boatmen
- CladeCladeA clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Tripartita- Superfamily Ochteroidea
- Family GelastocoridaeGelastocoridaeThe Gelastocoridae is a family of about 100 species of insects in the suborder Heteroptera. They are reminiscent of toads both in the warty appearance and hopping movements of some species.-Biology:...
– toad bugs - Family OchteridaeOchteridaeOchteridae is a family of insects commonly known as the velvety shore bugs. There are around 25 species. Their habit is the edge of ponds and other still waters....
– velvety shore bugs
- Family Gelastocoridae
- Clade Cibariopectinata (disputed)
- Family Triassocoridae (fossilFossilFossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
; tentatively placed here) - Superfamily Aphelocheiroidea
- Family Aphelocheiridae
- Family Potamocoridae
- Superfamily Naucoroidea
- Family NaucoridaeNaucoridaeNaucoridae is a small family of insects commonly known as the creeping water bugs. They are very similar in appearance and behavior to the giant water bugs , and also occur in ponds and other still waters. Occasionally, these insects can be found in damp places in a person's home, and are often...
– creeping water bugs
- Family Naucoridae
- Superfamily Notonectoidea
- Family NotonectidaeNotonectidaeNotonectidae is a cosmopolitan family of aquatic insects in the order Hemiptera, commonly called backswimmers because they swim upside down. They are all predators, up to nearly 2 cm in size. They are similar in appearance to Corixidae , but can be separated by differences in their...
– backswimmers
- Family Notonectidae
- Superfamily Pleoidea (sometimes included in Notonectoidea)
- Family Helotrephidae
- Family PleidaePleidaePleidae, the pygmy backswimmers, is a family of aquatic insects in the order Hemiptera . There are 37 species in three genera, distributed across most of the world, except the polar regions and remote oceanic islands.Pleidae belong to the Tripartita which contains the more advanced lineages of true...
– pygmy backswimmers
- Family Triassocoridae (fossil
- Superfamily Ochteroidea
Further reading
- Mikko Haaramo (2008): Mikko's Phylogeny ArchiveMikko's Phylogeny ArchiveMikko's Phylogeny Archive is an amateur paleontology website maintained by Mikko Haaramo, a student at the University of Helsinki's Department of Geology, Division of Geology and Palaeontology....
- Nepomorpha.