Corethrellidae
Encyclopedia
Corethrellidae is a family of parasitic midges, small flying insects belonging to the Order Diptera
, that are commonly known to parasitize frog
s. The members of the family are sometimes known as "frog-biting midges". The family currently consists of just two genera
, totalling around ninety seven species worldwide. There are several fossil species known. Most extant species are found in the lower latitudes, usually associated around the tropics
.
Adult female Corethrella are attracted to the mating calls of male frog
s, their chosen host taxa. As obligate external parasites, the midges feed almost-exclusively on the blood of these frogs. Because of this, Corethrella follow typical distribution patterns of external parasites and are restricted to only areas where there are abundant populations of their host frogs. It is most likely that female midges detect their hosts using a specialized organ called a Johnston's organ
; This is a collection of sensory cells found on the second antennae segment. There is evidence of host specificity and selection of particular biting sites for some species. Corethrella species have been observed sucking blood from individuals of the tree frog genus Hyla
. Specifically, the North American tree frog species Hyla avivoca, Hyla cinerea and Hyla gratiosa
were recorded as confirmed corethrellid hosts in a 1977 study.
A few, select species are known vectors of frog-specific species of the parasitic protozoan Trypanosoma
. Corethrellid parasitism is thus a recorded cause of trypanosomiasis
among host frog populations.
The family contains members that date all the way to the lower Cretaceous
Period some 110 million years ago. At least one species, Corethrella andersoni has been found in Burmese amber
deposits dating from this time.
Diptera
Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...
, that are commonly known to parasitize frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s. The members of the family are sometimes known as "frog-biting midges". The family currently consists of just two genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, totalling around ninety seven species worldwide. There are several fossil species known. Most extant species are found in the lower latitudes, usually associated around the tropics
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
.
Adult female Corethrella are attracted to the mating calls of male frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s, their chosen host taxa. As obligate external parasites, the midges feed almost-exclusively on the blood of these frogs. Because of this, Corethrella follow typical distribution patterns of external parasites and are restricted to only areas where there are abundant populations of their host frogs. It is most likely that female midges detect their hosts using a specialized organ called a Johnston's organ
Johnston's organ
Johnston's organ is a collection of sensory cells found in the pedicel of the antennae in the Class Insecta. Johnston's organ detects motion in the flagellum . It consists of over 200 scolopidia arrayed in a bowl shape, each of which contains a mechanosensory chordotonal neuron...
; This is a collection of sensory cells found on the second antennae segment. There is evidence of host specificity and selection of particular biting sites for some species. Corethrella species have been observed sucking blood from individuals of the tree frog genus Hyla
Hyla
The genus Hyla is one of approximately 38 genera in the New World family of tree frogs . The word Hyla translates to "tree," and tree frogs are indeed arboreal...
. Specifically, the North American tree frog species Hyla avivoca, Hyla cinerea and Hyla gratiosa
Hyla gratiosa
The barking tree frog is a tree frog, 5 to 7 centimeters long, and variable in color but easily recognizable due to the characteristic dark round markings on its dorsum. Individuals may be bright or dull green, brown, yellowish, or gray in color. It has prominent round toe pads and the male has a...
were recorded as confirmed corethrellid hosts in a 1977 study.
A few, select species are known vectors of frog-specific species of the parasitic protozoan Trypanosoma
Trypanosoma
Trypanosoma is a genus of kinetoplastids , a monophyletic group of unicellular parasitic flagellate protozoa. The name is derived from the Greek trypano and soma because of their corkscrew-like motion. All trypanosomes are heteroxenous and are transmitted via a vector...
. Corethrellid parasitism is thus a recorded cause of trypanosomiasis
Trypanosomiasis
Trypanosomiasis or trypanosomosis is the name of several diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus Trypanosoma. Approximately 500,000 men, women and children in 36 countries of sub-Saharan Africa suffer from human African trypanosomiasis which is caused by...
among host frog populations.
The family contains members that date all the way to the lower 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...
Period some 110 million years ago. At least one species, Corethrella andersoni has been found in Burmese amber
Amber
Amber is fossilized tree resin , which has been appreciated for its color and natural beauty since Neolithic times. Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewelry. There are five classes of amber, defined on the basis of their chemical constituents...
deposits dating from this time.