Helogenes
Encyclopedia
Helogenes is a genus
of catfish
(order
Siluriformes) of the family
Cetopsidae
. It includes four species
, H. castaneus, H. gouldingi, H. marmoratus, and H. uruyensis.
Helogeneinae is the sister taxon
of Cetopsinae, the other subfamily in the family Cetopsidae.
basin, the southern portions of the Orinoco
River basin, the coastal rivers of the Guianas, and at least the lower portions of the Tocantins River
. H. castaneus originates from the Guaviare River
and Meta River
drainages of the upper [rinoco in eastern Colombia
. H. gouldingi inhabits the Madeira River
basin in Brazil
. H. marmoratus is found in Atlantic drainages of Guianas, the upper Orinoco and Rio Negro systems, and the upper Amazon River basin. H. uruyensis is from the Uruyén River basin in Venezuela
.
base is short, the anal fin base is elongate, the dorsal and pectoral fins lack spines, the adipose fin is usually present, but is reduced or absent in one population of one species. Helogenes species grow to about 4.3–7.3 centimetre
s (1.7–2.9 in
) SL
.
s. H. marmoratus is nocturnal and feeds mainly on terrestrial insects, particularly ants. H. gouldingi has been found in small black-water tributaries. H. marmoratus is a typical inhabitant of black or clear waters, usually in forest streams with moderate to swift current flow over firm sand or gravel bottoms .
H. marmoratus lives hidden under plants, litter or plant debris. It has a colour pattern that resembles dead leaves. The fish may even lie on its side among the leaf litter as a form of camouflage
. It can easily be mistaken as a piece of dead wood when it rests on its side, motionless on the bottom. It often swims on one side in undulating movements. When disturbed, H. marmoratus will move upwards through the root-tangle, exposing its head or fore body above the water surface. If disturbed further, it will quickly swim in an upright position towards the nearest debris shelter. Also, H. marmoratus is known to jump on the bank during rotenone
fishing by Tukano and Tuyuka indigenous people, then jump back to the stream after water renovation.
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...
of catfish
Catfish
Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...
(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...
Siluriformes) of the family
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...
Cetopsidae
Cetopsidae
Cetopsidae is a small family of catfishes , commonly called the whale catfishes.-Taxonomy:This family contains five genera. It is divided into two subfamilies, Cetopsinae and Helogeneinae. Helogeneinae was previously a family-level group, but now it has been reclassified as a subfamily of Cetopsidae...
. It includes four 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...
, H. castaneus, H. gouldingi, H. marmoratus, and H. uruyensis.
Helogeneinae is the sister taxon
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 Cetopsinae, the other subfamily in the family Cetopsidae.
Distribution
Helogenes species occur through much of the Amazon RiverAmazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
basin, the southern portions of the Orinoco
Orinoco
The Orinoco is one of the longest rivers in South America at . Its drainage basin, sometimes called the Orinoquia, covers , with 76.3% of it in Venezuela and the remainder in Colombia...
River basin, the coastal rivers of the Guianas, and at least the lower portions of the Tocantins River
Tocantins River
The Tocantins is a river in Brazil, the central fluvial artery of the country. In the Tupi language, its name means "toucan's beak" . It runs from south to north for about 2,640 km. It is not really a branch of the Amazon River, although usually so considered, since its waters flow into the...
. H. castaneus originates from the Guaviare River
Guaviare River
The Guaviare is a tributary of the Orinoco located in Colombia.The Guaviare has its source in two other rivers, the Ariari and the Guayabero, which in turn have their own sources in the eastern part of the Andes. At long, it is the longest river on the Orinoco and is navigable for of its total...
and Meta River
Meta River
The Meta River is formed in the Meta Department, Colombia by the confluence of the Humea, Guatiquía and Guayuriba rivers. It flows east-northeastward across the Llanos Orientales plains of Colombia through an ancient fault...
drainages of the upper [rinoco in eastern Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
. H. gouldingi inhabits the Madeira River
Madeira River
The Madeira River is a major waterway in South America, approximately 3,250 km miles long The Madeira is the biggest tributary of the Amazon...
basin in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. H. marmoratus is found in Atlantic drainages of Guianas, the upper Orinoco and Rio Negro systems, and the upper Amazon River basin. H. uruyensis is from the Uruyén River basin in Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
.
Description
In Helogenes, the dorsal finDorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
base is short, the anal fin base is elongate, the dorsal and pectoral fins lack spines, the adipose fin is usually present, but is reduced or absent in one population of one species. Helogenes species grow to about 4.3–7.3 centimetre
Centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...
s (1.7–2.9 in
Inch
An 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...
) SL
Fish measurement
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:...
.
Ecology
Helogenes species feed on allochthonous insectInsect
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. H. marmoratus is nocturnal and feeds mainly on terrestrial insects, particularly ants. H. gouldingi has been found in small black-water tributaries. H. marmoratus is a typical inhabitant of black or clear waters, usually in forest streams with moderate to swift current flow over firm sand or gravel bottoms .
H. marmoratus lives hidden under plants, litter or plant debris. It has a colour pattern that resembles dead leaves. The fish may even lie on its side among the leaf litter as a form of camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
. It can easily be mistaken as a piece of dead wood when it rests on its side, motionless on the bottom. It often swims on one side in undulating movements. When disturbed, H. marmoratus will move upwards through the root-tangle, exposing its head or fore body above the water surface. If disturbed further, it will quickly swim in an upright position towards the nearest debris shelter. Also, H. marmoratus is known to jump on the bank during rotenone
Rotenone
Rotenone is an odorless chemical that is used as a broad-spectrum insecticide, piscicide, and pesticide. It occurs naturally in the roots and stems of several plants such as the jicama vine plant...
fishing by Tukano and Tuyuka indigenous people, then jump back to the stream after water renovation.