Denticetopsis
Encyclopedia
Denticetopsis is a genus
of catfish
es (order
Siluriformes) of the family
Cetopsidae
. It includes seven species
, D. epa, D. iwokrama, D. macilenta, D. praecox, D. royeroi, D. sauli, and D. seducta.
that also includes two species previously assigned to the now invalid genus Pseudocetopsis (D. macilenta, D. praecox), together with three species described as new in 2005 (D. epa, D. iwokrama, D. seducta).
. D. epa is known from several localities in the lower portions of the Tocantins River
basin. D. iwokrama is only known from the type locality
in the Siparuni River
basin in Guyana
. D. macilenta is only known from a limited area in the Potaro River
basin of northern Guyana. D. praecox is known from the Baria River of the upper Rio Negro basin in southern Venezuela
. D. royeroi is only known from the holotype
collected in a tributary to the upper Negro River in Venezuela. D. sauli is only know from the Pamoni River in the Casiquiare River basin of the upper Negro River system of Venezuela. D. seducta has a relatively wide,
albeit scattered, distribution in the central and western portions of the Amazon
basin and possibly the southwestern portions of the Orinoco
River basin; it is relatively disjunct from the other species of Denticetopsis.
The possession of a first pectoral-fin ray that is spinous for the basal one-half of its length further separates Denticetopsis from Cetopsis and Paracetopsis, both of which lack a spinous first pectoral-fin ray. Denticetopsis is further distinguished from Cetopsidium
in the lack of the dorsal-spine
locking mechanism and in the having a lateral line
extending either only onto the abdomen or distinctly further posteriorly onto the caudal peduncle, instead of terminating above the base of the anal fin.
Most Denticetopsis have a moderately elongate body (though moderately stout in D. macilenta and deep in D. royeroi) that is slightly compressed (laterally or transversely, depending on species) anteriorly and becoming progressively distinctly compressed posteriorly. The body depth at the dorsal fin origin is usually about one-quarter of the fish's standard length
, but can be as low as one-fifth and as high as almost one-third. In most species, the lateral line is complete, unbranched in midlateral, extending from the vertical through the pectoral fin base to the caudal peduncle; however, in D. royeroi and D. sauli, it is incomplete, interrupted, and restricted to the abdomen. The dorsal profile of the body tends to be nearly straight to slightly convex; the ventral profile is slightly convex to convex at the abdomen and is usually approximately straight but posterodorsally slanted along the base of the anal fin.
Except for D. macilenta which has a distinctly rounded head and snout, the head of Denticetopsis species in profile is acutely triangular overall with a bluntly pointed snout. The eyes are situated on the sides of the head and are visible from above but not from below. The mouth is inferior, the width from approximately one-half to two-thirds of the length of the head. In most species of Denticetopsis, the medial mental barbels
are slightly shorter than the lateral mental barbels, with the latter approximately equal in length to the slender maxillary barbels. However, in C. sauli both pairs of mental barbels are approximately the same length and shorter than the maxillary barbels, and in C. royeroi all three pairs of barbels are approximately the same length.
The dorsal fin is moderately large overall. The dorsal fin spinelet is absent. The anal fin base is usually moderately long but may be long. The pelvic fins are usually moderate but may be moderately long, though in D. sauli they are short. The pectoral fin length is about one-half the length of the head length.
Denticetopsis species range from 1.8–6.7 centimetres (.71–2.6 in) SL
.
Sexual dimorphism
in the shape of the dorsal, pectoral, and anal fins has not been described in species of Denticetopsis, despite the presence of these traits in Cetopsis and Cetopsidium. It is possible that male D. praecox reach sexual maturity at a smaller size than females of the same species.
from 4.3–5.0. Stomachs of two examined specimens of this species contained larva
l chironomids
and other larval insect remains.
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...
es (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 seven 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...
, D. epa, D. iwokrama, D. macilenta, D. praecox, D. royeroi, D. sauli, and D. seducta.
Taxonomy
The original concept of Denticetopsis described by Ferraris in 1996 was restricted to two species, D. royeroi and D. sauli. These two species have proved to be a subunit of a larger cladeClade
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...
that also includes two species previously assigned to the now invalid genus Pseudocetopsis (D. macilenta, D. praecox), together with three species described as new in 2005 (D. epa, D. iwokrama, D. seducta).
Distribution
Denticetopsis species are distributed in South AmericaSouth America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. D. epa is known from several localities in 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...
basin. D. iwokrama is only known from the type locality
Biological type
In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...
in the Siparuni River
Siparuni River
The Siparuni River is a river in the Potaro-Siparuni Region of Guyana. It is a tributary of the Essequibo River. Tributaries of the Siparuni River include the Takutu River , Burro-Burro River, Tipuru River and Levai Creek....
basin in Guyana
Guyana
Guyana , officially the Co-operative Republic of Guyana, previously the colony of British Guiana, is a sovereign state on the northern coast of South America that is culturally part of the Anglophone Caribbean. Guyana was a former colony of the Dutch and of the British...
. D. macilenta is only known from a limited area in the Potaro River
Potaro River
The Potaro River is a river in Guyana in northern South America.The source of the Potaro River is in the Mount Ayanganna area of the Pakaraima Mountains in the North Rupununi Savannahs...
basin of northern Guyana. D. praecox is known from the Baria River of the upper Rio Negro basin in southern 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...
. D. royeroi is only known from the holotype
Biological type
In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...
collected in a tributary to the upper Negro River in Venezuela. D. sauli is only know from the Pamoni River in the Casiquiare River basin of the upper Negro River system of Venezuela. D. seducta has a relatively wide,
albeit scattered, distribution in the central and western portions of the Amazon
Amazon 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 and possibly the southwestern 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; it is relatively disjunct from the other species of Denticetopsis.
Description
Denticetopsis can be distinguished from other genera of Cetopsinae by a number of characteristics. The margin of the caudal fin is either shallowly forked and symmetrical or obliquely truncate. The outer most rays are no more than one and one-half times the length of the inner most rays; in other genera of Cetopsinae, these rays are one and three-quarters to two times the length of the innermost rays. The medial most pelvic-fin ray has a membranous attachment to the body for the basal third to fourth of its length instead of the basal-most half of its length.The possession of a first pectoral-fin ray that is spinous for the basal one-half of its length further separates Denticetopsis from Cetopsis and Paracetopsis, both of which lack a spinous first pectoral-fin ray. Denticetopsis is further distinguished from Cetopsidium
Cetopsidium
Cetopsidium is a genus of catfishes of the family Cetopsidae. It includes seven species, C. ferreirai, C. minutum, C. morenoi, C. orientale, C. pemon, C. roae, and C...
in the lack of the dorsal-spine
Dorsal 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...
locking mechanism and in the having a lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
extending either only onto the abdomen or distinctly further posteriorly onto the caudal peduncle, instead of terminating above the base of the anal fin.
Most Denticetopsis have a moderately elongate body (though moderately stout in D. macilenta and deep in D. royeroi) that is slightly compressed (laterally or transversely, depending on species) anteriorly and becoming progressively distinctly compressed posteriorly. The body depth at the dorsal fin origin is usually about one-quarter of the fish's standard length
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:...
, but can be as low as one-fifth and as high as almost one-third. In most species, the lateral line is complete, unbranched in midlateral, extending from the vertical through the pectoral fin base to the caudal peduncle; however, in D. royeroi and D. sauli, it is incomplete, interrupted, and restricted to the abdomen. The dorsal profile of the body tends to be nearly straight to slightly convex; the ventral profile is slightly convex to convex at the abdomen and is usually approximately straight but posterodorsally slanted along the base of the anal fin.
Except for D. macilenta which has a distinctly rounded head and snout, the head of Denticetopsis species in profile is acutely triangular overall with a bluntly pointed snout. The eyes are situated on the sides of the head and are visible from above but not from below. The mouth is inferior, the width from approximately one-half to two-thirds of the length of the head. In most species of Denticetopsis, the medial mental barbels
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...
are slightly shorter than the lateral mental barbels, with the latter approximately equal in length to the slender maxillary barbels. However, in C. sauli both pairs of mental barbels are approximately the same length and shorter than the maxillary barbels, and in C. royeroi all three pairs of barbels are approximately the same length.
The dorsal fin is moderately large overall. The dorsal fin spinelet is absent. The anal fin base is usually moderately long but may be long. The pelvic fins are usually moderate but may be moderately long, though in D. sauli they are short. The pectoral fin length is about one-half the length of the head length.
Denticetopsis species range from 1.8–6.7 centimetres (.71–2.6 in) 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:...
.
Sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in the shape of the dorsal, pectoral, and anal fins has not been described in species of Denticetopsis, despite the presence of these traits in Cetopsis and Cetopsidium. It is possible that male D. praecox reach sexual maturity at a smaller size than females of the same species.
Ecology
D. praecox have been found in a cobble-pebble habitat of black water streams that ranged in pHPH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
from 4.3–5.0. Stomachs of two examined specimens of this species contained larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l chironomids
Chironomidae
Chironomidae are a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae...
and other larval insect remains.