Physopyxis
Encyclopedia
Physopyxis is a genus
of catfish
es (order
Siluriformes) of the family
Doradidae
. It includes three species, P. ananas, P. cristata, and P. lyra.
in northeastern Peru
) to the Uatumã River
, a left bank tributary to the Amazon in eastern Amazonas State, Brazil
. P. ananas has the widest distribution among the species of the genus, occurring throughout lowlands in entire Amazon (including Rio Negro) and Essequibo River
basins. P. cristata has only been recorded from middle portion of the Negro River basin.
. Their pectoral fin spine reaches the base of the anal fin, and the dorsal fin
spine is serrated
only at the anterior margin of its base. There are three pairs of barbels
, one pair of maxillary barbels and two pairs of mental barbels. The dorsal and pectoral fin spines are strongly ossified and well-developed.
P. cristata can be differentiated from the other species by its incomplete lateral line
and a series of small spines along its dorsal midline. The other two species have complete lateral lines with well-developed plates that extend to the caudal fin. P. lyra has only one series of spines on its lateral plates and its adipose fin is usually present. The lateral plates have two or more series of spines in P. ananas, and the adipose fin is usually absent.
plants, like Symmeria paniculata (Polygonaceae
). P. lyra is predominantly nocturnal, and spends most of day time sheltered among submersed root mats or buried in sand. P. ananas and P. lyra have been found together among the submerged roots of aquatic macrophytes (Paspallum repens, Poaceae
) at Amanã Lake, Japurá River
basin. They were also collected together in Nanay
upstream from Iquitos
. Dwarf cichlids of the genus Apistogramma
and juvenile specimens of Amblydoras
were found in the same habitat as P. cristata.
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...
Doradidae
Doradidae
Doradidae is a family of catfishes also known as thorny catfishes or talking catfishes. These fish are native to South America, primarily in Brazil, Peru, and the Guianas.Doradids are omnivorous.-Taxonomy:...
. It includes three species, P. ananas, P. cristata, and P. lyra.
Distribution
P. lyra is known from the Ampyiacu River (and lowland portions of other tributaries to the upper 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...
in northeastern Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
) to the Uatumã River
Uatumã River
The Uatumã River is a river flowing through the state of Amazonas in the Manaus area of Brazil.A tributary of the Amazon River, it is known for its extensive peacock population. ....
, a left bank tributary to the Amazon in eastern Amazonas State, 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...
. P. ananas has the widest distribution among the species of the genus, occurring throughout lowlands in entire Amazon (including Rio Negro) and Essequibo River
Essequibo River
The Esequibo River is the largest river in Guyana, and the largest river between the Orinoco and Amazon. Rising in the Acarai Mountains near the Brazil-Guyana border, the Essequibo flows to the north for 1,010 km through forest and savanna into the Atlantic Ocean.-Geography:There are countless...
basins. P. cristata has only been recorded from middle portion of the Negro River basin.
Description
Physopyxis have an extremely small size among doradids, not exceeding 31 millimetres (1.2 in) SLFish 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:...
. Their pectoral fin spine reaches the base of the anal fin, and the dorsal fin
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...
spine is serrated
Serrated Edge
Serrated Edge is the second album by Tempest. It was their first with a fiddler, and was released in 1992.-Tracks:#Hal-an Tow #Raggle Taggle Gypsy #A Kiss in the Morning Early...
only at the anterior margin of its base. There are three pairs of 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...
, one pair of maxillary barbels and two pairs of mental barbels. The dorsal and pectoral fin spines are strongly ossified and well-developed.
P. cristata can be differentiated from the other species by its incomplete 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...
and a series of small spines along its dorsal midline. The other two species have complete lateral lines with well-developed plates that extend to the caudal fin. P. lyra has only one series of spines on its lateral plates and its adipose fin is usually present. The lateral plates have two or more series of spines in P. ananas, and the adipose fin is usually absent.
Habitat
Physopyxis species are usually found in places with accumulated organic debris, like dense meshes of roots of floating macrophytes that are abundant in rivers with turbid water or submerged litter banks. Specimens also can be found among submerged leaf litter and among root mats of riparianRiparian zone
A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth. Plant habitats and communities along the river margins and banks are called riparian vegetation, characterized by...
plants, like Symmeria paniculata (Polygonaceae
Polygonaceae
Polygonaceae is a family of flowering plants known informally as the "knotweed family" or "smartweed family"— "buckwheat family" in the United States. The name is based on the genus Polygonum and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum. The name refers...
). P. lyra is predominantly nocturnal, and spends most of day time sheltered among submersed root mats or buried in sand. P. ananas and P. lyra have been found together among the submerged roots of aquatic macrophytes (Paspallum repens, Poaceae
Poaceae
The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...
) at Amanã Lake, Japurá River
Japurá River
The Japurá River or Caquetá River is a river about long rising as the Caquetá River in the Andes in the Southwest of Colombia. It flows southeast into Brazil, where it is called the Japurá. The Japurá enters the Amazon River through a network of channels...
basin. They were also collected together in Nanay
Nanay
The Nanay River is tributary river to the Amazon River, west of the Napo in Peru. The Nanay is one of the three rivers that surround the jungle city of Iquitos, making it an island. Other nearby settlements on the river include the villages of Santo Tomás, Padre Cocha, and Santa Clara. During...
upstream from Iquitos
Iquitos
Iquitos is the largest city in the Peruvian rainforest, with a population of 370,962. It is the capital of Loreto Region and Maynas Province.Located on the Amazon River, it is only above sea level, although it is more than from the mouth of the Amazon at Belém on the Atlantic Ocean...
. Dwarf cichlids of the genus Apistogramma
Apistogramma
Apistogramma is a genus of approximately a hundred species of fish from the family Cichlidae found in tropical areas of the Amazon basin and Venezuela. Apistogramma literally means "irregular lateral line" referring to a common trait of the species under this taxon...
and juvenile specimens of Amblydoras
Amblydoras
Amblydoras is a genus of catfishes of the family Doradidae. This genus includes, A. affinis, A. bolivarensis, A. gonzalezi, A. monitor, and A. nauticus....
were found in the same habitat as P. cristata.