Hypophthalmus

Taxobox
name = "Hypophthalmus"
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Siluriformes
familia = Pimelodidae
genus = "Hypophthalmus"
genus_authority = Cuvier, 1829
binomial = "Hypophthalmus edentatus"
binomial_authority = Spix & Agassiz, 1829
binomial2 = "Hypophthalmus fimbriatus"
binomial2_authority = Kner, 1857
binomial3 = "Hypophthalmus marginatus"
binomial3_authority = Valenciennes, 1840
binomial4 = "Hypophthalmus oremaculatus"
binomial4_authority = Nani & Fuster, 1947
synonyms =
*"Hypophthalmus"
Spix & Agassiz, 1829
*"Notophthalmus"
Hyrtl, 1859
*"Pseudohypophthalmus"
Bleeker, 1862

"Hypophthalmus" is a genus of catfishes (order Siluriformes) of the family Pimelodidae. It includes four species, "H. edentatus", "H. fimbriatus", "H. marginatus", and "H. oremaculatus".cite journal|url=http://silurus.acnatsci.org/ACSI/library/biblios/2007_Ferraris_Catfish_Checklist.pdf|title=Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types|first=Carl J., Jr.|last=Ferraris|journal=Zootaxa|volume=1418|pages=1–628|year=2007|format=PDF]

Taxonomy

This genus has been classified within its own family "Hypophthalmidae".cite journal|url=http://wfsc.tamu.edu/winemiller/lab/Lopez&W-Hypophth-IEFW00.pdf|title=A review of Venezuelan species of "Hypophthalmus" (Siluriformes: Pimelodidae)|first=Hernan|last=Lopez-Fernandez|coauthors=Winemiller, Kirk O.|journal=Ichthyol. Explor. Freshwaters|volume=11|issue=1|pages=35–46|date=March 2000|format=PDF] cite book|title=Fishes of the World|last=Nelson|first=Joseph S.|publisher=John Wiley & Sons, Inc|year=2006|isbn=0-471-25031-7] However, it has since been reclassified as a member of Pimelodidae; it is thought to be most closely related to "Parapimelodus".

Distribution

"H. edentatus" is found in the Amazon and Orinoco River basins and Atlantic coastal rivers of Guyana and Suriname. "H. fimbriatus" inhabits the Amazon River at Santarém and Rio Negro basin in Brazil and Venezuela. "H. marginatus" originates from the Amazon and Orinoco River basins and major rivers of French Guiana and Suriname. "H. oremaculatus" is distributed in the Paraná River basin, Brazil and Argentina.

Description

Fish of this genus have scale less skin, three pairs of barbels (one maxillary and two mandibular), and small eyes located lateroventrally in a position about mid-length of the head. The body is laterally compressed, bearing a long-based anal fin that runs from the anus to the anterior margin of the caudal peduncle. The dorsal, pectoral, and pelvic fins have a narrow base and lack spines. The posterior margin of the caudal fin is either deeply forked or emarginate, depending on the species.

Ecology

"Hypophthalmus" are unusual among neotropical fishes in their habit of specialized plankton-feeding, collecting plankton by straining water over the fine sieve created by numerous long, thin gill rakers. "H. edentatus" feeds primarily on cladocerans, copepods, and ostracods. It also feeds on debris and other plankton. "H. fimbriatus" has a diet comprised primarily of zooplankton, especially cladocerans and copepods. On the other hand, "H. marginatus" feeds primarily on phytoplankton. "H. edentatus" appears to follow the vertical movement of plankton throughout the day.

"H. edentatus" is a pelagic species which lives in schools near the surface of the water over muddy bottoms.FishBase species|genus=Hypophthalmus|species=edentatus|year=2007|month=June] Ovaries start to develop in November when the water level starts to rise. Fractional spawning occurs between February and April. The female lays down 50,000 to 100,000 eggs according to body weight. Juveniles inhabit the lower part of streams in estuaries, while adults are found more upstream.

"H. edentatus" and "H. marginatus" are more common in clear and whitewater habitats and are extremely limited or nonexistent in blackwater habitats. "H. edentatus" and "H. marginatus" occur in some of the same habitats; however, "H. marginatus" are more common in river and creek channel habitats while "H. edentatus" are more common from aquatic floodplains, including seasonally flooded lagoons. "H. marginatus" has a forked caudal fin, which is more efficient in a habitat with faster moving water. "H. edentatus" has an emarginate caudal fin, which is less vulnerable to fin-nipping by piranhas which are more abundant in slow-moving waters. "H. fimbriatus" may be restricted to blackwater habitats. "H. edentatus" are most common in lagoons and floodplains during the dry season, and move into flooded savannas during the rainy season. "H. marginatus" prefers to stay in larger, permanent water bodies.

References