The Upper Essequibo Conservation Concession is a reserve in central-eastern Guyana managed by Con... more The Upper Essequibo Conservation Concession is a reserve in central-eastern Guyana managed by Conservation International. The site is uninhabited by people and poorly studied. The first scientific fish survey was in 2007 in conjunction with the filming of the BBC nature documentary Lost Land of the Jaguar. Aquatic habitats were primarily flowing water, ranging from the main channel of the Essequibo River to small forest creeks. Ponds and seasonally flooded forests were uncommon. Large predatory fishes were abundant in the Essequibo River. Fishes tolerant of low oxygen levels were common in flooded forests and small forest creeks. There was zero similarity between the fish assemblages of the Essequibo River and flooded forests / small forest creeks. The rest of the habitats and fish assemblages formed a continuum between these extremes. Imminent threats to the Upper Essequibo Conservation Concession include logging, mining, and over-fishing. Because of the heterogeneous distribution ...
Gill rakers in the fish family Catostomidae (Teleostei: Ostariophysi: Cypriniformes) are examined... more Gill rakers in the fish family Catostomidae (Teleostei: Ostariophysi: Cypriniformes) are examined in functional, allometric, and evolutionary contexts. Catostomids are predominantly benthic feeders. Individuals take in a mouthful of substrate and prey, reject the substrate, but selectively retain the prey. Original observations and comparisons with work on Cyprinus carpio indicate that during prey processing the branchial basket and rakers of catostomids function by moving toward the palatal organ (muscular pad suspended from the roof of the pharynx) while bulges form on the surface of the palatal organ, pinching prey between palatal organ and rakers. Water currents then wash away the substrate. A dozen raker parameters were measured in Catostomus commersonii (19--429 mmSL), Ictiobus bubalus (25--309 mmSL), Erimyzon sucetta (41--194 mmSL), and Hypentelium nigricans (39--197 mmSL). Rakers are added until approximately 100 mmSL. Allometric changes in raker number and size are not correlated with ontogenetic niche shifts. Size of the fish is the best predictor of raker parameters, although the exact ontogenetic trajectory may change when rakers are no longer added. Characteristics of the rakers were analyzed within the framework of a phylogeny and comparisons were made between apomorphic (derived) and plesiomorphic states while taking into consideration hypothesized selective regimes. This Homology Approach takes advantage of the individuality of the Catostomini and Moxostomatini lineages to compare evolution as change over time. Twenty-six catostomid species and two cyprinid species were chosen to represent the phylogenetic, morphological, and ecological diversity. Raker width and length of knobs on the surface of the rakers are correlated with prey size, which is consistent with hypothesized action of natural selection. Distance between rakers and distance between knobs are correlated with substrate size, which is consistent with hypothesized action of natural selection. Unknown factors influenced knob height. Raker length and height are correlated with pharynx size. Lateral projections were found to be hypertrophied in some taxa that could effectively sieve prey from the medium. Multiple factors, including phylogenetically inherited traits and natural selection, influenced the evolution of catostomid gill rakers uniquely in different lineages.Ph.D.Biological SciencesZoologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123088/2/3058075.pd
Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured... more Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured in the upper Caura River, Orinoco River basin, Venezuela. The new species is recognized by the following combination of characters: abdomen naked; two or three preanal plates; a bony plate before each branchial opening; seven lateral plates between the pectoral and pelvic fins; maxillary barbel short and attached to the oral disk by a fleshy fold; head dorsal surface and anterior portion of the body light or dark yellow with numerous, round black spots; posterior region of the body light or dark yellow with five black transverse bands, dorsal central area of the two anterior bands diffused. The discovery of this new species extends the distribution of the genus northwest to include the Orinoco River basin on the northern slope of the Guyana shield.
Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured... more Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured in the upper Caura River, Orinoco River basin, Venezuela. The new species is recognized by the following combination of characters: abdomen naked; two or three preanal plates; a bony plate before each branchial opening; seven lateral plates between the pectoral and pelvic fins; maxillary barbel short and attached to the oral disk by a fleshy fold; head dorsal surface and anterior portion of the body light or dark yellow with numerous, round black spots; posterior region of the body light or dark yellow with five black transverse bands, dorsal central area of the two anterior bands diffused. The discovery of this new species extends the distribution of the genus northwest to include the Orinoco River basin on the northern slope of the Guyana shield.
The Upper Essequibo Conservation Concession is a reserve in central-eastern Guyana managed by Con... more The Upper Essequibo Conservation Concession is a reserve in central-eastern Guyana managed by Conservation International. The site is uninhabited by people and poorly studied. The first scientific fish survey was in 2007 in conjunction with the filming of the BBC nature documentary Lost Land of the Jaguar. Aquatic habitats were primarily flowing water, ranging from the main channel of the Essequibo River to small forest creeks. Ponds and seasonally flooded forests were uncommon. Large predatory fishes were abundant in the Essequibo River. Fishes tolerant of low oxygen levels were common in flooded forests and small forest creeks. There was zero similarity between the fish assemblages of the Essequibo River and flooded forests / small forest creeks. The rest of the habitats and fish assemblages formed a continuum between these extremes. Imminent threats to the Upper Essequibo Conservation Concession include logging, mining, and over-fishing. Because of the heterogeneous distribution ...
Gill rakers in the fish family Catostomidae (Teleostei: Ostariophysi: Cypriniformes) are examined... more Gill rakers in the fish family Catostomidae (Teleostei: Ostariophysi: Cypriniformes) are examined in functional, allometric, and evolutionary contexts. Catostomids are predominantly benthic feeders. Individuals take in a mouthful of substrate and prey, reject the substrate, but selectively retain the prey. Original observations and comparisons with work on Cyprinus carpio indicate that during prey processing the branchial basket and rakers of catostomids function by moving toward the palatal organ (muscular pad suspended from the roof of the pharynx) while bulges form on the surface of the palatal organ, pinching prey between palatal organ and rakers. Water currents then wash away the substrate. A dozen raker parameters were measured in Catostomus commersonii (19--429 mmSL), Ictiobus bubalus (25--309 mmSL), Erimyzon sucetta (41--194 mmSL), and Hypentelium nigricans (39--197 mmSL). Rakers are added until approximately 100 mmSL. Allometric changes in raker number and size are not correlated with ontogenetic niche shifts. Size of the fish is the best predictor of raker parameters, although the exact ontogenetic trajectory may change when rakers are no longer added. Characteristics of the rakers were analyzed within the framework of a phylogeny and comparisons were made between apomorphic (derived) and plesiomorphic states while taking into consideration hypothesized selective regimes. This Homology Approach takes advantage of the individuality of the Catostomini and Moxostomatini lineages to compare evolution as change over time. Twenty-six catostomid species and two cyprinid species were chosen to represent the phylogenetic, morphological, and ecological diversity. Raker width and length of knobs on the surface of the rakers are correlated with prey size, which is consistent with hypothesized action of natural selection. Distance between rakers and distance between knobs are correlated with substrate size, which is consistent with hypothesized action of natural selection. Unknown factors influenced knob height. Raker length and height are correlated with pharynx size. Lateral projections were found to be hypertrophied in some taxa that could effectively sieve prey from the medium. Multiple factors, including phylogenetically inherited traits and natural selection, influenced the evolution of catostomid gill rakers uniquely in different lineages.Ph.D.Biological SciencesZoologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123088/2/3058075.pd
Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured... more Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured in the upper Caura River, Orinoco River basin, Venezuela. The new species is recognized by the following combination of characters: abdomen naked; two or three preanal plates; a bony plate before each branchial opening; seven lateral plates between the pectoral and pelvic fins; maxillary barbel short and attached to the oral disk by a fleshy fold; head dorsal surface and anterior portion of the body light or dark yellow with numerous, round black spots; posterior region of the body light or dark yellow with five black transverse bands, dorsal central area of the two anterior bands diffused. The discovery of this new species extends the distribution of the genus northwest to include the Orinoco River basin on the northern slope of the Guyana shield.
Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured... more Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured in the upper Caura River, Orinoco River basin, Venezuela. The new species is recognized by the following combination of characters: abdomen naked; two or three preanal plates; a bony plate before each branchial opening; seven lateral plates between the pectoral and pelvic fins; maxillary barbel short and attached to the oral disk by a fleshy fold; head dorsal surface and anterior portion of the body light or dark yellow with numerous, round black spots; posterior region of the body light or dark yellow with five black transverse bands, dorsal central area of the two anterior bands diffused. The discovery of this new species extends the distribution of the genus northwest to include the Orinoco River basin on the northern slope of the Guyana shield.
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