Document Detail


Feeding dynamics and ecomorphology of Oligosarcus jenynsii (Gunther, 1864) and Oligosarcus robustus (Menezes, 1969) in the Lagoa Fortaleza, southern Brazil.
MedLine Citation:
PMID:  16680315     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Oligosarcus jenynsii and Oligosarcus robustus are fishes of Characidae family that occur in Rio Grande do Sul, Uruguay and northern Argentina. This work purported to study the feeding dynamics (repletion and hepatosomatic indexes and condition factor) over time, and to investigate the coexistence of these two species by evaluating the partition of resources using qualitative and quantitative analyses of diet, temporal and spatial segregation throughout the water column and some ecomorphological aspects of the species in the Lagoa Fortaleza. Specimens were sampled monthly, from May 2000 to April 2001 during 24 h/month, using stationary gill nets of different mesh sizes. The records of each individual included total and standard length; total, stomach and liver weight; sex and stomach repletion. The variation of the mean values of repletion index and relative frequencies of stomach repletion stages indicate that O. jenynsii and O. robustus do not present seasonal differences in feeding intensity. The hepatosomatic index shows an allocation of energy to the liver during every period except reproduction, when part of the energy is used for gonad maturation. The estimated condition factor for both species reveals an increase in the reproductive period, evidencing the influence of gonads upon the condition of the fish. The diet analysis revealed that O. robustus is piscivorous, whereas O. jenynsii is a generalist carnivore, tending to piscivory as well. The active period of O. robustus is more concentrated at sunrise and sunset, whereas O. jenynsii is continually active, a characteristic related to hunting for prey. The ecomorphological analysis revealed differences between the two species in the dimensions of the mouth. Evidence suggests that the species coexist, sharing food sources, differing in oral morphology but ingesting similar prey, possibly because food is not a limiting factor in the environment.
Authors:
D M Nunes; S M Hartz
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-05-02
Journal Detail:
Title:  Brazilian journal of biology = Revista brasleira de biologia     Volume:  66     ISSN:  1519-6984     ISO Abbreviation:  Braz J Biol     Publication Date:  2006 Feb 
Date Detail:
Created Date:  2006-05-08     Completed Date:  2006-08-31     Revised Date:  2007-09-06    
Medline Journal Info:
Nlm Unique ID:  101129542     Medline TA:  Braz J Biol     Country:  Brazil    
Other Details:
Languages:  eng     Pagination:  121-32     Citation Subset:  IM    
Affiliation:
Programa de Pós-Graduação em Ecologia, Universidade Federal do Rio Grande do Sul, CEP 91501-970, Porto Alegre, RS, Brazil.
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MeSH Terms
Descriptor/Qualifier:
Animals
Brazil
Ecosystem*
Feeding Behavior / classification,  physiology*
Female
Fishes / anatomy & histology,  classification,  physiology*
Gastrointestinal Contents*
Male
Organ Size
Seasons

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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