By Alejandro Yafe, Marcelo Loureiro, Flavio Scasso, and Federico Quintans.
Abtract:
Diet of two cichlid species, Cichlasoma facetum (Jenyns,
1842), and Gymnogeophagus rhabdotus Hensel, 1870, was studied in Rodo Lake,
an urban hypertrophic lake in Uruguay. The stomach contentsfrom 192 individuals
of C. facetum and 202 of G. rhabdotus, obtained through seasonal sampling
in the year 2000, were analyzed. The occurrence frequency and the alimentary
importance index of each food item were calculated for each season and size
class in both species. Cichlasoma facetum fed upon insects (mainly chironomid
larvae and pupae), fish (Cnesterodon decemmaculatus Jenyns, 1842), and vegetals
(algae, periphyton and macrophytes debris); large individuals also fed upon
the freshwater shrimp Palaemonetes argentinus Nobili, 1901. Gymnogeophagus
rhabdotus consumed zooplankton (mainly copepods), vegetals (algae and detritus)
and Chironomidae larvae in a lesser extent.
By Eliana Feldberg and Luiz Antonio Carlos Bertollo.
Abtract:
Gymnogeophagus balzanii (Pisces: Cichlidae) is characterized by the fact that its somatic cells (kidneys and gills) exhibit 2n = 48 chromosomes. Analysis of testis cells not only revealed the occurrence of the expected haploid number equal to 24, but also showed the presence of a few extra chromosomes. As a viable hypothesis, we propose that these are supernumerary chromosomes which are absent in the somatic cells analyzed.
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