ABSTRACT
Polypteridae (Cladistia) is a family of archaic fishes, confined to African freshwaters. On account of their primitiveness in anatomical and morphological characters and mosaic relationships among lower Osteichthyans fishes, they constitute an important subject for the study of evolution in vertebrates. Very little is known about the karyological structure of these species. In this article, a cytogenetic analysis on twenty specimens of Polypterus senegalus (Cuvier, 1829) was performed using both classical and molecular techniques. Karyotype (2n=36; FN=72), chromosome location of telomeric sequences (TTAGGG)(n), (GATA)(7) repeats and ribosomal 5S and 18S rRNA genes were examined by using Ag-NOR, classical C-banding, CMA(3) staining and FISH. Staining with Ag-NOR showed the presence of two GC rich NORs on the p arm of the chromosome pair no. 1. CMA(3) marked all centromerical and some (no. 1 and no. 14) telomeric regions. FISH with 5S rDNA marked the subtelomeric region of the q arm of the chromosome pair no. 14. FISH with 18S rDNA marked the telomeric region of the p arm of the chromosome pair no. 1, previously marked by Ag-NOR. (GATA)(7) repeats marked the subtelomeric regions of all chromosome pairs, with the exclusion of the no. 1, 3 and 14. Hybridization with telomeric probes (TTAGGG)(n) showed bright signals at the end of all chromosomes. After cloning, the 5SrDNA alignment revealed an organization of sequences made up of two different classes of tandem arrays (5S type I and 5S type II) of different lengths.
Subject(s)
DNA, Ribosomal/genetics , Genome, Helminth/genetics , Gnathostoma/genetics , RNA, Ribosomal, 5S/genetics , Animals , Azure Stains , Base Sequence , Chromosome Banding , Chromosomes/genetics , Consensus Sequence/genetics , Female , Gnathostoma/cytology , In Situ Hybridization, Fluorescence , Karyotyping , Male , Metaphase/genetics , Microsatellite Repeats , Molecular Sequence Data , Sequence Analysis, DNAABSTRACT
Gnathostomosis is an emerging public health problem in Sinaloa, Mexico, where an increasing number of human cases have been diagnosed since 1989. The present study was carried out to determine the presence of the parasite in other natural hosts from the area. Birds, fish, opossums and raccoons were captured from local dams and lagoons. The flesh from bird and fish specimens was ground and examined under a 100 W light bulb. Larvae were processed for light and electron microscopy. A total of 368 advanced stage 3 (AL3) larvae were found in 300 ichthyophagous birds, with Egretta alba exhibiting the highest infection rate. A total of 4,156 fish were examined, of which six species were infected with AL3 larvae: Arius guatemalensis (blue sea catfish), Dormitator latifrons (Pacific fat sleeper), Gobiomorus sp. (fat sleeper), Oreochromis sp. (Nile tilapia), Cichlasoma beani (Sinaloan cichlid or green guapote) and Eleotris picta (spotted sleeper). Twenty larvae from birds were used to infect domestic cats and dogs. Young adult worms were recovered from the stomach of a cat with a 17 day infection and from a dog with a 35 day infection. Larvae exhibited four rows of hooklets on the head bulb, whereas the young adults had nine rows of hooklets. The cuticular spines of adult worms along the body evolved from single-pointed, bi- or trifurcated spines. Nuclei were counted in intestinal cells examined in serial sections of larvae recovered from a great heron and a fish, in which a mean of 1.6 nuclei/cell was found, corresponding to data published for Gnathostoma binucleatum. Although the external morphology of both larvae and adults are in agreement with previous descriptions of Gnathostoma spinigerum, the results indicate that natural host infections in Sinaloa may be caused by either G. spinigerum or G. binucleatum.
