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Karyotypes of Basilichthys microlepidotus and B. australis (Pisces: Atherinidae)

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... Silversides are represented in Chile by the family Atherinopsidae and two genera: Basilichthys and Odontesthes with at least three freshwater species each (WHITE, 1985;DYER, 1997DYER, , 1998DYER, , 2000. Basilichthys is composed of two species groups: the microlepidotus species group with B. australis from Rio Maipo south to Chiloé Island, and B. microlepidotus from Rio Aconcagua north to Rio Huasco (ARRATIA et al., 1981;CAMPOS, 1984;CAMPOS etaL, 1984;GAJARDO, 1987GAJARDO, ,1992DYER, 1997DYER, , 2000. Both species are not clearly distinguished morphologically and are seemingly sympatric but allotopic in Río Aconcagua. ...
... Both species are not clearly distinguished morphologically and are seemingly sympatric but allotopic in Río Aconcagua. The karyotypic difference of 2n=26 for B. microlepidotus and 2n= 28 for B. australis is the single feature distinguishing both species (GAJARDO, 1992). The semotilus species group is composed of B. semotilus and B. archaeus in Peru, and a new species from the Rio Loa in northern Chile. ...
... Silversides are represented in Chile by the family Atherinopsidae and two genera: Basilichthys and Odontesthes with at least three freshwater species each (WHITE, 1985;DYER, 1997DYER, , 1998DYER, , 2000. Basilichthys is composed of two species groups: the microlepidotus species group with B. australis from Rio Maipo south to Chiloé Island, and B. microlepidotus from Rio Aconcagua north to Rio Huasco (ARRATIA et al., 1981;CAMPOS, 1984;CAMPOS etaL, 1984;GAJARDO, 1987GAJARDO, ,1992DYER, 1997DYER, , 2000. Both species are not clearly distinguished morphologically and are seemingly sympatric but allotopic in Río Aconcagua. ...
... Both species are not clearly distinguished morphologically and are seemingly sympatric but allotopic in Río Aconcagua. The karyotypic difference of 2n=26 for B. microlepidotus and 2n= 28 for B. australis is the single feature distinguishing both species (GAJARDO, 1992). The semotilus species group is composed of B. semotilus and B. archaeus in Peru, and a new species from the Rio Loa in northern Chile. ...
... These patterns are common in fish and play a significant role in fish chromosomal evolution (i.e., Cyprinidae, Uyeno & Miller, 1973;Cichlidae, Thompson, 1979;Atherinopsidae, Jeffrey & Fitzsimons, 1987;Uribe-Alcocer et al., 2002;Muñoz et al., 2006;Carangidae, Lobotidae and Sciaenidae, Tripathy & Das, 1988;and Batrachoididae, Merlo et al., 2005). Particularly within Atheriniformes the FN is very variable, with chromosome arms recorded from 44 to 86, and such variation has been related to pericentric inversion rearrangements (Jeffrey & Fitzsimons, 1987;Warkentine et al., 1987;Sola et al., 1988;Gajardo, 1992;Uribe-Alcocer et al., 2002;Da Silva Cortinhas et al., 2003;Sczepanski et al., 2007). ...
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Within its genus, Chirostoma humboldtianum is one of the species with the widest distribution, inhabiting lake and pond environments along the Lerma-Santiago basin in the Mexican Plateau. Although the species is of great ichthyological, economic, and cultural relevance, factors related to human activity such as habitat loss, pollution, overfishing, and introduction of non-native fish have played important roles in the decline and disappearance of populations. With the aim of describing the karyotype of the species, 22 specimens of C. humboldtianum were collected and their chromosomes obtained from gills based on Denton (1973). Here we reveal intraspecific chromosome variation, characterized by five cytotypes found in four studied populations: 1) Las Tazas, Tiacaque dam (2n = 48, FN = 58) with chromosome formula 6m + 4sm + 38t; 2); Villa Victoria dam (2n = 48, FN = 54) 2m + 2sm + 2st + 42t; 3) Tepuxtepec dam, with two cytotypes (2n = 48, FN = 50) 8m + 2sm + 38t and (4n = 96, FN = 116) 8m + 2st + 38t; 4) and San Pedro Lagunillas lagoon (2n = 48, FN = 58) 8m + 2sm + 38t. We observed chromosome variation in the morphology of pairs 1, 2, 4, and 5. Results allow us to suggest that pericentric inversions are the source of intraspecific chromosome variation. Comparative analyses support the hypothesis that the karyotype of the population from Villa Victoria dam represents the primitive form for the species.
... These patterns are common in fish and play a significant role in fish chromosomal evolution (i.e., Cyprinidae, Uyeno & Miller, 1973;Cichlidae, Thompson, 1979;Atherinopsidae, Jeffrey & Fitzsimons, 1987;Uribe-Alcocer et al., 2002;Muñoz et al., 2006;Carangidae, Lobotidae and Sciaenidae, Tripathy & Das, 1988;and Batrachoididae, Merlo et al., 2005). Particularly within Atheriniformes the FN is very variable, with chromosome arms recorded from 44 to 86, and such variation has been related to pericentric inversion rearrangements (Jeffrey & Fitzsimons, 1987;Warkentine et al., 1987;Sola et al., 1988;Gajardo, 1992;Uribe-Alcocer et al., 2002;Da Silva Cortinhas et al., 2003;Sczepanski et al., 2007). ...
Article
Within its genus, Chirostoma humboldtianum is one of the species with the widest distribution, inhabiting lake and pond environments along the Lerma-Santiago basin in the Mexican Plateau. Although the species is of great ichthyological, economic, and cultural relevance, factors related to human activity such as habitat loss, pollution, overfishing, and introduction of non-native fish have played important roles in the decline and disappearance of populations. With the aim of describing the karyotype of the species, 22 specimens of C. humboldtianum were collected and their chromosomes obtained from gills based on Denton (1973). Here we reveal intraspecific chromosome variation, characterized by five cytotypes found in four studied populations: 1) Las Tazas, Tiacaque dam (2n = 48, FN = 58) with chromosome formula 6m + 4sm + 38t; 2); Villa Victoria dam (2n = 48, FN = 54) 2m + 2sm + 2st + 42t; 3) Tepuxtepec dam, with two cytotypes (2n = 48, FN = 50) 8m + 2sm + 38t and (4n = 96, FN = 116) 8m + 2st + 38t; 4) and San Pedro Lagunillas lagoon (2n = 48, FN = 58) 8m + 2sm + 38t. We observed chromosome variation in the morphology of pairs 1, 2, 4, and 5. Results allow us to suggest that pericentric inversions are the source of intraspecific chromosome variation. Comparative analyses support the hypothesis that the karyotype of the population from Villa Victoria dam represents the primitive form for the species.
... En Chile encontramos a 8. microlepidotus en ríos desde Río Huasco hasta Río Aconcagua, y 8. australis en ríos y lagos desde Río Maipo hasta la Isla Grande de Chiloé. La distinción entre ambas especies y por ende su distribución, no está del todo claro (ARRATIA, 1981;GAJARDO, 1987GAJARDO, , 1988GAJARDO, , 1992. Las dos especies pertenecen al grupo de especies microlepidotus, requiriéndose un estudio morfométrico más detallado o molecular para distinguir claramente ambas aspecies, haciendo énfasis en las poblaciones de las cuencas de los ríos Aconcagua y Maipo. ...
... En Chile encontramos a 8. microlepidotus en ríos desde Río Huasco hasta Río Aconcagua, y 8. australis en ríos y lagos desde Río Maipo hasta la Isla Grande de Chiloé. La distinción entre ambas especies y por ende su distribución, no está del todo claro (ARRATIA, 1981;GAJARDO, 1987GAJARDO, , 1988GAJARDO, , 1992. Las dos especies pertenecen al grupo de especies microlepidotus, requiriéndose un estudio morfométrico más detallado o molecular para distinguir claramente ambas aspecies, haciendo énfasis en las poblaciones de las cuencas de los ríos Aconcagua y Maipo. ...
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The present paper reviews the systematics of marine and freshwater species of Chilean silversides. Resulting from a phylogenetic systematic revision of the order Atheriniformes the traditional concept of the family Atherinidae is that of a polyphyletic assemblage. The New World silversides, Menidiinae and Atherinopsinae, are part of the family Atherinopsidae. Atherinopsinae is composed of two tribes with antitropical distribution (North America: Atherinopsini; South America: Sorgentinini). Sorgentinini is distributed in marine and freshwaters across the southern cone of South America, from northern Peru and southern Brazil to the southern tip of Tierra del Fuego, including the Falkland Islands in the Atlantic and the Juan Fernandez Archipelago in the Pacific. The phylogenetic hypothesis of relationships among species is based on a cladistic analysis using parsimony. There are at least 13 atheriniform species in Chile of the genera Notocheirus (Notocheiridae), Atherinella, Basilichthys, and Odontesthes (Atherinopsidae). Notocheirus hubbsi is under study awaiting more specimens to determine whether its spiny head morphology is evidence of sexual dimophism or a new species. The only member of the subfamily Menidiinae registered in Chile is Atherinella nocturna, appearing occasionally in the north in association with El Niño S.O. events. The majority of silverside species in Chile belong to the subfamily Atherinopsinae. Basilichthys is composed of at least five species, three of which are present in Chile: B. microlepidotus, B. australes, and B. sp., the latter species belonging to the semotilus group and found in
... Both New World (Atherinopsidae) and Old World (Atherinidae) silversides (Dyer & Chernoff, 1996; Dyer, 1998) present an overall uniformity in morphology and life history strategies, with many species forming isolated or semi-isolated populations (Bamber & Henderson, 1988; Creech, 1992a Creech, , 1991 Beheregaray & Levy, 2000). Because of this uniformity, interpopulational and interspecific differences were sought by means of genetic and morphometric techniques (Gajardo, 1987Gajardo, , 1988 Prodohl & Levy, 1989; Gajardo, 1992; Creech, 1991 Creech, , 1992a Bemvenuti, 1997; Gallego et al., 1998; Beheregaray & Levy, 2000). Differences in life cycle, age, and growth between populations and species have also been discussed (Prince & Potter, 1983; Klink & Eckmann, 1985; Potter et al., 1986; Bemvenuti, 1987; Becker, 1995; Scasso & Campos, 1999). ...
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The age and growth of three silverside species are described, and a discussion on possible phylogenetic constraints on life-history characteristics is presented. Samples were collected monthly between March 1992 and February 1993 in three freshwater coastal lakes. Standard length-total length (Ls-Lt) and weight-length (Wt-Lt) relationships studied showed interspecific differences in comparisons between juveniles and adults, males and females. Age was determined by scales. The three species presented a life-cycle duration of 4 to 5 years, with growth coefficients values (K) between 0.37 and 0.63, and asymptotic lengths between 211 and 257 mm. Some interspecific differences may be useful for distinguishing between species (sexual and life-stage related patterns in Ls-Lt and Wt-Lt). The observed life-cycle ranges and maximum sizes were compared to those of other silversides and revealed a pattern coherent with available phylogenetic hypotheses at the supra-generic level, indicating that some life-history characteristics may be subject to phylogenetic constraints.
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p>A database containing data from cytogenetic studies of Chilean fish species is documented for the first time. The cytogenetic data compiled for Chilean fishes include 28 species belonging to 11 families, 9 orders and 16 genera, taking as reference 18 publications since 1972. The application of a variety of cytogenetic methods has provided information on chromosome number, karyotype morphology, genome size, and /or location of different DNA sequences. These data represent only ca. 2.7% of Chile’s fish diversity.</p
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The Chilean native freshwater ichthyofauna is composed of 11 families, 17 genera and about 44 species, including two lampreys. The Chilean biogeographic province has 81% of the species endemic, 40% of which are classified as endangered. The most abundant groups are the siluriforms (11 species), osmeriforms (9 species) and atheriniforms (7 species). Other groups represented in Chile are the cyclostomous Petromyzontiformes (2 species), and the teleostean characiforms (4 species), cyprinodontiforms (6 species), perciforms (4 species) and mugiliforms (1). The South Central area of the Chilean Province has the highest species richness, whereas the northern and southern areas are poorer in species numbers. Due to its origin, percentage of endemism and primitive characters, the ichthyological fauna of Chile has a high biogeographic and conservation value, however, there are important knowledge gaps in the systematics, distribution and biology of these freshwater fishes.
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There is still doubt as to the number of species of the freshwater Chilean ichthyofauna, 64 % of which have conservation problems. One of the groups is that of the silversides of the genus Basilichthys. Three morphological species of this genus have been described in Chile with disjoint distributions: Basilichthys semotilus, B. microlepidotus and B. australis; the latter two overlap in distribution only in the Aconcagua River and are not easily distinguishable by morphological and meristic characters. In order to evaluate the efficacy of identification of these species by molecular techniques, we analyzed the sequence of 9 % of the mitochondrial DNA (Control Region and COI) of individuals from the Loa River (21°41' S) to the Valdivia River (39°50' S), adding meristic features for B. microlepidotus and B. australis in order to study population variation to clarify the taxonomy of the native species of the genus. The phylogenetic analysis showed that the individuals of Basilichthys semotilus form an haplogroup separated from the other species of the genus; however, B. australis and B. microlepidotus form a monophyletic group that shares the most common haplotypes. An analysis of meristic information showed no statistically significant differences in the number of lateral line scales or number of rays in the fins between B. microlepidotus and B. australis. These results do not support the current classification for the latter two species; there appears to be one group in the extreme north of the country (Basilichthys semotilus) and a second group in central Chile which should be called B. microlepidotus. This information will be useful to review the conservation status of the Chilean fauna.
Article
Full-text available
The Chilean native freshwater ichthyofauna is composed of 11 families, 17 genera and about 44 species, including two lampreys. The Chilean biogeographic province has 81% of the species endemic, 40% of which are classified as endangered. The most abundant groups are the siluriforms (11 species), osmeriforms (9 species) and atheriniforms (7 species). Other groups represented in Chile are the cyclostomous Petromyzontiformes (2 species), and the teleostean characiforms (4 species), cyprinodontiforms (6 species), perciforms (4 species) and mugiliforms (1). The South Central area of the Chilean Province has the highest species richness, whereas the northern and southern areas are poorer in species numbers. Due to its origin, percentage of endemism and primitive characters, the ichthyological fauna of Chile has a high biogeographic and conservation value, however, there are important knowledge gaps in the systematics, distribution and biology of these freshwater fishes.
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This paper describes the karyotype of Odontesthes regia by means of Giemsa staining, C-banding, to reveal the distribution of the constitutive heterochromatin, and by Ag-staining and fluorescent in situ hybridization (FISH), to locate ribosomal genes (rDNA). The chromosome diploid modal count in the species was 2n = 48. The karyotype is composed of one submetacentric pair (pair 1), 16 subtelocentric pairs (pairs 2 to 17), and 7 acrocentric pairs (pairs 18 to 24). With the exception of pair 1 it was not possible to classify the homologous chromosomes accurately because differences in chromosome size were too slight between adjacent pairs. The distribution of C-banded heterochromatin allowed for a more accurate matching of the majority of chromosomes of the subtelocentric series. Silver staining of metaphase spreads allowed for the identification of Nucleolus Organizer Regions (Ag-NOR) on pair 1. FISH experiments showed that 18S rDNA sequences were located, as expected, in the same chromosome pair identified as the Ag-NOR-bearing one. Key words: Karyotype, NOR, C-bands, FISH
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Cytogenetic studies were performed on specimens of Atherinella brasiliensis from Laranjeiras Bay (Paraná State, Brazil). All specimens had a diploid number of 48 chromosomes, with a karyotype constituted by 4m+14sm+18st+12a and fundamental number of 84. The C-positive heterochromatin was distributed over the nucleolar organizer regions (NORs) in the centromeric regions and on short arms of metacentric and submetacentric chromosomes. Most of this heterochromatin was AT-rich, except in the NORs, which were rich in GC, as detected by double staining with chromomycin A3/4′-6-diamin-2-phenylindole. Single NORs were located at terminal positions of a submetacentric pair, as confirmed by fluorescent in situ hybridization with 18S rDNA probes. Both techniques showed a size heteromorphism between the homologous chromosomes. The 5S rDNA clusters were located in terminal positions on two chromosomal pairs and also displayed a size heteromorphism. Despite the conserved diploid number, the data on the karyotype microstructure help characterize the cytogenetic profile of this group.
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Karyotype analyses of three Chirostoma species, C. estor, C. patzcuaro, and C. jordani from Mexico, are presented. C. estor and C. jordani have both a diploid number of 2N = 48 and a fundamental number of NF = 68, but different karyotype formulae. The co-occurrence of these karyotypes with morphometric and allozymatic primitive features so far reported suggests that the ancestral karyotype of the genus Chirostoma was similar to the one shown by these species. The divergent karyotype of C. patzcuaro (2N = 44 and NF = 44) could be related to its endemism and to the relatively small size of its populations.
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Testicular structure in Salmoniformes, Perciformes, Cypriniformes, and Atheriniformes has been examined and reinterpreted on the basis of two different tubular types, distinguished from each other by the intratubular distribution of spermatogonia. In the salmoniform, perciform, and cypriniform teleosts studied, spermatogonia are distributed along the entire length of the testicular tubules. However, in the atheriniform teleosts spermatogonia are restricted to the distal end of the tubule. Sperm development in teleosts is cystic, cysts being comprised of Sertoli-cell processes. In both testicular types described, Sertoli cells phagocytize spermatid residual bodies. Together witb the germ cells, they comprise the only intratubular cell types within the teleostean testis. Boundary cells are located immediately outside of the tubule basement membrane. They do not form a complete layer over the tubule surface; therefore, interstitial Leydig cells and blood vessels may border directly upon the tubular basement membrane.
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HARDER, W. 1975. Anatomy of fishes. 2d ed. E. Schweitzerbart'sche Verlagsbuchhandlung, Stutt-gart, Germany. MILLER, P. J. 1973. The osteology and adaptive fea-tures of Rhyacichthys aspro (Teleostei: Gobioidei) and the classification of gobioid fishes. J. Zool., London 171:397-434.
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