Pedro Jara-Seguel

CHROMOSOME NUMBERS OF CHILEAN PTERIDOPHYTES: FIRST CONTRIBUTION

Mitotic chromosome counts in Chilean pteridophytes confirm the diploidy described for Equisetum L. (2n = 216) and Blechnum L. (2n = 66), as well as the tetraploidy of Asplenium L. (2n = 144). Megalastrum spectabile (Kaulf.) A.R.Sm. et R.C.Moran is diploid (2n = 82), while in metaphases of Polystichum subintegerrimum (Hook. et Arn.) R.A.Rodr. chromosome numbers from ca. 311 to 328 were counted. Tetraploidy was also described in Adiantum chilense Kaulf. (2n = 116)

Karyotype study in the surf clam Mesodesma donacium Lamarck, 1818 (Bivalvia: Veneroida: Mesodesmatidae)

Mesodesma donacium es un almeja distribuida desde Sechura Bay (5°S) en el Norte de Peru hasta la isla de Chiloe (43oS) en el sur de Chile. Debido a la importancia economica de esta especie, su poblacion ha sido reducida en los ultimos anos. En este trabajo se describe por primera vez la morfologia cariotipica de M. donacium, como antecedentes adicionales taxonomicos, ecologicos, morfologicos y reproductivos descritos previamente para la especie. M. donacium muestra un cariotipo diploide 2n=38 con un par metacentrico, quince submetacentricos y tres pares cromosomicos subtelocentricos. La longitud total del set haploide fue de 42,4 mm y el tamano cromosomico medio fue de 2,2 mm. M. donacium mostro una similitud en el numero cromosomico con otras especies del Orden Veneroida, sin embargo fueron encontradas diferencias en tamano y morfologia de los cromosomas. Se discuten las relaciones citogeneticas entre M. donacium y otras especies de Veneroida

Karyological studies in Chilean species of Bomarea and Leontochir (Alstroemeriaceae)

Abstract Species from two genera belonging to the Alstroemeriaceae, Bomarea and Leontochir, were cytogenetically studied and compared to determine their detailed karyotypic composition. Bomarea is a polytypic genus represented by 100 species, with a distribution range from Mexico and Antilles (24°N) to Argentina (29°S) and Chile (17–40°S). In contrast Leontochir is a monotypic genus, endemic to the coastal area of the Atacama Desert in Chile (28°S). Bomarea salsilla, B. involucrosa, and Leontochir ovallei have a karyotype 2n = 18 with similar chromosome morphology. These data confirm the close relationship between both genera, suggested by earlier studies.

Karyological study in fifteen Leucocoryne taxa (Alliaceae)

The karyotype of fifteen Leucocoryne taxa was studied, assessing characteristics such as chromosome morphology and size, secondary constriction location, and asymmetry level. Two groups of Leucocoryne taxa were described based on chromosome number (2n = 10 and 2n = 18) and karyotype asymmetry. The haploid karyotype formula for the group 2n = 10 was 3m + 2st (or 2t), whereas for the group 2n = 18 was 7m + 2st (or 2t). Such results corroborate the karyotype descriptions previously carried out for some taxa of the genus. Leucocoryne taxa showed a high resemblance in chromosome morphology, but inter-specific differences were found in mean chromosome size. These data and previous studies based on gross chromosome morphology support Crosa’s hypothesis, which suggests that the cytotype 2n = 10 is diploid and perhaps ancestral, whereas that the cytotype 2n = 18 is tetraploid but with an additional chromosome fusion being probably a derived status.

Nuclear DNA content in Galaxias maculatus (Teleostei: Osmeriformes: Galaxiidae)

The nuclear DNA content (2C value) was determined in the commercial fish Galaxias maculatus (Galaxiidae) was determined by microdensitometry of erythrocyte n...

Comparación del cariotipo de Eucalyptus globulus y Eucalyptus cladocalyx (Myrtaceae)

A B S T R A C T Mitotic metaphase plates were analyzed in Eucalyptus globulus Labill. and Eucalyptus cladocalyx F. Muell. The chromosomes were observed by squashing root tips, pre-treated with 8Hydroxyquinoline and stained with the Feulgen reaction. Both, E. globulus and E. cladocalyx had a karyotype of 2n = 22, with 1A symmetry level, and chromosome sizes varying between 0.68 and 2.03 ∝m. Mean chromosome size differed significantly between E. cladocalyx (1.42 ∝m) and E. globulus (1.02 ∝m) (P < 0.01). The greater chromosomal size of E. globulus suggests a greater amount of DNA, probably originated by structural alterations. This evolutionary pattern of karyotype morphology might be associated, as well, with a high level of conservation in chromosome morphology.

Contenido de ADN nuclear en el congrio colorado Genypterus chilensis (Guichenot, 1881) (Actinopterygii: Ophidiidae)

Los estudios sobre contenido de ADN nuclear en el genero Genypterus son escasos, y el presente trabajo entrega por primera vez la estimacion del contenido de ADN nuclear de Genypterus chilensis con un valor 2C = 1,0 + 0,06 pg, valor cercano al descrito para otras especies de Ophidiidae que varian entre 1,2 y 1,68 pg.

Life Histories and Dynamics of Stream and Lacustrine Populations of Musculium argentinum (D'Orbigny, 1842) (Bivalvia: Sphaeriidae) from Southern Chile

ABSTRACT Life histories and population dynamics of two populations of Musculium argentinum, one inhabiting a fluvial environment and the other a lacustrine one, are compared. Musculium argentinum is oviparous, iteroparous, and sequential incubator, reproducing throughout the year. The life cycle pattern of the fluvial population, unlike the lacustrine one, is characterized by seasonal reproductive variations, more marked in spring and summer, higher fertility and population reproductive productivity (potential recruitment), higher number of marsupial sacs per hemibranch, and smaller size of first reproduction. The content of organic matter and water flow would be the main factors determining the higher population density observed in the fluvial population.

Some Aspects of the Reproductive Biology of Two Populations of Musculium argentinum (D'Orbigny, 1835) (Bivalvia: Sphaeriidae) from Southern Chile

ABSTRACT Sphaerids have adopted a variety of life strategies that have allowed them to show a cosmopolitan distribution. Among these strategies, those related to reproduction, such as sexuality (hermaphroditism), offspring incubation, fertility, number of generations per year, times an individual reproduces during its lifespan, among others, have been decisive with regard to its permanence in time and space, and to colonize and maintain populations in permanent or temporary freshwater bodies. The aim of the current study is to compare reproductive traits of 2 Musculium argentinum populations inhabiting different environments (stream and lake) to determine the potential influence of the environment on reproduction of these populations. During 1 y (October 2006 to 2007) monthly samples were taken at 2 study sites: Lautaro stream (38°32′ S, 72°27′ W) and La Poza, Villarrica Lake (39°16′27″ S, 71°58′54″ W). Sixty specimens were collected monthly from each population. Valve length of each specimen of the sample was registered to determine the size structure of each population. Fifty animals of known valve length were dissected to determine presence and number of brooding sacs in the inner hemibranches, number of embryos in each sac, and number of newly hatched clams. Ten specimens were processed for optical microscopy with routine histological techniques to characterize the gonad activity pattern. Results indicate that M. argentinum is hermaphroditic in both populations, with gonadal activity throughout the year, iteroparous, and with embryos in brooding sacs and newly hatched clams present year-round. These results indicate that differences in the environment did not produce major changes in reproductive strategies in both M. argentinum populations studied.

Chromosome number of two Chilean species of Nothofagus (Nothofagaceae)

Se documenta un numero cromosomico 2n = 26 (x = 13) para Nothofagus dombeyi (Mirb.) Oerst. y N. glauca (Phil.) Krasser, el cual es similar al descrito previamente para otras especies del genero. Se incrementan a 13 las especies de Nothofagus con numero cromosomico conocido, existiendo dos numeros basicos (x = 13, 14).