INCO partner 6: UBA
Partner name: Departamento de Ciencias Biologicas, Facultad de Ciencias Exactas y
Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Nunez, Pab. II, 4P, C1428
EHA Buenos Aires, Argentina
tel. 54-1-45763349 ; fax 54-1-45763384 ; email : cohen@bg.fcen.uba.ar
Responsible scientist: Graciela Cohen
a) New Artemia records from Argentina and the cytogenetic specific identification
of these new populations
 Cytogenetic characterization of some new recorded Argentinean populations
New recorded populations: Pampa de las Salinas (San Luis Province), Salinas Grandes (NW
Córdoba Province), La Antigua Saline (La Rioja Province).
Conventional staining, C and DAPI banding and Nor-Ag was performed for the
Cytogenetic analysis. In the three populations the meiosis and meiotic figures were regular
and the haploid and diploid numbers as well as the number of chromocentres in interphasic
cells of nauplii gave similar results and were compatible with Artemia franciscana (2n=42,
n=21). Also, it were observed until four nucleoli in somatic cells implying at least two pairs
NOR.
These results were not published yet.
We have presented our partial results in the XXXI Congreso Argentino de Genética (La
Plata, 17th-20th September, 2002) with the presentation of:
“Análisis citogenético de tres nuevas poblaciones de A. franciscana (Crustacea,
Branchiopoda: Anostraca) en las provincias argentinas de La Rioja, Córdoba y San
Luis.”
Authors: Lipko P., Papeschi A.G & Cohen R.G.
 Cytogenetic variability of four Argentinean populations belonging to both A
persimilis and A. franciscana species and the range of a hypothetic hybrid zone.
Analyzed A. franciscana populations: La Antigua Saline (La Rioja Province), Salinas
Grandes (NW Córdoba Province), Pampa de las Salinas (San Luis Province)
Analyzed A. persimilis population: Salitral de la Vidriera (Buenos Aires Province)
The cytogenetic variability was evaluated by conventional staining; C, DAPI and AgNOR banding.
The former three populations gave similar results compatible with A. franciscana
(2n=42, n=21), while Salitral de la Vidriera would correspond to A. persimilis (2n=44). While
in Pampa de las Salinas and Salinas Grandes many chromocenters C+/DAPI+ were observed,
in Salitral de la Vidriera only one or two small chromocenters C+/DAPI+ were detected.
These results were not published yet.
We have presented our partial results in IV Jornadas de la Sociedad Argentina de
Biología (Buenos Aires, 6th December, 2002) with the presentation of:
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“Cytogenetic analysis of four argentine populations of Artemia (Crustacea,
Branchiopoda: Anostraca).”
Lipko P., Papeschi A. & Cohen R.G.
The abstracts of all the presentations will be published during 2003 in Biocell 26(2),
corresponding to August 2002.
The cytogenetics results presented in both above mentioned Scientific Meetings will be
completed to be published during 2003.
b) Characterization of some Artemia franciscana populations from the Córdoba
Province
Populations from Córdoba Province analyzed: Las Tunas Lagoon, Mar Chiquita Lake and
Salinas Grandes.
These characterizations were performed by means of Morphology, Biometry of cysts
and nauplii, Morphometry of adults, Cross-breedings and Lipid profiles, in collaboration with
the Spanish team directed by Dr. F. Amat.
This research reports the presence of Artemia franciscana in Mar Chiquita salt lake and
in Las Tunas lagoon, as well as at a shallow lake in Salinas Grandes (Córdoba Province). The
population from Mar Chiquita shows cross fertility with A. franciscana original from San
Francisco Bay (California-USA). Both populations from Mar Chiquita and Las Tunas show
cross fertility between them and reproductive isolation with A. persimilis from Hidalgo (La
Pampa Province).The Biometry of cysts and nauplii, and reproductive characteristics
displayed by the population from Las Tunas lagoon provide additional support to the
hypothetic existence of an occasional hybridization between A. franciscana and A. persimilis
(Papeschi et al., 2000).
We have finished the revision of the manuscript in collaboration with Dr Amat
team, but it is not published yet.
c) Distributional areas of A. persimilis and A. franciscana populations from
Argentina and Chile. Is the contact zone between both areas a hybrid zone?
We have pointed out that it seems to be a certain kind of latitudinal limit between
the
Argentinean populations assigned to A franciscana and to A. persimilis about 35 °- 36° S:
northern this latitude all the populations were assigned to A. franciscana; southern this
latitude, they belong to A. persimilis. The same could occur in our neighboring country,
Chile. However, we have found, southern this limit the population of Las Tunas Lagoon (33°
44´S). In fact this population conforms by Morphology and Morphometry of adults to A.
franciscana. However, owing to our Cytogenetic analysis, Biometry of cysts and inter and
intraspecific Cross-breedings results (see Point b), we have hypothesized the presence of an
occasional hybridization in this population. This hybridization maybe due to the permanent
contribution of cysts from populations of both species close to Las Tunas Lagoon by means
of winds or waterfowls. Since individuals with the morphotype of A. persimilis were not ever
observed in several Las Tunas Lagoon samplings, probably this population is made up of
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hybrids and introgressants in addition to the parental form, A. franciscana. Therefore now we
are supposing the existence of not just a line but a wide ecotonal zone where contact the
distribution areas of both species. In this area, where evident geographical barrier were not
found, we propose the existence of a hybrid zone. As the Pichilemu Chilean population is
located at this latitudinal range, and the specific identification of this population has been
rather controversial, we suppose that here also could be occurring hybridization and we will
go on working with the Chilean partner in this line. Now, we are looking for some new
techniques to confirm the presence of hybridization in both countries.
Some of these results were presented and discussed during the last workshop in Beijing.
We have also included some previous results of the Cytogenetic analysis of these populations
(Papeschi et al., 2000. Hereditas 133: 159-166.).
We have planned with Dr. G. Gajardo a research in collaboration about this subject.
Also we have studied the possibility to cooperate both partners in a conjoint research
with the Spanish team aiming to evaluate the latitudinal and specific variation of the number
of chromocenters of at least Chilean and Argentinean populations, and to give some evolutive
interpretation of these variability.
On the other hand we have talked with Dr. Abatzopoulos on the possibility to train in
his laboratory a person of our team in ADNm techniques during 2003, for specific
identification of our populations, including those supposedly hybrids, in order to give more
support to our hybridization hypothesis.
d) Fast method for discriminate between A.persimilis and A. franciscana populations
based on morphology.
We have found some few morphological features that allow us to make a preliminary and
fast
identification between both American species. This morphological tool though simple seems
to be useful when the samples are fixed, as in scientific collections, and nor cysts neither alive
adults were available. Also in the laboratory, as a fast control avoiding contamination when
we are working with populations from both species simultaneously.
In order to give support to our method we will perform a discriminant multivariate
analysis including data of fresh adult specimens (both sexes) of diverse populations together
with data of fixed specimens, belonging to scientific collections. The main problem we will
overcome is the contracted state of some fixed specimens.
e) Reproductive characterization. The reproductive and brood cycles of Artemia
persimilis from Colorada Chica lagoon (La Pampa, Province) both in paired or virginal
females, at the laboratory.
We have proposed a model for the sequence of stages and their relative duration in a
complete brood cycle (successive and overlapped reproductive cycles) at laboratory
conditions, in paired and virginal females of A. persimilis from Colorada Chica (La Pampa
Province) population. While a clutch of oocytes begins to mature at the ovaries (ovarian
period), the nauplii, cysts or unfertilised products of a previous clutch are developing at the
oviducts, ovisac or being released to the medium (oviduct-ovisac period). The whole brood
cycle in both types of females took six days. However they differed in the partial duration of
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some stages. We discussed the observed differences and added certain observations on the
amplexus.
We have published our results in Hydrobiologia 486 (2002): 279-288.
f) Effect of diverse saline treatments in different periods of the life cycle (cyst,
postmetanaupliar, adult) of two Argentinean Artemia populations, belonging to A.
persimilis and A. franciscana.
This experimental work was developed for a student to obtain her Msc*. The Thesis was
defended in 23th December 2002 and the results remain still unpublished.
* Licenciatura en Ciencias Biológicas
Title of the Thesis:
“Estudio comparativo del efecto de diversos tratamientos salinos, en distintas etapas del
ciclo ontogenético de dos especies del crustáceo Artemia (Branchiopoda, Anostraca) en
condiciones de Laboratorio.” 82 pp. Hemeroteca Facultad de Ciencias Exactas y Naturales,
Universidad de Buenos Aires.
g) For the coming year in early January 2003, going on with this experimental research line, a
student making her Mscs.* on this subject will go for training with Dr F. Amat to the Instituto
de Torre de la Sal (Castellón, Spain).
*Licenciatura en Ciencias Biológicas
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