Cytogenetic variability and
differentiation in Artemia (Branchiopoda: Anostraca) populations
from the Yucatán Peninsula, México
L. Torrentera, F.A. Abreu-Grobois-2002
Hydrobiologia, 486 (1): 303-314
Chromosome numbers in somatic (naupliar) and germinal
(adult male) cells of bisexual Artemia populations from the Yucatán
Peninsula, SE México (Celestun, CEL;
Chuburna, CHUB; Xtampu, XTAM; and Las Coloradas, COL), were compared to
those from San Francisco Bay (SFB) and Great Salt Lake (GSL) individuals.
Diploid and haploid counts permitted a double-check on results. SFB and GSL
samples had low variability in number of chromosomes, with strong modal
values of 2n=42 and n=21, typical for A. franciscana.
Chromosome counts in the Yucatán brine
shrimp samples indicated deviations from the normal 2n=42 karyotype
(heteroploidy): COL had chromosome modes of 2n=42 and n=21;
CEL of 2n=40 and n=20; CHUB had 2n=44 and n=22;
XTAM 2n=48 and n=24. Chromocenter abundance
(heterocromatic blocks of highly repetitive DNA) among populations indicated
that the North American brine shrimp from SFB and GSL had a mean of 15.9 and
15.1 chromocenters, respectively. From the Yucatán
brine shrimp, COL had a variable number of chromocenters, ranging from 5 to
15 with a mean value of 9.9. The other three Artemia populations
had much fewer chromocenters (CEL 1–3, XTAM
1–8, and CHUB 1–4).
Heteromorphic sex chromosomes were apparent in some Yucatán
karyotypes preparations. The haplotype condition in the Yucatán
Artemia populations, though similar to that found in some Italian A.
salina populations, is reported for the first time in New World Artemia.
This cytological characteristic of the Yucatán
Artemia, in conjunction with their morphological and allozyme
differentiation, could provide new insight for the role of chromosome
rearrangements in the evolutionary process of Artemia in the New
Ecology and Evolution, State University of New York, Stony Brook, NY, 11794
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