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J. Moll. Stud. (2002), 68, 17-23
© The Malacological Society of London
2002
COMPARATIVE STUDY OF CYTOPLASMIC ACTIN DNA SEQUENCES FROM SIX SPECIES OF PLANORBIDAE (GASTROPODA: BASOMMATOPHORA)
The Department of Biology, University of New Mexico, 269 Castetter Hall, Albuquerque, NM 87131, USA. Phone + 1 (505) 2772743. Fax + 1 (505) 2770304.
E-mail coenadem{at}unm.edu
Full-length actin-encoding sequences were PCR-amplified from genomic DNA of
six planorbid species; Biomphalaria glabrata (Say; M-line strain),
B. alexandrina (Ehrenberg), B. pfeifferi (Krauss), B.
tenagophila (Orbigny), B. obstructa (Morelet) and Helisoma
trivolvis (Say), using primers designed from a previously reported B.
glabrata cytoplasmic (ß) actin cDNA. The amplified sequences
contained two conserved exons (126 nt and 1005 nt, respectively), separated by
an intron that varied in size between snail species (ranging from 671 to 794
nt). Sequence similarities occurred between the introns of the actin genes
from B. glabrata, B. alexandrina and B. pfeifferi and
between those from B. tenagophila and B. obstructa, yet
considerable differences were evident between these two groups and the intron
derived from H. trivolvis. Analysis of exons for sequence
similarities, the presence of conserved residues (deduced amino acids), and
construction of gene trees indicated that these planorbid genes encode
cytoplasmic (ß) actins rather than muscular (
) actins. Southern
blotting and hybridisation experiments suggested that B. glabrata and
H. trivolvis may have multiple (up to 5) actin genes, and it can not
be ruled out that actin sequences obtained from different planorbid species
were derived from paralogous genes. Interestingly however, the gene trees
resolved actins derived from gastropod, cephalopod and bivalve molluscs. The
sequences presented add to the growing body of information on the molecular
biology of planorbid snails.
(Received 19 February 2001; accepted 14 June 2001)